Dear Tom,
My biology teacher mentioned that changes in the climate caused a mass extinction of life 250 million years ago. What were those changes?
Richard DiPietro
Dear Richard,
Explanations for the Permian-Triassic Extinction of 250 million years ago, an event that wiped away 95 percent of species at that time, are incomplete, but it was probably the result of a series of natural disasters.
Volcanic eruptions in Siberia injected greenhouse gases into the atmosphere, and planetary temperatures jumped 10 degrees. Methane ice in sea beds thawed as ocean temperatures rose, releasing methane gas (20 times as potent a greenhouse gas as carbon dioxide), and temperatures rocketed up 30-50 degrees. The methane then sapped atmospheric oxygen, whose concentration collapsed almost below life-sustaining levels.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
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