April 23, 2008

Arctic Haze Examined for Signs of Climate Change

Although carbon dioxide and greenhouse gases are known to be the root cause of global warming, scientists have set out in government research planes to determine if airborne particles known as aerosols are also causing the rise in Arctic temperatures.

Using technology such as mass spectroscopy, a technique that is used to find the composition of a physical sample, researchers hope to identify the components of the Arctic haze as well as discover where it came from and how it interacts with the clouds, the sunlight and the snow cover.

The research is commissioned by NASA, the Department of Energy and the National Oceanic Atmospheric Administration, and involves about 275 scientists and support staff and five aircraft.

Chemical analysis of their collected samples show a "United Nations of pollution" caused by particles that can be traced to their sources throughout Asia, Europe and North America.

"The Arctic is a melting pot for mid-latitude pollution," said Daniel Jacob, a Harvard scientist involved with the research. "We have signatures of just about everything you can imagine flying around in the Arctic."

Glenn Shaw took a light meter to Barrow, America's northernmost community. He thought he would find an area rich with the cleanest air on earth.

"I was expecting to set a record," he said, "because at the northern tip of Alaska, there's no industry, and the idea was that this must be the cleanest place, essentially, almost, on planet Earth."

"The important thing was, and is, this is aerosol material that is traveling over three or four thousand miles, which was unprecedented at the time," he said, referring to pollutants discovered by the team.

Another issue on the researchers' agenda is determining how the size and density of the particles of soot alter the type and longevity of clouds. Also, they hope to find out whether the airborne particles reflect heat back into space or absorb it, said Greg McFarquhar, researcher at the University of Illinois.

"How much of this aerosol is there?" asked A.R. Ravishankara of NOAA's Earth System Research Laboratory. "Do they absorb light? Do they scatter light? Do they make clouds brighter or dimmer? Are they getting to the ice surface? Because if you add these absorbing particles to the ice surface, it could actually enhance the melting."

If aerosols prove to be a major factor in warming, Ravishankara said, removing them could yield relatively fast benefits for the environment.

"It lasts only for a few days, and then it's removed from the atmosphere, unlike carbon dioxide, which stays with us for hundreds of years," he said. "Aerosols can be a way to do something very quickly."


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