The National Science Foundation (NSF)-funded researchers, led by scientists at the Georgia Institute of Technology, also have developed a new instrument for measuring the conditions and time needed for a particle to become a cloud droplet. This will help scientists determine how various types of emissions affect cloud formation.
Georgia Tech scientist Athanasios Nenes will present a lecture on the work at the American Geophysical Union's fall meeting in San Francisco on Dec. 17. The session is titled "Tropospheric Aerosol Processes: The Physical and Chemical Aging of Aerosol Particles and Their Impacts."
Clouds play a critical role in climate, Nenes explained. Low, thick clouds cool the earth by reflecting solar radiation whereas high, thin clouds have warming properties by trapping infrared radiation emitted by the earth.
Scientists have learned that human activities influence cloud formation. Airborne particles released by smokestacks, charcoal grills and car exhaust restrict the growth of cloud droplets, causing condensing water to spread out among a larger number of smaller droplets. Known as the "indirect aerosol effect," it gives clouds more surface area and reflectivity, which translates into greater cooling power. The clouds may also have less chance of forming rain, which allows cloud to remain longer for cooling.
"Of all the components of climate change, the aerosol indirect effect has the greatest potential cooling effect, yet quantitative estimates are highly uncertain," said Nenes. "We need to get more rigorous and accurate representation of how particles modify cloud properties. Until the aerosol indi