1 00:00:01,802 --> 00:00:04,803 The Arctic... 2 00:00:04,805 --> 00:00:07,840 the Antarctic... 3 00:00:07,842 --> 00:00:10,609 our planet's ice worlds. 4 00:00:10,611 --> 00:00:14,480 Vast, frozen, and empty. 5 00:00:14,482 --> 00:00:16,048 ♪ ♪ 6 00:00:16,050 --> 00:00:19,351 Yet hidden in these rocks, 7 00:00:19,353 --> 00:00:20,452 buried under the oceans... 8 00:00:20,454 --> 00:00:22,087 PILOT: Control, boulder board. 9 00:00:22,089 --> 00:00:25,057 JOHNSON: ...and trapped in the ice 10 00:00:25,059 --> 00:00:28,494 are clues that reveal a totally different past. 11 00:00:28,496 --> 00:00:30,329 Oh my God, look at this. 12 00:00:30,331 --> 00:00:31,764 Full of surprises... 13 00:00:31,766 --> 00:00:34,033 It's like a whole forest. 14 00:00:34,035 --> 00:00:36,268 I'm Kirk Johnson 15 00:00:36,270 --> 00:00:41,106 and I'm headed out on an adventure back in time... 16 00:00:41,108 --> 00:00:43,308 Just walking around, carrying a mammoth tusk. 17 00:00:43,310 --> 00:00:46,111 ...and around the globe, 18 00:00:46,113 --> 00:00:49,381 from one polar extreme to the other, 19 00:00:49,383 --> 00:00:51,717 to discover an Earth totally different... 20 00:00:51,719 --> 00:00:52,785 It just looks like Mars. 21 00:00:52,787 --> 00:00:55,687 ...from the planet we know today. 22 00:00:55,689 --> 00:00:58,791 This place, this is so totally amazing 23 00:00:58,793 --> 00:01:03,896 An Arctic that was once a warm, humid swamp; 24 00:01:03,898 --> 00:01:07,633 Antarctica full of dinosaurs; 25 00:01:07,635 --> 00:01:11,403 and a time when ice sheets extended from pole to pole, 26 00:01:11,405 --> 00:01:14,840 turning earth into a giant snowball. 27 00:01:14,842 --> 00:01:19,578 What powerful forces drove the poles to such extremes? 28 00:01:19,580 --> 00:01:22,014 And what does it mean for our planet's future? 29 00:01:22,016 --> 00:01:23,682 (squawking) 30 00:01:23,684 --> 00:01:25,918 ♪ ♪ 31 00:01:25,920 --> 00:01:28,053 Find out the true power of ice. 32 00:01:28,055 --> 00:01:30,289 This is amazing out here. 33 00:01:30,291 --> 00:01:32,357 "Polar Extremes," 34 00:01:32,359 --> 00:01:35,527 right now, on "NOVA." 35 00:01:38,165 --> 00:01:43,068 ♪ ♪ 36 00:01:43,070 --> 00:01:44,236 Major funding for "NOVA" is provided by the following: 37 00:01:55,015 --> 00:01:57,149 JOHNSON: We're right at the mouth 38 00:01:57,218 --> 00:02:00,452 of the Ilulissat Icefjord. 39 00:02:00,521 --> 00:02:02,421 This place is a dream. 40 00:02:02,490 --> 00:02:07,659 ♪ ♪ 41 00:02:13,000 --> 00:02:15,400 It's almost unimaginable to think 42 00:02:15,469 --> 00:02:18,737 that I can paddle a kayak around in a landscape 43 00:02:18,806 --> 00:02:22,941 of floating, frozen ice. 44 00:02:23,010 --> 00:02:24,710 Think about all the other places you could be right now, 45 00:02:24,778 --> 00:02:26,311 then think about where you actually are. 46 00:02:26,380 --> 00:02:28,881 ♪ ♪ 47 00:02:28,949 --> 00:02:32,651 These icebergs are amazing, 48 00:02:32,720 --> 00:02:34,319 and they come in all sizes, 49 00:02:34,388 --> 00:02:36,822 from the size of little, tiny ice cubes 50 00:02:36,891 --> 00:02:41,426 all the way up to the size of mountains. 51 00:02:41,495 --> 00:02:44,196 ♪ ♪ 52 00:02:44,265 --> 00:02:45,597 Believe it not, 53 00:02:45,666 --> 00:02:49,234 we live on a planet whose fate is determined by ice. 54 00:02:49,303 --> 00:02:51,803 You wouldn't think it living at mid-latitudes, 55 00:02:51,872 --> 00:02:54,573 but here in Greenland, it's really obvious. 56 00:02:54,642 --> 00:02:56,808 ♪ ♪ 57 00:02:56,877 --> 00:03:00,145 There is so much ice in glaciers and ice caps, 58 00:03:00,214 --> 00:03:02,848 mostly up here in the Arctic 59 00:03:02,917 --> 00:03:05,450 and down in the Antarctic. 60 00:03:05,519 --> 00:03:07,252 When you add it all up, 61 00:03:07,321 --> 00:03:11,657 it's 70% of Earth's fresh water. 62 00:03:11,725 --> 00:03:14,826 I'm paddling towards two of the most spectacular icebergs 63 00:03:14,895 --> 00:03:17,696 I've ever seen in my life. 64 00:03:17,765 --> 00:03:20,532 This stuff looks so solid, 65 00:03:20,601 --> 00:03:24,836 so vast, so permanent. 66 00:03:24,905 --> 00:03:28,173 But looking around at these giant floating mountains, 67 00:03:28,242 --> 00:03:32,578 you've got to wonder, "How did all this ice get here? 68 00:03:32,646 --> 00:03:35,280 How long did it take to form?" 69 00:03:35,349 --> 00:03:40,085 And, of course, "How long will it last?" 70 00:03:40,154 --> 00:03:43,488 For the whole time that humans have been on this planet-- 71 00:03:43,557 --> 00:03:46,291 around 300,000 years-- 72 00:03:46,360 --> 00:03:50,529 there's always been ice at the poles. 73 00:03:50,598 --> 00:03:53,699 But if you look at the entire history of Earth, 74 00:03:53,767 --> 00:03:56,134 Homo sapiens' existence has happened 75 00:03:56,203 --> 00:03:58,036 in just the blink of an eye. 76 00:03:58,105 --> 00:04:02,007 If we could travel back in time-- 77 00:04:02,076 --> 00:04:04,309 hundreds of millions of years-- 78 00:04:04,378 --> 00:04:07,479 what would the Arctic and Antarctic look like? 79 00:04:07,548 --> 00:04:09,982 Ice at the polar extremes 80 00:04:10,050 --> 00:04:12,484 is vital to the health of our planet. 81 00:04:12,553 --> 00:04:17,756 If it disappears, what can the past tell us about the future? 82 00:04:17,825 --> 00:04:22,027 How close are we to a tipping point? 83 00:04:27,635 --> 00:04:30,569 ♪ ♪ 84 00:04:30,638 --> 00:04:33,438 (voiceover): That took me by surprise. 85 00:04:33,507 --> 00:04:35,374 To answer these questions, 86 00:04:35,442 --> 00:04:38,977 I'm joining scientists working around the world... 87 00:04:39,046 --> 00:04:40,145 Oh, yeah! 88 00:04:40,214 --> 00:04:41,813 Digging... Oh! 89 00:04:41,882 --> 00:04:43,582 There's a perfect three-million-year-old clam! 90 00:04:43,651 --> 00:04:45,350 This is like a window to the past. 91 00:04:45,419 --> 00:04:46,418 JOHNSON: Drilling... 92 00:04:46,487 --> 00:04:47,819 JIM WHITE: You can actually see 93 00:04:47,888 --> 00:04:50,289 the annual layers, even at this level. 94 00:04:50,357 --> 00:04:52,057 JOHNSON: And probing... 95 00:04:52,126 --> 00:04:54,126 DAVID HOLLAND: First we're going to lower the probe. Probe deployed. 96 00:04:54,194 --> 00:04:55,360 JOHNSON: To unlock the hidden history... 97 00:04:55,429 --> 00:04:56,762 Okay, so it's cold. 98 00:04:56,830 --> 00:04:59,364 JOHNSON: You're better than me, I'll tell you. 99 00:04:59,433 --> 00:05:02,200 ...of the polar extremes. 100 00:05:02,269 --> 00:05:06,605 ♪ ♪ 101 00:05:08,575 --> 00:05:10,575 Oh, yes! 102 00:05:10,644 --> 00:05:12,811 I'm a paleontologist. 103 00:05:12,880 --> 00:05:14,346 Get-get this edge right here. 104 00:05:14,415 --> 00:05:15,681 Yes, sir. 105 00:05:15,749 --> 00:05:18,250 JOHNSON: I love finding fossils of all kinds, 106 00:05:18,319 --> 00:05:21,820 but I have a special place in my heart for fossil plants. 107 00:05:21,889 --> 00:05:24,456 (laughing) 108 00:05:24,525 --> 00:05:26,158 MAN: Oh, my God. 109 00:05:26,226 --> 00:05:29,795 JOHNSON: Like this palm frond I found in Alaska a few years ago. 110 00:05:29,863 --> 00:05:31,163 Whoa. 111 00:05:31,231 --> 00:05:33,732 (plane engine droning) 112 00:05:33,801 --> 00:05:36,368 My first stop on this journey is one 113 00:05:36,437 --> 00:05:38,804 of the most remote places on Earth, 114 00:05:38,872 --> 00:05:43,041 with some surprising secrets locked in its rocks. 115 00:05:43,110 --> 00:05:46,511 I'm on my way to Ellesmere Island, 116 00:05:46,580 --> 00:05:50,315 high in the Canadian Arctic, next door to Greenland, 117 00:05:50,384 --> 00:05:53,952 and it's only 800 miles from the North Pole. 118 00:05:54,021 --> 00:05:57,122 We just crossed over latitude 77, 119 00:05:57,191 --> 00:05:58,790 and we just left Grise Fiord, 120 00:05:58,859 --> 00:06:01,393 which is the northernmost town in North America, 121 00:06:01,462 --> 00:06:02,627 and we're going north. 122 00:06:02,696 --> 00:06:05,764 ♪ ♪ 123 00:06:05,833 --> 00:06:09,534 There's just clouds and ice and rock. 124 00:06:09,603 --> 00:06:13,939 It just looks like Mars, it's a magical place. 125 00:06:14,007 --> 00:06:18,510 This far north, there are no roads, no airports, 126 00:06:18,579 --> 00:06:20,379 and definitely no runways. 127 00:06:20,447 --> 00:06:21,880 He's coming in right now. 128 00:06:21,949 --> 00:06:26,418 Landing on uncharted ground is a nail-biting experience. 129 00:06:26,487 --> 00:06:28,587 Hold tight, hold tight. 130 00:06:28,655 --> 00:06:29,821 Even for a seasoned Arctic guide 131 00:06:29,890 --> 00:06:31,690 like Jason Hillier. 132 00:06:31,759 --> 00:06:35,794 (plane droning) 133 00:06:39,767 --> 00:06:41,433 There we go. 134 00:06:41,502 --> 00:06:43,835 That's what we call an... 135 00:06:43,904 --> 00:06:47,105 That's an Arctic landing right there. 136 00:06:47,174 --> 00:06:49,574 He hit the brakes pretty hard. 137 00:06:49,643 --> 00:06:51,209 Whoo! 138 00:06:51,278 --> 00:06:52,844 That was awesome. 139 00:06:52,913 --> 00:06:55,113 HILLIER: Terra firma. 140 00:06:55,182 --> 00:06:57,282 JOHNSON: Ellesmere! 141 00:06:57,351 --> 00:06:59,451 JOHNSON: You got to have a really good reason 142 00:06:59,520 --> 00:07:01,486 to want to land a plane here. 143 00:07:01,555 --> 00:07:02,821 It's a great place to be; I mean, 144 00:07:02,890 --> 00:07:03,889 this is a most beautiful spot. 145 00:07:03,957 --> 00:07:06,992 (engine droning) 146 00:07:11,532 --> 00:07:13,865 There's always the moment when that Twin Otter leaves, 147 00:07:13,934 --> 00:07:16,001 and you're standing here realizing that 148 00:07:16,069 --> 00:07:17,903 there's nobody for hundreds of miles around. 149 00:07:17,971 --> 00:07:22,407 You're all alone out in the amazing, wide world. 150 00:07:22,476 --> 00:07:24,176 Time to get down to business. 151 00:07:24,244 --> 00:07:25,510 I know. 152 00:07:25,579 --> 00:07:27,612 JOHNSON: I've come here to try and figure out 153 00:07:27,681 --> 00:07:31,650 what life was like in the Arctic millions of years ago. 154 00:07:31,718 --> 00:07:34,920 There's a two-month-long window in summer 155 00:07:34,988 --> 00:07:38,123 when conditions are right for fossil-hunting. 156 00:07:38,192 --> 00:07:41,226 This is also a trip back in time for me. 157 00:07:41,295 --> 00:07:46,898 I first came here in 1984, when I was only 23 years old. 158 00:07:46,967 --> 00:07:49,701 My first trip to Ellesmere Island 159 00:07:49,770 --> 00:07:52,103 changed the way I looked at planet Earth. 160 00:07:52,172 --> 00:07:54,206 It sealed my fate. 161 00:07:54,274 --> 00:07:58,610 After that trip, I knew I had to become a paleontologist. 162 00:07:58,679 --> 00:08:00,679 Yeah, these are good memories. 163 00:08:00,747 --> 00:08:02,848 It's great to be back here. 164 00:08:02,916 --> 00:08:05,250 In addition to Jason, 165 00:08:05,319 --> 00:08:07,252 Dave Briggs is here to protect us 166 00:08:07,321 --> 00:08:08,286 from any stray polar bears. 167 00:08:08,355 --> 00:08:09,354 Okay. 168 00:08:09,423 --> 00:08:10,555 JOHNSON: And completing the team 169 00:08:10,624 --> 00:08:14,092 is fellow paleontologist Jaelyn Eberle. 170 00:08:14,161 --> 00:08:18,096 ♪ ♪ 171 00:08:18,165 --> 00:08:19,798 Once camp is set up, 172 00:08:19,867 --> 00:08:21,867 Jason is going to help me find a special site 173 00:08:21,935 --> 00:08:27,138 that I never got to see the last time I was here. 174 00:08:27,207 --> 00:08:28,974 It's just straight northwest 175 00:08:29,042 --> 00:08:30,709 for four kilometers. Right. 176 00:08:30,777 --> 00:08:32,210 Just a little bit of a hike. 177 00:08:32,279 --> 00:08:34,880 Then we, uh, sort of head northwest, I guess. 178 00:08:34,948 --> 00:08:37,282 ♪ ♪ 179 00:08:37,351 --> 00:08:40,752 JOHNSON: The beds are dipping pretty steeply here. 180 00:08:40,821 --> 00:08:43,088 HILLIER: Yeah, it's definitely something we have to be careful of 181 00:08:43,156 --> 00:08:45,524 with this mud. 182 00:08:45,592 --> 00:08:49,094 ♪ ♪ 183 00:08:49,162 --> 00:08:51,062 There's a bit of a precipice over there, 184 00:08:51,131 --> 00:08:54,366 although it's generally in the direction of where we're going. 185 00:08:54,434 --> 00:08:57,035 ♪ ♪ 186 00:08:57,104 --> 00:09:00,705 JOHNSON: Our target is several hours' hike from our camp. 187 00:09:00,774 --> 00:09:03,241 ♪ ♪ 188 00:09:03,310 --> 00:09:07,412 This frozen tundra may look barren, 189 00:09:07,481 --> 00:09:12,717 but for me as a paleobotanist, this is geologic heaven. 190 00:09:12,786 --> 00:09:15,754 There are a few small Arctic wildflowers 191 00:09:15,822 --> 00:09:17,255 and some scrappy ground cover. 192 00:09:17,324 --> 00:09:21,326 But the nearest living tree is a thousand miles south of here. 193 00:09:21,395 --> 00:09:22,994 HILLIER: You know, the coordinates are, they're, 194 00:09:23,063 --> 00:09:25,196 our best guess are somewhere in this vicinity. 195 00:09:25,265 --> 00:09:28,667 JOHNSON: Finally, we reach what I've been looking for. 196 00:09:28,735 --> 00:09:31,336 Wow! 197 00:09:31,405 --> 00:09:34,005 Oh, my God, there's some amazing stumps here. 198 00:09:34,074 --> 00:09:35,607 Look at this. 199 00:09:35,676 --> 00:09:40,345 Sticking out of the hillside are a bunch of weird brown rocks. 200 00:09:40,414 --> 00:09:43,315 These are petrified tree stumps. 201 00:09:43,383 --> 00:09:44,916 HILLIER: Wow. 202 00:09:44,985 --> 00:09:46,384 One, two, three, four, 203 00:09:46,453 --> 00:09:50,522 five, six, seven, eight, nine, ten, 11, 12, 204 00:09:50,591 --> 00:09:52,324 13, 14, 205 00:09:52,392 --> 00:09:55,493 15, 16, 17, 18. 206 00:09:55,562 --> 00:10:01,866 In one view, 18 trunks in place. 207 00:10:01,935 --> 00:10:04,102 Ah, this is incredible, man. 208 00:10:04,171 --> 00:10:05,670 This is, this is amazing. It's like a whole forest. 209 00:10:05,739 --> 00:10:08,974 Look at that one, that one is just perfect. 210 00:10:09,042 --> 00:10:10,875 You can see the whole shape of the trunk. 211 00:10:10,944 --> 00:10:15,013 It's quite an amazing thing-- just insane. 212 00:10:15,082 --> 00:10:19,551 This is a stone tree trunk, it's a petrified tree. 213 00:10:19,620 --> 00:10:21,119 It used to be a growing tree, 214 00:10:21,188 --> 00:10:24,289 then it got buried and turned into stone. 215 00:10:24,358 --> 00:10:26,992 Geologists have dated these trees 216 00:10:27,060 --> 00:10:30,128 to around 50 million years ago. 217 00:10:30,197 --> 00:10:32,230 Back then, this treeless hillside 218 00:10:32,299 --> 00:10:35,667 would have been completely different. 219 00:10:35,736 --> 00:10:37,302 There's a lot of clues here 220 00:10:37,371 --> 00:10:40,005 to how this forest got to be the way it is. 221 00:10:40,073 --> 00:10:43,074 The first is that all these stone trunks are surrounded 222 00:10:43,143 --> 00:10:46,077 by coal-- black rock, 223 00:10:46,146 --> 00:10:48,179 which is a very strong signal that these trees, 224 00:10:48,248 --> 00:10:50,315 when they were growing, were growing in a swamp. 225 00:10:50,384 --> 00:10:54,953 The second clue are these radiating roots. 226 00:10:55,022 --> 00:10:57,722 In swamps, roots grow out and not down. 227 00:10:57,791 --> 00:11:04,396 ♪ ♪ 228 00:11:08,001 --> 00:11:11,536 But what kind of trees were these? 229 00:11:14,508 --> 00:11:16,975 These rocks are just chunky silt stones 230 00:11:17,044 --> 00:11:19,177 that are quite near the petrified forest, 231 00:11:19,246 --> 00:11:20,478 and I'm breaking them apart 232 00:11:20,547 --> 00:11:22,313 because I'm looking for fossil leaves. 233 00:11:22,382 --> 00:11:24,049 If I can find the leaves that go with those trees, 234 00:11:24,117 --> 00:11:26,117 I can put that forest back together again. 235 00:11:26,186 --> 00:11:28,219 Come to papa. 236 00:11:30,490 --> 00:11:32,524 Ah, now, here we go. 237 00:11:34,795 --> 00:11:36,861 Here's a close-up of that thing. 238 00:11:36,930 --> 00:11:37,796 What have you got? 239 00:11:37,864 --> 00:11:39,064 This is metasequoia, 240 00:11:39,132 --> 00:11:40,932 little needles. 241 00:11:41,001 --> 00:11:43,401 It's the dawn redwood, 242 00:11:43,470 --> 00:11:45,870 it's a conifer, and these whole sprigs will fall off, 243 00:11:45,939 --> 00:11:47,706 as they've done here, and land in the mud. 244 00:11:47,774 --> 00:11:50,675 This used to be mud, now it's a rock. 245 00:11:50,744 --> 00:11:55,246 It would go with those trunks, the petrified forest. 246 00:11:55,315 --> 00:11:56,981 (blows dust off rock) 247 00:11:57,050 --> 00:11:58,750 Together, these leaves and the tree trunks 248 00:11:58,819 --> 00:12:01,086 give us a window into the past. 249 00:12:02,756 --> 00:12:06,224 50 million years ago, this dry, barren tundra 250 00:12:06,293 --> 00:12:07,659 was a warm, humid swamp... 251 00:12:07,728 --> 00:12:10,595 (insects chirping) 252 00:12:10,664 --> 00:12:15,667 covered with lotus plants, ferns, and metasequoia trees 253 00:12:15,736 --> 00:12:18,570 that were as tall as 150 feet. 254 00:12:18,638 --> 00:12:21,740 ♪ ♪ 255 00:12:21,808 --> 00:12:27,779 The area covered in ice today was once a massive forest 256 00:12:27,848 --> 00:12:32,717 that stretched all the way up to the edge of the Arctic Ocean. 257 00:12:32,786 --> 00:12:38,022 Water ran off the land, forming a surface layer of fresh water. 258 00:12:38,091 --> 00:12:39,724 Instead of sea ice, 259 00:12:39,793 --> 00:12:43,261 the North Pole was covered in subtropical floating ferns. 260 00:12:43,330 --> 00:12:48,466 ♪ ♪ 261 00:12:48,535 --> 00:12:52,370 The Ellesmere we see today looks very different, 262 00:12:52,439 --> 00:12:56,541 but one peculiarity of the Arctic summer remains the same. 263 00:12:56,610 --> 00:12:58,042 One of the things about working in the Arctic 264 00:12:58,111 --> 00:13:00,044 is that the sun literally never goes down. 265 00:13:00,113 --> 00:13:02,147 It just goes around and around in the sky. 266 00:13:02,215 --> 00:13:03,548 That means there's never any night, 267 00:13:03,617 --> 00:13:05,083 and it never gets dark. 268 00:13:05,152 --> 00:13:08,286 It's midnight right now-- take a look outside my tent. 269 00:13:08,355 --> 00:13:11,923 Yep, it looks pretty bright out there. 270 00:13:11,992 --> 00:13:14,659 But-but I want to go to sleep, so I'm going to go to sleep. 271 00:13:14,728 --> 00:13:16,494 Here's how we do it. 272 00:13:16,563 --> 00:13:20,131 Close the tent. (pulling zipper) 273 00:13:20,200 --> 00:13:25,503 Zip up the sleeping bag and put on the face mask. 274 00:13:25,572 --> 00:13:28,139 Good night. 275 00:13:30,076 --> 00:13:32,877 In the morning, I head out to join Jaelyn Eberle. 276 00:13:32,946 --> 00:13:36,447 While I've been out looking for fossil plants, 277 00:13:36,516 --> 00:13:39,250 she's been hunting for the animals that lived 278 00:13:39,319 --> 00:13:42,020 in this warm polar swamp 50 million years ago. 279 00:13:44,791 --> 00:13:46,891 Maybe through here? And then up and over 280 00:13:46,960 --> 00:13:48,226 and then back down the other side. 281 00:13:48,295 --> 00:13:49,794 EBERLE: I think so, yeah. 282 00:13:49,863 --> 00:13:51,296 I'll put my boots on then. Do you have boots? 283 00:13:51,364 --> 00:13:52,630 I've got sandals. 284 00:13:52,699 --> 00:13:54,999 All right, you're better than me, I'll tell you. 285 00:13:55,068 --> 00:13:56,334 (both chuckle) 286 00:13:56,403 --> 00:13:59,370 We're going. 287 00:13:59,439 --> 00:14:01,005 Okay, so it's cold. 288 00:14:01,074 --> 00:14:03,808 I wouldn't want it to be any deeper. 289 00:14:03,877 --> 00:14:05,076 There we go. 290 00:14:05,145 --> 00:14:06,611 JOHNSON: You beauty. 291 00:14:06,680 --> 00:14:09,214 EBERLE: All right. 292 00:14:09,282 --> 00:14:12,984 JOHNSON: Jaelyn's spent many summers up here searching for fossils. 293 00:14:13,053 --> 00:14:15,119 EBERLE: I do love the Arctic. 294 00:14:15,188 --> 00:14:17,522 I've been coming up for... oh wow, 295 00:14:17,591 --> 00:14:19,457 I think ten field seasons now. 296 00:14:19,526 --> 00:14:22,627 And almost everything you pick up is undiscovered, 297 00:14:22,696 --> 00:14:23,895 that's something that 298 00:14:23,964 --> 00:14:27,899 doesn't, to me, ever get old. 299 00:14:27,968 --> 00:14:30,335 That's exciting. 300 00:14:30,403 --> 00:14:33,371 JOHNSON: Searching for animal fossils in the permafrost is really tough. 301 00:14:33,440 --> 00:14:34,973 They're little bits and pieces, 302 00:14:35,041 --> 00:14:36,641 so they're not going to show up a lot. 303 00:14:36,710 --> 00:14:38,877 I think we're going to need to crawl. 304 00:14:38,945 --> 00:14:40,211 JOHNSON: The annual freezing and thawing 305 00:14:40,280 --> 00:14:42,447 break up the bones into tiny fragments. 306 00:14:42,515 --> 00:14:44,415 Eh. 307 00:14:44,484 --> 00:14:47,285 Eh, probably not, but, um, 308 00:14:47,354 --> 00:14:48,453 could be a little piece of bone. 309 00:14:48,521 --> 00:14:50,054 Tooth of anything right now 310 00:14:50,123 --> 00:14:53,224 actually would be great, 'cause they're pretty rare. 311 00:14:53,293 --> 00:14:55,693 Even the bits and pieces are pretty rare at this site. 312 00:14:55,762 --> 00:14:59,464 JOHNSON: After around four hours of crawling about-- 313 00:14:59,532 --> 00:15:02,300 today, nada. 314 00:15:02,369 --> 00:15:04,802 But over the years, Jaelyn's team 315 00:15:04,871 --> 00:15:08,406 has unearthed a fantastic collection of creatures. 316 00:15:08,475 --> 00:15:10,108 EBERLE: These guys are pretty impressive. 317 00:15:10,176 --> 00:15:14,012 Looks like two jawbones missing their teeth 318 00:15:14,080 --> 00:15:15,780 Yes, that's right. So it's a... 319 00:15:15,849 --> 00:15:19,584 And those come from a mammal called Coryphodon, 320 00:15:19,653 --> 00:15:22,287 and there are no Coryphodons living today. 321 00:15:22,355 --> 00:15:24,422 An analogy you could use today 322 00:15:24,491 --> 00:15:26,524 would be something like a pygmy hippo. 323 00:15:26,593 --> 00:15:28,559 And living in the rivers and stuff like that? 324 00:15:28,628 --> 00:15:30,228 Yeah, probably, living in the rivers 325 00:15:30,297 --> 00:15:31,329 and the swamps and munching 326 00:15:31,398 --> 00:15:33,498 on aquatic plants and... Right. 327 00:15:34,734 --> 00:15:37,435 JOHNSON: Coryphodon was a hippo-like mammal 328 00:15:37,504 --> 00:15:40,405 with short tusks and a tiny brain 329 00:15:40,473 --> 00:15:43,107 that weighed just three ounces. 330 00:15:43,176 --> 00:15:47,111 Standing around three feet high and eight feet long, 331 00:15:47,180 --> 00:15:49,180 Coryphodon was a vegetarian 332 00:15:49,249 --> 00:15:53,318 that rooted around the swamp for its food. 333 00:15:53,386 --> 00:15:54,986 Paleontologists have found fossils 334 00:15:55,055 --> 00:15:57,488 of all sorts of animals here. 335 00:15:57,557 --> 00:16:00,491 With warm temperatures all year round back then, 336 00:16:00,560 --> 00:16:06,331 there were turtles, tapir, and even alligators. 337 00:16:06,399 --> 00:16:08,466 ♪ ♪ 338 00:16:08,535 --> 00:16:10,868 The fossils we find here on Ellesmere Island 339 00:16:10,937 --> 00:16:14,405 tell a remarkable story. 340 00:16:14,474 --> 00:16:19,077 The Arctic was warm and wet, with no ice in sight. 341 00:16:19,145 --> 00:16:20,578 It was filled with plants and animals 342 00:16:20,647 --> 00:16:23,381 similar to ones you might see today 343 00:16:23,450 --> 00:16:27,185 in the swamps of Louisiana or the Amazon. 344 00:16:27,253 --> 00:16:31,155 The frozen north was a completely different world 345 00:16:31,224 --> 00:16:34,058 50 million years ago. 346 00:16:34,127 --> 00:16:36,527 ♪ ♪ 347 00:16:36,596 --> 00:16:39,464 And that's got to make you wonder, 348 00:16:39,532 --> 00:16:43,434 "If it was like this at the North Pole, 349 00:16:43,503 --> 00:16:46,104 what was happening at the other end of the earth?" 350 00:16:48,675 --> 00:16:51,342 10,000 miles south of Ellesmere 351 00:16:51,411 --> 00:16:53,344 is the world's wildest continent, 352 00:16:53,413 --> 00:16:57,315 the most extreme place on the planet. 353 00:16:57,384 --> 00:16:59,817 There's one word that describes Antarctica, 354 00:16:59,886 --> 00:17:03,554 and that word is ice. 355 00:17:03,623 --> 00:17:07,558 And the entire continent is one ice-bound mass. 356 00:17:07,627 --> 00:17:10,995 ♪ ♪ 357 00:17:11,064 --> 00:17:14,732 In fact, 90% of the ice on planet Earth 358 00:17:14,801 --> 00:17:17,969 is here in Antarctica. 359 00:17:18,038 --> 00:17:23,141 With a record low temperature of minus-128 degrees Fahrenheit, 360 00:17:23,209 --> 00:17:28,246 this continent is officially the coldest place on Earth. 361 00:17:28,314 --> 00:17:33,651 Even in summer, the temperatures rarely ever get above freezing. 362 00:17:33,720 --> 00:17:38,089 Antarctica is the size of all the United States plus Mexico, 363 00:17:38,158 --> 00:17:40,258 and it's covered with a sheet of ice 364 00:17:40,326 --> 00:17:43,895 that in some places is almost three miles thick. 365 00:17:43,963 --> 00:17:47,965 That's a lot of ice. 366 00:17:48,034 --> 00:17:50,435 ♪ ♪ 367 00:17:50,503 --> 00:17:56,674 But has Antarctica always been deep-frozen like this? 368 00:17:56,743 --> 00:17:58,843 To investigate, I've come to Nelson Island, 369 00:17:58,912 --> 00:18:01,679 off the Antarctic peninsula. 370 00:18:01,748 --> 00:18:04,615 I'm joining paleontologist Marcelo Leppe 371 00:18:04,684 --> 00:18:07,418 from the Chilean Antarctic Institute. 372 00:18:07,487 --> 00:18:11,322 Marcelo's taking me to a small island... 373 00:18:13,126 --> 00:18:17,128 one of the few spots with exposed land, 374 00:18:17,197 --> 00:18:20,331 where he and his team have been hunting for fossils. 375 00:18:20,400 --> 00:18:22,266 LEPPE: After a week, we didn't find a, 376 00:18:22,335 --> 00:18:23,868 a fossil. Wow, 377 00:18:23,937 --> 00:18:25,169 you looked for a whole week and you found nothing? Yeah. 378 00:18:25,238 --> 00:18:27,271 We started to make a hole in the ground, 379 00:18:27,340 --> 00:18:29,273 just close to the, to the sea, 380 00:18:29,342 --> 00:18:31,876 and we found the-the outcrop. Just by accident. 381 00:18:32,912 --> 00:18:34,846 Do you think we can find it today? 382 00:18:34,914 --> 00:18:36,280 Uh, I-I hope so. 383 00:18:36,349 --> 00:18:37,648 (both chuckling) 384 00:18:37,717 --> 00:18:40,017 ♪ ♪ 385 00:18:40,086 --> 00:18:43,521 JOHNSON: The outcrop we're after is only accessible at low tide, 386 00:18:43,590 --> 00:18:48,726 so we've had to time our landing just right. 387 00:18:48,795 --> 00:18:50,962 Let's drop our gear here, huh. 388 00:18:52,799 --> 00:18:53,865 It's cold. 389 00:18:53,933 --> 00:18:55,433 Yeah, it's Antarctica. It should be. 390 00:18:55,502 --> 00:18:56,701 (both chuckle) 391 00:18:56,769 --> 00:19:00,438 ♪ ♪ 392 00:19:00,507 --> 00:19:02,673 Just like on Ellesmere Island, 393 00:19:02,742 --> 00:19:08,412 the bedrock on this beach is tens of millions of years old. 394 00:19:08,481 --> 00:19:09,747 (shoveling continues) 395 00:19:09,816 --> 00:19:11,849 ♪ ♪ 396 00:19:11,918 --> 00:19:12,984 Ah. 397 00:19:13,052 --> 00:19:13,985 Not a great one, 398 00:19:14,053 --> 00:19:15,319 but it's definitely a fossil. 399 00:19:15,388 --> 00:19:17,088 We're in the right spot. 400 00:19:18,324 --> 00:19:21,225 Crawling around on this rocky landscape today, 401 00:19:21,294 --> 00:19:24,262 it's hard to believe that anything could ever grow here. 402 00:19:26,566 --> 00:19:28,733 Antarctica has no trees at all. 403 00:19:28,801 --> 00:19:30,368 (voiceover): Just mosses and lichens 404 00:19:30,436 --> 00:19:33,304 and only two species of flowering plants. 405 00:19:33,373 --> 00:19:35,473 So you find a fossil plant here, 406 00:19:35,542 --> 00:19:38,776 it's telling you about a very different world indeed. 407 00:19:40,513 --> 00:19:42,380 But after just ten minutes of digging... 408 00:19:42,448 --> 00:19:43,614 Ooh. 409 00:19:43,683 --> 00:19:44,982 (voiceover): We find something incredible. 410 00:19:45,051 --> 00:19:46,651 Ah, wow! 411 00:19:46,719 --> 00:19:48,686 Just like that. 412 00:19:48,755 --> 00:19:52,423 (voiceover): A beautifully preserved leaf from an ancient beech tree. 413 00:19:52,492 --> 00:19:54,825 That one looks like a modern beech. 414 00:19:54,894 --> 00:19:56,961 It's the size of a beech leaf, wow. 415 00:19:57,030 --> 00:19:58,162 And it's large. 416 00:19:58,231 --> 00:19:59,397 You can see that it's the middle section. 417 00:19:59,465 --> 00:20:01,799 There's the main vein, the lateral veins. 418 00:20:01,868 --> 00:20:04,702 Leaf would have been about that long and about that wide. 419 00:20:04,771 --> 00:20:06,804 And these very straight secondary veins 420 00:20:06,873 --> 00:20:08,873 are typical of the beech family, 421 00:20:08,942 --> 00:20:11,876 a northern, temperate-forest tree, 422 00:20:11,945 --> 00:20:13,377 a tree that's deciduous, 423 00:20:13,446 --> 00:20:16,814 you see it growing in New York City and in London. 424 00:20:16,883 --> 00:20:19,283 And here is a chunk of it 425 00:20:19,352 --> 00:20:20,952 from the beach in Antarctica, 426 00:20:21,020 --> 00:20:22,853 next to an iceberg, 427 00:20:22,922 --> 00:20:25,523 on a very cold day. 428 00:20:25,592 --> 00:20:26,924 Oh, look at that one. 429 00:20:26,993 --> 00:20:28,226 That's great. 430 00:20:28,294 --> 00:20:30,695 We're finding forest tree leaves, 431 00:20:30,763 --> 00:20:33,864 and they're found in great numbers, all together 432 00:20:33,933 --> 00:20:37,468 like leaf litter, implying the forest was right here, 433 00:20:37,537 --> 00:20:40,137 where we are standing-- or kneeling, right now. 434 00:20:40,206 --> 00:20:43,407 (digging and brushing continue) 435 00:20:43,476 --> 00:20:47,545 (voiceover): These fossil leaves reveal a very different picture 436 00:20:47,614 --> 00:20:50,881 of Nelson Island from the landscape we see today. 437 00:20:50,950 --> 00:20:54,418 83 million years ago, 438 00:20:54,487 --> 00:20:58,623 this frigid place was covered in a verdant forest 439 00:20:58,691 --> 00:21:02,927 of southern beech, ginkgoes, and tree ferns, 440 00:21:02,996 --> 00:21:09,367 with mild temperatures rarely dropping below freezing. 441 00:21:09,435 --> 00:21:11,736 ♪ ♪ 442 00:21:11,804 --> 00:21:16,274 And it wasn't just this one spot. 443 00:21:16,342 --> 00:21:18,009 I've just been on the beach, 444 00:21:18,077 --> 00:21:20,745 found these amazing fossil leaves. 445 00:21:20,813 --> 00:21:22,513 These leaves, on the other hand, 446 00:21:22,582 --> 00:21:25,216 are from a different place, they're from southern Chile. 447 00:21:25,285 --> 00:21:27,652 We're here, here's a 700-mile gap, 448 00:21:27,720 --> 00:21:28,919 and here is southern Chile. 449 00:21:28,988 --> 00:21:31,856 This leaf here is from southern South America 450 00:21:31,924 --> 00:21:34,292 and is very characteristic of the beech family. 451 00:21:34,360 --> 00:21:36,427 As is this leaf from Antarctica, 452 00:21:36,496 --> 00:21:37,962 that we just collected this morning. 453 00:21:38,031 --> 00:21:40,398 So we have Chile and Antarctica, 454 00:21:40,466 --> 00:21:44,268 pretty strong evidence that these two places were connected. 455 00:21:45,705 --> 00:21:46,971 We've known for a while 456 00:21:47,040 --> 00:21:49,907 that Earth's crust is broken into plates 457 00:21:49,976 --> 00:21:53,377 that slide and collide on top of hot, flowing rocks 458 00:21:53,446 --> 00:21:55,279 deep beneath the surface. 459 00:21:55,348 --> 00:21:57,114 Evidence like matching fossils 460 00:21:57,183 --> 00:22:03,120 from South America, Antarctica, and even Australia 461 00:22:03,189 --> 00:22:04,989 tells us that these three continents 462 00:22:05,058 --> 00:22:08,693 were once joined together and covered with a vast forest 463 00:22:08,761 --> 00:22:11,696 stretching across the South Pole. 464 00:22:11,764 --> 00:22:14,365 ♪ ♪ 465 00:22:14,434 --> 00:22:18,569 So, with all these trees and a nice, warm climate, 466 00:22:18,638 --> 00:22:24,008 what kinds of creatures lived on this ancient southern continent? 467 00:22:24,077 --> 00:22:27,478 Although fossils have been found in Antarctica, 468 00:22:27,547 --> 00:22:31,549 some of the biggest clues are in Patagonia. 469 00:22:31,617 --> 00:22:36,287 ♪ ♪ 470 00:22:36,289 --> 00:22:38,556 At a remote site in Argentina, 471 00:22:38,558 --> 00:22:41,258 a team of paleontologists has just discovered 472 00:22:41,260 --> 00:22:43,027 the remains of a forest dweller. 473 00:22:43,029 --> 00:22:45,463 DIEGO POL: Here we are. 474 00:22:45,465 --> 00:22:47,932 JOHNSON: It must have had a very large appetite. 475 00:22:47,934 --> 00:22:50,334 This guy was, you know, all scattered around, 476 00:22:50,336 --> 00:22:52,103 all the bones. 477 00:22:52,105 --> 00:22:56,774 JOHNSON: The leader of the expedition is Diego Pol. 478 00:22:56,843 --> 00:22:59,610 POL: We found the entire forelimb. 479 00:22:59,679 --> 00:23:01,412 Okay, that's great. And the other hind limb 480 00:23:01,481 --> 00:23:02,680 and then some vertebrae 481 00:23:02,749 --> 00:23:04,615 and the tail and so on. 482 00:23:04,684 --> 00:23:10,388 JOHNSON: All these parts add up to a 69-million-year-old dinosaur. 483 00:23:10,456 --> 00:23:11,922 MAN: Let's go. 484 00:23:11,991 --> 00:23:13,824 JOHNSON: I'm just going to start chipping away at this thing. 485 00:23:13,893 --> 00:23:16,360 POL: Yeah. 486 00:23:16,429 --> 00:23:19,530 JOHNSON: The key thing to not destroying a dinosaur fossil 487 00:23:19,599 --> 00:23:23,434 is do not let a paleobotanist in the dinosaur quarry. 488 00:23:23,503 --> 00:23:26,003 'Cause we tend to break big rocks with pickaxes 489 00:23:26,072 --> 00:23:27,171 and sledge hammers, 490 00:23:27,240 --> 00:23:29,373 and these guys use little, tiny picks 491 00:23:29,442 --> 00:23:32,376 and brushes. 492 00:23:32,445 --> 00:23:34,245 We're not trying to expose the bone, 493 00:23:34,313 --> 00:23:35,980 we're just trying to undercut it gently 494 00:23:36,048 --> 00:23:38,182 and get the rock removed. 495 00:23:38,251 --> 00:23:41,719 So, I'll just carefully pick around here at the base. 496 00:23:41,788 --> 00:23:44,021 (picks clanking) 497 00:23:44,090 --> 00:23:47,258 See how delicate I am? 498 00:23:47,326 --> 00:23:49,427 You know, I'm doing a beautiful job 499 00:23:49,495 --> 00:23:53,831 of carefully extracting this bone from its rocky tomb, 500 00:23:53,900 --> 00:23:59,003 where it's lain undisturbed for 69 million years. 501 00:23:59,071 --> 00:24:02,840 (voiceover): I need to watch my hammer with this specimen, 502 00:24:02,909 --> 00:24:04,842 because it's pretty unique. 503 00:24:04,911 --> 00:24:06,477 This is a dinosaur without a name. 504 00:24:06,546 --> 00:24:10,247 It's a new species of dinosaur, and that's a really cool thing. 505 00:24:10,316 --> 00:24:14,852 (voiceover): Diego's team has just discovered a new species of titanosaur... 506 00:24:14,921 --> 00:24:17,254 (pick scraping) 507 00:24:17,323 --> 00:24:19,490 ...a plant-eating dinosaur 508 00:24:19,559 --> 00:24:24,762 with a long tail, long neck, and small head. 509 00:24:24,831 --> 00:24:27,531 Titanosaurs could become so big 510 00:24:27,600 --> 00:24:30,367 because there was so much vegetation. 511 00:24:30,436 --> 00:24:32,837 And some species grew to be the biggest animals 512 00:24:32,905 --> 00:24:34,772 that ever walked on land. 513 00:24:34,841 --> 00:24:38,108 ♪ ♪ 514 00:24:38,177 --> 00:24:42,012 POL: Some people estimate these animals were eating, like, 515 00:24:42,081 --> 00:24:44,315 a thousand pounds plant material per day. 516 00:24:44,383 --> 00:24:46,750 A thousand pounds a day? A thousand pounds a day. 517 00:24:46,819 --> 00:24:48,619 Like half a ton of vegetables a day. 518 00:24:48,688 --> 00:24:50,454 The original vegans, right? 519 00:24:50,523 --> 00:24:52,223 Oh, my God. 520 00:24:52,291 --> 00:24:55,693 POL: Yeah, these animals probably had a pretty big home range. 521 00:24:55,761 --> 00:24:57,461 They'd go and destroy one forest for a while 522 00:24:57,530 --> 00:24:58,529 At a time... 523 00:24:58,598 --> 00:25:00,231 Then go destroy another forest. 524 00:25:00,299 --> 00:25:02,666 POL: And then come back. 525 00:25:02,735 --> 00:25:04,668 JOHNSON: With South America and Antarctica connected 526 00:25:04,737 --> 00:25:06,637 into one continuous continent, 527 00:25:06,706 --> 00:25:09,607 these munching monsters had plenty of forest to roam 528 00:25:09,675 --> 00:25:12,610 in search of a good meal. 529 00:25:12,678 --> 00:25:14,678 Did they have any titanosaurs from Antarctica? 530 00:25:14,747 --> 00:25:16,447 Yeah, actually, there is one. 531 00:25:16,516 --> 00:25:18,249 I mean, they found a single bone. 532 00:25:18,317 --> 00:25:20,484 It was found in Antarctic peninsula. 533 00:25:20,553 --> 00:25:21,785 One bone? A single bone. 534 00:25:21,854 --> 00:25:22,887 A tail bone. Wow. 535 00:25:22,955 --> 00:25:25,122 What a lucky find that was. Yeah. 536 00:25:25,191 --> 00:25:26,190 That's amazing. 537 00:25:26,259 --> 00:25:27,358 So, we're really looking at an animal 538 00:25:27,426 --> 00:25:28,659 that could have walked easily 539 00:25:28,728 --> 00:25:30,094 to Antarctica. Absolutely, this... 540 00:25:30,162 --> 00:25:31,862 For a good sandwich. Yeah. 541 00:25:31,931 --> 00:25:33,497 (picks clinking) 542 00:25:33,566 --> 00:25:36,367 JOHNSON: This fossil is a fantastic find. 543 00:25:36,435 --> 00:25:39,436 But in 2014, not far from here, 544 00:25:39,505 --> 00:25:43,841 Diego and his team uncovered a creature even more awesome. 545 00:25:43,910 --> 00:25:48,445 ♪ ♪ 546 00:25:48,514 --> 00:25:51,415 This is the femur we collected yesterday. 547 00:25:51,484 --> 00:25:54,718 It's big, but it's nothing compared the biggest dinosaurs. 548 00:25:54,787 --> 00:25:58,722 This one is the largest one ever found. 549 00:25:58,791 --> 00:25:59,890 All right. 550 00:25:59,959 --> 00:26:02,459 Check out the size of those vertebrae. 551 00:26:02,528 --> 00:26:05,229 Each single backbone is about four feet tall. 552 00:26:05,298 --> 00:26:09,033 I'm a big guy... 553 00:26:09,101 --> 00:26:11,535 but this bone dwarfs me. 554 00:26:11,604 --> 00:26:13,504 (voiceover): I'm lying next to the eight-foot-long 555 00:26:13,573 --> 00:26:18,542 titanosaur thigh bone that Diego's team unearthed. 556 00:26:18,611 --> 00:26:20,644 ♪ ♪ 557 00:26:20,713 --> 00:26:26,550 And just in case you can't picture how big this was... 558 00:26:26,619 --> 00:26:28,786 This thing is absolutely immense. 559 00:26:28,854 --> 00:26:32,289 (voiceover): There's a life-size model of this 75-ton beast 560 00:26:32,358 --> 00:26:37,728 that greets you when you drive in from the local airport. 561 00:26:37,797 --> 00:26:38,996 I've seen the bones, 562 00:26:39,065 --> 00:26:40,431 but I haven't seen the reconstruction before. 563 00:26:40,499 --> 00:26:44,835 ♪ ♪ 564 00:26:44,904 --> 00:26:50,441 Patagotitan, the world's largest dinosaur. 565 00:26:51,777 --> 00:26:53,143 It's incredible to realize 566 00:26:53,212 --> 00:26:55,913 that animals like this once roamed 567 00:26:55,982 --> 00:26:59,617 between South America 568 00:26:59,685 --> 00:27:02,453 and Antarctica. 569 00:27:02,521 --> 00:27:04,655 So what's going on here? 570 00:27:04,724 --> 00:27:08,525 Dinosaurs near the South Pole... (dinosaur bellows) 571 00:27:08,594 --> 00:27:12,663 and swampy forests in the North-- 572 00:27:12,732 --> 00:27:15,332 were the poles really that warm back then? 573 00:27:18,304 --> 00:27:21,138 Or could there be another explanation? 574 00:27:23,476 --> 00:27:25,643 What about those tectonic plates 575 00:27:25,711 --> 00:27:28,078 that move the continents around? 576 00:27:28,147 --> 00:27:29,580 Could this be the reason that 577 00:27:29,649 --> 00:27:31,882 we find these warm-weather fossils 578 00:27:31,951 --> 00:27:35,085 in the polar regions today? 579 00:27:35,154 --> 00:27:36,754 Sometimes people tell me that, "Well, wait, 580 00:27:36,822 --> 00:27:38,989 "plate tectonics mean that landmasses can move around, 581 00:27:39,058 --> 00:27:40,958 "and maybe those fossils you're finding 582 00:27:41,027 --> 00:27:42,626 "were deposited at mid-latitudes 583 00:27:42,695 --> 00:27:45,362 then brought to the Arctic by continental drift." 584 00:27:45,431 --> 00:27:46,697 It's a good thing to think about, 585 00:27:46,766 --> 00:27:48,832 but we actually know where the continents were 586 00:27:48,901 --> 00:27:50,067 when they were there. 587 00:27:50,136 --> 00:27:51,669 We actually know those positions. 588 00:27:51,737 --> 00:27:53,070 And we know for sure 589 00:27:53,139 --> 00:27:55,239 that Antarctica was down by the South Pole 590 00:27:55,307 --> 00:27:57,841 and the lands at Ellesmere Island were up by the North Pole 591 00:27:57,910 --> 00:28:01,311 when they were forested by these warm forests. 592 00:28:01,380 --> 00:28:04,381 So, it's a good idea, but the science says, "Nope, 593 00:28:04,450 --> 00:28:08,118 there really were polar warm forests." 594 00:28:08,187 --> 00:28:10,254 ♪ ♪ 595 00:28:10,322 --> 00:28:13,557 The entire planet really was warmer, 596 00:28:13,626 --> 00:28:17,161 and all the polar ice we see today didn't exist 597 00:28:17,229 --> 00:28:20,698 tens of millions of years ago. 598 00:28:20,766 --> 00:28:23,701 That is pretty weird. 599 00:28:23,769 --> 00:28:25,903 But there's an even weirder part 600 00:28:25,971 --> 00:28:30,841 of the story of ice on this planet. 601 00:28:30,910 --> 00:28:33,644 This time, the evidence isn't at the poles. 602 00:28:33,713 --> 00:28:35,446 ♪ ♪ 603 00:28:35,514 --> 00:28:38,415 It's in the hottest place on Earth. 604 00:28:38,484 --> 00:28:42,152 ♪ ♪ 605 00:28:42,221 --> 00:28:45,923 Welcome to Death Valley. 606 00:28:45,991 --> 00:28:49,393 I'm here at the National Park's official weather station 607 00:28:49,462 --> 00:28:51,428 at the appropriately named Furnace Creek. 608 00:28:51,497 --> 00:28:55,999 Ranger Alex Rothermel is letting me take today's measurements. 609 00:28:56,068 --> 00:28:58,469 So this is our rain gauge. 610 00:28:58,537 --> 00:29:01,004 It hasn't rained in a while. 611 00:29:01,073 --> 00:29:02,840 Ow, it's always... Is it hot? 612 00:29:02,908 --> 00:29:04,475 Yeah, it's metal. 613 00:29:04,543 --> 00:29:06,110 Hold this? Okay, yeah. 614 00:29:06,178 --> 00:29:08,312 We'll see if there's any water in it. 615 00:29:08,380 --> 00:29:10,848 Ooh, that is certainly hot. Yeah, it's metal. 616 00:29:10,916 --> 00:29:14,051 All right, there's nothing in it. 617 00:29:14,120 --> 00:29:15,119 Dust! 618 00:29:15,187 --> 00:29:16,286 (both laughing) 619 00:29:16,355 --> 00:29:18,856 This is the temperature gauge. 620 00:29:18,924 --> 00:29:20,124 I see, so it's in the shade. 621 00:29:20,192 --> 00:29:21,125 Let's see on this... 622 00:29:21,193 --> 00:29:23,093 I'm reading like 103 and a half, 623 00:29:23,162 --> 00:29:25,162 is that what you get? Yeah. 624 00:29:25,231 --> 00:29:26,296 And you check this every day? 625 00:29:26,365 --> 00:29:27,931 Yeah, we do, and then we record it. 626 00:29:28,000 --> 00:29:30,601 July to August, it's been something like 28 days 627 00:29:30,669 --> 00:29:32,936 over 120 this year. Wow. 628 00:29:33,005 --> 00:29:34,638 So you've got a pretty legitimate claim 629 00:29:34,707 --> 00:29:35,739 to be one of the hottest places 630 00:29:35,808 --> 00:29:37,007 on the planet. Yeah. 631 00:29:37,076 --> 00:29:38,308 Oh, we are the hottest place on the planet. 632 00:29:38,377 --> 00:29:39,743 All right, so, 633 00:29:39,812 --> 00:29:42,012 you actually hold the all-time record here? Yes. 634 00:29:42,081 --> 00:29:43,313 And you love this place? Yeah. 635 00:29:43,382 --> 00:29:44,848 This is the best national park. 636 00:29:44,917 --> 00:29:47,484 It's the best place on Earth, I love it here. 637 00:29:47,553 --> 00:29:49,286 And the hottest place on Earth. Yes. 638 00:29:49,355 --> 00:29:53,590 ♪ ♪ 639 00:29:53,659 --> 00:29:57,361 JOHNSON: But has it always been that way? 640 00:29:57,429 --> 00:30:00,931 Geologist Francis Macdonald has spent many years 641 00:30:01,000 --> 00:30:03,634 battling the heat in these desert hills, 642 00:30:03,702 --> 00:30:06,203 searching for clues that might reveal the secrets 643 00:30:06,272 --> 00:30:09,039 of Death Valley's past. 644 00:30:09,108 --> 00:30:10,908 MACDONALD: Why I really like coming out here 645 00:30:10,976 --> 00:30:13,143 is that all of this raw rock. 646 00:30:13,212 --> 00:30:17,047 Here in Death Valley, you're not limited by rock, 647 00:30:17,116 --> 00:30:18,715 you're limited by how far you can walk out there 648 00:30:18,784 --> 00:30:20,450 in this hot weather. 649 00:30:20,519 --> 00:30:23,320 JOHNSON: The rocks here date back to a time way before the dinosaurs, 650 00:30:23,389 --> 00:30:28,192 long before trees or even plants existed. 651 00:30:28,260 --> 00:30:33,697 MACDONALD: Why, in this rock formed 640 million years ago, 652 00:30:33,766 --> 00:30:35,666 do we have these rocks within the rock? 653 00:30:35,734 --> 00:30:37,234 This one's a granite. Okay. 654 00:30:37,303 --> 00:30:39,937 And it's surrounded by this pink sand 655 00:30:40,005 --> 00:30:41,939 and silt and mud. 656 00:30:42,007 --> 00:30:44,074 And here's another quartzite piece. 657 00:30:44,143 --> 00:30:46,043 Here's a-a piece of carbonate. 658 00:30:46,111 --> 00:30:47,678 They're different rock types, 659 00:30:47,746 --> 00:30:50,214 they're telling you about where they originally formed. 660 00:30:50,282 --> 00:30:51,715 JOHNSON: These rocks came from a whole bunch 661 00:30:51,784 --> 00:30:53,350 of different places? All over the place. 662 00:30:55,221 --> 00:30:57,988 JOHNSON: What could have brought this strange mixture of rocks here 663 00:30:58,057 --> 00:31:00,824 and encased them in silt? 664 00:31:00,893 --> 00:31:02,359 MACDONALD: We need a process 665 00:31:02,428 --> 00:31:05,596 that's just going pick up rocks from all over 666 00:31:05,664 --> 00:31:09,733 and dump-truck them into a pile of mud and sand. 667 00:31:09,802 --> 00:31:11,902 And we do know one process that does that, 668 00:31:11,971 --> 00:31:13,837 and that's glaciers. 669 00:31:13,906 --> 00:31:15,505 So, we're sitting here in Death Valley, 670 00:31:15,574 --> 00:31:19,443 and it's about 95 degrees, and you're pointing to a rock 671 00:31:19,511 --> 00:31:20,777 and saying that 672 00:31:20,846 --> 00:31:23,981 it was deposited by a giant slab of glacial ice? 673 00:31:24,049 --> 00:31:25,115 So work with me here 674 00:31:25,184 --> 00:31:26,450 a little bit. Okay. 675 00:31:26,518 --> 00:31:28,018 You've got to use your, use your imagination. 676 00:31:28,087 --> 00:31:29,953 ♪ ♪ 677 00:31:30,022 --> 00:31:31,488 JOHNSON: What these rocks tell us 678 00:31:31,557 --> 00:31:35,092 is that 640 million years ago, 679 00:31:35,160 --> 00:31:38,996 the climate here in Death Valley must have been much colder. 680 00:31:39,064 --> 00:31:42,900 So cold that what's now a scorching desert 681 00:31:42,968 --> 00:31:45,435 was covered in giant sheets of ice 682 00:31:45,504 --> 00:31:49,239 as big as you'd find in the polar regions today. 683 00:31:49,308 --> 00:31:54,044 The idea of an ice-covered Death Valley is strange enough. 684 00:31:54,113 --> 00:31:58,148 But these rocks tell us something even more astonishing 685 00:31:58,217 --> 00:32:00,284 about how far the ice extended. 686 00:32:00,352 --> 00:32:01,885 Even though here we're sitting today 687 00:32:01,954 --> 00:32:06,423 at, say, about 35 degrees north of the equator, 688 00:32:06,492 --> 00:32:11,161 we know 640 million years ago this was far further south, 689 00:32:11,230 --> 00:32:13,397 and it was situated very close to the equator. 690 00:32:13,465 --> 00:32:15,666 ♪ ♪ 691 00:32:15,734 --> 00:32:18,135 JOHNSON: Earth's tectonic plates have shifted quite a bit 692 00:32:18,203 --> 00:32:22,039 over the last 640 million years. 693 00:32:22,107 --> 00:32:25,309 Back then, Death Valley was part of a huge landmass 694 00:32:25,377 --> 00:32:28,946 that sat right on the equator. 695 00:32:29,014 --> 00:32:32,215 So, if the ice made it to here, 696 00:32:32,284 --> 00:32:36,119 it likely stretched all the way from both north and south 697 00:32:36,188 --> 00:32:38,922 until it met in the middle, 698 00:32:38,991 --> 00:32:42,859 making the entire planet a snowball Earth. 699 00:32:42,928 --> 00:32:49,599 ♪ ♪ 700 00:32:49,668 --> 00:32:54,037 For me, this is a pretty mind-blowing realization. 701 00:32:54,106 --> 00:32:56,273 Wherever you are in the world, 702 00:32:56,342 --> 00:32:59,476 by uncovering evidence in the rocks and fossils, 703 00:32:59,545 --> 00:33:01,778 you can travel back in time 704 00:33:01,847 --> 00:33:03,447 and reveal that Earth's climate 705 00:33:03,515 --> 00:33:06,016 has undergone incredible changes. 706 00:33:06,085 --> 00:33:09,486 ♪ ♪ 707 00:33:09,555 --> 00:33:13,156 You have to split a huge amount of rocks to find a fossil. 708 00:33:13,225 --> 00:33:14,591 ♪ ♪ 709 00:33:14,660 --> 00:33:16,326 The only way to find them is just to work your way down 710 00:33:16,395 --> 00:33:17,594 through the layers. 711 00:33:17,663 --> 00:33:18,962 ♪ ♪ 712 00:33:19,031 --> 00:33:21,865 So, just sort of chop a staircase down the hill. 713 00:33:21,934 --> 00:33:23,967 Sometimes an entire hill. 714 00:33:24,036 --> 00:33:25,502 (pick clinking) 715 00:33:25,571 --> 00:33:29,606 In fact, we can use the chemistry of rocks and fossils 716 00:33:29,675 --> 00:33:36,113 to find the temperature at the time those rocks formed. 717 00:33:36,181 --> 00:33:39,816 Piecing together data from sites across the globe, 718 00:33:39,885 --> 00:33:42,986 scientists can build a temperature timeline 719 00:33:43,055 --> 00:33:47,791 going all the way back to 500 million years ago. 720 00:33:47,860 --> 00:33:51,461 Laying out Earth's temperature like this, 721 00:33:51,530 --> 00:33:54,331 you can see a pattern. 722 00:33:54,400 --> 00:33:58,435 The climate fluctuates between long periods when it's warm, 723 00:33:58,504 --> 00:34:02,172 with no ice at all-- hothouse worlds-- 724 00:34:02,241 --> 00:34:04,207 and cooler episodes 725 00:34:04,276 --> 00:34:07,577 with ice caps at at least one of the poles-- 726 00:34:07,646 --> 00:34:10,547 icehouse worlds. 727 00:34:10,616 --> 00:34:15,118 The hot climates are three times as common as cold climates. 728 00:34:15,187 --> 00:34:17,721 And yet, perhaps surprisingly, 729 00:34:17,790 --> 00:34:20,557 we live in one of the icehouse worlds today. 730 00:34:20,626 --> 00:34:24,928 ♪ ♪ 731 00:34:24,997 --> 00:34:28,365 Today, we live on a planet that has ice at both poles. 732 00:34:28,434 --> 00:34:31,101 We think that's normal, 'cause that's our world. 733 00:34:31,170 --> 00:34:32,736 But when we look at the fossil record, 734 00:34:32,805 --> 00:34:36,473 we realize that our planet has only had four episodes 735 00:34:36,542 --> 00:34:38,542 where there's been glacial ice. 736 00:34:38,610 --> 00:34:42,946 Only about 25% of the last 500 million years 737 00:34:43,015 --> 00:34:45,282 has our planet been like it is today. 738 00:34:45,350 --> 00:34:48,418 ♪ ♪ 739 00:34:48,487 --> 00:34:50,120 So, why is this? 740 00:34:50,189 --> 00:34:54,858 Why has Earth spent so much of its past as a hothouse-- 741 00:34:54,927 --> 00:34:57,494 much warmer than it is now? 742 00:34:57,563 --> 00:35:02,332 We can find clues from a close neighbor in our solar system. 743 00:35:02,401 --> 00:35:04,067 I'm looking at Venus. 744 00:35:04,136 --> 00:35:05,635 It's the third-brightest thing in the sky 745 00:35:05,704 --> 00:35:06,770 after the sun and the moon. 746 00:35:06,839 --> 00:35:09,706 It's also one of our nearest planets. 747 00:35:09,775 --> 00:35:12,008 But Venus has a very unusual feature-- 748 00:35:12,077 --> 00:35:14,144 it's about 800 degrees Fahrenheit 749 00:35:14,213 --> 00:35:16,713 on the surface of Venus; it's hot enough to melt lead. 750 00:35:16,782 --> 00:35:18,482 ♪ ♪ 751 00:35:18,550 --> 00:35:20,183 (voiceover): Why is Venus so hot? 752 00:35:20,252 --> 00:35:24,254 It is a little bit closer to the sun than we are, 753 00:35:24,323 --> 00:35:27,757 but not enough to explain the huge temperature difference. 754 00:35:27,826 --> 00:35:29,693 ♪ ♪ 755 00:35:29,761 --> 00:35:32,696 We found the answer back in 1967, 756 00:35:32,764 --> 00:35:38,635 when the Soviets sent the Venera 4 space probe to Venus. 757 00:35:38,704 --> 00:35:43,206 Just before it was crushed by the huge atmospheric pressure, 758 00:35:43,275 --> 00:35:47,310 the spacecraft beamed back its precious data. 759 00:35:47,379 --> 00:35:49,946 It had identified one critical component 760 00:35:50,015 --> 00:35:52,115 of the planet's atmosphere. 761 00:35:52,184 --> 00:35:54,050 The reason Venus is so hot 762 00:35:54,119 --> 00:35:56,586 is that its atmosphere is composed almost entirely 763 00:35:56,655 --> 00:35:59,389 of carbon dioxide, 95%. 764 00:35:59,458 --> 00:36:01,825 ♪ ♪ 765 00:36:01,894 --> 00:36:04,928 This thick atmosphere, rich in CO2, 766 00:36:04,997 --> 00:36:09,032 acts like an insulating blanket. 767 00:36:09,101 --> 00:36:13,537 Most energy from the sun passes through this layer, 768 00:36:13,605 --> 00:36:16,640 but when it radiates back from the planet's surface, 769 00:36:16,708 --> 00:36:19,910 the carbon dioxide traps the heat. 770 00:36:19,978 --> 00:36:21,878 This is the greenhouse effect, 771 00:36:21,947 --> 00:36:24,447 which drove Venus to get hotter and hotter. 772 00:36:24,516 --> 00:36:27,250 ♪ ♪ 773 00:36:29,988 --> 00:36:33,690 It didn't just heat up-- it boiled. 774 00:36:33,759 --> 00:36:36,526 Venus is a clear example of a runaway greenhouse climate, 775 00:36:36,595 --> 00:36:39,262 what happens when you get too much carbon dioxide 776 00:36:39,331 --> 00:36:42,098 in your atmosphere. 777 00:36:42,167 --> 00:36:45,368 (voiceover): So if carbon dioxide can warm up a planet, 778 00:36:45,437 --> 00:36:49,673 is this what created all those hothouse worlds in Earth's past? 779 00:36:49,741 --> 00:36:52,375 (insects chirping) 780 00:36:52,444 --> 00:36:55,779 How can we know how much CO2 was in the atmosphere 781 00:36:55,847 --> 00:36:57,380 millions of years ago? 782 00:36:57,449 --> 00:36:59,649 (gate creaks) 783 00:36:59,718 --> 00:37:01,218 ♪ ♪ 784 00:37:01,286 --> 00:37:04,754 The answer may be hiding in some very special leaves. 785 00:37:04,823 --> 00:37:08,758 And deep in a forest just outside Washington, D.C., 786 00:37:08,827 --> 00:37:12,596 is an experiment to try and unlock their secrets. 787 00:37:12,664 --> 00:37:15,966 The experiment is being run by one of my former students, 788 00:37:16,034 --> 00:37:17,200 Rich Barclay. 789 00:37:17,269 --> 00:37:18,235 Hey, Rich. 790 00:37:18,303 --> 00:37:19,869 Oh, hey, Kirk. How's it going, man? 791 00:37:19,938 --> 00:37:21,504 Good to see you. Hey, welcome to the Fossil Atmospheres Experiment. 792 00:37:21,573 --> 00:37:25,875 JOHNSON: He's investigating the ginkgo tree. 793 00:37:25,944 --> 00:37:27,744 The ginkgo is pretty special, 794 00:37:27,813 --> 00:37:30,580 because fossils tell us that this species has survived 795 00:37:30,649 --> 00:37:35,852 almost unchanged for the last 200 million years. 796 00:37:35,921 --> 00:37:38,755 Since all plants use carbon dioxide to grow, 797 00:37:38,824 --> 00:37:40,724 a plant that's been around that long 798 00:37:40,792 --> 00:37:45,128 might be able to tell us how CO2 levels have changed. 799 00:37:45,197 --> 00:37:49,132 Rich is growing them in custom-made atmospheres 800 00:37:49,201 --> 00:37:51,134 to see how different amounts of carbon dioxide 801 00:37:51,203 --> 00:37:53,370 affect the leaves. 802 00:37:53,438 --> 00:37:54,604 So each of the chambers in here 803 00:37:54,673 --> 00:37:56,706 has a-a different CO2 concentration. 804 00:37:56,775 --> 00:38:00,577 This is a control tree, at 400 parts per million. 805 00:38:00,646 --> 00:38:02,479 600, the next treatment up. 806 00:38:02,547 --> 00:38:03,613 800 parts per million. 807 00:38:03,682 --> 00:38:06,149 The final tree at 1,000 parts per million. 808 00:38:06,218 --> 00:38:07,284 Can we go in there? 809 00:38:07,352 --> 00:38:09,185 We can go into the, into the chamber, yeah. 810 00:38:09,254 --> 00:38:12,989 This tree is growing at 1,000 parts per million. 811 00:38:13,058 --> 00:38:14,124 We put a tag around the branch, 812 00:38:14,192 --> 00:38:16,626 so you can just wrap that around the branch. 813 00:38:16,695 --> 00:38:18,161 JOHNSON: And so I take the leaf that's right above that one? 814 00:38:18,230 --> 00:38:19,396 Yep, that one right there is fine. 815 00:38:19,464 --> 00:38:20,797 So, what we do with the leaf 816 00:38:20,866 --> 00:38:22,265 is we take it back to the lab, 817 00:38:22,334 --> 00:38:23,867 and we can look at the-the details 818 00:38:23,935 --> 00:38:25,635 of the leaves under a microscope. 819 00:38:25,704 --> 00:38:29,673 JOHNSON: The leaves all look pretty much the same to me. 820 00:38:29,741 --> 00:38:31,408 But put them under a microscope, 821 00:38:31,476 --> 00:38:35,011 and you see something really cool. 822 00:38:35,080 --> 00:38:37,681 This is the surface of a ginkgo leaf 823 00:38:37,749 --> 00:38:38,882 from this experiment. 824 00:38:38,950 --> 00:38:40,950 You have to go in about 200 times magnification. 825 00:38:41,019 --> 00:38:44,087 JOHNSON: Now, you can see that the leaf from today's atmosphere 826 00:38:44,156 --> 00:38:47,924 is perforated with tiny holes called stomata. 827 00:38:47,993 --> 00:38:51,127 This is where the plants take in the carbon dioxide 828 00:38:51,196 --> 00:38:55,098 they need for photosynthesis 829 00:38:55,167 --> 00:38:57,167 And what Rich is discovering 830 00:38:57,235 --> 00:39:00,070 is that adding extra CO2 does something striking 831 00:39:00,138 --> 00:39:01,738 to the stomata. 832 00:39:01,807 --> 00:39:03,206 Then I've got this one. 833 00:39:03,275 --> 00:39:05,241 And it's really obvious to me 834 00:39:05,310 --> 00:39:07,510 that there's far fewer pores on this one. 835 00:39:07,579 --> 00:39:10,213 BARCLAY: That one's from the 1,000-ppm chambers. 836 00:39:10,282 --> 00:39:14,818 As CO2 increases, they don't need as many stomata, 837 00:39:14,886 --> 00:39:16,052 they can become more efficient. 838 00:39:16,121 --> 00:39:17,387 JOHNSON: More CO2, less stomata. 839 00:39:17,456 --> 00:39:19,756 BARCLAY: More CO2, fewer stomata. 840 00:39:19,825 --> 00:39:22,659 JOHNSON: This happens with all kinds of plants 841 00:39:22,728 --> 00:39:25,762 that take in carbon dioxide. 842 00:39:25,831 --> 00:39:28,164 But because ginkgoes have been around for 200 million years, 843 00:39:28,233 --> 00:39:32,736 they can preserve a snapshot of Earth's CO2 levels 844 00:39:32,804 --> 00:39:35,171 in the deep past. 845 00:39:35,240 --> 00:39:37,307 This is a fossil of ginkgo. 846 00:39:37,376 --> 00:39:39,442 It sure is, it's like, 847 00:39:39,511 --> 00:39:41,444 it really looks like ginkgo, I mean, this leaf and that leaf 848 00:39:41,513 --> 00:39:43,713 are almost identical. 849 00:39:43,782 --> 00:39:46,015 How old is this one? 850 00:39:46,084 --> 00:39:47,717 This fossil is 56 million years old. 851 00:39:47,786 --> 00:39:50,420 And then when you take that, you can put it under a microscope 852 00:39:50,489 --> 00:39:54,724 and see the exact same features as you find on the modern. 853 00:39:54,793 --> 00:39:56,626 JOHNSON: Right there on the fossil is 854 00:39:56,695 --> 00:39:58,161 the pattern of stomata: 855 00:39:58,230 --> 00:40:01,865 many fewer than on the leaves today. 856 00:40:01,933 --> 00:40:03,967 Fossils from all around the world 857 00:40:04,035 --> 00:40:05,935 help us estimate CO2 levels 858 00:40:06,004 --> 00:40:08,338 going back more than 400 million years. 859 00:40:10,609 --> 00:40:13,109 If we look back on our temperature timeline, 860 00:40:13,178 --> 00:40:17,480 we see that when CO2 levels are high, it's hot. 861 00:40:17,549 --> 00:40:22,585 And when CO2 levels drop, it cools. 862 00:40:22,654 --> 00:40:26,623 When this ginkgo was alive 56 million years ago-- 863 00:40:26,691 --> 00:40:29,459 about the same time that swampy forests 864 00:40:29,528 --> 00:40:31,227 were growing on Ellesmere Island in the Arctic-- 865 00:40:31,296 --> 00:40:33,430 the amount of CO2 in the air 866 00:40:33,498 --> 00:40:35,932 was roughly four times what it is today. 867 00:40:38,003 --> 00:40:41,204 So, where did all that CO2 come from? 868 00:40:43,175 --> 00:40:47,744 ♪ ♪ 869 00:40:47,813 --> 00:40:52,949 One possibility is from deep inside the Earth. 870 00:40:53,018 --> 00:40:55,118 Here at Mammoth Lakes in California, 871 00:40:55,187 --> 00:41:00,390 the ground is belching out steam and gas, 872 00:41:00,459 --> 00:41:04,661 and the pools are literally boiling beneath our feet. 873 00:41:04,729 --> 00:41:06,529 Because right under these mountains 874 00:41:06,598 --> 00:41:08,198 is one of the largest super-volcanoes 875 00:41:08,266 --> 00:41:09,666 in America. 876 00:41:09,734 --> 00:41:11,668 Wow, this place is pretty cool. 877 00:41:11,736 --> 00:41:13,036 Yeah, it's amazing, isn't it? 878 00:41:13,104 --> 00:41:14,804 JOHNSON: Geologist Kayla Iacovino 879 00:41:14,873 --> 00:41:17,073 studies volcanoes all over the world. 880 00:41:17,142 --> 00:41:18,575 We don't want to get too close 881 00:41:18,643 --> 00:41:19,943 to the edge of the water here. 882 00:41:20,011 --> 00:41:21,544 The ground is quite unstable. 883 00:41:21,613 --> 00:41:22,712 If you did fall through, 884 00:41:22,781 --> 00:41:23,880 that would be very, very bad news, so... 885 00:41:23,949 --> 00:41:25,081 Okay, I won't do that. 886 00:41:25,150 --> 00:41:27,450 Do you want hold on to this, carry it off... 887 00:41:27,519 --> 00:41:29,419 Yeah, I hold this, right? All right, here we go. 888 00:41:29,488 --> 00:41:31,921 JOHNSON: Kayla's taking measurements 889 00:41:31,990 --> 00:41:33,490 to monitor the volcano's activity, 890 00:41:33,558 --> 00:41:35,225 starting with temperature. 891 00:41:35,293 --> 00:41:36,860 It's like trout fishing. 892 00:41:36,928 --> 00:41:38,228 You sneak out to the edge of a creek, 893 00:41:38,296 --> 00:41:39,429 you lower the line over the edge... 894 00:41:39,498 --> 00:41:41,664 And you wait, yeah. ...you're waiting. 895 00:41:41,733 --> 00:41:44,300 JOHNSON: Next, she needs to measure the composition 896 00:41:44,369 --> 00:41:47,971 of the gas rising out of the ground. 897 00:41:48,039 --> 00:41:50,073 So you want to use this little tiny mud pot? 898 00:41:50,141 --> 00:41:52,275 Yeah, this looks like a good one. 899 00:41:52,344 --> 00:41:53,843 This is a CO2 meter. Okay. 900 00:41:53,912 --> 00:41:56,546 and it can tell us the concentration 901 00:41:56,615 --> 00:41:58,515 of carbon dioxide in the gases that we measure. 902 00:41:58,583 --> 00:42:02,118 JOHNSON: The level of carbon dioxide in the air 903 00:42:02,187 --> 00:42:04,921 is around 410 parts per million. 904 00:42:04,990 --> 00:42:08,024 But the reading from the mud pot is much higher. 905 00:42:08,093 --> 00:42:09,058 There we go, 906 00:42:09,127 --> 00:42:11,060 3,000 parts per million of CO2 Wow. 907 00:42:12,564 --> 00:42:14,664 The magma that sits deep within the Earth 908 00:42:14,733 --> 00:42:16,299 contains lots of carbon. 909 00:42:16,368 --> 00:42:20,436 When this magma gets close to the surface-- at a volcano-- 910 00:42:20,505 --> 00:42:25,074 that carbon is released into the air as carbon dioxide. 911 00:42:25,143 --> 00:42:28,278 Kayla is part of a team of scientists 912 00:42:28,346 --> 00:42:30,647 measuring how much CO2 is being released 913 00:42:30,715 --> 00:42:33,783 from volcanoes all over the world. 914 00:42:33,852 --> 00:42:35,785 This is basically volcano by volcano by volcano? 915 00:42:35,854 --> 00:42:36,953 That's how it's done, 916 00:42:37,022 --> 00:42:38,321 they actually look at individual volcanoes? 917 00:42:38,390 --> 00:42:39,956 Yep, and they kind of add them up together. 918 00:42:40,025 --> 00:42:43,960 JOHNSON: Even volcanoes encased in ice, 919 00:42:44,029 --> 00:42:45,895 like Mount Erebus in Antarctica, 920 00:42:45,964 --> 00:42:48,164 are spewing out carbon dioxide. 921 00:42:48,233 --> 00:42:53,503 Mount Etna in Italy is built on carbon-rich rocks 922 00:42:53,572 --> 00:42:58,508 and belches out more CO2 than almost any other volcano. 923 00:42:58,577 --> 00:43:01,711 When geologists estimate all the CO2 924 00:43:01,780 --> 00:43:03,613 coming out of volcanoes today, 925 00:43:03,682 --> 00:43:08,084 the total is around 300 million tons a year. 926 00:43:08,153 --> 00:43:11,621 That might sound like a lot, but it's not enough 927 00:43:11,690 --> 00:43:14,824 to significantly change global temperature. 928 00:43:14,893 --> 00:43:16,192 The amount of CO2 coming out of volcanoes today 929 00:43:16,261 --> 00:43:17,827 just doesn't even come close. Huh. 930 00:43:17,896 --> 00:43:20,263 It's tiny compared to the amount of CO2 931 00:43:20,332 --> 00:43:21,598 that humans are putting out, 932 00:43:21,666 --> 00:43:23,399 for example. 933 00:43:23,468 --> 00:43:25,635 What it takes to actually warm the planet 934 00:43:25,704 --> 00:43:28,338 from a volcano, from volcanic CO2, 935 00:43:28,406 --> 00:43:30,406 is a massive amount of CO2 put out 936 00:43:30,475 --> 00:43:32,308 over a very long period of time. 937 00:43:32,377 --> 00:43:34,444 ♪ ♪ 938 00:43:34,512 --> 00:43:37,213 JOHNSON: Today, Earth's volcanoes are relatively quiet 939 00:43:37,282 --> 00:43:41,250 and aren't cooking up a whole lot of CO2. 940 00:43:41,319 --> 00:43:43,519 But in the past, it's been a very different story. 941 00:43:43,588 --> 00:43:45,755 ♪ ♪ 942 00:43:45,824 --> 00:43:49,726 This ten-mile-wide basin looks peaceful today. 943 00:43:49,794 --> 00:43:52,929 But many thousands of years ago, 944 00:43:52,998 --> 00:43:55,932 it was the site of a huge eruption 945 00:43:56,001 --> 00:44:00,937 that spewed out 150 cubic miles of lava and ash. 946 00:44:01,006 --> 00:44:03,539 And this is just one spot. 947 00:44:03,608 --> 00:44:06,676 We know that at certain points throughout Earth's long history, 948 00:44:06,745 --> 00:44:09,579 volcanoes and other geologic activity 949 00:44:09,648 --> 00:44:15,385 released much more CO2 into the atmosphere than today. 950 00:44:15,453 --> 00:44:19,455 And sometimes this continued for millions and millions of years. 951 00:44:19,524 --> 00:44:21,758 That's what geologists think 952 00:44:21,826 --> 00:44:23,793 must have kept the planet so warm 953 00:44:23,862 --> 00:44:28,031 during all those long periods when Earth was a hothouse, 954 00:44:28,099 --> 00:44:31,267 giving us warm polar forests teeming with life. 955 00:44:31,336 --> 00:44:33,569 ♪ ♪ 956 00:44:33,638 --> 00:44:38,141 But if volcanic activity keeps releasing carbon dioxide, 957 00:44:38,209 --> 00:44:41,110 why hasn't CO2 built up in our atmosphere, 958 00:44:41,179 --> 00:44:43,980 making our planet overheat like Venus? 959 00:44:44,049 --> 00:44:46,949 ♪ ♪ 960 00:44:47,018 --> 00:44:49,018 Earth must have something Venus doesn't-- 961 00:44:49,087 --> 00:44:53,556 a way of taking carbon dioxide out of the atmosphere 962 00:44:53,625 --> 00:44:55,591 and putting it somewhere else. 963 00:44:55,660 --> 00:44:57,694 It turns out here in the mountains of Alaska, 964 00:44:57,762 --> 00:44:59,128 I'm experiencing it. 965 00:44:59,197 --> 00:45:01,731 What's falling on my hands and my face right now 966 00:45:01,800 --> 00:45:06,202 is rain in the mountains, and it's got dissolved CO2 in it. 967 00:45:06,271 --> 00:45:10,640 Rain absorbs CO2 from the air, 968 00:45:10,709 --> 00:45:14,544 and then the raindrops combine to form streams 969 00:45:14,612 --> 00:45:17,113 that eventually become fast-flowing rivers. 970 00:45:17,182 --> 00:45:19,882 The dissolved CO2 makes the water slightly acidic, 971 00:45:19,951 --> 00:45:22,719 helping it erode and weather rocks, 972 00:45:22,787 --> 00:45:27,557 releasing elements like calcium, magnesium, and silicon. 973 00:45:27,625 --> 00:45:30,026 ♪ ♪ 974 00:45:30,095 --> 00:45:31,160 Riding these rapids gives me a sense 975 00:45:31,229 --> 00:45:33,096 of just how powerful this river is. 976 00:45:33,164 --> 00:45:34,464 Yeah! 977 00:45:34,532 --> 00:45:36,065 Whoa! 978 00:45:36,134 --> 00:45:38,701 Off the edge, yes! 979 00:45:38,770 --> 00:45:41,304 It's like a saw that's cutting right down, 980 00:45:41,372 --> 00:45:43,106 the canyons are just cutting their way 981 00:45:43,174 --> 00:45:45,441 into the mountain range and just chopping them in half. 982 00:45:45,510 --> 00:45:47,510 (voiceover): The water I'm rafting on now 983 00:45:47,579 --> 00:45:50,179 is full of just the right chemical elements 984 00:45:50,248 --> 00:45:53,549 that will help lock up carbon. 985 00:45:53,618 --> 00:45:56,185 ♪ ♪ 986 00:45:56,254 --> 00:45:57,420 (laughing) 987 00:45:57,489 --> 00:45:58,654 That was awesome. 988 00:45:58,723 --> 00:46:01,557 Eventually, all the water in this river 989 00:46:01,626 --> 00:46:03,326 will end up in the Pacific Ocean, 990 00:46:03,394 --> 00:46:06,696 and with it, all of those dissolved minerals. 991 00:46:06,765 --> 00:46:09,665 Once they reach the ocean, 992 00:46:09,734 --> 00:46:12,869 the dissolved elements are taken in by tiny sea creatures 993 00:46:12,937 --> 00:46:16,105 and used to build their shells. 994 00:46:16,174 --> 00:46:17,340 Over millions of years, 995 00:46:17,408 --> 00:46:20,143 these shells drop down to the sea floor, 996 00:46:20,211 --> 00:46:23,412 forming layers of limestone, 997 00:46:23,481 --> 00:46:26,115 locking the carbon that used to be in the atmosphere 998 00:46:26,184 --> 00:46:28,184 into rocks. 999 00:46:28,253 --> 00:46:30,386 It's the final stage of a process 1000 00:46:30,455 --> 00:46:32,155 that's been driving our climate 1001 00:46:32,223 --> 00:46:36,793 for millions of years-- the carbon cycle. 1002 00:46:36,861 --> 00:46:39,028 There's a finite amount of carbon on planet Earth. 1003 00:46:39,097 --> 00:46:40,797 When that carbon is in the ground, 1004 00:46:40,865 --> 00:46:45,001 locked up in rocks or sediments, then the planet is cool. 1005 00:46:45,069 --> 00:46:46,869 And when that carbon is up in the atmosphere 1006 00:46:46,938 --> 00:46:49,672 as carbon dioxide, the planet warms. 1007 00:46:49,741 --> 00:46:52,208 And the climate history of our planet is this tug and pull 1008 00:46:52,277 --> 00:46:55,578 between carbon in the ground and carbon in the atmosphere. 1009 00:46:55,647 --> 00:46:57,914 ♪ ♪ 1010 00:46:57,982 --> 00:46:59,949 We can see how this balance plays out 1011 00:47:00,018 --> 00:47:02,919 on the planet's southernmost active volcano, 1012 00:47:02,987 --> 00:47:05,721 Mount Erebus. 1013 00:47:05,790 --> 00:47:07,423 Here in Antarctica, 1014 00:47:07,492 --> 00:47:10,960 this mountain terrain is encased in ice year-round. 1015 00:47:11,029 --> 00:47:14,463 There is no rain, and there are no rivers. 1016 00:47:14,532 --> 00:47:18,434 The weathering part of the carbon cycle is stalled. 1017 00:47:18,503 --> 00:47:22,905 Meanwhile, the volcano continues to spew out CO2. 1018 00:47:22,974 --> 00:47:25,775 ♪ ♪ 1019 00:47:25,844 --> 00:47:28,644 Mount Erebus is a window into what it was like 1020 00:47:28,713 --> 00:47:31,681 640 million years ago during snowball Earth, 1021 00:47:31,749 --> 00:47:35,751 when the planet was covered in ice. 1022 00:47:35,820 --> 00:47:39,488 With CO2 from ice-covered volcanoes building up, 1023 00:47:39,557 --> 00:47:45,061 the planet eventually got warm enough to melt the snowball. 1024 00:47:45,129 --> 00:47:48,464 If adding CO2 is how we melt a frozen planet, 1025 00:47:48,533 --> 00:47:50,433 then how do we freeze a warm one? 1026 00:47:50,501 --> 00:47:54,303 ♪ ♪ 1027 00:47:54,372 --> 00:47:56,939 About 50 million years ago, 1028 00:47:57,008 --> 00:47:59,976 after more than 200 million years in a hothouse, 1029 00:48:00,044 --> 00:48:03,246 carbon dioxide levels started to drop, 1030 00:48:03,314 --> 00:48:08,284 and the Earth began to cool. 1031 00:48:08,353 --> 00:48:12,455 Eventually, gigantic ice sheets began to form, 1032 00:48:12,523 --> 00:48:18,094 first in the Antarctic, and then the Arctic. 1033 00:48:18,162 --> 00:48:22,031 A new era had begun that we still live in today-- 1034 00:48:22,100 --> 00:48:23,432 the icehouse. 1035 00:48:25,536 --> 00:48:29,505 But where did all this ice come from? 1036 00:48:29,574 --> 00:48:33,409 How do you build an ice sheet a mile or two thick 1037 00:48:33,478 --> 00:48:38,447 when you start with nothing? 1038 00:48:38,516 --> 00:48:41,751 To take a closer look at how ice sheets form, 1039 00:48:41,819 --> 00:48:43,419 I'm going to climb down into a glacier. 1040 00:48:43,488 --> 00:48:44,921 Do that. 1041 00:48:44,989 --> 00:48:48,457 With a little help from mountaineer Brian Rougeux. 1042 00:48:48,526 --> 00:48:49,458 Perfect. 1043 00:48:49,527 --> 00:48:51,294 Wish me luck. 1044 00:48:51,362 --> 00:48:52,528 Have fun down there. 1045 00:48:52,597 --> 00:48:55,164 JOHNSON: There's actually an overhang. 1046 00:48:55,233 --> 00:48:56,198 Yeah, get your butt 1047 00:48:56,267 --> 00:48:57,500 as low as you feel comfortable 1048 00:48:57,568 --> 00:48:59,135 and then take a step down. 1049 00:48:59,203 --> 00:49:02,138 JOHNSON: First, I have to hop over this year's snow layer. 1050 00:49:02,206 --> 00:49:03,306 It's quite a step. 1051 00:49:03,374 --> 00:49:04,440 Nice. 1052 00:49:04,509 --> 00:49:05,808 (Johnson laughs) 1053 00:49:05,877 --> 00:49:08,511 It's like a foot-and-a-half overlap, man. 1054 00:49:08,579 --> 00:49:10,146 Nice work. 1055 00:49:10,214 --> 00:49:12,348 JOHNSON: Beneath the overhang are snow layers 1056 00:49:12,417 --> 00:49:14,383 from previous years. 1057 00:49:14,452 --> 00:49:18,254 Pretty amazing to be hanging out here in this ice world 1058 00:49:18,323 --> 00:49:21,724 and to imagine how this ice even got here in the first place. 1059 00:49:21,793 --> 00:49:25,428 (voiceover): Each year, it snows in the winter. 1060 00:49:25,496 --> 00:49:28,464 In most places, snow melts in summer. 1061 00:49:28,533 --> 00:49:30,733 But here, the summers are so cold, 1062 00:49:30,802 --> 00:49:33,035 the ice never fully melts, 1063 00:49:33,104 --> 00:49:37,406 and next year's snowfall piles up on top. 1064 00:49:37,475 --> 00:49:39,208 Snows falls in the winter, 1065 00:49:39,277 --> 00:49:40,776 and it stays there throughout the summer, 1066 00:49:40,845 --> 00:49:43,813 and the next summer, and the next summer, 1067 00:49:43,881 --> 00:49:44,947 and the next summer. 1068 00:49:45,016 --> 00:49:46,482 (voiceover): Over many winters, 1069 00:49:46,551 --> 00:49:50,753 the snow pile gets higher and heavier, 1070 00:49:50,822 --> 00:49:52,154 compressing the snow. 1071 00:49:52,223 --> 00:49:54,924 (snow pack crunches down) 1072 00:49:54,993 --> 00:49:57,193 The weight of the snow pushes down 1073 00:49:57,261 --> 00:49:59,729 and compacts the underlying layers into ice. 1074 00:49:59,797 --> 00:50:01,564 ♪ ♪ 1075 00:50:01,632 --> 00:50:03,833 (voiceover): Over thousands of years, 1076 00:50:03,901 --> 00:50:08,904 these layers build up until they form an ice sheet, 1077 00:50:08,973 --> 00:50:12,575 and that's exactly what happened at our poles. 1078 00:50:12,643 --> 00:50:16,679 When carbon dioxide levels fell, 1079 00:50:16,748 --> 00:50:19,015 around 50 million years ago, 1080 00:50:19,083 --> 00:50:21,317 the temperature started to drop, 1081 00:50:21,386 --> 00:50:27,623 and ice eventually took hold at the bottom of the planet. 1082 00:50:27,692 --> 00:50:30,793 Our icehouse world started 34 million years ago, 1083 00:50:30,862 --> 00:50:32,428 here in Antarctica. 1084 00:50:32,497 --> 00:50:34,830 ♪ ♪ 1085 00:50:34,899 --> 00:50:37,333 But carbon dioxide wasn't the only culprit 1086 00:50:37,402 --> 00:50:40,169 responsible for the deep freeze. 1087 00:50:40,238 --> 00:50:44,340 It turns out there was something special about Antarctica-- 1088 00:50:44,409 --> 00:50:49,078 its position on the globe. 1089 00:50:49,147 --> 00:50:50,546 In that direction, 700 miles, 1090 00:50:50,615 --> 00:50:52,748 is the southern tip of South America. 1091 00:50:52,817 --> 00:50:54,817 In between me and South America 1092 00:50:54,886 --> 00:50:56,552 is what's called Drake Passage. 1093 00:50:56,621 --> 00:50:59,622 This stretch of water 1094 00:50:59,690 --> 00:51:02,358 is one of the most feared passages in the world. 1095 00:51:02,427 --> 00:51:04,460 It's got tremendous storms. 1096 00:51:04,529 --> 00:51:07,730 ♪ ♪ 1097 00:51:07,799 --> 00:51:10,199 I feel really lucky to be on a boat 1098 00:51:10,268 --> 00:51:11,467 where I'm not actually seasick, 1099 00:51:11,536 --> 00:51:14,003 'cause it's a nice flat, calm day here 1100 00:51:14,072 --> 00:51:17,039 but if we wait just a few hours, things can get pretty ugly. 1101 00:51:18,643 --> 00:51:21,210 (voiceover): The reason it's almost always stormy here 1102 00:51:21,279 --> 00:51:22,778 is because there's a powerful current 1103 00:51:22,847 --> 00:51:27,049 that constantly runs from west to east through this gap. 1104 00:51:27,118 --> 00:51:29,752 But it hasn't always been this way. 1105 00:51:29,821 --> 00:51:33,122 We know from fossils dating back to the dinosaurs 1106 00:51:33,191 --> 00:51:36,926 that Antarctica used to be connected to South America. 1107 00:51:36,994 --> 00:51:39,695 But around 30 to 40 million years ago, 1108 00:51:39,764 --> 00:51:42,098 the giant tectonic plates beneath the continents 1109 00:51:42,166 --> 00:51:44,667 gradually pulled apart... (cracking) 1110 00:51:44,735 --> 00:51:48,871 eventually creating Drake Passage. 1111 00:51:48,940 --> 00:51:51,173 Once Antarctica was free, 1112 00:51:51,242 --> 00:51:53,209 powerful currents started circling around 1113 00:51:53,277 --> 00:51:55,377 the entire continent. 1114 00:51:55,446 --> 00:51:58,314 This is the circumpolar current. 1115 00:51:58,382 --> 00:52:03,152 And it keeps the cold in Antarctica, 1116 00:52:03,221 --> 00:52:04,954 and it keeps the warm from Antarctica. 1117 00:52:05,022 --> 00:52:06,889 So it kind of keeps the refrigerator door closed 1118 00:52:06,958 --> 00:52:10,559 on this mighty, icy continent. 1119 00:52:10,628 --> 00:52:11,994 Because the current was then allowed 1120 00:52:12,063 --> 00:52:13,562 to go right around the continent-- 1121 00:52:13,631 --> 00:52:15,097 endlessly around, endlessly around, 1122 00:52:15,166 --> 00:52:17,733 keeping it cold and frozen. 1123 00:52:17,802 --> 00:52:19,235 (voiceover): We think it's right around this time 1124 00:52:19,303 --> 00:52:22,271 that summers down here got colder. 1125 00:52:22,340 --> 00:52:26,075 So cold that the winter's snow wouldn't melt. 1126 00:52:27,845 --> 00:52:29,712 Beginning at the South Pole, 1127 00:52:29,780 --> 00:52:33,149 the snow piled up and glaciers grew, 1128 00:52:33,217 --> 00:52:38,087 and slowly Antarctica started to freeze over. 1129 00:52:38,156 --> 00:52:41,090 But it would take millions of years more 1130 00:52:41,159 --> 00:52:43,425 for the Arctic to get its ice, 1131 00:52:43,494 --> 00:52:45,427 mainly because at the North Pole, 1132 00:52:45,496 --> 00:52:49,832 there is ocean rather than land, 1133 00:52:49,901 --> 00:52:54,036 and it's hard to form ice sheets on water. 1134 00:52:54,105 --> 00:52:56,872 But eventually it cooled enough 1135 00:52:56,941 --> 00:53:00,910 that ice began to form on the surrounding land. 1136 00:53:00,978 --> 00:53:07,016 And once it was there, ice sheets could spread quickly, 1137 00:53:07,084 --> 00:53:11,287 sometimes, even reaching Seattle, my home town. 1138 00:53:11,355 --> 00:53:14,823 This is my old neighborhood. 1139 00:53:14,892 --> 00:53:16,659 I lived here when I was eight years old 1140 00:53:16,727 --> 00:53:18,527 until I went to college. 1141 00:53:18,596 --> 00:53:19,929 I used to play in these forests-- 1142 00:53:19,997 --> 00:53:22,097 my house was only about a block away. 1143 00:53:22,166 --> 00:53:27,203 (voiceover): Walking around now, I see things I missed as a kid-- 1144 00:53:27,271 --> 00:53:32,441 clues in the landscape that tell me what happened here. 1145 00:53:32,510 --> 00:53:35,444 Plopped right in the middle of a nearby neighborhood 1146 00:53:35,513 --> 00:53:38,180 is something remarkable. 1147 00:53:38,249 --> 00:53:41,550 This is a huge rock. 1148 00:53:41,619 --> 00:53:43,919 I grew up in Seattle, 1149 00:53:43,988 --> 00:53:46,388 I never heard about this rock-- that kind of bothers me. 1150 00:53:46,457 --> 00:53:50,826 It's a gigantic boulder. 1151 00:53:50,895 --> 00:53:52,161 It's got trees growing around it, 1152 00:53:52,230 --> 00:53:53,562 so it's been here a long time. 1153 00:53:53,631 --> 00:53:56,699 It makes you ask the question, "How did it get here?" 1154 00:53:56,767 --> 00:53:59,235 (voiceover): To understand how, 1155 00:53:59,303 --> 00:54:02,071 you need to get the big picture. 1156 00:54:02,139 --> 00:54:05,507 And luckily, I know a place with a spectacular view, 1157 00:54:05,576 --> 00:54:08,510 a spot I dreamed of climbing when I was a kid. 1158 00:54:08,579 --> 00:54:10,279 Oh, yeah. 1159 00:54:10,348 --> 00:54:12,915 The top of the Seattle Space Needle. 1160 00:54:12,984 --> 00:54:15,451 This is fantastic. 1161 00:54:15,519 --> 00:54:17,253 You need to clip me in the back there? 1162 00:54:17,321 --> 00:54:19,989 First. Okay, I'm ready to go. 1163 00:54:20,057 --> 00:54:22,224 Oh, boy. 1164 00:54:23,628 --> 00:54:27,363 (voiceover): I'm 600 feet above the street, 1165 00:54:27,431 --> 00:54:30,299 no place to be if you're scared of heights. 1166 00:54:30,368 --> 00:54:32,635 But for me, 1167 00:54:32,703 --> 00:54:36,805 it's the perfect way to check out the city's contours. 1168 00:54:36,874 --> 00:54:40,976 ♪ ♪ 1169 00:54:41,045 --> 00:54:43,612 Oh, man, what a great place. 1170 00:54:43,681 --> 00:54:45,314 This is really phenomenal. 1171 00:54:45,383 --> 00:54:46,682 I never thought I'd be able to climb 1172 00:54:46,751 --> 00:54:48,417 to the top of the Space Needle in my hometown. 1173 00:54:48,486 --> 00:54:51,253 ♪ ♪ 1174 00:54:51,322 --> 00:54:53,922 And you really get to understand the landscape 1175 00:54:53,991 --> 00:54:55,858 when you view it from above. 1176 00:54:55,926 --> 00:54:58,460 You can see things you don't see when you're at human scale. 1177 00:54:58,529 --> 00:55:01,563 The hills have a grain to them-- north to south in this case. 1178 00:55:01,632 --> 00:55:04,800 (voiceover): They're all pointing in one direction, 1179 00:55:04,869 --> 00:55:07,236 as if something powerful flowed over them. 1180 00:55:07,305 --> 00:55:12,041 This is a landscape created by snow, 1181 00:55:12,109 --> 00:55:15,344 accumulating year after year, 1182 00:55:15,413 --> 00:55:18,614 to form a massive, moving ice sheet, 1183 00:55:18,683 --> 00:55:20,616 big enough to shape hills 1184 00:55:20,685 --> 00:55:24,553 and dump a huge boulder on what's now the edge of the city. 1185 00:55:24,622 --> 00:55:26,989 Around 17,000 years ago, 1186 00:55:27,058 --> 00:55:31,026 an ice sheet once towered 3,000 feet, 1187 00:55:31,095 --> 00:55:34,463 five times the height of the Space Needle. 1188 00:55:34,532 --> 00:55:36,665 Seattle was at the edge of a vast ice sheet 1189 00:55:36,734 --> 00:55:40,302 that covered half of North America. 1190 00:55:40,371 --> 00:55:46,108 In places, the ice was over two miles thick. 1191 00:55:46,177 --> 00:55:49,211 This landscape is my landscape of my childhood, 1192 00:55:49,280 --> 00:55:52,247 but it's also the landscape of glaciers. 1193 00:55:52,316 --> 00:55:55,484 It's just killer. 1194 00:55:55,553 --> 00:55:57,519 What a day in Seattle. 1195 00:55:57,588 --> 00:56:01,290 (voiceover): When you think about this whole area buried in ice, 1196 00:56:01,359 --> 00:56:03,025 it makes you wonder, 1197 00:56:03,094 --> 00:56:05,928 "How did anything live through this ice age?" 1198 00:56:05,996 --> 00:56:08,597 ♪ ♪ 1199 00:56:08,666 --> 00:56:12,368 To find out, I'm heading north to dig up some clues 1200 00:56:12,436 --> 00:56:16,839 buried at the edge of the Canadian Yukon, 1201 00:56:16,907 --> 00:56:19,475 home of the Klondike gold rush. 1202 00:56:19,543 --> 00:56:22,111 They're still mining gold here today, 1203 00:56:22,179 --> 00:56:24,880 but not with pans and shovels. 1204 00:56:24,949 --> 00:56:26,949 Now they use giant water jets 1205 00:56:27,017 --> 00:56:31,720 that make a firehose seem like a garden sprinkler. 1206 00:56:31,789 --> 00:56:33,555 These melt away the frozen earth 1207 00:56:33,624 --> 00:56:37,693 to uncover the gold-bearing gravels below. 1208 00:56:37,762 --> 00:56:39,862 But there are other treasures buried here-- 1209 00:56:39,930 --> 00:56:42,431 ice age bones. 1210 00:56:42,500 --> 00:56:46,902 Paleontologist Grant Zazula is always on call to retrieve them. 1211 00:56:48,606 --> 00:56:49,505 Hey, Logan, I'm Grant. 1212 00:56:49,573 --> 00:56:50,839 I'm Kirk. 1213 00:56:50,908 --> 00:56:51,940 I'm Logan. Good to meet you. 1214 00:56:52,009 --> 00:56:53,609 Can I have a go? Oh, yeah. 1215 00:56:53,677 --> 00:56:56,512 What do I do, just basically hold on? Yeah, nice, slow movements. 1216 00:56:56,580 --> 00:56:59,214 JOHNSON: Who doesn't love blasting a fire hose at something? 1217 00:56:59,283 --> 00:57:00,783 This is really fun! 1218 00:57:00,851 --> 00:57:04,453 There's a buried gravel layer that's got the gold in it. 1219 00:57:04,522 --> 00:57:07,556 And the silt that's frozen has all the bones in it. 1220 00:57:07,625 --> 00:57:10,726 So there's a layer of bones and a layer of gold-bearing gravel. 1221 00:57:10,795 --> 00:57:13,662 ZAZULA: And if there wasn't gold in this gravel, 1222 00:57:13,731 --> 00:57:16,598 then we'd have no ability to actually find any of these bones 1223 00:57:16,667 --> 00:57:18,333 because there's no way you're going to get through that 1224 00:57:18,402 --> 00:57:20,002 with a trowel, you know? Yeah. 1225 00:57:20,070 --> 00:57:22,571 Oh, look at that, that layer of ice is amazing I'm exposing. 1226 00:57:22,640 --> 00:57:26,308 ZAZULA: So that's 25,000- or 30,000-year-old ice in there. 1227 00:57:26,377 --> 00:57:28,777 JOHNSON: 25,000-year-old ice? Yeah. 1228 00:57:28,846 --> 00:57:32,714 JOHNSON: This permafrost layer is ground that's been permanently frozen 1229 00:57:32,783 --> 00:57:34,416 since the last ice age. 1230 00:57:35,519 --> 00:57:38,720 Once the hose breaks it up, we go hunting. 1231 00:57:38,789 --> 00:57:40,255 Oh, here we go. 1232 00:57:40,324 --> 00:57:41,690 Oh, yeah. 1233 00:57:41,759 --> 00:57:42,758 Wow! 1234 00:57:42,827 --> 00:57:44,793 Little bit of a scapula. 1235 00:57:44,862 --> 00:57:45,761 I think it's a horse. 1236 00:57:45,830 --> 00:57:47,229 Oh, wow. Yeah. 1237 00:57:47,298 --> 00:57:49,598 JOHNSON: Permafrost is amazing stuff, 1238 00:57:49,667 --> 00:57:52,034 because it's cold enough 1239 00:57:52,102 --> 00:57:53,469 to preserve the tissue of buried animals 1240 00:57:53,537 --> 00:57:56,405 as if they were in a freezer. 1241 00:57:56,474 --> 00:57:58,106 We've got a big beast over here, Kirk! 1242 00:57:58,175 --> 00:58:00,242 It's a big piece of mammoth. 1243 00:58:00,311 --> 00:58:01,343 Oh, it's huge. 1244 00:58:01,412 --> 00:58:02,511 Yeah, it is. 1245 00:58:02,580 --> 00:58:05,147 You'll have to shovel on your side. 1246 00:58:05,216 --> 00:58:07,382 Oh, it's still... it going in quite a ways. 1247 00:58:07,451 --> 00:58:09,017 Wow. 1248 00:58:09,086 --> 00:58:10,919 Smells like the Pleistocene. Smells good. 1249 00:58:10,988 --> 00:58:13,856 JOHNSON: It's the pelvis of a woolly mammoth. 1250 00:58:13,924 --> 00:58:15,057 This is still bone. 1251 00:58:15,125 --> 00:58:16,458 It's not like a dinosaur fossil 1252 00:58:16,527 --> 00:58:17,860 where it's been replaced by minerals. 1253 00:58:17,928 --> 00:58:19,194 This is still actual bone 1254 00:58:19,263 --> 00:58:20,896 even though it's thousands and thousands of years old. 1255 00:58:20,965 --> 00:58:21,997 We'd call it a fossil. 1256 00:58:22,066 --> 00:58:23,432 It's just not a petrified fossil. 1257 00:58:23,501 --> 00:58:24,733 Yeah, absolutely. 1258 00:58:24,802 --> 00:58:26,502 What have you got there, too? 1259 00:58:26,570 --> 00:58:28,871 It's probably a moose antler... 1260 00:58:28,939 --> 00:58:30,706 Oh wow, a moose! 1261 00:58:30,774 --> 00:58:31,707 Here's a tooth. 1262 00:58:31,775 --> 00:58:32,741 Is it a horse tooth? Oh yeah. 1263 00:58:32,810 --> 00:58:34,476 There are fossils everywhere here. 1264 00:58:34,545 --> 00:58:37,913 And this is... Oh, horse tibia, horse tibia. 1265 00:58:37,982 --> 00:58:39,214 This is like name that bone. Yeah. 1266 00:58:39,283 --> 00:58:40,616 Oh my God, this is... 1267 00:58:40,684 --> 00:58:42,384 This is an upper horse molar. 1268 00:58:42,453 --> 00:58:43,519 I'm not leaving. (laughs): Yeah. 1269 00:58:43,587 --> 00:58:44,553 I am not leaving. 1270 00:58:44,622 --> 00:58:45,721 Oh, what'd you get? 1271 00:58:45,789 --> 00:58:47,856 It's the chunk of the skull of a wolf. 1272 00:58:47,925 --> 00:58:49,791 ZAZULA: Wolf! Hey! First carnivore. 1273 00:58:49,860 --> 00:58:52,094 Three beautiful molars in here. 1274 00:58:52,162 --> 00:58:54,796 This is like taking candy from a baby. 1275 00:58:54,865 --> 00:58:55,831 Don't take my candy. 1276 00:58:55,900 --> 00:58:57,165 Oh, here's your candy. 1277 00:58:57,234 --> 00:58:58,667 (both laughing) 1278 00:58:58,736 --> 00:59:00,502 Oh, there's a tusk, right? Oh! 1279 00:59:00,571 --> 00:59:02,504 That's really cool. It's solid ivory in there. 1280 00:59:02,573 --> 00:59:04,606 We just found the tusk of a woolly mammoth. 1281 00:59:04,675 --> 00:59:05,807 There's the... 1282 00:59:05,876 --> 00:59:09,545 Just walking around carrying a mammoth tusk. 1283 00:59:09,613 --> 00:59:11,780 Like nothing's going on, on a summer's day. 1284 00:59:11,849 --> 00:59:14,650 These are blades of grass that were collected by an ice-age 1285 00:59:14,718 --> 00:59:16,785 Arctic ground squirrel, 30,000 years ago. 1286 00:59:16,854 --> 00:59:21,256 So this is a 30,000-year-old piece of ground squirrel poo? 1287 00:59:21,325 --> 00:59:24,359 Yeah, absolutely, yeah. 1288 00:59:24,428 --> 00:59:27,429 ZAZULA: I think everything that could be found has been found. 1289 00:59:27,498 --> 00:59:31,033 ♪ ♪ 1290 00:59:34,805 --> 00:59:37,372 JOHNSON: It's an impressive haul. 1291 00:59:37,441 --> 00:59:42,911 ♪ ♪ 1292 00:59:42,980 --> 00:59:46,348 We've got bison, mammoth, horse, 1293 00:59:46,417 --> 00:59:48,517 moose, caribou, 1294 00:59:48,586 --> 00:59:50,552 miscellaneous. ZAZULA: Carnivores. 1295 00:59:50,621 --> 00:59:51,820 Carnivores-- a wolf and a lion. 1296 00:59:53,090 --> 00:59:54,523 So what can these bones tell us 1297 00:59:54,592 --> 00:59:57,759 about life in the last ice age? 1298 00:59:57,828 --> 00:59:59,828 They're so perfectly preserved, 1299 00:59:59,897 --> 01:00:02,397 we can figure out how the animals 1300 01:00:02,466 --> 01:00:04,866 adapted to survive the harsh, cold climate. 1301 01:00:04,935 --> 01:00:06,368 (pen scratching) 1302 01:00:06,437 --> 01:00:09,371 Take woolly mammoths. 1303 01:00:09,440 --> 01:00:12,174 They would have stood about ten feet high 1304 01:00:12,242 --> 01:00:15,811 with giant tusks up to 12 feet long. 1305 01:00:15,879 --> 01:00:17,546 They evolved from the same ancestor 1306 01:00:17,615 --> 01:00:19,815 as modern-day elephants. 1307 01:00:19,883 --> 01:00:21,617 But to survive the colder climate... 1308 01:00:21,685 --> 01:00:23,018 (woolly mammoth bellows) 1309 01:00:23,087 --> 01:00:27,322 woolly mammoths developed long hair and small ears 1310 01:00:27,391 --> 01:00:29,558 that prevented them from losing too much of their body heat 1311 01:00:29,627 --> 01:00:33,428 through their skin. 1312 01:00:33,497 --> 01:00:38,967 There was no shortage of mammals living here. 1313 01:00:39,036 --> 01:00:41,203 228 bones. 1314 01:00:41,271 --> 01:00:42,671 (laughing) Whoo! 1315 01:00:42,740 --> 01:00:44,272 That's a... that's a big haul for a single day. 1316 01:00:44,341 --> 01:00:47,542 228 bones in four hours. (chuckling): Yeah. Yeah. 1317 01:00:47,611 --> 01:00:49,978 ♪ ♪ 1318 01:00:50,047 --> 01:00:53,949 JOHNSON: So, how did all these different mammals survive here 1319 01:00:54,018 --> 01:00:57,085 when we know that much of North America was buried under ice? 1320 01:00:58,689 --> 01:01:00,689 To thrive here they needed to eat-- 1321 01:01:00,758 --> 01:01:03,425 and this means something must have been different 1322 01:01:03,494 --> 01:01:07,329 in the Yukon. 1323 01:01:07,398 --> 01:01:09,231 When you have animals like woolly mammoths, 1324 01:01:09,299 --> 01:01:10,465 and bison, and horses, 1325 01:01:10,534 --> 01:01:12,200 which are animals that are big grazers. 1326 01:01:12,269 --> 01:01:13,535 They need to consume a lot of grass. 1327 01:01:13,604 --> 01:01:15,570 This is telling me that this landscape 1328 01:01:15,639 --> 01:01:17,639 is covered by expansive grasslands. 1329 01:01:17,708 --> 01:01:20,642 And there's like, there's no Arctic grasslands today at all. 1330 01:01:20,711 --> 01:01:22,511 No, absolutely, this is an extinct ecosystem. 1331 01:01:22,579 --> 01:01:25,914 This is an ecosystem that we have no analogues to 1332 01:01:25,983 --> 01:01:27,015 in the present-day environment. 1333 01:01:28,552 --> 01:01:31,486 JOHNSON: But if there was grassland here during the Ice Age, 1334 01:01:31,555 --> 01:01:34,056 that means-- unlike the rest of the north-- 1335 01:01:34,124 --> 01:01:37,526 this part of the continent was ice-free. 1336 01:01:37,594 --> 01:01:40,062 Places like Boston, and Seattle, and Chicago were covered by ice. 1337 01:01:40,130 --> 01:01:41,029 Yes. 1338 01:01:41,098 --> 01:01:42,464 Most of Alaska was not, 1339 01:01:42,533 --> 01:01:43,865 and the part of the Yukon that we're in, 1340 01:01:43,934 --> 01:01:45,033 was not covered by ice. 1341 01:01:45,102 --> 01:01:47,569 Climatologically, it's telling us that it was 1342 01:01:47,638 --> 01:01:49,871 almost too cold and too dry to support glaciers. 1343 01:01:49,940 --> 01:01:53,642 JOHNSON: While most of North America was icing over, 1344 01:01:53,711 --> 01:01:56,211 here in the far northwest, 1345 01:01:56,280 --> 01:02:00,248 there wasn't enough snow to build an ice sheet. 1346 01:02:00,317 --> 01:02:03,819 And with more of the planet's water now locked up in glaciers, 1347 01:02:03,887 --> 01:02:05,721 sea levels fell, 1348 01:02:05,789 --> 01:02:12,427 exposing new ice-free land between Alaska and Siberia-- 1349 01:02:12,496 --> 01:02:15,297 the Bering Land Bridge. 1350 01:02:15,365 --> 01:02:16,565 ZAZULA: This was a great place 1351 01:02:16,633 --> 01:02:17,966 to be during the ice age. 1352 01:02:18,035 --> 01:02:21,236 There was glaciers only probably 100 kilometers away, 1353 01:02:21,305 --> 01:02:24,239 but this is a little... little bit of an ice age oasis 1354 01:02:24,308 --> 01:02:26,108 for these animals because it was highly productive. 1355 01:02:26,176 --> 01:02:28,677 ♪ ♪ 1356 01:02:28,746 --> 01:02:30,979 JOHNSON: What's now forest and tundra 1357 01:02:31,048 --> 01:02:36,685 would have been more like a prairie covered in wild grasses, 1358 01:02:36,754 --> 01:02:39,121 and in summer, small flowering plants, 1359 01:02:39,189 --> 01:02:41,857 like poppies, buttercups, and sage. 1360 01:02:41,925 --> 01:02:44,392 ♪ ♪ 1361 01:02:44,461 --> 01:02:47,662 The ice eventually started to retreat, 1362 01:02:47,731 --> 01:02:51,099 leaving an ice-free corridor that allowed ice-age animals, 1363 01:02:51,168 --> 01:02:55,904 and later people, to migrate between Asia and North America. 1364 01:02:55,973 --> 01:02:58,306 ♪ ♪ 1365 01:02:58,375 --> 01:03:01,076 We still live in an icehouse world, 1366 01:03:01,145 --> 01:03:03,044 with ice at the poles, 1367 01:03:03,113 --> 01:03:05,714 but it's obviously nowhere near as cold 1368 01:03:05,783 --> 01:03:07,916 as the most extreme ice ages. 1369 01:03:07,985 --> 01:03:10,418 So, what's going on? 1370 01:03:13,991 --> 01:03:15,557 We can find the answer, 1371 01:03:15,626 --> 01:03:19,961 thanks to a large meteorite... 1372 01:03:20,030 --> 01:03:21,830 that struck the Arctic 1373 01:03:21,899 --> 01:03:24,699 three and a half million years ago, 1374 01:03:24,768 --> 01:03:29,471 creating a ten-mile-wide crater that became a lake. 1375 01:03:29,540 --> 01:03:34,776 Ever since the lake formed, even when it was covered in ice, 1376 01:03:34,845 --> 01:03:36,812 sediment-- 1377 01:03:36,880 --> 01:03:39,047 all the stuff floating or living in the water-- 1378 01:03:39,116 --> 01:03:43,752 has been settling down to the lake bottom, forming layers. 1379 01:03:43,821 --> 01:03:45,887 Locked inside these thin layers 1380 01:03:45,956 --> 01:03:49,424 is a detailed history of our current icehouse, 1381 01:03:49,493 --> 01:03:52,460 stretching back three and a half million years. 1382 01:03:52,529 --> 01:03:57,799 Today, Lake El'gygytgyn lies 60 miles north 1383 01:03:57,868 --> 01:04:00,368 of the Arctic Circle in Russia. 1384 01:04:00,437 --> 01:04:06,875 Back in 2009, scientists set out to unearth the secrets 1385 01:04:06,944 --> 01:04:09,945 buried deep beneath the frozen lake. 1386 01:04:10,013 --> 01:04:11,813 But it wasn't easy. 1387 01:04:11,882 --> 01:04:12,948 JOHNSON: And good. 1388 01:04:13,016 --> 01:04:14,416 One more. 1389 01:04:14,484 --> 01:04:15,617 JOHNSON: Julie Brigham-Grette 1390 01:04:15,686 --> 01:04:19,387 was a leader of this extreme expedition. 1391 01:04:19,456 --> 01:04:21,122 JOHNSON: There's lots of lakes in the world, 1392 01:04:21,191 --> 01:04:24,960 but why that one? Turns out this meteorite hit 1393 01:04:25,028 --> 01:04:27,395 right smack dab in the largest 1394 01:04:27,464 --> 01:04:30,232 unglaciated area in the entire Arctic. 1395 01:04:30,300 --> 01:04:33,001 We put a 100-ton drill rig out on the lake ice 1396 01:04:33,070 --> 01:04:36,705 and then drilled from that platform. 1397 01:04:36,773 --> 01:04:38,540 JOHNSON: The team only had a short window, 1398 01:04:38,609 --> 01:04:40,041 in the very depths of winter, 1399 01:04:40,110 --> 01:04:46,214 when the lake ice was strong enough to support the drill rig. 1400 01:04:46,283 --> 01:04:48,650 Over 50 scientists from four countries 1401 01:04:48,719 --> 01:04:50,151 camped out on the frozen lake, 1402 01:04:50,220 --> 01:04:55,557 working in temperatures often 30 to 40 degrees below zero. 1403 01:04:55,626 --> 01:04:57,158 ♪ ♪ 1404 01:04:57,227 --> 01:04:59,561 This was the one of the most difficult and dangerous 1405 01:04:59,630 --> 01:05:02,430 drilling projects ever attempted. 1406 01:05:02,499 --> 01:05:04,132 Slide it just a little bit. 1407 01:05:04,201 --> 01:05:07,068 So I feel privileged that Julie's letting me handle 1408 01:05:07,137 --> 01:05:08,069 these precious cores. 1409 01:05:08,138 --> 01:05:10,305 This is a nice look... okay. Yeah. 1410 01:05:10,374 --> 01:05:13,108 So this goes around this side. 1411 01:05:13,176 --> 01:05:17,746 JOHNSON: This 1,000-foot length of core is the longest continuous record 1412 01:05:17,814 --> 01:05:21,283 of Arctic climate we have. 1413 01:05:21,351 --> 01:05:24,586 So a single layer, like this little layer right here, 1414 01:05:24,655 --> 01:05:26,321 that's telling you what was happening 1415 01:05:26,390 --> 01:05:27,389 to the climate on that day. 1416 01:05:27,457 --> 01:05:28,623 Yeah. 1417 01:05:28,692 --> 01:05:31,159 We're extracting the climate history. 1418 01:05:31,228 --> 01:05:33,762 So you've basically got a mud record 1419 01:05:33,830 --> 01:05:37,232 of 3.6 million years of climate in the Russian Arctic. 1420 01:05:37,301 --> 01:05:38,566 Yeah. 1421 01:05:38,635 --> 01:05:40,168 This is just a small part, 1422 01:05:40,237 --> 01:05:41,202 but we have the entire core 1423 01:05:41,271 --> 01:05:44,339 represented here in photographs, 1424 01:05:44,408 --> 01:05:47,943 which allow us to then look at the entire core over time. 1425 01:05:48,011 --> 01:05:49,311 That's great, you can scroll through it. 1426 01:05:49,379 --> 01:05:52,047 ♪ ♪ 1427 01:05:52,115 --> 01:05:57,185 JOHNSON: Layer by layer, Julie has pieced together an astonishing story. 1428 01:05:57,254 --> 01:05:59,988 BRIGHAM-GRETTE: We can zoom in on this 1429 01:06:00,057 --> 01:06:01,589 older part of the record. 1430 01:06:01,658 --> 01:06:05,126 JOHNSON: Pollen, spores, and other fossils in the mud layers 1431 01:06:05,195 --> 01:06:07,262 from three and a half million years ago, 1432 01:06:07,331 --> 01:06:10,465 reveal a climate warmer than today. 1433 01:06:10,534 --> 01:06:13,635 Back then, this Arctic lake was surrounded by hemlock 1434 01:06:13,704 --> 01:06:16,204 and hazelnut trees, 1435 01:06:16,273 --> 01:06:19,474 and the water was teeming with life. 1436 01:06:19,543 --> 01:06:21,376 Creatures tunneled into the lake bottom, 1437 01:06:21,445 --> 01:06:22,744 stirring up the mud layers, 1438 01:06:22,813 --> 01:06:26,014 and leaving them smooth. 1439 01:06:26,083 --> 01:06:29,918 But then here, around 2.6 million years ago, 1440 01:06:29,987 --> 01:06:32,754 there's a sudden change. 1441 01:06:32,823 --> 01:06:35,590 These dark striped layers come from a time when the lake 1442 01:06:35,659 --> 01:06:38,927 was completely frozen over all year round, 1443 01:06:38,996 --> 01:06:42,964 with no plants or animals living on the lake bed. 1444 01:06:43,033 --> 01:06:45,600 You could have ice skated across the lake in July. 1445 01:06:45,669 --> 01:06:46,901 Wow. 1446 01:06:46,970 --> 01:06:48,136 That's cold. 1447 01:06:49,339 --> 01:06:51,673 Here, Julie can pinpoint the moment when this part 1448 01:06:51,742 --> 01:06:56,511 of the Arctic froze over 2.6 million years ago. 1449 01:06:56,580 --> 01:06:59,681 This isn't found anywhere earlier in the lake history. 1450 01:06:59,750 --> 01:07:02,884 All of a sudden, boom, comes the first glaciation. 1451 01:07:02,953 --> 01:07:04,719 Right. 1452 01:07:04,788 --> 01:07:06,788 JOHNSON: And here's what's really cool. 1453 01:07:06,857 --> 01:07:08,823 As we move along the length of the core, 1454 01:07:08,892 --> 01:07:11,393 these contrasting periods of warm and cold 1455 01:07:11,461 --> 01:07:15,263 pop up again and again. 1456 01:07:15,332 --> 01:07:17,866 The temperature swings between very cold periods, 1457 01:07:17,934 --> 01:07:19,267 called glacials, 1458 01:07:19,336 --> 01:07:22,737 when the ice sheets extend down over the continents, 1459 01:07:22,806 --> 01:07:25,740 and warmer inter-glacials, like today, 1460 01:07:25,809 --> 01:07:29,477 when there's still ice, but it's confined to the poles. 1461 01:07:29,546 --> 01:07:31,379 But what causes so much variation 1462 01:07:31,448 --> 01:07:34,582 within the icehouse world? 1463 01:07:34,651 --> 01:07:38,620 Why does the ice grow and shrink in such a regular rhythm? 1464 01:07:41,425 --> 01:07:43,758 ♪ ♪ 1465 01:07:43,827 --> 01:07:45,093 (birds twittering) 1466 01:07:45,162 --> 01:07:46,828 There's some changes in the Earth's climate 1467 01:07:46,897 --> 01:07:51,866 that are periodic-- we don't think anything about them-- 1468 01:07:51,935 --> 01:07:53,835 things like the change of the seasons. 1469 01:07:53,904 --> 01:07:59,607 ♪ ♪ 1470 01:07:59,676 --> 01:08:02,143 Let's call that fire sun, 1471 01:08:02,212 --> 01:08:05,080 and here's... I've got a little bit of a globe right here. 1472 01:08:05,148 --> 01:08:07,582 And we know that the sun is 93 million miles away 1473 01:08:07,651 --> 01:08:09,217 from planet Earth. 1474 01:08:09,286 --> 01:08:11,152 And what makes the seasons 1475 01:08:11,221 --> 01:08:12,654 is that the Earth is tilted, 1476 01:08:12,722 --> 01:08:15,590 so when the Northern Hemisphere is tilted towards the sun, 1477 01:08:15,659 --> 01:08:17,292 you have Northern Hemisphere summer. 1478 01:08:17,360 --> 01:08:18,359 Six months later 1479 01:08:18,428 --> 01:08:20,328 as the Earth rotates around the sun, 1480 01:08:20,397 --> 01:08:22,730 you have the Southern Hemisphere summer. 1481 01:08:22,799 --> 01:08:27,235 And that change of the seasons makes lots of sense to us. 1482 01:08:27,304 --> 01:08:28,970 But there are longer-term variations 1483 01:08:29,039 --> 01:08:31,706 in the Earth's climate too. 1484 01:08:31,775 --> 01:08:34,209 And these changes are also driven by the way 1485 01:08:34,277 --> 01:08:38,947 our planet moves around the sun and receives energy from it. 1486 01:08:39,015 --> 01:08:41,549 Our orbit is distorted by the gravitational pull 1487 01:08:41,618 --> 01:08:45,954 of the bigger planets-- Jupiter and Saturn. 1488 01:08:46,022 --> 01:08:47,522 Those big planets are pulling on Earth, 1489 01:08:47,591 --> 01:08:49,491 and they're bending and flexing 1490 01:08:49,559 --> 01:08:51,159 the Earth's orbit around the sun. 1491 01:08:51,228 --> 01:08:52,360 ♪ ♪ 1492 01:08:52,429 --> 01:08:54,429 The shape of our orbit gradually changes 1493 01:08:54,498 --> 01:08:58,133 from more circular to more oval. 1494 01:08:58,201 --> 01:09:01,936 And there are two other things that drive these climate cycles. 1495 01:09:02,005 --> 01:09:07,008 The tilt of the Earth shifts, and it wobbles on its axis. 1496 01:09:07,077 --> 01:09:10,044 All these changes over time add up to a repeating pattern 1497 01:09:10,113 --> 01:09:11,946 of warming and cooling, 1498 01:09:12,015 --> 01:09:15,650 over tens to hundreds of thousands of years, 1499 01:09:15,719 --> 01:09:20,421 where the ice grows and shrinks over and over again. 1500 01:09:23,827 --> 01:09:26,094 These swings in climate 1501 01:09:26,163 --> 01:09:29,164 can make it pretty challenging for life to thrive. 1502 01:09:31,001 --> 01:09:33,902 Even for a highly adaptable species like us. 1503 01:09:38,208 --> 01:09:41,209 The first humans appeared about 300,000 years ago 1504 01:09:41,278 --> 01:09:44,045 and they had to deal with very erratic climates-- 1505 01:09:44,114 --> 01:09:46,114 cold to hot to cold to hot. 1506 01:09:46,183 --> 01:09:50,485 But around 12,000 years ago, something changed. 1507 01:09:52,222 --> 01:09:55,924 From the depths of the last ice age, our planet warmed, 1508 01:09:55,992 --> 01:09:57,325 and the glaciers that covered 1509 01:09:57,394 --> 01:10:00,695 much of North America and Europe retreated. 1510 01:10:00,764 --> 01:10:05,466 As the ice melted, sea level started to rise, 1511 01:10:05,535 --> 01:10:07,802 flooding river mouths around the world 1512 01:10:07,871 --> 01:10:10,505 and building up deltas like the Nile, 1513 01:10:10,574 --> 01:10:12,674 and flood plains like the Indus Valley. 1514 01:10:16,346 --> 01:10:21,382 The flat, well-watered, fertile ground was ideal for farming. 1515 01:10:22,619 --> 01:10:24,652 And the spread of agriculture 1516 01:10:24,721 --> 01:10:27,589 would alter the course of human history. 1517 01:10:27,657 --> 01:10:29,557 Successful farming triggered the expansion 1518 01:10:29,626 --> 01:10:31,893 of civilization around the world. 1519 01:10:31,962 --> 01:10:34,596 And that depended on a stable climate. 1520 01:10:34,664 --> 01:10:38,499 We live in a world that's just right for human civilization-- 1521 01:10:38,568 --> 01:10:41,402 not too much ice and not too little ice. 1522 01:10:41,471 --> 01:10:42,837 ♪ ♪ 1523 01:10:42,906 --> 01:10:48,543 A perfect inter-glacial balance. 1524 01:10:48,612 --> 01:10:52,480 But now, the Earth's natural climate cycle 1525 01:10:52,549 --> 01:10:56,117 is being disrupted. 1526 01:10:56,186 --> 01:10:59,187 After hundreds of generations of humans have settled 1527 01:10:59,256 --> 01:11:01,256 across this icehouse world, 1528 01:11:01,324 --> 01:11:04,259 the planet's temperature is rising, 1529 01:11:04,327 --> 01:11:08,496 and the polar regions are changing. 1530 01:11:08,565 --> 01:11:10,832 So, what's happening, 1531 01:11:10,900 --> 01:11:14,168 and what does the future hold? 1532 01:11:16,873 --> 01:11:21,509 You might think of a glacier as a thermometer for the planet, 1533 01:11:21,578 --> 01:11:24,345 because it's basically a block of ice. 1534 01:11:24,414 --> 01:11:26,080 ♪ ♪ 1535 01:11:26,149 --> 01:11:30,618 In most places around the world, glaciers are diminishing. 1536 01:11:32,489 --> 01:11:35,290 Where glaciers that once were very extensive 1537 01:11:35,358 --> 01:11:37,525 now are shrinking back up their valleys. 1538 01:11:40,497 --> 01:11:43,131 Nowhere is that more dramatic 1539 01:11:43,199 --> 01:11:47,435 than at the mighty Jakobshavn Glacier in Greenland. 1540 01:11:47,504 --> 01:11:51,439 (people talking indistinctly) 1541 01:11:51,508 --> 01:11:53,074 I'm going to get my camera, I think. 1542 01:11:53,143 --> 01:11:55,677 (voiceover): I'm joining Denise and David Holland 1543 01:11:55,745 --> 01:11:58,846 and their team of scientists from New York University. 1544 01:11:58,915 --> 01:12:00,615 MALICK (on radio): Hello guys, are you all ready? 1545 01:12:00,684 --> 01:12:03,351 Yes, sir, we're ready. Ready. 1546 01:12:03,420 --> 01:12:06,354 JOHNSON: We're flying up to the edge of the massive ice sheet 1547 01:12:06,423 --> 01:12:09,357 that covers almost all of Greenland. 1548 01:12:09,426 --> 01:12:11,626 Oh, that's a huge iceberg down there! Yes. 1549 01:12:11,695 --> 01:12:13,995 The scale of this thing is, is amazing. 1550 01:12:14,064 --> 01:12:17,632 The team wants to understand how the ice behaves here. 1551 01:12:17,701 --> 01:12:19,934 BRIAN ROUGEUX (on radio): Malick, if you're able to drop me 1552 01:12:20,003 --> 01:12:22,136 and then take off for a bit, that, that makes it 1553 01:12:22,205 --> 01:12:24,339 quite a bit easier for me. 1554 01:12:24,407 --> 01:12:25,540 JOHNSON: Mountaineer Brian Rougeux 1555 01:12:25,608 --> 01:12:27,742 has to venture out between the crevasses, 1556 01:12:27,811 --> 01:12:30,845 to place GPS trackers at different spots 1557 01:12:30,914 --> 01:12:33,614 on this fast-moving, treacherous glacier. 1558 01:12:33,683 --> 01:12:35,216 MALICK (on radio): I'm going to put it on the ground. 1559 01:12:35,285 --> 01:12:36,784 I just need to find a spot. 1560 01:12:36,853 --> 01:12:39,020 JOHNSON: Lots of little crevasses here. 1561 01:12:39,089 --> 01:12:41,622 MALICK: Seems flat, but it's not flat at all. 1562 01:12:41,691 --> 01:12:42,957 Pretty windy up here. 1563 01:12:43,026 --> 01:12:44,425 JOHNSON: The 45-mile-per-hour winds 1564 01:12:44,494 --> 01:12:46,227 are too high for the pilot to risk touching down 1565 01:12:46,296 --> 01:12:47,628 completely on the ice. 1566 01:12:47,697 --> 01:12:50,031 DAVID: Malick, I'm going to open the door, okay? 1567 01:12:50,100 --> 01:12:51,332 MALICK: Yep. 1568 01:12:51,401 --> 01:12:53,034 JOHNSON: Brian will have to make a quick exit. 1569 01:12:53,103 --> 01:12:54,736 DAVID: So we're going to deploy carefully. 1570 01:12:54,804 --> 01:12:56,704 MALICK: Take care of the rotors, okay? 1571 01:12:56,773 --> 01:12:58,206 DAVID: Yep, Brian got the message on the rotors. 1572 01:12:58,274 --> 01:13:00,541 We're going to circle back for him later 1573 01:13:00,610 --> 01:13:02,410 in a few minutes, okay? 1574 01:13:02,479 --> 01:13:05,279 JOHNSON: I wouldn't want to be him, but I trust your judgment. 1575 01:13:05,348 --> 01:13:08,349 The solar-powered GPS instruments will measure 1576 01:13:08,418 --> 01:13:10,017 how fast the glacier is moving. 1577 01:13:10,086 --> 01:13:13,354 MALICK: Make sure that we know where he is. 1578 01:13:13,423 --> 01:13:16,157 ♪ ♪ 1579 01:13:16,226 --> 01:13:18,526 The little lake is a good landmark. 1580 01:13:18,595 --> 01:13:20,428 MARCO: Malick, do you read, it's Marco. 1581 01:13:20,497 --> 01:13:21,896 MALICK: Yeah, I read you. 1582 01:13:21,965 --> 01:13:26,501 MARCO: We are doing a circle around the position. 1583 01:13:26,569 --> 01:13:29,404 JOHNSON: That wind is howling out there. 1584 01:13:29,472 --> 01:13:31,472 Is he coming onboard again? 1585 01:13:31,541 --> 01:13:34,108 DAVID: He's now boarding, Brian's now on board, closing door. 1586 01:13:34,177 --> 01:13:35,376 All secure. 1587 01:13:35,445 --> 01:13:38,246 Well done. MALICK: Check. 1588 01:13:38,314 --> 01:13:40,348 JOHNSON: That's something. 1589 01:13:40,417 --> 01:13:42,350 Data from the trackers will be downloaded 1590 01:13:42,419 --> 01:13:43,851 back at the research base, 1591 01:13:43,920 --> 01:13:47,522 on a rocky outcrop near the glacier. 1592 01:13:47,590 --> 01:13:50,858 The team spends several weeks here each summer. 1593 01:13:50,927 --> 01:13:54,128 Aw, this is amazing out here! 1594 01:13:54,197 --> 01:13:55,296 It's awesome. 1595 01:13:55,365 --> 01:13:57,165 ♪ ♪ 1596 01:13:57,233 --> 01:13:58,966 JOHNSON: When you come to a place like this, you're blown away 1597 01:13:59,035 --> 01:14:01,936 by the vastness of the scale of the ice. 1598 01:14:05,141 --> 01:14:08,409 I'm right at the very head of the Jakobshavn Ice Fjord 1599 01:14:08,478 --> 01:14:12,713 and off in that direction is the massive ice sheet of Greenland. 1600 01:14:12,782 --> 01:14:16,484 And this glacier is the fastest moving glacier in the world, 1601 01:14:16,553 --> 01:14:19,654 and it's dumping icebergs out at a staggering rate. 1602 01:14:19,722 --> 01:14:24,525 ♪ ♪ 1603 01:14:24,594 --> 01:14:28,996 At the point where the glacier meets the ocean sits our camp. 1604 01:14:29,065 --> 01:14:31,566 This is the calving edge 1605 01:14:31,634 --> 01:14:34,268 where icebergs are launched. 1606 01:14:34,337 --> 01:14:36,871 The one that sank the "Titanic" probably came from here. 1607 01:14:36,940 --> 01:14:38,372 (iceberg rumbling) 1608 01:14:38,441 --> 01:14:41,509 One of the big questions here is: is this rate of ice flow 1609 01:14:41,578 --> 01:14:43,644 off Greenland unusual or not? 1610 01:14:43,713 --> 01:14:45,980 And the only way you can tell that is to watch it. 1611 01:14:47,550 --> 01:14:49,450 David Holland has a special camera 1612 01:14:49,519 --> 01:14:52,086 that takes an image of the calving edge every day 1613 01:14:52,155 --> 01:14:54,589 all year round. 1614 01:14:54,657 --> 01:14:57,458 This is a camera in a metal tube with a glass front on it. 1615 01:14:57,527 --> 01:14:58,659 DAVID: That's exactly it. 1616 01:14:58,728 --> 01:14:59,694 JOHNSON: You just pulled the SD card out. 1617 01:14:59,762 --> 01:15:01,028 And that's it, so that's the... 1618 01:15:01,097 --> 01:15:02,363 That's a year's worth of data? Yeah. 1619 01:15:02,432 --> 01:15:04,131 So let's have a look at it and see what we got. 1620 01:15:04,200 --> 01:15:06,000 Okay, definitely. Let's bring it back. 1621 01:15:06,069 --> 01:15:07,568 ♪ ♪ 1622 01:15:07,637 --> 01:15:09,370 JOHNSON: This is the last how many months? 1623 01:15:09,439 --> 01:15:12,306 DAVID: So, this is from last August until, I think, 1624 01:15:12,375 --> 01:15:14,208 approximately last December. 1625 01:15:15,945 --> 01:15:19,413 What you see is here in summer the glacier has retreated. 1626 01:15:19,482 --> 01:15:20,915 So it was way back there. It's way back there! 1627 01:15:20,984 --> 01:15:22,383 Yeah. 1628 01:15:22,452 --> 01:15:24,318 And as it becomes colder 1629 01:15:24,387 --> 01:15:26,587 in the environment, the glacier is advancing. 1630 01:15:26,656 --> 01:15:29,657 You can kind of see a wall here that's moving forward. 1631 01:15:29,726 --> 01:15:31,392 Now it's in the middle of the screen. 1632 01:15:31,461 --> 01:15:33,294 And you can see it moving here as the winter comes? 1633 01:15:33,363 --> 01:15:35,630 The wall is moving downstream. Yeah, yeah. 1634 01:15:35,698 --> 01:15:36,831 Wow! 1635 01:15:36,900 --> 01:15:38,099 I mean, when you look at a glacier, 1636 01:15:38,167 --> 01:15:39,534 it looks like it's just sitting there, 1637 01:15:39,602 --> 01:15:41,002 but this makes it look like a river. 1638 01:15:44,173 --> 01:15:45,907 DAVID: But the bigger picture we're looking at 1639 01:15:45,975 --> 01:15:48,242 is for the last 20 years, 1640 01:15:48,311 --> 01:15:52,280 this cycle has retreated many, many miles into the fjord. 1641 01:15:52,348 --> 01:15:56,250 ♪ ♪ 1642 01:15:56,319 --> 01:15:57,885 JOHNSON: Since the 1850s, 1643 01:15:57,954 --> 01:16:00,721 the Jakobshavn Glacier has been slowly decaying, 1644 01:16:00,790 --> 01:16:05,293 the calving edge inching its way backwards up the fjord. 1645 01:16:05,361 --> 01:16:07,562 And this century, it's been speeding up, 1646 01:16:07,630 --> 01:16:12,066 losing more than ten miles in a decade. 1647 01:16:12,135 --> 01:16:13,734 When I was here in '96, I would have seen it 1648 01:16:13,803 --> 01:16:15,303 way down the valley. That's right, that's right. 1649 01:16:15,371 --> 01:16:17,004 And now it's w... it's moved up. Yeah. 1650 01:16:17,073 --> 01:16:18,539 The year after you were here, 1651 01:16:18,608 --> 01:16:21,609 the, the major retreat started, 1997. 1652 01:16:21,678 --> 01:16:23,210 I didn't do it, I promise you. 1653 01:16:23,279 --> 01:16:26,047 JOHNSON: So what is happening here to cause this glacier 1654 01:16:26,115 --> 01:16:29,283 to retreat so quickly? 1655 01:16:29,352 --> 01:16:33,654 To try and find out, the team is taking to the air again. 1656 01:16:33,723 --> 01:16:36,490 This time they need to drop probes into the water 1657 01:16:36,559 --> 01:16:38,292 just in front of the calving edge. 1658 01:16:38,361 --> 01:16:40,094 ♪ ♪ 1659 01:16:40,163 --> 01:16:42,129 They'll measure how the water temperature changes 1660 01:16:42,198 --> 01:16:44,832 along the length and depth of the fjord. 1661 01:16:44,901 --> 01:16:46,734 The first hole you see. JOHNSON: Yeah. 1662 01:16:46,803 --> 01:16:48,970 We'll do that and then every three nautical miles. 1663 01:16:49,038 --> 01:16:50,938 JOHNSON: Yes. DAVID: Yup, yup. 1664 01:16:51,007 --> 01:16:54,241 That's not to say that I'm going to get it in the hole. 1665 01:16:54,310 --> 01:16:56,911 This could be my lucky year. 1666 01:16:56,980 --> 01:16:58,946 DAVID: Is it possible to go slightly lower? 1667 01:16:59,015 --> 01:17:01,882 DENISE: Okay, preparing probe. 1668 01:17:01,951 --> 01:17:05,519 JOHNSON: The helicopter hovers just above the surface. 1669 01:17:05,588 --> 01:17:07,955 After hitting the water, the probe sinks... 1670 01:17:08,024 --> 01:17:08,956 Probe deployed. 1671 01:17:09,025 --> 01:17:10,491 JOHNSON: ...and sends back 1672 01:17:10,560 --> 01:17:12,393 live temperature readings as it descends. 1673 01:17:12,462 --> 01:17:14,996 DAVID: 400 meters, temperature 1.6. 1674 01:17:15,064 --> 01:17:17,932 600 meters, temperature 1.7 1675 01:17:18,001 --> 01:17:19,367 Okay, that's it, hit the bottom, 1676 01:17:19,435 --> 01:17:22,236 790 meters, temperature 1.9. 1677 01:17:22,305 --> 01:17:24,872 JOHNSON: The team takes readings from 12 different positions 1678 01:17:24,941 --> 01:17:28,376 along the length of the fjord. 1679 01:17:28,444 --> 01:17:29,543 DAVID: 400 meters, 1680 01:17:29,612 --> 01:17:30,911 temperature 1.5. 1681 01:17:30,980 --> 01:17:32,980 DAVID: Okay, all done, Denise. 1682 01:17:33,049 --> 01:17:35,249 JOHNSON: The probes don't disappoint. 1683 01:17:35,318 --> 01:17:40,588 They reveal an invisible attack on the glacier from below. 1684 01:17:40,657 --> 01:17:43,124 Over recent decades, a deep current, 1685 01:17:43,192 --> 01:17:44,358 slightly warmer than the surface, 1686 01:17:44,427 --> 01:17:48,663 has been eating away the base of the glacier. 1687 01:17:48,731 --> 01:17:53,467 DAVID: The ocean seems to be in control of this 20-year retreat. 1688 01:17:53,536 --> 01:17:55,636 When we looked at the last few decades, 1689 01:17:55,705 --> 01:17:57,204 it's really quite remarkable. 1690 01:17:57,273 --> 01:17:58,706 The waters all along 1691 01:17:58,775 --> 01:18:03,844 the west coast of Greenland were cool right up until 1997. 1692 01:18:03,846 --> 01:18:07,815 And in one sudden year, warm water arrived, 1693 01:18:07,817 --> 01:18:10,484 so it really correlates well 1694 01:18:10,486 --> 01:18:14,321 with this sudden jump and retreat of the glacier. 1695 01:18:18,761 --> 01:18:20,528 (iceberg rumbling) 1696 01:18:20,530 --> 01:18:22,997 JOHNSON: When the warm water reaches the calving front, 1697 01:18:22,999 --> 01:18:25,700 it melts the glacier from below, 1698 01:18:25,702 --> 01:18:29,804 causing the ice above to collapse. 1699 01:18:29,806 --> 01:18:32,006 Later in the summer, David and Denise 1700 01:18:32,008 --> 01:18:34,075 witnessed one of the biggest calving events 1701 01:18:34,077 --> 01:18:36,911 ever captured on camera. 1702 01:18:36,913 --> 01:18:38,913 Over a period of just 30 minutes, 1703 01:18:38,915 --> 01:18:41,182 this iceberg four miles across-- 1704 01:18:41,184 --> 01:18:43,884 half the length of Manhattan-- 1705 01:18:43,886 --> 01:18:46,253 broke off from the ice sheet. 1706 01:18:50,493 --> 01:18:52,593 As the glacier's calving edge erodes, 1707 01:18:52,662 --> 01:18:55,896 the huge mass of ice behind it can accelerate down the valley, 1708 01:18:55,965 --> 01:18:58,599 toward the sea. 1709 01:19:00,002 --> 01:19:01,602 And it's not just the ice in glaciers 1710 01:19:01,671 --> 01:19:04,238 that's reached a tipping point. 1711 01:19:04,307 --> 01:19:07,208 Millions of square miles of sea ice 1712 01:19:07,276 --> 01:19:09,777 that forms when the ocean surface freezes 1713 01:19:09,846 --> 01:19:14,915 in the polar regions is under threat. 1714 01:19:14,984 --> 01:19:19,053 Each year, the sea ice at the poles melts and refreezes 1715 01:19:19,122 --> 01:19:20,654 with the seasons, 1716 01:19:20,723 --> 01:19:24,859 growing in the winter and shrinking in the summer. 1717 01:19:24,927 --> 01:19:26,694 But over the last 40 years, 1718 01:19:26,763 --> 01:19:30,898 the area covered by summer sea ice has been getting smaller. 1719 01:19:30,967 --> 01:19:36,103 With real consequences for people living in the Arctic. 1720 01:19:36,172 --> 01:19:37,738 ♪ ♪ 1721 01:19:37,807 --> 01:19:39,807 This is Shishmaref, 1722 01:19:39,876 --> 01:19:44,578 a small island off the northwest coast of Alaska. 1723 01:19:45,515 --> 01:19:46,814 JOHNSON: You must be Corey, yeah? 1724 01:19:46,883 --> 01:19:49,183 Welcome to Shishmaref! 1725 01:19:49,252 --> 01:19:50,885 This is our ride? All right. 1726 01:19:50,953 --> 01:19:53,521 Looks good to me. 1727 01:19:53,589 --> 01:19:54,555 (engines starting) 1728 01:19:54,624 --> 01:19:58,592 ♪ ♪ 1729 01:19:58,661 --> 01:20:02,062 JOHNSON: This place really is the front line of climate change. 1730 01:20:02,131 --> 01:20:05,699 This little coastal town in Alaska is only 30 miles 1731 01:20:05,768 --> 01:20:08,769 south of the Arctic Circle. 1732 01:20:08,838 --> 01:20:11,672 About 600 Inupiat people live here in Shishmaref, 1733 01:20:11,741 --> 01:20:13,240 on the shore of the Chukchi Sea. 1734 01:20:14,977 --> 01:20:17,511 Sea ice used to hug the shores of this remote island 1735 01:20:17,580 --> 01:20:19,547 for ten months of the year. 1736 01:20:19,615 --> 01:20:22,883 This community depends on the ice 1737 01:20:22,952 --> 01:20:26,720 to hunt for walrus and bearded seals for their food. 1738 01:20:26,789 --> 01:20:29,423 We're here in summer, but summer's getting longer, 1739 01:20:29,492 --> 01:20:33,227 For people who depend on sea ice for their food, 1740 01:20:33,296 --> 01:20:34,528 that's a big problem. 1741 01:20:38,534 --> 01:20:40,801 What year were you born? 1942. 1742 01:20:40,870 --> 01:20:43,971 Born in a tent five miles from here. 1743 01:20:44,040 --> 01:20:45,439 Growing up, what do you remember 1744 01:20:45,508 --> 01:20:47,141 about sea ice when you were a kid? 1745 01:20:47,210 --> 01:20:48,876 Well... 1746 01:20:48,945 --> 01:20:53,147 all these years, you know, the sea ice was dependable. 1747 01:20:53,216 --> 01:20:55,516 It used to get real thick because it used to freeze 1748 01:20:55,585 --> 01:20:57,384 before Thanksgiving. 1749 01:20:57,453 --> 01:21:01,222 The sea ice has gotten thin 1750 01:21:01,290 --> 01:21:02,423 and freezes later. 1751 01:21:02,491 --> 01:21:04,658 Last year it froze in January-- 1752 01:21:04,727 --> 01:21:07,795 we had waves in January 1753 01:21:07,864 --> 01:21:09,763 and it doesn't get thick at all-- 1754 01:21:09,832 --> 01:21:11,198 it breaks up fast. 1755 01:21:11,267 --> 01:21:13,601 When's the ice usually go melt off? 1756 01:21:13,669 --> 01:21:17,438 It used to melt off end of June, 1757 01:21:17,506 --> 01:21:19,707 because on my birthday, June 26, we... 1758 01:21:19,775 --> 01:21:22,042 me and my dad and my grandpa 1759 01:21:22,111 --> 01:21:24,311 we used to be hunting amongst the ice. 1760 01:21:24,380 --> 01:21:29,750 Not anymore, it goes away June 6, June 9. 1761 01:21:29,819 --> 01:21:32,386 JOHNSON: When the ice is thin, 1762 01:21:32,455 --> 01:21:35,356 it's really dangerous for the hunters. 1763 01:21:35,424 --> 01:21:38,125 This is footage captured last winter 1764 01:21:38,194 --> 01:21:42,463 by a local drone pilot, Dennis Davis. 1765 01:21:42,531 --> 01:21:44,832 During the hunting season, he flies his drone 1766 01:21:44,901 --> 01:21:49,570 to help the villagers find the safest path across the sea ice. 1767 01:21:49,639 --> 01:21:51,972 So this was back... Oh wow. 1768 01:21:52,041 --> 01:21:53,340 ...January 14. Okay. 1769 01:21:53,409 --> 01:21:55,609 There's almost no ice at all! Yeah. 1770 01:21:55,678 --> 01:21:59,813 JOHNSON: It's like 50 feet of ice, not a mile and not 15 miles of ice. 1771 01:21:59,882 --> 01:22:01,682 DAVIS: This is as far as you can go. 1772 01:22:01,751 --> 01:22:02,816 Look at this, we'll zoom in. 1773 01:22:02,885 --> 01:22:04,451 You can't even see any ice out there. 1774 01:22:04,520 --> 01:22:07,087 DAVIS: As far as you can see, there's no ice-- 1775 01:22:07,156 --> 01:22:10,324 I mean there's thin ice, but there's no real, real ice. 1776 01:22:10,393 --> 01:22:11,659 All this ice out here, 1777 01:22:11,727 --> 01:22:13,661 it's supposed to be frozen solid, 1778 01:22:13,729 --> 01:22:16,030 between three and six feet thick. 1779 01:22:16,098 --> 01:22:18,933 Is that a kind of unusual condition for January? 1780 01:22:19,001 --> 01:22:21,335 DAVIS: It's starting to be a normal. 1781 01:22:21,404 --> 01:22:23,003 JOHNSON: Okay. 1782 01:22:23,072 --> 01:22:26,073 DAVIS: Where the ocean is open, when it's supposed to be frozen. 1783 01:22:26,142 --> 01:22:30,044 ♪ ♪ 1784 01:22:32,081 --> 01:22:36,317 JOHNSON: And it's not just the ice that's disappearing. 1785 01:22:36,385 --> 01:22:39,486 The permafrost underneath this village is also thawing. 1786 01:22:39,555 --> 01:22:43,290 Warmer oceans are creating more violent storms, 1787 01:22:43,359 --> 01:22:45,259 and without the sea ice to protect it, 1788 01:22:45,328 --> 01:22:47,628 this coastline is now eroding fast, 1789 01:22:47,697 --> 01:22:50,664 up to 50 feet in a single year. 1790 01:22:50,733 --> 01:22:54,268 Every now and then, another house falls into the sea. 1791 01:22:54,337 --> 01:22:56,603 ♪ ♪ 1792 01:22:56,672 --> 01:22:58,238 Mo Kiyutelluk's house... 1793 01:22:58,307 --> 01:22:59,440 Hey, Mo. 1794 01:22:59,508 --> 01:23:00,574 (voiceover): ...was very nearly one of them. 1795 01:23:00,643 --> 01:23:02,042 How's it going man? Good to see you. Hi! 1796 01:23:02,111 --> 01:23:03,911 So this is the spot where the house used to be, huh? 1797 01:23:03,980 --> 01:23:04,945 Yeah. 1798 01:23:05,014 --> 01:23:07,548 That was your house? 1799 01:23:07,616 --> 01:23:10,651 There was permafrost under that-- nothing but ice. 1800 01:23:10,720 --> 01:23:11,885 Yeah, yeah. 1801 01:23:11,954 --> 01:23:13,954 Then apparently when the... as it melted, 1802 01:23:14,023 --> 01:23:17,057 it, it just kept on falling off. 1803 01:23:17,126 --> 01:23:18,325 How did they save your house? 1804 01:23:18,394 --> 01:23:21,295 Whole town took part in pulling it. 1805 01:23:21,364 --> 01:23:22,963 What-- they were pulling it by hand? 1806 01:23:23,032 --> 01:23:25,232 Yeah, the whole town! (laughs) 1807 01:23:25,301 --> 01:23:29,136 And that kept it from toppling in. 1808 01:23:29,205 --> 01:23:30,437 So this is your house, huh? 1809 01:23:30,506 --> 01:23:31,572 KIYUTELLUK: That's the one. 1810 01:23:31,640 --> 01:23:32,539 You saved it 1811 01:23:32,608 --> 01:23:33,841 from the water and you moved it 1812 01:23:33,909 --> 01:23:35,542 a long ways away from the water. 1813 01:23:35,611 --> 01:23:38,779 JOHNSON: Mo's house may have been saved for now... 1814 01:23:38,848 --> 01:23:40,948 but the elders realize that Shishmaref will eventually 1815 01:23:41,017 --> 01:23:42,383 be swallowed by the sea. 1816 01:23:43,719 --> 01:23:47,221 For the villagers, it will mean the old ways 1817 01:23:47,289 --> 01:23:50,591 of walrus and seal hunting are fading. 1818 01:23:53,396 --> 01:23:57,197 They're planning to move to a new site on the mainland. 1819 01:23:57,266 --> 01:24:00,067 Here there are plenty of berries to pick. 1820 01:24:01,937 --> 01:24:05,572 Coastal hunters turned gatherers. 1821 01:24:05,641 --> 01:24:06,840 It's going to be a really different lifestyle 1822 01:24:06,909 --> 01:24:08,542 for these guys. I think so, yeah. 1823 01:24:08,611 --> 01:24:11,979 ♪ ♪ 1824 01:24:12,048 --> 01:24:15,749 JOHNSON: Shishmaref is just one example. 1825 01:24:15,818 --> 01:24:18,052 Communities all over the Arctic will need to adapt 1826 01:24:18,120 --> 01:24:19,753 to a different way of life. 1827 01:24:23,692 --> 01:24:26,260 So what's driving this dramatic transformation? 1828 01:24:28,864 --> 01:24:30,130 We've seen that sea ice is retreating 1829 01:24:30,199 --> 01:24:34,401 and ice sheets are shrinking. 1830 01:24:34,470 --> 01:24:35,602 The answer to why that is happening, though, 1831 01:24:35,671 --> 01:24:37,504 is actually held in the ice itself. 1832 01:24:37,573 --> 01:24:43,210 ♪ ♪ 1833 01:24:43,279 --> 01:24:47,815 At an Arctic base, scientists from all around the world 1834 01:24:47,883 --> 01:24:50,984 are analyzing ancient ice. 1835 01:24:51,053 --> 01:24:54,054 The East Greenland Ice Core Project, or EGRIP, 1836 01:24:54,123 --> 01:24:56,123 is a huge experiment to drill down into 1837 01:24:56,192 --> 01:24:59,860 one of the biggest pieces of ice on our planet. 1838 01:24:59,929 --> 01:25:04,131 They want to understand how it's flowing and changing. 1839 01:25:04,200 --> 01:25:07,301 Here, in the middle of the Greenland ice sheet, 1840 01:25:07,369 --> 01:25:11,672 glaciologist Jim White is one of the frontline polar scientists 1841 01:25:11,740 --> 01:25:16,076 trying to decipher the history of climate locked in the ice. 1842 01:25:16,145 --> 01:25:17,111 WHITE: Hey, chief! 1843 01:25:17,179 --> 01:25:18,479 How you doing, my man? 1844 01:25:18,547 --> 01:25:20,414 Good. Good to see you. Good to see you! 1845 01:25:20,483 --> 01:25:21,715 JOHNSON: We know that in the deep past, 1846 01:25:21,784 --> 01:25:23,684 carbon dioxide seeping out of the ground 1847 01:25:23,752 --> 01:25:26,487 warmed Earth and created a hothouse. 1848 01:25:26,555 --> 01:25:29,756 But what's been happening to our atmosphere lately? 1849 01:25:29,825 --> 01:25:32,493 (machine cranking) 1850 01:25:32,561 --> 01:25:37,698 Jim and his team drill cores from deep inside the ice sheet. 1851 01:25:37,766 --> 01:25:41,068 The rig sits 23 feet beneath the surface of the ice 1852 01:25:41,137 --> 01:25:42,936 to shield it from the weather, 1853 01:25:43,005 --> 01:25:48,208 but it can still reach 30 degrees below zero down here. 1854 01:25:48,277 --> 01:25:51,278 WHITE: We're looking at ice that's about 10,000, 11,000 years old. 1855 01:25:51,347 --> 01:25:53,814 You can actually see the annual layers, 1856 01:25:53,883 --> 01:25:56,116 even at this level. 1857 01:25:56,185 --> 01:26:00,220 JOHNSON: Each ice layer represents a single year of snowfall. 1858 01:26:00,289 --> 01:26:03,123 When snow compresses into ice, it traps air, 1859 01:26:03,192 --> 01:26:06,393 forming bubbles of ancient atmosphere 1860 01:26:06,462 --> 01:26:11,198 that preserve the exact conditions when the snow fell. 1861 01:26:11,267 --> 01:26:15,002 WHITE: This is from one of the cores we just brought up. 1862 01:26:15,070 --> 01:26:17,404 What you see in here are little bubbles of air-- 1863 01:26:17,473 --> 01:26:23,010 time capsules of the atmosphere from 5,000, 6,000 years ago. 1864 01:26:23,078 --> 01:26:25,145 We can take this ice back to a lab, crush it, 1865 01:26:25,214 --> 01:26:28,182 release the air and measure how much carbon dioxide 1866 01:26:28,250 --> 01:26:31,885 was in the atmosphere 10,000 years ago. 1867 01:26:31,954 --> 01:26:33,887 JOHNSON: Using ice cores from Greenland, 1868 01:26:33,956 --> 01:26:36,323 and even older ones Antarctica, 1869 01:26:36,392 --> 01:26:39,059 scientists are able to read ancient CO2 levels 1870 01:26:39,128 --> 01:26:42,262 that go back more than 800,000 years. 1871 01:26:42,331 --> 01:26:45,432 WHITE: Our planet over the last 800,000 years 1872 01:26:45,501 --> 01:26:47,935 has really behaved within two boundaries-- 1873 01:26:48,003 --> 01:26:49,403 an upper boundary of CO2 1874 01:26:49,471 --> 01:26:52,372 that has never gotten more than about 300 parts per million, 1875 01:26:52,441 --> 01:26:54,174 and a lower boundary that never got much below 1876 01:26:54,243 --> 01:26:56,009 180 parts per million. 1877 01:26:57,947 --> 01:27:01,215 JOHNSON: For the most part, the ups and downs in the CO2 1878 01:27:01,283 --> 01:27:03,584 seem to be in sync with the natural cycles 1879 01:27:03,652 --> 01:27:06,620 we see in our climate history. 1880 01:27:06,689 --> 01:27:10,824 But as we get into the more recent past, something changes. 1881 01:27:10,893 --> 01:27:13,660 The amount of CO2 that we've added to the atmosphere, 1882 01:27:13,729 --> 01:27:15,696 that's now raised us up to 400 parts per million, 1883 01:27:15,764 --> 01:27:19,700 that takes us way out of whatever boundaries existed 1884 01:27:19,768 --> 01:27:21,902 over the last 800,000 years. 1885 01:27:21,971 --> 01:27:24,371 This occurred since, basically, the industrial revolution. 1886 01:27:24,440 --> 01:27:26,773 So it's the last 150 years or so. 1887 01:27:26,842 --> 01:27:29,276 Mostly in the last 50 years. 1888 01:27:29,345 --> 01:27:31,378 At some point in the recent past, 1889 01:27:31,447 --> 01:27:34,248 human beings became demonstrably 1890 01:27:34,316 --> 01:27:36,750 the largest agent of change 1891 01:27:36,819 --> 01:27:39,286 when it comes to greenhouse gases on this planet 1892 01:27:39,355 --> 01:27:40,821 in the last million years. 1893 01:27:40,889 --> 01:27:42,422 ♪ ♪ 1894 01:27:42,491 --> 01:27:44,658 JOHNSON: Throughout most of Earth's history, 1895 01:27:44,727 --> 01:27:47,261 every time carbon dioxide goes up, 1896 01:27:47,329 --> 01:27:50,163 our climate gets warmer. 1897 01:27:50,232 --> 01:27:54,701 And it's this rapid rise of CO2 over the last 150 years 1898 01:27:54,770 --> 01:27:56,670 that's warming our planet 1899 01:27:56,739 --> 01:28:01,141 and causing the ice in our polar regions to melt. 1900 01:28:01,210 --> 01:28:07,948 The only difference is this time the source of the CO2 is us. 1901 01:28:08,017 --> 01:28:10,984 ♪ ♪ 1902 01:28:11,053 --> 01:28:14,388 But is it really possible that human activity can be producing 1903 01:28:14,456 --> 01:28:16,590 enough CO2 to change our atmosphere-- 1904 01:28:16,659 --> 01:28:20,761 and our climate-- so dramatically? 1905 01:28:20,829 --> 01:28:23,363 Many people find it hard to believe that humans 1906 01:28:23,432 --> 01:28:27,000 are acting as a geologic force, outstripping even volcanoes, 1907 01:28:27,069 --> 01:28:29,603 as a contributor to global climate change. 1908 01:28:29,672 --> 01:28:34,374 ♪ ♪ 1909 01:28:34,443 --> 01:28:36,176 Have you ever thought about how much carbon 1910 01:28:36,245 --> 01:28:38,312 is in a gallon of gasoline? 1911 01:28:38,380 --> 01:28:39,946 Let's weigh it and find out. 1912 01:28:41,850 --> 01:28:45,786 A gallon of gasoline weighs about 6.3 pounds; 1913 01:28:45,854 --> 01:28:47,154 87% of that is carbon. 1914 01:28:47,222 --> 01:28:48,822 And that means there's five pounds of carbon 1915 01:28:48,891 --> 01:28:52,059 in a gallon of gasoline. 1916 01:28:52,127 --> 01:28:55,329 Think of that like a five pound bag of charcoal briquettes. 1917 01:28:55,397 --> 01:28:57,764 (engine rumbles) 1918 01:29:02,538 --> 01:29:07,074 When you burn gasoline, you create carbon dioxide and water. 1919 01:29:07,142 --> 01:29:10,877 Carbon dioxide is an odorless, invisible gas, 1920 01:29:10,946 --> 01:29:12,479 but think about this: 1921 01:29:12,548 --> 01:29:14,214 what if the carbon came out of your tailpipe, 1922 01:29:14,283 --> 01:29:17,517 not as carbon dioxide, but as solid chunks of carbon? 1923 01:29:19,855 --> 01:29:23,223 Kind of like car turds. 1924 01:29:23,292 --> 01:29:24,324 So if the average American car 1925 01:29:24,393 --> 01:29:28,195 gets around 25 miles to the gallon, 1926 01:29:28,263 --> 01:29:30,597 that means that every 25 miles, 1927 01:29:30,666 --> 01:29:34,101 you're dumping five-pounds of car turds out of your tailpipe. 1928 01:29:35,504 --> 01:29:40,040 The average mileage for each car is about 12,000 miles a year, 1929 01:29:40,109 --> 01:29:44,344 so that releases over a ton of carbon. 1930 01:29:44,413 --> 01:29:46,980 In the U.S., there are a total 1931 01:29:47,049 --> 01:29:49,449 of about 100 million cars on the road, 1932 01:29:49,518 --> 01:29:53,420 releasing about 330,000 tons of carbon per day. 1933 01:29:53,489 --> 01:29:56,356 ♪ ♪ 1934 01:29:56,425 --> 01:30:00,727 When we include the rest of the world's one billion cars, 1935 01:30:00,796 --> 01:30:05,899 we reach three million tons of car turds every day. 1936 01:30:05,968 --> 01:30:08,168 And that's just cars. 1937 01:30:08,237 --> 01:30:12,305 When we add in power plants, factories, aviation, 1938 01:30:12,374 --> 01:30:16,576 and agriculture and multiply it by 365, 1939 01:30:16,645 --> 01:30:19,746 the total carbon released by human activities in a year 1940 01:30:19,815 --> 01:30:23,617 is a massive 12.5 billion tons-- 1941 01:30:23,685 --> 01:30:27,087 enough to leave a pile of car turds four miles across 1942 01:30:27,156 --> 01:30:30,524 and over a mile high. 1943 01:30:30,592 --> 01:30:32,659 (penguin squawking) 1944 01:30:32,728 --> 01:30:36,129 Many scientists say we've entered a new geologic age: 1945 01:30:36,198 --> 01:30:38,832 the Anthropocene, 1946 01:30:38,901 --> 01:30:42,869 with humans now altering Earth's climate on a geologic scale. 1947 01:30:42,938 --> 01:30:45,272 ♪ ♪ 1948 01:30:45,340 --> 01:30:49,042 But what exactly will all this carbon dioxide do to the planet? 1949 01:30:51,146 --> 01:30:54,247 Rocks and fossils help us piece together the surprising history 1950 01:30:54,316 --> 01:30:56,716 of our planet and its life. 1951 01:30:56,785 --> 01:31:02,522 But can they help us predict the future? 1952 01:31:02,591 --> 01:31:05,959 Today, the carbon dioxide levels are 410 parts per million. 1953 01:31:06,028 --> 01:31:08,094 When was it last about that level? 1954 01:31:08,163 --> 01:31:09,996 Oh, about three million years ago. 1955 01:31:10,065 --> 01:31:11,431 So let's go back three million years 1956 01:31:11,500 --> 01:31:13,099 and see what Earth was like then. 1957 01:31:13,168 --> 01:31:15,469 ♪ ♪ 1958 01:31:15,537 --> 01:31:19,406 Back then, though there was ice at the South Pole, 1959 01:31:19,475 --> 01:31:21,475 the North was mostly ice-free. 1960 01:31:21,543 --> 01:31:25,378 ♪ ♪ 1961 01:31:25,447 --> 01:31:29,182 So, what impact did this have on the world? 1962 01:31:30,719 --> 01:31:31,985 To find out, 1963 01:31:32,054 --> 01:31:36,656 we need fossil beds that date back to that time. 1964 01:31:36,725 --> 01:31:40,193 ♪ ♪ 1965 01:31:40,262 --> 01:31:43,430 There's one 90 miles inland from Virginia Beach. 1966 01:31:45,100 --> 01:31:47,100 There's lots of white, crumbly stuff in here. 1967 01:31:47,169 --> 01:31:48,602 MAUREEN RAYMO: Yeah. Yeah. 1968 01:31:48,670 --> 01:31:51,104 JOHNSON: Geologist Maureen Raymo studies places like this 1969 01:31:51,173 --> 01:31:55,509 to try to predict what a warmer climate might have in store. 1970 01:31:55,577 --> 01:31:57,944 RAYMO: Super cool. 1971 01:31:58,013 --> 01:31:59,579 They didn't build rock hammers for digging in clay, 1972 01:31:59,648 --> 01:32:01,081 I'll tell you that much. 1973 01:32:01,149 --> 01:32:03,817 JOHNSON: To find what Maureen's looking for, 1974 01:32:03,886 --> 01:32:05,685 we need to dig deeper. 1975 01:32:05,754 --> 01:32:07,821 (chuckling): And my rock hammer just isn't going to cut it. 1976 01:32:07,890 --> 01:32:09,089 (backhoe beeping) 1977 01:32:09,157 --> 01:32:11,358 RAYMO: Digging tool of choice. 1978 01:32:11,426 --> 01:32:14,060 JOHNSON: Yeah, beats a shovel doesn't it? 1979 01:32:14,129 --> 01:32:15,996 (laughing): Yeah. 1980 01:32:16,064 --> 01:32:18,231 JOHNSON: We're trying to reach a layer of mud that dates back 1981 01:32:18,300 --> 01:32:19,766 three million years. 1982 01:32:19,835 --> 01:32:23,136 Can you bring a chunk of that black stuff up off the bottom? 1983 01:32:23,205 --> 01:32:25,238 We'll just dump it on this side. 1984 01:32:25,307 --> 01:32:26,540 Just like a little scoop. 1985 01:32:26,608 --> 01:32:29,376 Ooh, yeah! Oh, look at that thing. 1986 01:32:29,444 --> 01:32:31,411 RAYMO: Every geology department should have one. 1987 01:32:31,480 --> 01:32:32,946 (Kirk chortling) 1988 01:32:33,015 --> 01:32:34,180 JOHNSON: Thanks to the backhoe, 1989 01:32:34,249 --> 01:32:35,882 we hit a fossil jackpot. 1990 01:32:35,951 --> 01:32:37,417 Hey, thanks! 1991 01:32:37,486 --> 01:32:38,418 That's perfect. 1992 01:32:38,487 --> 01:32:39,686 That's awesome. 1993 01:32:39,755 --> 01:32:41,955 RAYMO: Ooh! Look at that! 1994 01:32:42,024 --> 01:32:43,156 That's a perfect 1995 01:32:43,225 --> 01:32:46,593 three-million-year-old clam right there. 1996 01:32:46,662 --> 01:32:49,229 Oh man, that could have been, like, alive yesterday! 1997 01:32:49,298 --> 01:32:50,263 Yeah! 1998 01:32:50,332 --> 01:32:51,965 That's beautiful. 1999 01:32:52,034 --> 01:32:55,402 JOHNSON: Places like this are pretty special for paleontologists. 2000 01:32:55,470 --> 01:32:57,337 This is great. RAYMO (laughing): Yeah! 2001 01:32:57,406 --> 01:32:59,205 A window to the past. 2002 01:32:59,274 --> 01:33:00,373 We're on a beach. 2003 01:33:00,442 --> 01:33:02,175 We're on a beach three million years ago. 2004 01:33:02,244 --> 01:33:04,177 ♪ ♪ 2005 01:33:04,246 --> 01:33:06,479 JOHNSON: It's incredible to think that this quarry, 2006 01:33:06,548 --> 01:33:08,415 90 miles inland today, 2007 01:33:08,483 --> 01:33:13,987 was once a beach teeming with corals and other marine life. 2008 01:33:14,056 --> 01:33:19,292 There was warm ocean water lapping against this shore. 2009 01:33:19,361 --> 01:33:21,595 Warmer world, warmer fossils, coral reefs. 2010 01:33:21,663 --> 01:33:23,096 It's amazing. 2011 01:33:23,165 --> 01:33:25,899 RAYMO: It's right before we slid into the ice ages. 2012 01:33:25,968 --> 01:33:30,770 JOHNSON: It's just solid black mud, full of clams. 2013 01:33:30,839 --> 01:33:32,372 JOHNSON: Three million years ago, 2014 01:33:32,441 --> 01:33:34,808 when the Earth was three or four degrees warmer 2015 01:33:34,876 --> 01:33:37,177 and there was no ice in the Arctic, 2016 01:33:37,245 --> 01:33:39,613 a lot of the water that is now locked up in glaciers 2017 01:33:39,681 --> 01:33:41,548 was in the ocean, 2018 01:33:41,617 --> 01:33:46,453 which means that the global sea level was about 60 feet higher. 2019 01:33:46,521 --> 01:33:49,923 According to Maureen's calculations, 2020 01:33:49,992 --> 01:33:52,392 this is how the East Coast would have looked. 2021 01:33:53,528 --> 01:33:55,495 If Earth continues to warm, 2022 01:33:55,564 --> 01:33:57,764 the coastline will start moving inland, 2023 01:33:57,833 --> 01:34:02,469 as the ocean returns to places it covered long ago. 2024 01:34:02,537 --> 01:34:04,170 Yeah. It doesn't seem like much, 2025 01:34:04,239 --> 01:34:07,407 but it gets you back to a time when you had shorelines 2026 01:34:07,476 --> 01:34:09,976 that were 80 miles further inland. 2027 01:34:10,045 --> 01:34:12,045 Right. 2028 01:34:12,114 --> 01:34:14,414 JOHNSON: Three million years ago is the last time 2029 01:34:14,483 --> 01:34:18,385 the CO2 in the atmosphere was as high as it is today-- 2030 01:34:18,453 --> 01:34:22,188 over 400 parts per million. 2031 01:34:22,257 --> 01:34:24,624 This is our window into our future. 2032 01:34:24,693 --> 01:34:27,293 So, how come our present sea level isn't right here now? 2033 01:34:27,362 --> 01:34:29,129 The ice sheets are out of equilibrium 2034 01:34:29,197 --> 01:34:30,730 with the atmosphere right now. 2035 01:34:30,799 --> 01:34:31,831 The atmosphere's warming, 2036 01:34:31,900 --> 01:34:34,234 we're adding more CO2 every year. 2037 01:34:34,302 --> 01:34:36,770 You could think of them like a frozen lasagna 2038 01:34:36,838 --> 01:34:38,905 you put in a pre-heated oven. 2039 01:34:38,974 --> 01:34:41,641 You know, and the oven is our atmosphere, warmer, 2040 01:34:41,710 --> 01:34:43,943 and the ice sheets are melting just like the lasagna 2041 01:34:44,012 --> 01:34:45,812 would slowly melt, and it take a while. 2042 01:34:45,881 --> 01:34:47,647 So, in the same way the lasagna's eventually 2043 01:34:47,716 --> 01:34:49,215 going to be ready to eat, 2044 01:34:49,284 --> 01:34:50,450 we'll eventually have higher sea levels. 2045 01:34:50,519 --> 01:34:51,451 (chuckling): We will. 2046 01:34:51,520 --> 01:34:52,686 So, the real question is: 2047 01:34:52,754 --> 01:34:54,020 how long it takes 2048 01:34:54,089 --> 01:34:55,889 for the ice sheets to melt, which conditions, right? 2049 01:34:55,957 --> 01:34:57,090 RAYMO: Exactly. 2050 01:34:57,159 --> 01:34:59,492 That's the question that is driving research 2051 01:34:59,561 --> 01:35:00,827 all over the world. 2052 01:35:00,896 --> 01:35:03,830 ♪ ♪ 2053 01:35:03,899 --> 01:35:06,366 JOHNSON: Thanks to us, CO2 levels are now rising past 2054 01:35:06,435 --> 01:35:10,704 410 parts per million and beyond, 2055 01:35:10,772 --> 01:35:15,008 at a rate the planet hasn't seen for millions of years. 2056 01:35:15,077 --> 01:35:18,945 So, what happens to life when things warm up so quickly? 2057 01:35:19,014 --> 01:35:20,814 ♪ ♪ 2058 01:35:20,882 --> 01:35:23,817 It turns out that the planet ran a similar experiment 2059 01:35:23,885 --> 01:35:27,620 56 million years ago. 2060 01:35:27,689 --> 01:35:30,657 And the Bighorn Basin in Wyoming 2061 01:35:30,726 --> 01:35:33,393 holds the secrets to what unfolded. 2062 01:35:37,766 --> 01:35:40,633 It's also one of my favorite fossil-finding spots. 2063 01:35:40,702 --> 01:35:42,469 ♪ ♪ 2064 01:35:42,537 --> 01:35:44,938 I'm joining paleontologist Jonathan Bloch 2065 01:35:45,006 --> 01:35:46,639 to see what we can discover. 2066 01:35:46,708 --> 01:35:48,508 It's warm enough out here. 2067 01:35:48,577 --> 01:35:50,643 BLOCH: Yeah. 2068 01:35:50,712 --> 01:35:53,012 JOHNSON: It might look like barren scrubland today, 2069 01:35:53,081 --> 01:35:55,982 but the fossils here suggest that these Badlands 2070 01:35:56,051 --> 01:35:59,652 were once teeming with all sorts of creatures. 2071 01:35:59,721 --> 01:36:04,324 ♪ ♪ 2072 01:36:04,392 --> 01:36:06,693 That is a tiny little bone. 2073 01:36:06,762 --> 01:36:11,531 ♪ ♪ 2074 01:36:11,600 --> 01:36:14,067 Sometimes we just wash these little tiny fossils 2075 01:36:14,136 --> 01:36:16,603 in our mouths and hope that it's not 2076 01:36:16,671 --> 01:36:18,772 rabbit poop or something like that. 2077 01:36:18,840 --> 01:36:20,206 I keep finding primates. 2078 01:36:21,943 --> 01:36:23,910 Oh, yeah. What did you find? 2079 01:36:23,979 --> 01:36:28,314 Let me see, it's got... maybe it's a lizard. 2080 01:36:28,383 --> 01:36:30,116 I have a jaw here, if you want to see one. 2081 01:36:30,185 --> 01:36:32,485 Oh, cool. 2082 01:36:32,554 --> 01:36:34,387 BLOCH: This is a lemur-like primate. 2083 01:36:34,456 --> 01:36:35,755 Oh wow. 2084 01:36:35,824 --> 01:36:37,924 One of the first primates in North America. 2085 01:36:37,993 --> 01:36:39,893 I want to find my own jaw now. (chuckling): Yeah. 2086 01:36:39,961 --> 01:36:41,528 JOHNSON: Is that another primate? 2087 01:36:41,596 --> 01:36:42,695 BLOCH: Yeah. 2088 01:36:42,764 --> 01:36:46,032 I've found three primates so far. 2089 01:36:46,101 --> 01:36:48,034 JOHNSON: The fact that we're finding all these animals, 2090 01:36:48,103 --> 01:36:50,103 tells me that this landscape 2091 01:36:50,172 --> 01:36:52,839 used to look very different from today. 2092 01:36:54,442 --> 01:36:55,942 So where to from here? 2093 01:36:56,011 --> 01:36:57,277 Let's just keep following around this ridge. Other side? Okay. 2094 01:36:57,345 --> 01:37:00,480 JOHNSON: For a start, if there were primates, 2095 01:37:00,549 --> 01:37:03,316 there must have been trees. 2096 01:37:03,385 --> 01:37:05,985 Around 56 million years ago, 2097 01:37:06,054 --> 01:37:10,089 this stretch of Wyoming was a warm, lush floodplain, 2098 01:37:10,158 --> 01:37:15,261 covered in a subtropical forest of laurels, legumes, and palms-- 2099 01:37:15,330 --> 01:37:18,231 a bit like northern Florida today. 2100 01:37:19,601 --> 01:37:23,203 There's one animal that was very abundant in these forests. 2101 01:37:23,271 --> 01:37:25,071 If I just gave you one of these teeth, 2102 01:37:25,140 --> 01:37:27,740 you would be able to say, "Oh, that's a horse"? 2103 01:37:27,809 --> 01:37:29,809 Right, I could tell it was a horse just based on 2104 01:37:29,878 --> 01:37:32,045 the way the cusps and the crests are organized 2105 01:37:32,113 --> 01:37:33,346 on the crown of the molar. 2106 01:37:33,415 --> 01:37:35,048 The teeth would also tell you how big the animal was? 2107 01:37:35,116 --> 01:37:36,649 Right, so the first horses look just like 2108 01:37:36,718 --> 01:37:38,551 what you're holding there. Okay. 2109 01:37:38,620 --> 01:37:40,486 So you've got a jaw there with a bunch of teeth in it 2110 01:37:40,555 --> 01:37:41,821 that are the size of some of 2111 01:37:41,890 --> 01:37:44,123 our modern domestic dogs, maybe about this big. 2112 01:37:44,192 --> 01:37:45,925 By any standard it is a small horse. 2113 01:37:47,329 --> 01:37:49,929 JOHNSON: These are the earliest horses to evolve on Earth, 2114 01:37:49,998 --> 01:37:52,699 56 million years ago. 2115 01:37:52,767 --> 01:37:56,002 And they lived right here in Wyoming. 2116 01:37:56,071 --> 01:37:59,772 These first horses were much smaller than today's. 2117 01:37:59,841 --> 01:38:01,674 (pen scratching) 2118 01:38:01,743 --> 01:38:05,778 They had a short muzzle, and three- and four-toed padded feet 2119 01:38:05,847 --> 01:38:07,914 with hooves at the end of each toe, 2120 01:38:07,983 --> 01:38:10,450 perfect for browsing in the damp forests. 2121 01:38:10,518 --> 01:38:12,919 (birds chirping) 2122 01:38:12,988 --> 01:38:15,221 But not long after these early horses appeared, 2123 01:38:15,290 --> 01:38:19,025 something dramatic happened, 2124 01:38:19,094 --> 01:38:22,128 and the story is written in the rocks. 2125 01:38:22,197 --> 01:38:23,930 You can see this very strong red bed. 2126 01:38:23,999 --> 01:38:25,265 It's just like a red strike across the hill. 2127 01:38:25,333 --> 01:38:27,533 Very persistent, really strong, it's really notable. 2128 01:38:27,602 --> 01:38:29,235 That's really towards the end of the event here. 2129 01:38:29,304 --> 01:38:30,470 The beginning is... 2130 01:38:30,538 --> 01:38:32,906 you have to drop down about 50 feet over there 2131 01:38:32,974 --> 01:38:35,541 to get to where it starts and it's marked by 2132 01:38:35,610 --> 01:38:37,076 kind of a gray bed there. 2133 01:38:37,145 --> 01:38:39,479 This represents how much time? 2134 01:38:39,547 --> 01:38:42,382 It represents maybe between 100,000 and 150,000 years. 2135 01:38:42,450 --> 01:38:44,817 ♪ ♪ 2136 01:38:44,886 --> 01:38:49,622 JOHNSON: In the gray layer of rock is evidence of a cataclysmic event. 2137 01:38:49,691 --> 01:38:51,557 When CO2 levels tripled, 2138 01:38:51,626 --> 01:38:55,795 skyrocketing to as high as 2,000 parts per million, 2139 01:38:55,864 --> 01:38:57,964 the hothouse got even hotter. 2140 01:39:00,201 --> 01:39:02,035 And this had a surprising effect on the animals 2141 01:39:02,103 --> 01:39:03,403 that were living here, 2142 01:39:03,471 --> 01:39:06,639 especially the horses. 2143 01:39:06,708 --> 01:39:09,108 BLOCH: What was really exciting for us 2144 01:39:09,177 --> 01:39:11,177 was as we were collecting through these rocks 2145 01:39:11,246 --> 01:39:12,478 that are stacked up through time, 2146 01:39:12,547 --> 01:39:13,813 this is what they look like 2147 01:39:13,882 --> 01:39:16,582 when we found them at the base of the section. 2148 01:39:16,651 --> 01:39:18,084 As we kept following higher and higher, 2149 01:39:18,153 --> 01:39:20,219 we noticed the horses became smaller. 2150 01:39:20,288 --> 01:39:22,922 Smaller than small? 2151 01:39:22,991 --> 01:39:24,290 Quite a bit actually. 2152 01:39:24,359 --> 01:39:25,892 What, like, 30%? Maybe 30%? 2153 01:39:25,961 --> 01:39:27,794 Yeah. Yeah. 2154 01:39:27,862 --> 01:39:29,562 So, we're going from like a cocker spaniel to a chihuahua 2155 01:39:29,631 --> 01:39:30,830 or something like that? Right. 2156 01:39:30,899 --> 01:39:32,665 But we found lots of them, hundreds of fossils, 2157 01:39:32,734 --> 01:39:34,233 and they... they show that pattern. 2158 01:39:34,302 --> 01:39:35,702 So it's a real pattern that emerged. 2159 01:39:35,770 --> 01:39:37,603 So, the big question was... 2160 01:39:37,672 --> 01:39:39,706 Why did these small horses get smaller? 2161 01:39:39,774 --> 01:39:41,774 Right. What we can tell through 2162 01:39:41,843 --> 01:39:44,277 the same interval of time as they're getting smaller 2163 01:39:44,346 --> 01:39:46,245 is that it's getting a lot warmer. 2164 01:39:46,314 --> 01:39:47,280 Global warming seems to be 2165 01:39:47,349 --> 01:39:49,215 controlling the size of the horses. 2166 01:39:49,284 --> 01:39:52,418 JOHNSON: Over just a few thousand years, 2167 01:39:52,487 --> 01:39:54,988 rapid warming turned the lush vegetation, 2168 01:39:55,056 --> 01:39:57,123 from subtropical wetlands 2169 01:39:57,192 --> 01:40:00,159 to drier forests. 2170 01:40:00,228 --> 01:40:02,161 Even minor variations in temperature 2171 01:40:02,230 --> 01:40:04,664 cause very rapid evolutionary change. 2172 01:40:04,733 --> 01:40:07,433 (pen scratching) 2173 01:40:07,502 --> 01:40:11,037 On land, horses and other mammals became smaller. 2174 01:40:13,842 --> 01:40:17,276 There's an evolutionary advantage: 2175 01:40:17,345 --> 01:40:20,780 smaller bodies lose heat more quickly. 2176 01:40:20,849 --> 01:40:23,649 In the oceans, warmer, more acidic conditions 2177 01:40:23,718 --> 01:40:28,755 wiped out many marine species completely. 2178 01:40:28,823 --> 01:40:30,356 This is one of the fastest warming events 2179 01:40:30,425 --> 01:40:32,492 we see in the fossil record. 2180 01:40:32,560 --> 01:40:35,528 And what scares me is that we're now warming up 2181 01:40:35,597 --> 01:40:37,730 our planet even faster. 2182 01:40:37,799 --> 01:40:39,165 So one of the challenges for you 2183 01:40:39,234 --> 01:40:41,934 is to understand just how similar this is 2184 01:40:42,003 --> 01:40:43,870 to our present situation? Right. 2185 01:40:43,938 --> 01:40:46,105 And I guess in terms of what it does to the animals and plants? 2186 01:40:46,174 --> 01:40:48,007 Right, that's exactly correct. 2187 01:40:48,076 --> 01:40:50,109 And that's why it's important to look throughout Earth's history 2188 01:40:50,178 --> 01:40:51,444 at events like this 2189 01:40:51,513 --> 01:40:53,913 to look to see if there are any rules governing, 2190 01:40:53,982 --> 01:40:56,616 you know, how plants and animals might respond to climate change 2191 01:40:56,684 --> 01:40:58,518 to help inform us about the things we might be able 2192 01:40:58,586 --> 01:40:59,552 to expect in the future. 2193 01:40:59,621 --> 01:41:03,456 ♪ ♪ 2194 01:41:03,525 --> 01:41:07,093 JOHNSON: What happened back then took tens of thousands of years. 2195 01:41:07,162 --> 01:41:09,462 ♪ ♪ 2196 01:41:09,531 --> 01:41:11,697 The warming on our planet today is happening 2197 01:41:11,766 --> 01:41:13,499 over just a few hundred years. 2198 01:41:13,568 --> 01:41:16,669 ♪ ♪ 2199 01:41:16,738 --> 01:41:19,105 Are we on our way to ending today's icehouse 2200 01:41:19,174 --> 01:41:22,942 moving into a hothouse, with no ice on the poles, 2201 01:41:23,011 --> 01:41:26,779 for the first time in human history? 2202 01:41:26,848 --> 01:41:29,715 If that happens, it's not just the wild, 2203 01:41:29,784 --> 01:41:32,518 natural world that will be transformed, 2204 01:41:32,587 --> 01:41:36,322 with species disappearing forever. 2205 01:41:36,391 --> 01:41:38,024 The crops we depend on for food 2206 01:41:38,093 --> 01:41:43,763 will be vulnerable to the extreme hothouse weather. 2207 01:41:43,832 --> 01:41:46,766 And with all of Antarctica's ice melted, 2208 01:41:46,835 --> 01:41:48,501 sea levels around the globe 2209 01:41:48,570 --> 01:41:50,770 could rise by more than 200 feet. 2210 01:41:50,839 --> 01:41:53,806 But we wouldn't even need to go all the way back 2211 01:41:53,875 --> 01:41:56,409 to a full hothouse Earth to feel the effects. 2212 01:41:56,478 --> 01:42:01,514 Just melting Greenland and some of Antarctica 2213 01:42:01,583 --> 01:42:03,416 would move the shoreline far enough inland 2214 01:42:03,485 --> 01:42:05,251 to flood major cities 2215 01:42:05,320 --> 01:42:07,687 like Washington, DC, 2216 01:42:07,755 --> 01:42:09,021 London, 2217 01:42:09,090 --> 01:42:11,224 and Shanghai; 2218 01:42:11,292 --> 01:42:15,661 and to cover an awful lot of Florida. 2219 01:42:15,730 --> 01:42:19,432 Today, we are approaching a tipping point. 2220 01:42:19,501 --> 01:42:22,635 But how close are we? 2221 01:42:24,105 --> 01:42:26,439 Hidden deep in the Canadian Rockies is a place 2222 01:42:26,508 --> 01:42:29,442 that could give us an early warning of what lies ahead. 2223 01:42:29,511 --> 01:42:33,446 It's a unique cave that for geologists 2224 01:42:33,515 --> 01:42:36,349 could act like a canary in the coal mine. 2225 01:42:37,852 --> 01:42:41,821 Although I'm a thousand miles south of the Arctic Circle, 2226 01:42:41,890 --> 01:42:45,391 this cave stays cold all year round. 2227 01:42:45,460 --> 01:42:48,161 The rock and soil beneath the surface are permanently frozen 2228 01:42:48,229 --> 01:42:49,529 all through the summer. 2229 01:42:49,597 --> 01:42:51,130 (metal rattling) 2230 01:42:51,199 --> 01:42:53,499 I'm here with geologist Jeremy Shakun 2231 01:42:53,568 --> 01:42:57,136 and mountain guide Dave Stark. 2232 01:42:57,205 --> 01:42:58,271 SHAKUN: Getting a little tight, huh? 2233 01:42:58,339 --> 01:43:00,439 JOHNSON: I'm crawling already. 2234 01:43:00,508 --> 01:43:03,176 The ground inside this cave has been frozen 2235 01:43:03,244 --> 01:43:05,578 since the last ice age. 2236 01:43:05,647 --> 01:43:08,481 This is 10,000 years of permafrost. 2237 01:43:08,550 --> 01:43:10,216 SHAKUN: You can feel it getting cold fast. 2238 01:43:10,285 --> 01:43:11,450 JOHNSON: Yeah. 2239 01:43:11,519 --> 01:43:12,818 (voiceover): To preserve this unique cave, 2240 01:43:12,887 --> 01:43:14,253 it's closed to the public. 2241 01:43:15,557 --> 01:43:19,125 Even scientists restrict their visits to once every few years. 2242 01:43:19,194 --> 01:43:21,894 This is really cool back in here now, it's opening up. 2243 01:43:23,064 --> 01:43:24,897 Whoa! Look at this chamber! 2244 01:43:24,966 --> 01:43:30,069 Now we're in an auditorium, with a ginormous rock fall. 2245 01:43:30,138 --> 01:43:32,505 Wow. 2246 01:43:32,574 --> 01:43:35,641 15 minutes in, and there's a spectacular change. 2247 01:43:35,710 --> 01:43:38,744 Oh my God, look at this! 2248 01:43:38,813 --> 01:43:40,713 You crawl in hands and knees. Okay. 2249 01:43:40,782 --> 01:43:43,482 Watch your heads, I'll go in first. 2250 01:43:43,551 --> 01:43:45,785 Cold knees. 2251 01:43:45,853 --> 01:43:48,821 JOHNSON: It's like a gigantic igloo! 2252 01:43:48,890 --> 01:43:50,556 How deep is the ice you're crawling on? 2253 01:43:50,625 --> 01:43:53,626 SHAKUN: I don't know, but you can see way down. 2254 01:43:53,695 --> 01:43:56,362 JOHNSON: Oh God! Holy moly. 2255 01:43:58,633 --> 01:43:59,732 Be careful. 2256 01:43:59,801 --> 01:44:01,367 SHAKUN: You got to see these. 2257 01:44:01,436 --> 01:44:04,637 Super weird. 2258 01:44:04,706 --> 01:44:06,772 ♪ ♪ 2259 01:44:06,841 --> 01:44:09,175 It's like-- Oh (bleep)! 2260 01:44:09,244 --> 01:44:10,209 (laughs) 2261 01:44:10,278 --> 01:44:12,078 SHAKUN: That's crazy though. 2262 01:44:12,146 --> 01:44:14,080 I mean this is like... 2263 01:44:14,148 --> 01:44:17,250 it's like being inside rock candy. 2264 01:44:17,318 --> 01:44:20,786 JOHNSON: This is unbelievable. 2265 01:44:20,855 --> 01:44:22,722 This is one of the most amazing places I've ever been 2266 01:44:22,790 --> 01:44:24,190 on this planet. 2267 01:44:25,960 --> 01:44:27,593 (voiceover): The ground's so cold here, 2268 01:44:27,662 --> 01:44:30,830 any moisture in the air freezes to the cave walls, 2269 01:44:30,898 --> 01:44:33,499 forming enormous crystals of ice. 2270 01:44:33,568 --> 01:44:35,501 They're... but they're big, they're like five inches across. 2271 01:44:35,570 --> 01:44:37,003 SHAKUN: Like the size of your hand, right? 2272 01:44:37,071 --> 01:44:38,738 JOHNSON: I've never seen ice crystals like this. 2273 01:44:38,806 --> 01:44:40,006 SHAKUN: No. 2274 01:44:40,074 --> 01:44:43,242 There's some that are like big dinner plates. 2275 01:44:43,311 --> 01:44:46,712 I feel like I'm in a crystal chandelier factory. 2276 01:44:46,781 --> 01:44:48,614 This stuff looks like glass, not ice. 2277 01:44:48,683 --> 01:44:52,752 ♪ ♪ 2278 01:44:52,820 --> 01:44:54,787 Holy cow! 2279 01:44:58,026 --> 01:44:59,392 (laughing): This place 2280 01:44:59,460 --> 01:45:02,962 is so totally amazing, I can hardly believe it. 2281 01:45:03,031 --> 01:45:08,000 ♪ ♪ 2282 01:45:08,069 --> 01:45:10,670 SHAKUN: And actually it's pretty crazy, some of these 2283 01:45:10,738 --> 01:45:13,339 are dripping just a little bit. 2284 01:45:13,408 --> 01:45:14,707 JOHNSON: It's very clear 2285 01:45:14,776 --> 01:45:16,375 that just our bodies in here, if we stay much longer, 2286 01:45:16,444 --> 01:45:18,377 are going to change the temperature of this place. 2287 01:45:18,446 --> 01:45:21,681 And we're looking at kind of a remnant of an ice world. 2288 01:45:21,749 --> 01:45:22,982 SHAKUN: Yup. 2289 01:45:23,051 --> 01:45:25,685 It's... it's amazing, this is an ice world 2290 01:45:25,753 --> 01:45:28,154 that's changed into a non-ice world. 2291 01:45:28,222 --> 01:45:30,990 Let's, uh... let's duck and go. 2292 01:45:31,059 --> 01:45:33,492 (microphone rumbling) All right... 2293 01:45:33,561 --> 01:45:35,127 Stay low. 2294 01:45:35,196 --> 01:45:37,897 JOHNSON: This crystal cavern is a reminder 2295 01:45:37,965 --> 01:45:40,099 that we are still living in an icehouse world, 2296 01:45:40,168 --> 01:45:45,304 but it looks fragile, on the cusp of change. 2297 01:45:45,373 --> 01:45:47,940 This is treacherous going in here, man. 2298 01:45:48,009 --> 01:45:49,942 SHAKUN: Slick rock. 2299 01:45:50,011 --> 01:45:52,578 JOHNSON: Slick, jagged, loose rock. 2300 01:45:52,647 --> 01:45:54,714 (voiceover): If we go deeper into the cave system, 2301 01:45:54,782 --> 01:45:58,184 we can see what happened when it warmed in the past. 2302 01:45:58,252 --> 01:45:59,652 So, the farther back in the cave, 2303 01:45:59,721 --> 01:46:01,554 the further back we go in time. 2304 01:46:01,622 --> 01:46:03,622 SHAKUN: Yep. 2305 01:46:03,691 --> 01:46:05,257 JOHNSON: Wow. 2306 01:46:05,326 --> 01:46:08,728 SHAKUN: Oh, wow, that is totally peeling away from the ceiling. 2307 01:46:08,796 --> 01:46:11,330 Like right over your head. 2308 01:46:11,399 --> 01:46:16,402 Right, like this ice at our feet, 2309 01:46:16,471 --> 01:46:17,770 seems like it came from up there. 2310 01:46:17,839 --> 01:46:21,273 (quietly): Wow, that's crazy. 2311 01:46:21,342 --> 01:46:24,577 JOHNSON: In here, we find the flip side of the ice chandeliers, 2312 01:46:24,645 --> 01:46:27,580 evidence from a warmer inter-glacial world, 2313 01:46:27,648 --> 01:46:30,049 the last time this crystal cave melted. 2314 01:46:30,118 --> 01:46:35,287 SHAKUN: See, that's the kind of stuff that would be so cool to date. 2315 01:46:35,356 --> 01:46:37,390 This is the stuff that gives us a glimpse into 2316 01:46:37,458 --> 01:46:38,357 a past warmer world 2317 01:46:38,426 --> 01:46:40,159 when this whole cave was thawed out 2318 01:46:40,228 --> 01:46:41,394 and there wasn't any ice. 2319 01:46:41,462 --> 01:46:43,396 It's not forming now because it's cold in here 2320 01:46:43,464 --> 01:46:44,663 and we don't have running water. 2321 01:46:44,732 --> 01:46:46,365 But if we were in some warm time in the past 2322 01:46:46,434 --> 01:46:47,566 when this cave was thawed, 2323 01:46:47,635 --> 01:46:49,402 so the water comes down from the surface above, 2324 01:46:49,470 --> 01:46:50,803 dissolves some of that rock, 2325 01:46:50,872 --> 01:46:53,205 you'd have sheets of water running down this 2326 01:46:53,274 --> 01:46:55,508 and it has little minerals dissolved in it, 2327 01:46:55,576 --> 01:46:56,642 and when they run down the surface, 2328 01:46:56,711 --> 01:46:58,577 they deposit these crystals. 2329 01:46:58,646 --> 01:47:00,413 And layer by layer they build this thing up. 2330 01:47:00,481 --> 01:47:01,580 JOHNSON: There're beautiful things. 2331 01:47:01,649 --> 01:47:02,782 Oh, it's awesome, So let me show you this. 2332 01:47:02,850 --> 01:47:05,418 Check this out here. 2333 01:47:05,486 --> 01:47:07,586 Here's a flow stone that's actually from this cave. 2334 01:47:07,655 --> 01:47:08,621 It looks like toffee. 2335 01:47:08,689 --> 01:47:10,222 Yeah, absolutely, right? 2336 01:47:10,291 --> 01:47:12,258 Layers of caramel-colored stuff in there, right? Absolutely. 2337 01:47:12,326 --> 01:47:14,693 SHAKUN: And so the way this one worked is, 2338 01:47:14,762 --> 01:47:17,229 oldest right here, and then with time 2339 01:47:17,298 --> 01:47:19,498 it kept adding more and more and more layers to it. 2340 01:47:19,567 --> 01:47:20,866 So it would have been something, you know, 2341 01:47:20,935 --> 01:47:22,168 growing like that out of the wall. 2342 01:47:22,236 --> 01:47:23,335 I got you. 2343 01:47:23,404 --> 01:47:25,971 And just layer upon layer gets added. 2344 01:47:26,040 --> 01:47:27,273 JOHNSON: What are you measuring? 2345 01:47:27,341 --> 01:47:28,574 So, basically, we're measuring 2346 01:47:28,643 --> 01:47:29,875 when there's water flowing right? Okay. 2347 01:47:29,944 --> 01:47:32,311 It tells us when this thing was growing. 2348 01:47:32,380 --> 01:47:33,312 Like this one, for instance, 2349 01:47:33,381 --> 01:47:35,247 from this cave, we dated it. 2350 01:47:35,316 --> 01:47:37,116 It's 400,000 years old. 2351 01:47:37,185 --> 01:47:38,751 400,000? 400,000. 2352 01:47:38,820 --> 01:47:41,086 How much warmer was it 400,000 years ago? 2353 01:47:41,155 --> 01:47:42,621 How much heating did it take 2354 01:47:42,690 --> 01:47:45,324 to thaw out this permafrost? 2355 01:47:45,393 --> 01:47:46,358 What's the danger line? 2356 01:47:46,427 --> 01:47:48,761 And, interestingly, 400,000 years ago, 2357 01:47:48,830 --> 01:47:49,962 the world was warmer, 2358 01:47:50,031 --> 01:47:51,931 but just like a couple degrees. 2359 01:47:51,999 --> 01:47:53,732 It's sort of like the where we expect to be 2360 01:47:53,801 --> 01:47:55,801 middle, later part of this century. 2361 01:47:55,870 --> 01:47:57,503 ♪ ♪ 2362 01:47:57,572 --> 01:48:00,573 JOHNSON: If history repeats itself, the permafrost in this cave 2363 01:48:00,641 --> 01:48:03,209 could be on the brink of melting again. 2364 01:48:04,812 --> 01:48:06,278 SHAKUN: What's wild about it is it contains 2365 01:48:06,347 --> 01:48:09,882 a ton of frozen carbon, um, and it's, it's a ton. 2366 01:48:09,951 --> 01:48:12,818 It's twice as much carbon as already in the atmosphere. 2367 01:48:12,887 --> 01:48:14,653 But were is that carbon coming from? 2368 01:48:14,722 --> 01:48:17,056 It's just old dead stuff. 2369 01:48:17,124 --> 01:48:20,092 It's just old plants and animals that at one point were alive. 2370 01:48:20,161 --> 01:48:21,460 They have carbon in them, they die, 2371 01:48:21,529 --> 01:48:22,828 it goes down into that soil. 2372 01:48:22,897 --> 01:48:25,598 So, right now, it's frozen, it's turned off, 2373 01:48:25,666 --> 01:48:26,799 it's not going anywhere 2374 01:48:26,868 --> 01:48:28,601 until you dial up the temperature a little bit. 2375 01:48:28,669 --> 01:48:29,835 Open the freezer door, 2376 01:48:29,904 --> 01:48:31,203 it starts to melt... 2377 01:48:31,272 --> 01:48:33,005 And all that meat will just start rotting. 2378 01:48:33,074 --> 01:48:36,275 Burping out methane and warming things up even more. 2379 01:48:36,344 --> 01:48:39,678 How much global warming can you do before these caves, 2380 01:48:39,747 --> 01:48:40,946 this Arctic permafrost, 2381 01:48:41,015 --> 01:48:42,414 thaws out? Right. 2382 01:48:42,483 --> 01:48:44,283 And it was dripping when we walked in here. 2383 01:48:44,352 --> 01:48:45,651 Yeah. 2384 01:48:45,720 --> 01:48:47,920 Which I think means we're tipping back. 2385 01:48:47,989 --> 01:48:49,321 Come back in 50 years or something 2386 01:48:49,390 --> 01:48:51,657 and these things are going to be regrowing again. 2387 01:48:51,726 --> 01:48:52,658 Okay, yikes. Yeah. 2388 01:48:52,727 --> 01:48:54,460 Yeah, that's serious. Yeah. 2389 01:48:54,529 --> 01:48:57,129 ♪ ♪ 2390 01:48:57,198 --> 01:48:59,765 JOHNSON: If the permafrost thaws in here, 2391 01:48:59,834 --> 01:49:03,936 and across all the frozen land at the polar extremes, 2392 01:49:04,005 --> 01:49:08,107 a massive release of methane and CO2 will speed up global warming 2393 01:49:08,175 --> 01:49:10,042 all over the planet, 2394 01:49:10,111 --> 01:49:13,445 creating an unprecedented threat to humanity. 2395 01:49:13,514 --> 01:49:17,016 ♪ ♪ 2396 01:49:17,084 --> 01:49:21,287 There have been thousands of generations of humans, 2397 01:49:21,355 --> 01:49:23,255 and here I sit at the moment 2398 01:49:23,324 --> 01:49:25,891 that humans have flipped the switch 2399 01:49:25,960 --> 01:49:29,895 that might take planet Earth from an icehouse climate 2400 01:49:29,964 --> 01:49:33,566 to a hothouse climate. 2401 01:49:33,634 --> 01:49:37,269 The clues to what could happen next are out there, 2402 01:49:37,338 --> 01:49:41,206 hidden in the most remote spots of the Arctic 2403 01:49:41,275 --> 01:49:44,977 and the Antarctic. 2404 01:49:45,046 --> 01:49:47,479 Wow! This is... this is amazing. 2405 01:49:47,548 --> 01:49:49,448 ♪ ♪ 2406 01:49:49,517 --> 01:49:51,850 JOHNSON: This has been an amazing journey, 2407 01:49:51,919 --> 01:49:54,587 from pole to pole and back in time. 2408 01:49:54,655 --> 01:49:56,121 ♪ ♪ 2409 01:49:56,190 --> 01:49:59,625 We've seen climates were much warmer than they are today 2410 01:49:59,694 --> 01:50:00,926 and much colder. 2411 01:50:00,995 --> 01:50:04,597 ♪ ♪ 2412 01:50:04,665 --> 01:50:06,332 We've seen that in the past, 2413 01:50:06,400 --> 01:50:08,233 more carbon dioxide... 2414 01:50:08,302 --> 01:50:10,135 Perfect three-million-year-old clam right there! 2415 01:50:10,204 --> 01:50:12,838 (voiceover): ...warmed the planet 2416 01:50:12,907 --> 01:50:15,674 and raised sea levels. 2417 01:50:15,743 --> 01:50:17,977 These snapshots from Earth's history 2418 01:50:18,045 --> 01:50:20,679 show us the direction we could be heading. 2419 01:50:20,748 --> 01:50:22,715 ♪ ♪ 2420 01:50:22,783 --> 01:50:26,452 Now we have to ask ourselves: is this the world we want? 2421 01:50:27,655 --> 01:50:30,856 There's almost no ice at all. 2422 01:50:30,925 --> 01:50:34,994 Humans are geology, we are impacting this planet. 2423 01:50:35,062 --> 01:50:38,263 And the future is dramatically uncertain. 2424 01:50:38,332 --> 01:50:41,734 ♪ ♪ 2425 01:50:41,802 --> 01:50:45,004 It's the first time that a mammal has actually changed 2426 01:50:45,072 --> 01:50:46,672 the composition of the earth's atmosphere 2427 01:50:46,741 --> 01:50:51,343 and driven a dramatic change in the earth's climate. 2428 01:50:51,412 --> 01:50:53,946 It's us. 2429 01:50:54,015 --> 01:50:55,848 The question is: 2430 01:50:55,916 --> 01:50:58,917 are we clever enough and forward-thinking enough 2431 01:50:58,986 --> 01:51:01,186 to flip that switch back? 2432 01:51:01,255 --> 01:51:07,192 ♪ ♪ 2433 01:51:17,972 --> 01:51:21,707 ♪ ♪ 2434 01:51:33,220 --> 01:51:35,187 To order this program on DVD, 2435 01:51:35,256 --> 01:51:40,259 visit ShopPBS or call 1-800-PLAY-PBS. 2436 01:51:40,327 --> 01:51:43,095 Episodes of "NOVA" are available with Passport. 2437 01:51:43,164 --> 01:51:46,632 "NOVA" is also available on Amazon Prime Video. 2438 01:51:46,701 --> 01:51:51,537 ♪ ♪