Exactly what climate change will mean for Utah remains unknown, says a Utah State University scientist. But what isn't in doubt, adds Frederick H. Wagner, is that climate change is happening and that it will mean higher temperatures and more precipitation.
Together, those factors point to differences in the yearly snowpack runoff, the annual replenishment of reservoirs across the West.
A professor emeritus in USU's Department of Wildland Resources, Wagner keeps busy on many projects, including editing a book that updates earlier research on climate change. He was pleased when former Vice President Al Gore won part of the Nobel Peace Prize for his work calling attention to the issue, and glad that polls show two-thirds of the American public believe global warming is occurring and that it's probably caused by humans.
In 1991, Congress chartered a study on the effects of climate change, with experts examining different parts of the United States. For this effort, the country was divided into 19 regions.
Wagner was a coordinator of the assessment of the nine-state Rocky Mountain-Great Basin region, which includes Utah. In February 2003, the work was published as "Preparing for Climate Change: The Potential Consequences of Climate Variability and Change." The regional section is titled "Rocky Mountain/Great Basin Regional Climate Change Assessment."
Scientists have predicted that the atmosphere's carbon dioxide load could double this century. The increase in the greenhouse gas is blamed on human activities such as power plant emissions and tailpipe exhaust.
For the nine-state assessment, the National Center for Atmospheric Research in Boulder, Colo., provided a projection about what would happen if CO2 went up as much as believed, he said. The doubling has been predicted, Wagner added, but nobody can be sure this will actually take place.
The models showed that temperatures would rise and precipitation would go up. The higher temperatures should cause an increase in evapo-transpiration; the term refers to evaporation of water from soil, lakes and rivers, as well as plants releasing water vapor.
If the temperature prediction comes true, "there's going to be more evaporation off of Lake Powell and also the Colorado River," he said.
About 85 percent of the water that humans use in the West comes from reservoirs, rivers or lakes supplied by mountain streams. The streams are "fed by the melting of snowpacks," he added.
"Now, what's happening all over the West is the snowpacks are shrinking."
It's not that less precipitation is falling but that global warming is changing the snow accumulation, he said.
Ever since the West was settled, late fall and early winter snow would begin to pile up in the mountains. "But now, with higher temperatures, that precipitation ... is now falling as rain and running off right away." It does not contribute to the snowpack and is lost to human use. "The reverse is happening in the spring," with early warm weather reducing the snow accumulation.
"So the bottom line is we have shrinking snowpacks" and the seasonality of precipitation is changing, Wagner said.
Agricultural irrigation and hydropower electrical generation could be affected, he added. "And of course, we have domestic use of water, particularly in the summer when we're watering our lawns and our yards."
But what about the predicted increase in precipitation? Will that offset the changes in the runoff? Possibly yes, but it's still too early to tell, according to Wagner.
A series of new models have been drafted, he said, "and they're all over the map in predicting precipitation."Wagner would like to see more study of possible changes in Utah's stream-flow. "We definitely need more research, no question on that."
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