Aerosols (NASA)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 the US National Aeronoutics and Space Administration (NASA) and the U.S. Climate Change Science Program.

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.

Current predictions of how much Earth’s average surface temperature will increase in the future fall in a wide range. If the amount of carbon dioxide and other greenhouse gases double from the levels in the atmosphere in 1990, the increase in temperature is expected to be from 2.2 to 7.9 degrees Fahrenheit, according to the U.N. Intergovernmental Panel on Climate Change.

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.

“The influence of aerosols on climate is not yet adequately taken into account in our computer predictions of climate,” said Mian Chin, alead author from NASA’s Goddard Space Flight Center.  “An improved representation of aerosols in climate models is essential to more accurately predict the climate changes.”

(NASA Release)

 

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