Cotton crops in the future will be subjected to weather conditions for which they were not bred. Currently, atmospheric carbon dioxide concentration is about 360 ppm, and there is general agreement among climatic and atmospheric scientists that the atmospheric carbon dioxide concentration could range from 510 to 760 ppm some time in the middle or latter part of the 21st century. Global circulation models predict that increased concentrations of carbon dioxide and other radiative gases would cause warming of the earth's surface and other weather changes. Since cotton growth and yield are controlled by weather, it behooves us to understand the implications of such weather changes on agriculture.