Effect of 2 X CO sub(2) Climatic Warming on Water Temperature and Agricultural Potential in China

Effects of carbon dioxide-induced climate change on agriculture in China are studied. For a doubling of CO sub(2), rice transplanting dates are about 20-30 days earlier and the rice cultivation period is longer than under current conditions. The effective water temperature is more than 700-1200 degree days for semi-arid regions of China, and more than 1300-2000 degree days for the major rice-producing regions. These conditions would push the northern limit of rice cultivation to south of the Huang He. But shallow water temperature increases also could drive up evaporation by about 16%-40%. Even with an increase in precipitation, water loss due to evaporation would cause a shortage of water resources available for rice cultivation.