Hotter Utah — not all bad?

A rising Great Salt Lake, a shrinking mountain snowpack and cutthroat trout that can't find streams cold enough to swim in — these are some of the possibilities if Utah's temperatures keep getting hotter, says Fred Wagner.

But there are some occasional pluses to global warming, Wagner told a climate change symposium this week at the Utah Department of Environmental Quality. The meeting of the Governor's Blue Ribbon Council on Climate Change is aimed at developing state policies to document and reduce greenhouse gas emissions in Utah.

Predicted rising temperatures and rising precipitation levels could also mean a longer growing season for farmers and longer grazing season for ranchers, said Wagner, professor emeritus of wildland resources at Utah State University.

When it comes to the study of climate — with its solar cycles and Pacific decadal oscillation and anthropogenic forcing — nothing is simple, as the past week's symposium underscored. The people who study climate change look both at what has already happened and at computer models of what might happen in the future.

Already, says Wagner, Utah has seen a mean annual temperature increase of 3 degrees Fahrenheit between 1894 and 2004 (much of that increase coming in nighttime temperatures) and an increase in precipitation of 14 percent during that same period. Or, as Wagner puts it, "the wet years are getting wetter and the dry years are not quite as dry."

Despite all that wetness and because of the increased temperatures, in the late fall and late spring, Utah's mountains are getting more rain than snow, and the rain is going immediately into the ground rather than into a snowpack that could turn into spring runoff to provide enough water for lawns and farms. On the other hand, increased precipitation could offset the runoff problem.

Data run by the National Center for Atmospheric Research in Boulder for a nine-state region that includes Utah showed that if carbon dioxide emissions double (a typical prediction), this will mean an increase in annual temperatures of between 6.5 and 11.7 degrees F (depending on who's doing the calculating) by the end of this century. It will also mean an increase in precipitation of at least 54 percent and possibly as much as 184 percent.

That poses significant questions of whether Utah's dams, reservoirs and aqueducts will be able to contain all that water, Wagner said. Considering a 12 percent rise in precipitation in the 20 years prior to the 1980s flooding of the Great Salt Lake that threatened I-80 and the airport, the projections mean that "the Wasatch Front will be in a heap of trouble."