CSSP Report Calls for More Study on Aerosols

Scientists need a more detailed understanding of how human-produced atmospheric particles, called aerosols, affect climate in order to produce better predictions of Earth's future climate, according to a NASA-led report issued by the U.S. Climate Change Science Program on Jan. 16.

"Atmospheric Aerosol Properties and Climate Impacts," is the latest in a series of Climate Change Science Program reports that addresses various aspects of the country's highest priority climate research, observation and decision-support needs. The study's authors include scientists from NASA, the National Oceanic and Atmospheric Administration, and the Department of Energy.

"The influence of aerosols on climate is not yet adequately taken into account in our computer predictions of climate," said Mian Chin, report coordinating lead author from NASA's Goddard Space Flight Center in Greenbelt, Md. "An improved representation of aerosols in climate models is essential to more accurately predict the climate changes."

Aerosols are suspended solid or liquid particles in the air that often are visible as dust, smoke, and haze. Aerosols come from a variety of natural and human processes. On a global basis, the bulk of aerosols originate from natural sources, mainly sea salt, dust, and wildfires. Human-produced aerosols arise primarily from a variety of combustion sources. They can be the dominant form of aerosol in and downwind of highly populated and industrialized regions, and in areas of intense agricultural burning.

Although Earth's atmosphere consists primarily of gases, aerosols and clouds play significant roles in shaping conditions at the surface and in the lower atmosphere. Aerosols typically range in diameter from a few nanometers to a few tens of micrometers. They exhibit a wide range of compositions and shapes, but aerosols between 0.05 and 10 micrometers in diameter dominate aerosols' direct interaction with sunlight. Aerosols also can produce changes in cloud properties and precipitation, which, in turn, affect climate.

The role of greenhouse gases in global warming is fairly well established, but the degree to which the cooling effect of human-produced aerosols offsets the warming is still inadequately understood. The report states that scientists should strive to improve their understanding of aerosols' climate influences with the goal of cutting that range of uncertainty by nearly two-thirds.

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