The Barnett paper I quoted below talks about hydrologic changes “already diagnosed in some regions.” A reminder for those of you in the Western U.S. – we’re one of those regions.

See, for example, Phil Mote’s January 2005 Bulletin of the American Meteorological Society paper (blogged here and newspapered here (sub. req.)):

Warmer Winters are Dissipating the West’s Much-Needed Snowpacks

By John Fleck
Journal Staff Writer

Snow was more than 3-feet deep last March 1 at the Chamita snowpack gauge in the mountains of northern New Mexico. By April 1, it was gone— a month earlier than normal.

All over the West, it was the same story. A dry spell conspired with record-breaking temperatures to decimate the snowpacks.

Water managers had to rapidly adjust as their inventory of stored winter precipitation shrank.

Climate scientists say the remarkable dwindling snowpacks of 2004 was an extreme event, the worst in many ways since record-keeping began.

But new research suggests that the spring of 2004 is also part of a trend. Over the last 50 years, the mountain snowpacks on which the western United States depends for its water supplies have shrunk.

It is not necessarily snowing less. It is simply warmer, which means that more water evaporates and that the snow that is left melts sooner.

“It’s a consistent message,” said Tom Pagano, a snowpack forecaster at the Natural Resources Conservation Service in Portland, Ore. “Snowpack has been on the decline.”

New research suggests that New Mexico has so far bucked the 50-year trend. But with global temperatures warming, research suggests the same thing is likely here.

“The accumulation of greenhouse gases is exerting a stronger and stronger influence on the climate of the West,” said Philip Mote, a climate researcher at the University of Washington.