Changes In Earth's Orbit Were Key To Antarctic Warming That Ended Last Ice Age

vinces99 writes "For more than a century scientists have known that Earth's ice ages are caused by the wobbling of the planet's orbit, which changes its orientation to the sun and affects the amount of sunlight reaching higher latitudes, particularly the polar regions. The Northern Hemisphere's last ice age ended about 20,000 years ago, and most evidence has indicated that the ice age in the Southern Hemisphere ended about 2,000 years later, suggesting that the south was responding to warming in the north. But new research published online Aug. 14 in Nature (abstract) shows that Antarctic warming began at least 2,000, and perhaps 4,000, years earlier than previously thought."

Comments

Re:Ice ages are caused by planetary wobbles

[rgbatduke]

You might want to look at two things. One is the actual thermal record over geological time, which shows intervals of extremely rapid natural warming and cooling. Second, you might want to consider the fact that much of that record is essentially smeared out by imprecision in the proxies used so that one is comparing two different kinds of averages -- one averaged over a very short time interval, and another where the average might well be over a period longer than the entire time we have had thermometers. If you then perform a regression estimate of extrema, you will conclude that no, it cannot be safely or reasonably concluded that the "very very fastest warming we've seen is attributed to man".

Curiously, not even most climate scientists would assert such a thing, I don't think. Some might. For one thing, there hasn't been any statistically significant warming for roughly 16 years, in spite of "man". For another, some unknown fraction of the observed warming post Little Ice Age was natural -- all of it, up to perhaps 1950, and very likely some of it since then as well. There are plenty of natural things that produce rapid warming, and cooling, as evidenced by the geological record. We just don't understand them yet.

rgb