In Hot Water: Ice Age Defrosted By Warming Ocean

Warmer waters in the deep Pacific triggered the end of the last ice age, preceding the rise in greenhouse gas levels.Earth's climate can be sensitive, changing after a variety of events. A volcanic eruption or meteorite impact, for instance, can send enough particles into the air to block the sun and cool the climate. A thickening blanket of greenhouse gases can trap heat. And, more commonly, according to some scientists, slight changes in Earth's orientation toward the sun can cause it to cool or warm in so-called Milankovitch cycles (named after the Serbian engineer who first described them). Now, new evidence from a marine sediment core from the deep Pacific points to warmer ocean waters around Antarctica (in sync with the Milankovitch cycle)u"not greenhouse gasesu"as the culprit behind the thawing of the last ice age. Ice cores drawn from Antarctica and Greenland have shown that carbon dioxide (CO2) levels in the atmosphere began to rise at roughly the same time as the vast ice sheets began to melt. But it remained unclear exactly which came first: melting ice and warming seas released more CO2 or more CO2 led to melting ice and warming seas...