Soot's role in warming underestimated

Matt McGrath in BBC News: New research says that black carbon, or soot, is making a much larger contribution to global warming than previously recognised. Scientists say that particles from diesel engines and wood burning could be having twice as much warming effect as assessed in past estimates.

They say it ranks second only to carbon dioxide as the most important climate warming agent. The research has been published in the Journal of Geophysical Research-Atmospheres.

Black carbon aerosols have been known to warm the atmosphere for many years by absorbing sunlight. They also speed the melting of ice and snow. This new study concludes the dark particles are having a warming effect approximately two thirds that of carbon dioxide, and greater than methane.

"The large conclusion is that forcing due to black carbon in the atmosphere is larger," lead author Sarah Doherty told BBC News. "The value the IPCC gave in their 4th assessment report in 2007 is half of what we are presenting in this report - it's a little bit shocking,"...

An open wood fire, shot by Edoddridge, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Wildfires darkening Greenland snowpack, increasing melting

Ohio State University: Satellite observations have revealed the first direct evidence of smoke from Arctic wildfires drifting over the Greenland ice sheet, tarnishing the ice with soot and making it more likely to melt under the sun.

At the American Geophysical Union meeting this week, an Ohio State University researcher presented images from NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, which captured smoke from Arctic fires billowing out over Greenland during the summer of 2012.

Jason Box, associate professor of geography at Ohio State, said that researchers have long been concerned with how the Greenland landscape is losing its sparkly reflective quality as temperatures rise. The surface is darkening as ice melts away, and, since dark surfaces are less reflective than light ones, the surface captures more heat, which leads to stronger and more prolonged melting.

Researchers previously recorded a 6 percent drop in reflectivity in Greenland over the last decade, which Box calculates will cause enough warming to bring the entire surface of the ice sheet to melting each summer, as it did in 2012. But along with the melting, researchers believe that there is a second environmental effect that is darkening polar ice: soot from wildfires, which may be becoming more common in the Arctic.

“Soot is an extremely powerful light absorber,” Box said. “It settles over the ice and captures the sun’s heat. That’s why increasing tundra wildfires have the potential to accelerate the melting in Greenland.”

... in the Arctic, rising temperatures may be causing tundra wildfires to become more common. To find evidence of soot deposition from these fires, Box and his team first used thermal images from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) to identify large fires in the region. Then they used computer models to project possible smoke particle trajectories, which suggested that the smoke from various fires could indeed reach Greenland....

Glaciers and icebergs at Cape York, Greenland, shot by Brocken Inaglory, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license