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We are all seeing rather less of the Sun. Scientists looking at five decades of sunlight measurements have reached the disturbing conclusion that the amount of solar energy reaching the Earth's surface has been gradually falling. Paradoxically, the decline in sunlight may mean that global warming is a far greater threat to society than previously thought.
No season brings more surprises than an Alaskan summer. It lures hummingbirds up from the tropics, exposes deserts in the Arctic and relies on parachuting firefighters to tackle forest fires in its vast wilderness. Summer is a narrow window of plenty, when the land is bathed in 24-hour sunlight - but in this land of extremes, you can have too much of a good thing.
NASA satellites have mapped Earth's gravity and discovered mysterious spots where gravity is weaker; how earthquakes change the planet's gravitational field.
S1E5 • Secrets of the Earth • 2013 • Environment
All over the world, scientists are discovering traces of ancient floods on a scale that dwarfs even the most severe flood disasters of recent times. What triggered these cataclysmic floods, and could they strike again? In the Channeled Scablands of Washington State, the level prairie gives way to bizarre, gargantuan rock formations: house-sized boulders seemingly dropped from the sky, a cliff carved by a waterfall twice the height of Niagara, and potholes large enough to swallow cars. Like forensic detectives at a crime scene, geologists study these strange features and reconstruct catastrophic Ice Age floods more powerful than all the world’s top ten rivers combined. NOVA follows their efforts to uncover the geologic fingerprints of other colossal megafloods in Iceland and, improbably, on the seabed of the English Channel. There, another deluge smashed through a land bridge connecting Britain and France hundreds of thousands of years ago and turned Britain into an island for the first time. These great disasters ripped through terrain and transformed continents in a matter of hours—and similar forces reawakened by climate change are posing an active threat to mountain communities throughout the world today.
NOVA PBS • 2017 • Environment
