By Diana Setterberg, MSU News Service
BOZEMAN – A team including a Montana State University snow scientist has published research showing that a severe snow drought, like the one that affected the western U.S. in 2026, would occur four times less frequently during the preindustrial period than in the current era of climate change.
The findings were published July 20 by the journal Proceedings of the National Academy of Sciences . Marianne Cowherd, assistant professor in the Department of Earth Sciences in MSU's College of Letters and Science , together with scientists from the University of Wyoming and Colorado School of Mines, conducted the study.
"What we experienced this spring was really strange, and we wanted to use the tools that we have available to increase our understanding of climate and snowpack," Cowherd said. "When Bridger Bowl closed early and it was warm in February, people wanted to know if this is because of climate change or is this variability from a normal year? We can use statistics to answer that question."
Operating under the premise that climate change is human caused, a presumption that Cowherd said has been established in previous studies, the team set out to quantify just how unusual the winter of 2026 was in the study area encompassing 11 Pacific and Mountain West states, including Montana. Using a physics-based computer weather model that incorporates satellite observations and measurements of the amount of liquid water in a snowpack, the team compared the recorded snowpack levels on March 15 for every year in that time span. The results indicated that while the 2026 snowpack did not represent a record low, it measured at or below the 10th percentile across the study area since 1987 – the lowest observed in the western U.S. in that 40-year period.
The team then verified that its computer model could reproduce the 2026 western U.S. snow drought before proceeding to simulate winters under two different climates. The first was today's climate, from the year 2016 projected out to 2036. The second was the climate of the preindustrial world from 1850 to 1900, before large-scale, human-caused carbon emissions were a factor. Cowherd said that the model's simulations helped researchers understand what the climate was like in the preindustrial period and established statistical distribution, which is useful for understanding if a drought like 2026's would have occurred without climate change.
The models predicted that snow drought would occur every 6.8 years in the current climate but once every 30 years in the preindustrial climate.
"We found it is not impossible for these types of events to happen without climate change, but they're so much more rare," Cowherd said.
