Dr. Roger Pielke forwarded me his latest paper published in the JOURNAL OF GEOPHYSICAL RESEARCH, for release. It has quite a different take on the issue of regional warming in Alaska. Given the emotional testimony given in congress this week by Cheryl Charlee Lockwood, who is a recent high school graduate and works in the Alaska Youth for Environmental Action program, before the House Select Committee on Energy Independence and Global Warming, this study seemed relevant to current events.
From the abstract:
“Invasive shrubs and soot pollution both have the potential to alter the surface energy balance and timing of snow melt in the Arctic. Shrubs reduce the amount of snow lost to sublimation on the tundra during the winter leading to a deeper end-of-winter snowpack. The shrubs also enhance the absorption of energy by the snowpack during the melt season by converting incoming solar radiation to longwave radiation and sensible heat. Soot deposition lowers the albedo of the snow, allowing it to more effectively absorb incoming solar radiation and thus melt faster.”
“The results of the simulations suggest that a complete invasion of the tundra by shrubs leads to a 2.2°C warming of 3 m air temperatures and a 108 m increase in boundary layer depth during the melt period. The snow-free date also occurred 11 d earlier despite having a larger initial snowpack. The results also show that a decrease in the snow albedo of 0.1, owing to soot pollution, caused the snow-free date to occur 5 d earlier. The soot pollution caused a 1.0°C warming of 3 m air temperatures.”
The entire paper can be viewed here (PDF file) There is some precededence for the soot theory, as seen in this 2003 NASA News Release where they say “…black soot may be responsible for 25 percent of observed global warming over the past century.”