Study: Future snowmelt in West twice as early as expected; threatens ecosystems and water reserves

Purdue University: According to a new study, global warming could lead to larger changes in snowmelt in the western United States than was previously thought, possibly increasing wildfire risk and creating new water management challenges for agriculture, ecosystems and urban populations. Researchers, including a Purdue University professor of earth and atmospheric sciences, discovered that a critical surface temperature feedback is twice as strong as what had been projected by earlier studies.

The high-resolution climate model used by the team was better able to reproduce the complex topography of the western United States and capture details of the effect of snow cover on the climate system, as well as the historical record of runoff. The findings will be published in an upcoming issue of Geophysical Research Letters and are now available online at the journal's Web site.

Noah Diffenbaugh, senior author of the paper and an associate professor of earth and atmospheric sciences at Purdue, said the influence of melting snow on regional climate is far greater than that of increased greenhouse gases alone. "The heat trapping from elevated greenhouse gases triggers the warming, but the additional warming caused by the loss of snow is what really creates the big changes in surface runoff," said Diffenbaugh, who also is a member of Purdue's Climate Change Research Center. "Scientists have known about this general effect for years. The big surprise here is how much the complex topography plays a role, essentially doubling the threat to water resources in the West."…

The figure shows projected future changes in the timing of runoff in snow-dominated areas of the western United States. The timing of runoff shifts earlier in almost all areas as greenhouse gas concentrations increase. These snow-dominated areas currently act as natural reservoirs, with melting in the spring and summer providing critical fresh water throughout the western United States. A shift to earlier runoff could pose challenges for human consumption, agriculture, wildfire management and sensitive ecosystems. (Purdue University image/Diffenbaugh Laboratory)