USGS: Global Warming Drives Rockies Snowpack Loss Unrivaled in 800 Years, Threatens Western Water Supply

A US Geological Survey study released today suggests that snowpack declines in the Rocky Mountains over the last 30 years are unusual compared to the past few centuries. Prior studies by the USGS and other institutions attribute the decline to unusual springtime warming, more precipitation falling now as rain rather than snow and earlier snowmelt.

The warming and snowpack decline are projected to worsen through the 21st century, foreshadowing a strain on water supplies. Runoff from winter snowpack — layers of snow that accumulate at high altitude — accounts for 60 to 80 percent of the annual water supply for more than 70 million people living in the western United States.

That’s from a USGS news release for an important new study in Science, “The Unusual Nature of Recent Snowpack Declines in the North American Cordillera” (subs. req’d).

What’s most worrisome is that we now have three major trends driven by human emissions of greenhouse gases that threaten to significantly worsen drought and water problems in the West and Southwest:

  1. Less precipitation in many areas (see NCAR analysis warns we risk multiple, devastating global droughts even on moderate emissions path)
  2. Less snowpack, as this USGS study found
  3. Hotter temperatures (see SW could see a 60-year drought like that of 12th century — only hotter — this century)

Assuming the anti-science disinformers continue to block any serious action, these catastrophic changes will last a long, long time (see NOAA: Climate change “largely irreversible for 1000 years,” with permanent Dust Bowls in Southwest and around the globe).

For the record, it was the possibility of losing the Sierra snowpack in the second half of the century that led our Nobel prize-winning Energy Secretary to warn in 2009, “Wake up,” America, “we’re looking at a scenario where there’s no more agriculture in California.”

Here’s more on the new study:

USGS scientists, with partners at the Universities of Arizona, Washington, Wyoming, and Western Ontario, led the study that evaluated the recent declines using snowpack reconstructions from 66 tree-ring chronologies, looking back 500 to more than 1,000 years. The network of sites was chosen strategically to characterize the range of natural snowpack variability over the long term, and from north to south in the Rocky Mountains.

With a few exceptions (the mid-14th and early 15th centuries), the snowpack reconstructions show that the northern Rocky Mountains experience large snowpacks when the southern Rockies experience meager ones, and vice versa. Since the 1980s, however, there were simultaneous declines along the entire length of the Rocky Mountains, and unusually severe declines in the north.

“Over most of the 20th century, and especially since the 1980s, the northern Rockies have borne the brunt of the snowpack losses,” said USGS scientist Gregory Pederson, the lead author of the study. “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. Also, winter storm tracks were displaced to the south in the early 20th century and post-1980s. Forest fires were larger, more frequent and harder to fight, while Glacier National Park lost 125 of its 150 glaciers.”

But what about all that snow we got this year?

USGS scientist and co-author Julio Betancourt explains that “The difference in snowpack along the north and south changed in the 1980s, as the unprecedented warming in the springtime began to overwhelm the precipitation effect, causing snowpack to decline simultaneously in the north and south. Throughout the West, springtime tends to be warmer during El Niño than La Niña years, but the warming prior to the 1980s was usually not enough to offset the strong influence of precipitation on snowpack.”

The La Niña episode this year is an example with lots of snow in the north while severe drought afflicts the south. But, in the north, this year’s gains are only a small blip on a century-long snowpack decline.

The bottom line is that the climate has changed, perhaps permanently:

This study supports research by others estimating that between 30–60 percent of the declines in the late 20th century are likely due to greenhouse gas emissions. The remaining part of the trend can be attributed to natural decadal variability in the ocean and atmosphere, which is making springtime temperatures that much warmer.

What we have seen in the last few decades may signal a fundamental shift from precipitation to temperature as the dominant influence on western snowpack” Pederson said.

What’s particularly worrisome is that we’ve seen these dramatic and harmful changes already — and we’ve only warmed about a degree and a half Fahrenheit in the past century. The problem for our children and grandchildren is that if we continue anywhere near our current greenhouse gas emissions pathway, we are on track to warm five times times that or more this century (see M.I.T. doubles its 2095 warming projection to 10°F with 866 ppm and Arctic warming of 20°F ).


Another 2011 study, “The Last Drop: Climate Change and the Southwest Water Crisis,” finds that drought and reduced precipitation in the U.S. SW alone could cost up to $1 trillion by century’s end.

The time to act was a long time ago, but now is still better than later.

Related Post:

Below are the earlier comments from the Facebook commenting system:

Matthew Stephen Hall

To the West it all flows to fill Lake Powell, Lake Mead, Lake Havasu to irrigate a few thousand golf courses 🙁

June 15 at 12:08amChris Paradise

Chalk another one up for Skep Sci’s “supports AGW” bubbles. I also like the preemptive addressing of the “this year it snowed a packload” argument, as that is likely to be one of the first questions asked (either aggressively or as an authentic question) after seeing the report. It never hurts to remind people that weather will be weather, but the climate trends are pretty clear by this point.

June 13 at 6:51pmMark David Oliver​world/2011/jun/13/extreme-​weather-flooding-droughts-​fires

June 14 at 7:21am

They’re already fighting over access to Colorado River water for irrigation. It really upsets the rich ranchers that Native Americans have unlimited access to the river water while the ranchers have to get permits, waiting period and limited access.This conflict will get worse, spread to other watersheds & eventually lead to people getting injured over water disputes.Now you see why the Bush family bought 90,000 acres in Paraguay that sits atop the largest freshwater aquafier in the western hemisphere.

June 14 at 2:29pmJoy Hughes

“Whiskey’s for drinkin’, water’s for fightin’ over…” There has always been fighting over water here in the West. On the creek where I live, before the turn of the last century, a man was killed with an irrigation shovel.

June 14 at 11:58pmJoan Savage

One feature that has been brought up in news stories, but not so much in the Science article, is a fear of too-rapid melt of the snow pack leading to more flooding. One of the beauties of the snow pack for water supply in the past has been gradual release for irrigation and urban use, but that’s at risk with a rapid melt. I haven’t yet found a data set that shows rate of melt compared over the years.

June 13 at 11:37pmJulia Kuglen

Not as far west as the Rockies, but in drought territory:

“Llano is experiencing its worst drought in more than half a century, city officials said.

As of Wednesday, the Llano River, which normally courses through town at 158 cubic feet per second this time of year, was flowing at 3.8 cubic feet per second — the slowest since 1953, according to the U.S. Geological Survey. The river is the city’s sole source of drinking water.


Officials expect the river’s flow to stop as soon as the end of this week, prompting bans on personal car washing, sprinkler use and pool filling.

The city has between 60 and 90 days of untreated water stored behind two dams, said City Manager Finley deGraffenried. But with the water as low as it is, it might be too cloudy or contain too much algae to be treated.

When those stores are gone, the city may need to dig wells or truck in water, deGraffenried said.”

June 16 at 12:12amTyler Austin

The wheat crop in Alberta is crap this year, expect higher bread prices as we export our surplus down south. Oh and lumber paper pulp is also going to skyrocket as the north here is to muddy for extraction.

June 15 at 1:55pm


I dunno. Cliff Mass has a more benign take on this study. He makes some good points.http://cliffmass.blogspot.​com/2011/06/scary-snowpack​-stories.html


June 14 at 1:34am

George Ennis

Curious why Mr. Mass has no comments on his blog from one of the report writers. After all they are at the same university. It would be interesting to see such a discussion.

June 14 at 10:00am

Leif Erik Knutsen

Cliff is also relating to the West Coast ranges which because of the moderating effect of the Pacific are experiencing some of the least long term response. Thou the average snow pack is remaining “average”, cycles and extremes do appear to be intensifying to this long term resident and weather watcher.

June 14 at 10:12am

Sallie Coffman

Scary stuff!

June 13 at 10:56pm