Increasing atmospheric CO 2: effects on crop yield, water use and climate

Abstract

Probable effects of increasing global atmospheric CO 2 concentration on crop yield, crop water use, and world climate are discussed. About 430 observations of the yields of 37 plant species grown with CO 2 enrichment were extracted from the literature and analyzed. CO 2 enrichment increased agricultural weight yields by an 36%. Additional analysis of 81 experiments which had controlled CO 2 concentrations showed that yields will probably increase by 33% with a doubling of atmospheric CO 2 concentration. Another 46 observations of the effects of CO 2 enrichment on transpiration were extracted and averaged. These data showed that a doubling of CO 2 concentration could reduce transpiration by 34%, which combined with the yield increase, indicates that water use efficiency may double. Several theoretical models have predicted that the doubling of atmospheric CO 2 concentration will increase the earth's temperature by 2–3°C, which could seriously disrupt agricultural production. More recent empirical evidence suggests that the warming may only be about 0.25°C, so the primary effects on agriculture are likely to be the beneficial increases in crop yields and water use efficiency.