Discussion of climate change today makes people think global warming. About 13,000 years ago, though, Earth’s climate shifted abruptly in the other direction. Temperatures dropped 14 degrees Fahrenheit on average in parts of the Northern Hemisphere within just a couple of years.
Scientists have different ideas why, but evidence is mounting that the crash of an asteroid or comet into our planet triggered the cooling. University of South Carolina archaeologist Christopher Moore examined the muck from the bottom of a nearby lake for clues about what could have caused the temperature drop. What he found in the sediment layers – some of which had been down there at least 20,000 years – adds support to the idea that an extraterrestrial impact is to blame.
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The muck that’s been accumulating at the bottom of this lake for 20,000 years is like a climate time capsule.
Christopher R. Moore
Christopher R. Moore, University of South Carolina
Why did Earth's climate rapidly cool 12,800 years ago? Evidence is mounting that a comet or asteroid collision is to blame, with new support coming from the bottom of a South Carolina lake.
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Politics + Society
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Jeremy Wildeman, University of Bath
For international observers, it may be stunning to see Justin Trudeau's government reduced to a minority after his meteoric rise to power in 2015. It happened because he disappointed his progressive base.
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Bernd Reiter, University of South Florida
Randomly selecting citizens to take turns governing offers the promise of reinvigorating struggling democracies, making them more responsive to citizen needs and preferences.
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Joseph Cabosky, University of North Carolina at Chapel Hill
Millennials are now between about 23 and 38 -- and the group is more diverse than it often gets credit for.
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From our international editions
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Felicia Vachon, Dalhousie University
Do animals have their own culture? A researcher studying the culture of whales argues that they do. She says understanding that may be one way to save them from extinction.
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Rebecca Ananian-Welsh, The University of Queensland
Our national security laws are uniquely broad and complex – and media freedom too often becomes entangled in them. It's time to enshrine this freedom as a central part of our democracy.
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Amelia Hadfield, University of Surrey
MPs were supposed to vote either for or against the prime minister's deal in a special weekend session. But things didn't quite work out like that.
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