Report: Greater Yellowstone area expected to become warmer, drier with changing climate

MSU News Service
Ag News

BOZEMAN – According to a new scientific report, the temperature has increased and snowfall has decreased in the Greater Yellowstone area since 1950 as a result of climate change, trends that are likely to continue through the rest of the century.

“The Greater Yellowstone Climate Assessment,” was authored by scientists at Montana State University, the U.S. Geological Survey and the University of Wyoming.

The researchers studied past, present and future climate change in the Greater Yellowstone area, or GYA, including from 1950 to 2018, and evaluated how those changes could progress by the year 2100 based on different greenhouse gas emission scenarios.

They found that the average temperature in the area increased by 2.3 degrees Fahrenheit since 1950 and could increase by 5-10 degrees by the year 2100.

“The GYA is valued for its forests, rivers, fish and wildlife,” said Steve Hostetler, a USGS scientist and co-lead on the report. “The climate changes described in this study will likely affect ecosystems in the region and the communities that depend on them.”

The new report also found that by the end of the century in the GYA:

  • Annual precipitation could increase by 9-15%, but the combination of elevated temperatures and higher evaporation rates will likely make future conditions drier in the summer.
  • Reduced soil moisture in summer will be an additional stress on plant communities and could make drought and wildfires more common.
  • With little to no mitigation of future emissions, there could be 40-60 more days per year exceeding 90 degrees in Bozeman and Jackson, Pinedale and Cody, Wyoming.

“The assessment is intended to provide the best available science on past, present and future conditions in the GYA so that people and communities have needed information to plan ahead,” said Cathy Whitlock, Regents Professor Emerita of Earth sciences at MSU and report co-lead.

The report also documents the effects of climate change on the GYA over recent decades, including:

  • The average temperature was as high or higher than any period in the last 20,000 years — and likely the warmest in 800,000 years — according to geologic studies.
  • The growing season has lengthened by nearly two weeks since 1950.
  • Average annual snowfall decreased by 23 inches since 1950, and measurable snow has become rare in June and September.

“The decrease in snow is due to the increase in temperature over time, which caused more precipitation to fall as rain instead of snow,” said report co-author Bryan Shuman, Wyoming Excellence Chair in geology and geophysics at the University of Wyoming.

The report also found that earlier snowmelt shifted the peak streamflow eight days earlier since 1925, reduced water supplies in summer and contributed to wildfires.

“Based on nearly 50 interviews with community leaders, city officials, agencies, businesses, citizens and ranchers, water and the need for more climate information are top concerns for folks in the GYA,” said co-author Charles Wolf Drimal from the nonprofit Greater Yellowstone Coalition.

The new report is a collaboration between scientists, resource managers, nonprofit organizations and tribal communities from Montana, Wyoming and Idaho. For more information on research in the GYA, visit the USGS Northern Rocky Mountain Science Center, MSU and University of Wyoming websites.