Extra Co2 Isn't All Bad

SOME GOOD NEWS ON THE climate front: In simulating the expected 21st century climate, Agriculture Dept. researchers in Arizona have found crop yields improve substantially when the atmosphere contains extra carbon dioxide. Plus, the crops seem to absorb much of the excess CO2, which may alleviate global warming.

The tests in a 20-acre field at the U.S. Water Conservation Laboratory, near Phoenix, were the largest ever outside of a greenhouse. Researchers blew pure carbon dioxide gas--the same kind used to carbonate soda--onto the crops. When carbon dioxide levels were raised 50%, cotton yields rose 50%, and wheat yields rose 10% to 25%, says Bruce A. Kimball, a USDA soil scientist. The cotton crop got by with no increase in water, and wheat used 10% less.

The tests may also shed light on why atmospheric CO2 hasn't risen as much as expected from the increased burning of hydrocarbons. Cotton in particular absorbs excess carbon rapidly, according to Steven W. Leavitt, an associate professor at the University of Arizona's Laboratory of Tree-Ring Research. It's unclear whether natural vegetation does as well.

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