Climate report cites risks for Colorado

Todd Hartman, Rocky Mountain News

Published April 7, 2007 at midnight

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The Front Range could see more air pollution, more cases of West Nile virus and an increased risk of wildfires and reservoir-clogging sediment as global temperatures rise.

The forecasts were based on the latest international assessment of the impacts of climate change released Friday in Brussels, Belgium, and discussed via teleconference by a team of five researchers with the Boulder-based National Center for Atmospheric Research who contributed to the report.

Scientists repeated warnings that the Rocky Mountains are likely to see a drop in snowpack and earlier snowmelt as temperatures increase. But they also raised newer concerns about smog, disease threats and wildfire risks, all applicable to Colorado and the Denver region.

The metro area, struggling with unhealthy smog levels, could see the problem get worse, since ground-level ozone, a major component of smog, is formed when certain pollutants bake in clear, hot, stagnant skies.

Scientists cited research predicting a 68 percent rise in unhealthy smog days in the eastern United States by 2050, but they noted the problem applied in any urban areas with elevated ozone levels.

Prevalence of the mosquito-borne West Nile virus, which hit Colorado hard in 2003, could increase with warming weather, said Jonathan Patz, an NCAR affiliate based at the University of Wisconsin-Madison.

"Studies have shown that our particular American strain of West Nile virus, the New York strain, shows particular sensitivity to warmer temperatures," Patz said.

He cautioned against assigning simple "winners and losers" to climate change. A longer growing season that could benefit some American farmers, he said, may have drawbacks for others.

He noted a study that found warming winters in Russia brought an increase in prevalence of the often-fatal hantavirus carried by deer mice and occasionally spread to people. The disease has claimed several Colorado victims in the past decade.

The NCAR scientists based their comments on the latest report from the Intergovernmental Panel on Climate Change, which has tracked studies of global warming since the U.N. assembled the panel in 1988.

In February, the IPCC issued a report finding a 90 percent certainty that human activities - including emissions of carbon dioxide from cars and power plants - were the primary cause of warming.

The latest report, released Friday, focused more on global warming's regional impacts on people, species and water.

In Colorado, warming is likely to deplete snowpack and lead to earlier melt-off in spring, creating a ripple effect in the forest by drying up soil moisture, leaving trees more susceptible to insect damage and wildfires.

"The melting snowpack is also going to increase wildfire activity, and Denver is probably the poster child for that," said Kathleen Miller, an NCAR scientist who wrote a chapter on global warming's impact on fresh water.

Miller said that earlier melt- off and more fires expose reservoirs to more dirt and debris that flow off the landscape when rainstorms hit fire- scarred land.

She noted that Denver Water is still recovering from sediment flows that poured into Cheesman Reservoir after the massive Hayman Fire in 2002.

Colorado and the southwestern U.S. may suffer the same fate that threatens other heavily populated arid and semi-arid regions. Such locales, including the Mediterranean basin, northeast Brazil and southern Africa, are likely to see water supplies decline 10 percent to 30 percent by mid-century, Miller said.

Stephen Saunders, president of the Rocky Mountain Climate Organization, called the latest report "the most authoritative statement possible that climate disruption is already showing up in the American West as less snow, less water, more drought and more wildfire."

hartmant@RockyMountainNews.com or 303-954-5048

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