Sept. 7, 2007 — The emerging story of a global climate shift a third of a billion years ago seems to be a prequel to what climate scientists expect from the current trend in global warming.
Using the same sort of Global Circulation Models as those which predict climate change today, University of Michigan researcher Christopher Poulsen and his colleagues have reproduced what might have happened on the supercontinent Pangea in the late Paleozoic era, about 300 million years ago, when the polar ice melted.
"During this time you see all kinds of environmental changes," said Poulsen, referring to the fossils and chemical evidence left in rocks.
Temperatures spiked at the equator and plants' ranges were changing quickly. There were at least three major advances of ice sheets at high latitudes, followed by thaws.
"The question is," he added, "How much can these ice sheets influence changes in the tropics?"
One way to try and answer that question is with a climate model.
The researchers set up a climate model for the late Paleozoic Earth in the same way climate scientists use them for today’s Earth. The main difference is that no one has a lot of detail about the height of all the mountains and the exact details of geography in the Paleozoic. So the model was necessarily coarser than those used for the modern Earth, Poulsen explained.
"So we ran these experiments and found we were able to get quite dramatic changes," Poulsen told Discovery News.
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They showed that melting large to moderately-sized high-latitude ice sheets resulted in a reversal of tropical trade winds and big expansions of low-latitude desert areas into what had been warm temperate forests. Their report appears in the September issue of the journal Geology.
