Roughly 20,000 years ago the great ice sheets that buried much of Asia, Europe and North America stopped their creeping advance. Within a few hundred years sea levels in some places had risen by as much as 10 meters—more than if the ice sheet that still covers Greenland were to melt today. This freshwater flood filled the North Atlantic and also shut down the ocean currents that conveyed warmer water from equatorial regions northward. The equatorial heat warmed the precincts of Antarctica in the Southern Hemisphere instead, shrinking the fringing sea ice and changing the circumpolar winds. As a result—and for reasons that remain unexplained—the waters of the Southern Ocean may have begun to release carbon dioxide, enough to raise concentrations in the atmosphere by more than 100 parts per million over millennia—roughly equivalent to the rise in the last 200 years. That
CO2 then warmed the globe, melting back the continental ice sheets and ushering in the current climate that enabled humanity to thrive.
That, at least, is the story told by a new paper published in
Nature on April 5 that
reconstructs the end of the last ice age. Researchers examined sediment cores collected from deep beneath the sea and from lakes as well as the tiny bubbles of ancient air trapped inside ice cores taken from Antarctica, Greenland and elsewhere. (
Scientific American is part of Nature Publishing Group.) The research suggests that—contrary to some prior findings—CO2 led the prior round of global warming rather than vice versa, just as it continues to do today thanks to rising emissions of CO2 and other greenhouse gases.
What Thawed the Last Ice Age?
This one seems to speak to your particular question, except they aren't completely sure. It wasn't cars, for sure, that caused it. However, there doesn't look to have ever been an increase so rapid in 200 years. That's where we seem to come in. You'll like this article if you haven't already seen it.
Climate myths: It’s been far warmer in the past, what’s the big deal?