New study shows that, ‘…natural climate swings and global warming appears to be driving a long-term decline in snowpack along the Rocky Mountains’


From The Christian Science Monitor (Pete Spotts):

“I was shocked” when this result emerged, says Gregory Pederson, a hydrologist at the US Geological Survey’s Northern Rocky Mountain Science Center in Bozeman, Mont., who led the [study] effort. Similar shifts show up in the 1300s and 1400s, when the Rockies experienced warming periods, he says, but temperatures then weren’t nearly as warm as today. Nor was the shift as strong. Many studies have documented the West’s declining snowpack. And at least as early as 2005, some researchers began to notice the potential regime shift that Dr. Pederson and his colleagues see, notes Klaus Wolter, a researcher at the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, Colo…

The new study, conducted by a team of scientists in the United States and Canada, drew on tree-ring records that the team related to snowpack. The scientists focused on three broad regions in the Rockies that host the headwaters for major Western river systems, such as the Columbia, Missouri, and Colorado Rivers. While the shrinking snowpack in the 20th and early 21st centuries is not unprecedented from a climate-history standpoint, at no time in the past 800 years have so many people relied so heavily on these winter snows for their fresh water…

Typically, gains and losses of mountain snowpack seesaw between the northern and southern Rockies with these natural swings in Pacific climate patterns, Pederson explains. This feature stands out in the team’s data throughout the past millennium, with a couple of notable exceptions around 1350 and the early 1400s, when warmer average temperatures reduced snowpack up and down the length of the Rockies at the same time. The seesaw still occurs to some extent. But since the 1980s, snowpacks again have been declining along the entire length of North America’s geological spine, regardless of the state of these natural climate swings.

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