How Does Anthropogenic Haze Influence Climate?
high resolution 1000-pixel wide image (1.1 MB JPEG) Greenhouse gases act broadly to warm the atmosphere, but human-induced aerosols (particles in the atmosphere) generate negative forcings?that is cooling of the atmosphere by reflection of the sun’s energy away from Earth. The above photograph from the Space Shuttle was featured in an article in Science magazine this week (Science vol. 300: 1103-1104). It shows haze from China spread over the Pacific Ocean, on March 4, 1996. In the Science article, Anderson and coworkers point out that greenhouse gas forcing on climate is fairly well understood, but the effect of aerosols is not. Two ways of estimating the “forcing,” or push, on global climate caused by aerosols give inconsistent results. So-called “inverse” calculations constrain such cooling to a range of ?1.0 to ?1.9 Watts per square meter, whereas “forward” calculations suggest far greater negative forcing, a
