Global warming to boost cotton yields. (Earth Science: from San Francisco, at the 2001 fall meeting of the American Geophysical Union).

There may be one small consolation for global warming: There'll be a good supply of breathable fabrics.

Scientists predict that the atmospheric concentration of carbon dioxide in the year 2060 will be twice that measured before the industrial revolution, says Linda O. Mearns, a climatologist at the National Center for Atmospheric Research in Boulder, Colo. She and her colleague Ruth Doherty, also of the center, used global and regional climate models to estimate the effects of that boost in carbon dioxide on U.S. agriculture.

When researchers consider only expected changes in temperature and precipitation in their predictions of agricultural effects, cotton yields in the regional model drop about 10 percent below current values. If the scientists include the fertilizing effect of increased carbon dioxide, yields jump 5 percent over today's production.

The biggest boost--a hike of 26 percent over the current cotton crop--comes when farmers in the models take advantage of a longer growing season by planting earlier. That, plus the climate changes, would result in heftier and more abundant cotton bolls on each plant at harvest time, says Mearns. --S.P.