Climate change in the Sierra

From the Stockton Record:

By Alex Breitler
Record Staff Writer
December 06, 2007 6:00 AM
The Sierra Nevada gazed upon by your grandchildren may be a vastly different range than it is today.

When they swim in its high mountain lakes, they may no longer see the bottom. The fish that tug on their poles may be different than the ones you catch today.

Wildfires may threaten their homes more often. And their favorite ski runs may no longer exist.

Global warming will have many undesired effects in California, but it will hit hardest John Muir's "Range of Light," experts said Wednesday.

The Sierra's plants and animals, its lakes and streams, and some of the charms that draw humans from the Central Valley and beyond are threatened, scientists and advocates said.

The Sierra Nevada Conservancy, a three-year-old state agency charged with safeguarding the region, held a symposium in Gold Rush country highlighting the many ways climate change will attack - or in some cases is attacking - the Sierra.

"It is simply unprecedented," said Dan Cayan, a meteorologist with the Scripps Institute of Oceanography in San Diego.

Global temperatures have jumped on average 1.1 degrees in recent decades, he said, and will increase another 2 to 10 degrees or more in coming decades, depending on how successful we are at reducing greenhouse gas emissions.

In the Sierra, the snowpack could shrink in half by the end of the century, Cayan said. Snow levels will climb on average 1,500 feet, and resorts may see lower-elevation ski runs turn to rock.

"You can see the changes coming," said Kathy Hubbard, deputy director of the California Ski Industry Association.

Already, runoff from winter snow is beginning up to three to four weeks earlier than normal, Cayan said. This is trouble for much of the state, which relies on the Sierra for 60 percent of its freshwater supply.

Water managers fear reservoirs will either be overwhelmed by massive amounts of rain that currently falls as snow and sits on hillsides until melting in the spring or will shrivel during extended droughts.

And there will be floods. In May 2005, the Yosemite Valley was swamped after a warm storm melted mountain snow. All it took was 1 inch of rain.

Expect more of the same, Cayan said.

Among other predicted changes:

» Global warming will force high-elevation species, such as tiny rodents and butterflies, to migrate uphill until they run out of room.

» Trees will sprout where they haven't grown before and die where they have grown in the past.

» More frequent wildfires of greater than 1,000 acres will threaten mountain and foothill communities, which will face longer summertime fire seasons, Cayan said.

» Ice on mountain lakes will melt earlier, producing algae blooms that cloud up the water and harm fish.

Lake Tahoe has heated by about one-half degree in the past 30 years, enough for warm-water invasive fish, such as bass, to flourish near the shorelines, threatening native species, said Sudeep Chandra, a water quality expert at the University of Nevada, Reno.

Organizers of Wednesday's event touted California as a leader in the search for solutions, including alternative energy projects and strict tailpipe emission standards.

The ski industry's Hubbard said some resorts are taking action. Kirkwood Ski Resort on Highway 88 east of Stockton has a new carpool program to encourage skiers to downshift on driving, she said.

But it's already too late to eliminate future warming altogether, Cayan said.

To a temperature increase of 2 to 4 degrees - enough to disrupt mountain ecosystems and cause water supply worries - we are already "committed," he said.

Reporter Alex Breitler can be reached at (209) 546-8295 or abreitler@recordnet.com.