11,000 years ago, much of the world we know was cold - really cold. Glaciers covered Scotland, Scandinavia, Russia, New England, New York, and much of the upper Midwest in what is today the United States.
Scientists have long suspected that carbon dioxide helped warm the earth and end the Ice Age, but they also knew Earth warmed before atmospheric CO₂ increased. Antarctic ice sampling is one of the most commonly-used methods of studying climate history.
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"So which came first in the Antarctic, warming or CO₂?" NPR wrote.
A new theory suggests that a wobble in Earth's gyration may have exposed the Arctic ice caps to the sun, melting ice which entered the oceanic "conveyor belt" that affects climate by circulating different-temperature waters around the globe, according to NPR.
The fresh water entered in a particularly crucial part of the conveyor belt — the North Atlantic — gumming up the gears, causing warm water to stay near Antarctica.
"Eventually, ocean currents and wind patterns changed and carbon dioxide rose up out of the Southern oceans and into the atmosphere," NPR wrote.
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The report, published this week in the journal Nature, "offers a response to those skeptical about human-caused global warming," who have pointed out that CO₂ rose after Earth began to warm, according to The Christian Science Monitor.
The "research found that the amount of CO₂ it took to end the ice age is about the same amount as humans have added to the atmosphere in the past century," NPR wrote.