Spring 2002 Vol. 2 No. 1
Climate Change Shows That History Indeed Repeats Itself
Normal variability in the climate can cause odd weather patterns, such as the unusually warm temperatures felt across much of the northern United States this past winter. But what if, over the course of a few short years, typically frigid Boston suddenly seemed more like milder Atlanta in the winter months? That may not sound too bad to some folks in Boston, but they might feel differently, considering the possible repercussions.
Abrupt climate change is the subject of a recent National Research Council report that says the likelihood of sudden climate shifts needs to be studied more closely, especially given the current global warming trend. Scientists don't know enough to predict when abrupt changes will occur, but they know from the Earth's history that periods of gradual change, like now, were punctuated by episodes of severe floods and droughts and sudden changes in average temperatures -- 18 degrees Fahrenheit in 10 years in some places.
The committee that wrote the report was chaired by Pennsylvania State University's Richard B. Alley, who has made several trips to Greenland and Antarctica, where he and his colleagues have drilled almost two miles deep into the ice to discover what the climate was like thousands of years ago. Past atmospheric conditions are frozen in time, so to speak, in tiny gas bubbles trapped within each layer of ice.
The records in the ice cores show repeated instances of large and abrupt climate changes in the last 100,000 years. The most notable occurred when gradual warming at the end of the last ice age triggered an abrupt cooling period, which finished with an especially sudden warming about 12,000 years ago. Since then, less dramatic -- though still abrupt -- climate changes have occurred, including last century's rapid warming of the North Atlantic from 1920 to 1930 and the Dust Bowl drought of the 1930s.
When the climate is being forced to change -- as is the case now with greenhouse gases that are warming the planet -- it increases the number of mechanisms that can spark an abrupt change, the report says. To better understand these mechanisms, especially those that occur during warming trends, researchers need to improve computer models that simulate abrupt climate change. The ultimate goal should be to accurately forecast such events.
In the meantime, surprises are inevitable.
"There's no need to panic," says Alley, "since humans should be able to adapt to these climate changes, although poorer countries will have a harder time doing so."
But that is no reason for complacency either, the report says. Strategies should be pursued to reduce human and ecological vulnerabilities, including slowing down the pace of global warming. "Slowing down a little may help us a lot," says Alley. "An abrupt change is harder to deal with than a gradual one." -- Bill Kearney
Abrupt Climate Change: Inevitable Surprises. Committee on Abrupt Climate Change: Implications for Science and Public Policy; Polar Research Board, Ocean Studies Board, and Board on Atmospheric Sciences and Climate; Division on Earth and Life Studies (2001, 244 pp.; ISBN 0-309-07434-7; available from National Academy Press, tel. 1-800-624-6242; $39.95 plus $4.50 shipping for single copies).
The study was chaired by Richard B. Alley, Evan Pugh Professor of Geosciences, and Associate of the Environment Institute, College of Earth and Mineral Sciences, Pennsylvania State University, University Park. The study was funded by the U.S. Global Change Research Program and the National Bureau of Economic Research Program on Environmental Economics, Yale University.