They can be hazardous to human health and the environment.
Aerosol particles also affect the Earth's surface temperature by reflecting light back into space.
The variable cooling and heating that results is, in part, how aerosols modify the stability that dictates atmospheric vertical motion and cloud formation.
Aerosols also affect cloud microphysics because they serve as nuclei around which water droplets or ice particles form.
Both processes can affect cloud properties and rainfall. Different processes may work in harmony or offset each other, leading to complex yet inconclusive interpretations, scientists say, of their long-term net effect.
Researchers agree that greenhouse gases and aerosol particles are two major agents dictating climate change.
The mechanisms of climate warming effects of increased greenhouse gases are clear: they trap solar energy absorbed at the Earth's surface and prevent it from being radiated as heat back into space.
The climate effects of increased aerosols are much less certain.
"This study demonstrates the importance and value of keeping a long record of continuous and comprehensive measurements to identify and quantify the important roles of aerosols in climate processes," says Steve Schwartz, a scientist at Brookhaven National Laboratory.
"While the mechanisms for some of these effects remain uncertain, the well-defined relationships discovered demonstrate their significance," says Schwartz. "Controlling for these processes in models remains a future challenge, but this study clearly points to important directions."
"The findings from ground measurements of long-term effects are consistent with the global effects revealed from satellite measurements reported in our separate study," says Li.
"They attest to the needs of tackling the climate and en
|Contact: Cheryl Dybas|
National Science Foundation