Moffett Field, CA — A recent NASA study links natural and human-made aerosol particles to how much Earth warms or cools. Earth's atmosphere acts as a protective shield that regulates how much solar energy the planet absorbs or deflects. The Intercontinental Chemical Transport Experiment studied how chemicals and pollution affect that protective shield by measuring air flowing from North America and across the Atlantic Ocean.

"The majority of aerosols form a layer of haze near the Earth's surface, which can cause either a cooling or warming effect, depending on aerosol type and location," said Jens Redemann, lead author of the science paper at NASA Ames Research Center, Moffett Field, Calif.

Different types of aerosol particles can influence visible light and other kinds of radiation, affecting climate and temperatures, the scientists reported. "Changing the flow of radiation – including light – above and within the atmosphere changes the energy available for driving Earth's climate," said Phil Russell, also a NASA Ames scientist.

"Our study measured how aerosols change the flow of solar energy," Russell said. This solar energy includes visible light and also radiation at shorter and longer wavelengths in the ultraviolet and infrared ranges.

To find out the extent to which tiny particles in the air could affect climate, NASA scientists flew in a low-flying aircraft over the dark waters of the Gulf of Maine. Two types of instruments on the aircraft measured radiation from the sun.

Radiometers – devices that measure the intensity of radiant energy – measured total solar energy coming from all directions. At the same time, a sun photometer – an instrument that measures the intensity of the sun’s light – measured sunlight coming directly, straight from the sun through the atmosphere. The quantity of aerosols in the atmosphere between the sun photometer and the sun is proportional to the difference between the light intensity measured by the sun photometer and the amount of light that would pass through an aerosol-free atmosphere.

Combining measurements of total solar light intensity from all directions, solar light intensity directly, straight from the sun, and the amount of aerosols in the atmospheric column, scientists can estimate how much of the sun’s energy is scattered (redirected) and absorbed (causes heating) by atmospheric aerosols. These measurements are useful to climate scientists as a reality check for computer climate models.