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January 2002

Climate change could boost cotton yields

A study by ESIG scientists has found that cotton yields are likely to increase in the southeastern United States if carbon dioxide levels continue to rise as projected this century and if farmers adapt their agricultural practices to the resulting climate change.

Cotton harvesting in Texas. (Photo by David Nance, courtesy U.S. Department of Agriculture.)

Linda Mearns and Ruth Doherty, who co-authored the study, entered various scenarios into their computer models to simulate the effects of elevated levels of carbon dioxide (CO2), which enhances plant growth by stimulating photosynthesis.

“Cotton is a very important economic crop for U.S. agriculture,” says Linda. “This is the first time impacts of climate change on cotton production have been examined at this level of detail on a regional scale.”

The study relied on two climate models—a large-scale global model that used 300-by-300 kilometer (186-by-186 mile) grids, and a fine-scale regional model that used 50-by-50 kilometer (31-by-31 mile) grids. Using these two models, Linda and Ruth simulated three scenarios. The first scenario simply looked at the impact that climate change resulting from an instantaneous doubling of CO2 would have on cotton yields in the southeastern United States. The fine-scale model predicted a decrease of 10% in cotton yields over the region, while the large-scale model showed a 4% increase in yields.

When the climate change resulting from CO2 doubling was combined with the potential for enhanced cotton plant growth as a result of greater carbon availability, the fine-scale model showed a 5% increase in yields, while the large-scale model predicted a 16% increase. Finally, when the first two factors of CO2 doubling and enhanced growth were combined with farming adaptations, such as planting crops earlier to take advantage of a longer growing season, the fine-scale model predicted a 26% increase, while the large-scale model predicted a 36% increase.

The findings will be published this year in a special issue of the journal Climate Change. NASA and the Environmental Protection Agency funded the study. The research is part of a larger project that examines the effects of various climate change scenarios on yields of corn, wheat, sorghum, soybeans, and cotton in the southeastern United States.

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