The Southwestern U.S. — including a lot of Colorado — is facing an imminent transition to a permanently drier climate as a result of global climate change, according to a study published today in the journal Science.
The paper looked at projections from 19 different climate models for the region between 125 degrees west and 95 degrees W longitude and 25 degrees and 40 degrees N latitude. Baseline Road in Boulder County runs along the 40 degrees latitude parallel in Colorado.According to the paper, written by Richard Seager of the Lamont Doherty Earth Observatory of Columbia University and colleagues:
“If these models are correct, the levels of aridity of the recent multiyear drought, or the Dust Bowl and 1950s droughts, will, within the coming years to decades, become the new climatology of the American Southwest.”
Of the nineteen models the group looked at, only one predicted a wetter climate. Further, the extended drought that has hit the southwest over the last several year may mean that the transition to this drier climate is already under way.
The news may be less dire for Colorado than for the far Southwest, however, according to Linda Mearns, a senior scientist at the National Center for Atmospheric Research in Boulder. Mearns is the lead author on regional climate prediction for the Intergovernmental Panel on Climate Change.
Mearns says, “In the southwest, the likelihood of more severe droughts and more really extensive droughts is a real possibility. If I were governor of New Mexico or Arizona, I would look really hard at my twenty year plan for water resources and seriously consider these results.”
But you move northward in latitude, the prospect for rainfall improves. From a drier southwest, the rainfall patterns move through a “transition zone” between about 37 degrees and 42 degrees north latitude-roughly the southern and northern borders of Colorado-where it is very difficult to predict what might happen.
While the supply of water to the state is threatened by climate change, demand for water is expected to increase 53 percent between now and 2030, according to estimates by the Colorado Water Conservation Board.