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Arctic warming from aerosol particles
Although most climatologists seem to blame manmade greenhouse gases such as carbon dioxide for the warming trend in the Arctic that is causing a loss of Arctic ice and the melting of permafrost, some new research by scientists from the National Aeronautics and Space Administration has discovered that 45 percent or more of the warming may, in fact, result from the presence in the Arctic atmosphere of tiny particles known as aerosols.
The particles, which can be emitted into the atmosphere as solids or liquids from a wide variety of sources including fires, volcanic eruptions and industrial activity, can affect the climate by either reflecting or absorbing the sun’s radiation. Reflection of the radiation causes cooling, while absorption of the radiation causes warming.
“There’s a tendency to think of aerosols as small players, but they’re not,” said Drew Shindell, a climate scientist in the NASA Goddard Institute for Space Studies and leader of a team investigating the regional climatic effects of aerosols, carbon dioxide and ozone. “Right now, in the mid-latitudes of the northern hemisphere and in the Arctic, the impact of the aerosols is just as strong as that of the greenhouse gases.”
Sulfates, black carbon Using a computer model that couples the behavior of the atmosphere with that of the oceans, the scientists determined that two human-generated aerosols, sulfates and black carbon, play especially important roles in regulating climate change. Sulfates, products of the burning of oil and coal, cool the climate; black carbon, a soot-like product from the burning of a variety of fuels, warms the climate.
And, while U.S. and European emissions regulation has reduced sulfate emissions in recent years, black carbon emissions have risen steadily, especially from Asia. The net consequence has been an increase in the warming effect of the aerosols, the scientists concluded.
That warming effect has likely become especially prevalent in the Arctic, in part because of the proximity of the Arctic to major industrial sources of aerosol materials, and in part because precipitation that would otherwise flush particulate matter from the air is relatively sparse at high latitudes, Shindell said. In the Antarctic, where aerosols are less abundant, warming has been significantly lower than in the Arctic, he said.
“We will have very little leverage over climate in the next couple of decades if we’re just looking at carbon dioxide,” Shindell said. “If we want to try to stop the Arctic summer sea ice from melting completely over the next few decades, we’re much better off looking at aerosols and ozone.”
—Alan Bailey
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