Some scientists predict that climatic changes could alter historic precipitation patterns, and reduce available water supplies. Carbon dioxide loading of the atmosphere caused by fossil-fuel combustion, mostly in coal-burning power plants, threatens a significant climate change…. A National Academy of Sciences report estimates that the resulting temperature increase and reduction in precipitation could diminish water supplies by almost forty percent in the Upper Colorado Region.
David Getches, Competing Demands for the Colorado River, University of Colorado Law Review, 1984
OK, that was a few weeks ago, but you get my point. People have been talking about this for a very long time.