WASHINGTON — Rising temperatures will cause Oregon’s snowpack to melt earlier and lead to drier summers, raising fears of increased catastrophic wildfires, a new Obama administration report on climate change warned last week.
Between 1895 and 2011, temperatures increased across the Pacific Northwest by an average of 1.3 degrees, according to the National Climate Assessment, an interagency report released Tuesday that summarizes the latest science on climate change.
Scientific models predict that by the end of this century, average temperatures in the region will increase by an additional 3.3 to 9.7 degrees.
As a result, Oregon’s snowpack will melt three to four weeks earlier in the year by 2050, putting additional strain on a much-in-demand resource.
Summers will be up to 10 percent drier, further reducing water flows in rivers and streams, according to projections.
“These reduced flows will require more tradeoffs among objectives of the whole system of reservoirs, especially with the added challenges of summer increases in electric power demand for cooling and additional water consumption by crops and forests,” the report’s chapter on the Pacific Northwest states.
Reduced access to water will increase competition in the region’s forests, making trees more vulnerable to insects and disease, the report continues. Catastrophic wildfires, which have grown significantly larger and more destructive since 1970, will continue to increase.
Under a scenario where heat-trapping greenhouse gas emissions continue to increase dramatically, models predict that by 2080, the probability of 2.2 million acres burning in the region each year will be 50 percent, a tenfold increase from current conditions.
To put that in context, last year 4.3 million acres burned nationwide, down from 9.3 million acres in 2012, which was one of the three worst fire years on record, according to the National Interagency Fire Center. Six of the worst fire years since 1960 have happened in the last decade.
“Wildfire, insects and diseases are already transforming the areas around us,” said Phil Mote, director of the Oregon Climate Change Research Institute and a co-author of the National Climate Assessment’s Northwest chapter.
“When these very large fires occur, they’re occurring in proportions that are historically unprecedented.”
Michael Strobel, director of the U.S. Department of Agriculture’s National Water and Climate Center in Portland, said the report’s findings weren’t surprising, but the increased level of scientific certainty behind them make them more compelling.
“What we’re saying isn’t really new. We’re saying it more definitely,” he said. “We’re stating it more firmly now that I think the evidence is stronger.”
Particularly in the West, where much of the precipitation comes as high-altitude snow across tall mountains, snowpack acts as nature’s reservoir system, he said.
Unlike in the taller Rockies, temperatures at the peak of the Cascades often hover around freezing, he said.
“Small changes here in temperature, even a few degrees, makes a huge difference on snowpack,” he said.
If the region is warmer and drier, particularly in the summer months, water will become scarcer, as more is lost to evaporation and to parched ground, much as a dry sponge will absorb water that would flow over a wet one.
This will affect numerous aspects of life in Oregon. Much of Oregon’s agriculture relies on irrigation, and the state may face a reduction in viable cropland and output, according to a report prepared last year by the Oregon Climate Change Research Institute.
Reservoir management will become trickier when more water is released earlier in the year.
“Earlier snowmelt and peak flow means that more water will run off when it is not needed for human uses and that less water will be available to help satisfy early summer water demand,” the OCCRI’s report states.
Recreational activities — rafting, skiing, hunting, fishing, camping and hiking — will also be affected.
“It’s a change in the system, and that’s what we’re concerned about,” said Strobel, whose personal involvement with climate change research dates back to 1983, when he studied glaciers in Peru.
Strobel supervises the Natural Resource Conservation Service’s snow survey and water supply forecasting program, which has 885 automated snow-measuring sites complemented by 1,185 sites operated manually. Partly through the information this program provides, scientists can not only observe what happened historically but make increasingly accurate predictions about future events.
“Having good data is the critical piece here,” he said.
The national report represents a collection of aggregate risks posed by climate change, Mote said.
“Our objective was to collect those impacts and put them in a risk-framing matrix,” he said, where risk is defined as the product of likelihood and consequence.
While the results can appear dire, they also present an opportunity to modify our behavior and mitigate the impacts of climate change, he said.
“Climate change is real, it’s happening now and it’s affecting Americans. And there are opportunities now to affect the risk and magnitude,” he said.
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