WASHINGTON, June 10 (UPI) -- Unusual trends in the snowpack in the Rocky Mountains are likely linked to levels of greenhouse gas emissions, a U.S. government report finds.
A report from the U.S. Geological Survey and the Universities of Arizona, Washington, Wyoming and Western Ontario concludes that snowpack declines in the region during the last 30 years are "unusual" when compared with previous centuries.
Trends seen from historic snowpack reconstructions suggest that when the Northern Rockies have large snowpacks, the southern part of the range has lower ones and vice versa.
The USGS report finds that since the 1980s, however, both parts of the range experienced simultaneous declines with severity seen in the north.
The study backs research that the USGS said estimates that as much as 60 percent of the snowpack declines in the late 20th century are because of greenhouse gas emissions, which are linked to higher global temperature averages.
"Most of the land and snow in the northern Rockies sits at lower and warmer elevations than the southern Rockies, making the snowpack more sensitive to seemingly small increases in temperature," said USGS scientist Gregory Pederson, the lead author of the study, in a statement.
Runoff from winter snowpack makes up nearly 60 percent of the annual water supply for people in the western United States.