Low snow? Well, you're getting warm
Seattle Times science reporter
This winter's lower-than-average snowpack, a big factor in the West's current energy crunch, could end up the status quo over the next half-century if climate projections hold up.
"Those things we're seeing this year are a prelude of what is quite likely to become the norm in the new century," said Philip Mote, research scientist for the Climate Impacts Group at the University of Washington, which helped with a national assessment of the nation's upcoming climate changes.
One key difference: This winter has had little precipitation, either rain or snow. Future winters could see plenty of precipitation, but more in the form of rain as average annual temperatures rise.
That could provide more water for power generation in the winter, when demand is highest. But hydropower also depends heavily on snow, which can store 60 percent to 70 percent of the water that runs through the region's dams in the spring and summer months, said Mote.
"As we eat into that natural storage as the temperature rises, the ability to store water for summer use drops dramatically," he said.
The lack of precipitation this winter has made it difficult for the Bonneville Power Administration (BPA) to provide power now and save water both for future power and the migration of endangered salmon runs this spring and summer. To assure a sufficient supply and avoid the extremely high prices for supplemental power on the spot market, the BPA Thursday and yesterday ran more water through its system than its salmon-recovery plan recommends.
Meanwhile, the snowpack is about 60 percent of the 30-year average, said Scott Pattee, water-supply specialist for the federal Natural Resources Conservation Service, primary snow-data agency in the state. In the Skagit River basin, source of 20 percent to 40 percent of power for Seattle City Light, the snowpack is at 44 percent, lowest in the state.
Since October, rainfall at Seattle-Tacoma International Airport has been 8 inches below normal, said Cliff Mass, UW professor of atmospheric sciences.
"That's like missing over a whole month of rain," Mass said.
Temperatures have been at or below normal, with no major warm-ups, so what snow has fallen in the mountains has stayed, he said.
"This is not the global-warming scenario," he said. "This is a profound lack of precipitation."
But global warming, atmospheric warming brought on by the increased use of fossil fuels, could contribute dramatically to the region's future climate, according to work the UW climate group did for the U.S. Global Change Research Program.
To be sure, there is no universal agreement on the effects of global warming. At the BPA, spokesman Ed Mosey pointed out that snowpack has been above average for the past five years.
"How do you predict a trend when for the past five years things have been so good?" Mosey said.
The UW's Mote concedes that while temperature forecasts are fairly strong, precipitation forecasts are less so.
More than a half-dozen climate models studied by his group project average annual temperatures in the Northwest will rise about 5 degrees by 2050. On average, a one-degree increase raises the snow line by 300 feet, Mote said.
Moreover, the group predicts warmer, wetter winters will lead to more severe flooding and summer water shortages as there is less snowpack. Snowpack throughout the Northwest would be reduced, and the Columbia Basin's could be as little as half its current average.
And what snow falls will melt sooner. Peak stream flows will be lower, the group predicts, and will peak sooner, leading to more late-summer shortages.