A University of Montana climate scientist said Friday that as global warming drives up temperatures, farmers in eastern Montana can expect continued strains on water supplies, even if rainfall amounts return to normal. Ecology professor Steve Running was on the United Nations panel that was a co-recipient of the 2007 Nobel Peace Prize along with Al Gore. In an address to the Northern Plains Resource Council Friday, he said a temperature increase of just a few degrees Fahrenheit has accelerated evaporation enough to diminish the region's water supplies. The problem is expected to continue even if the region emerges from a recent drought. "Even if we have the exact same precipitation this year as we had 50 years ago, the fact that it's a couple of degrees warmer means it's going to be drier," Running said. "We have some real decisions to make. We're not going to slide by. There's either going to be less irrigation or there's going to be less water in our streams." Although some climate models predict less precipitation across the West in general, on a local level there is less certainty. In the last 50 years, for example, average annual precipitation has declined by about 2 inches in Billings, but has increased by about an inch in Bozeman and Missoula. The rise in temperature, however, is more certain, Running said. In March, when snowpacks begin to melt, temperatures compared with 50 years ago are up 6.2 degrees in Billings, 7.7 degrees in Bozeman and 4. 6 degrees in Missoula. Running said that factor alone ensures the region's overall "water balance" will dip.