Williams said warming at 10,000 feet and lower may be causing enhanced surface water evaporation and transport that moves westward and higher in the mountains, with the water vapor being converted to snow that falls atop the Continental Divide. Snow cover increases reflectivity of incoming sunlight, further cooling the alpine area and overriding the overall warming signal in the West, which is believed to be a 2 or 3 degree Fahrenheit rise over the past decade due to rising greenhouse gases.
"These two Niwot Ridge stations are less than five miles away from each other -- you can see one from the other -- but there are totally different trends occurring," he said. In many places in the mountainous West, only a small increase in temperature can cause the climate to cross a "threshold" that triggers earlier and more intense snow melting, said Williams, principal investigator on a 2011 grant of $5.9 million from NSF to CU to continue long-term ecological studies at Niwot Ridge.
With snowpack roughly half of normal in 2012 and snow melting in the high country that began more than three months earlier than last year, the outlook is not good for montane and subalpine forests in Colorado and other parts of the West, he said.
Low snowpack and early melt invariably have a huge impact on the Colorado economy, said Williams. Despite near record snowfall in 2010-11, warming temperatures have caused less snow and shorter winters in recent years and affected the ski industr
|Contact: Mark Williams|
University of Colorado at Boulder