ANN ARBOR—Atmospheric researchers have provided observational evidence that burning fossil fuels has a direct impact on the solar radiation reflectivity of clouds, thereby contributing to global climate change.

Joyce Penner, professor in the University of Michigan Department of Atmospheric, Oceanic and Space Sciences, U-M graduate student Yang Chen, and assistant professor Xiquan Dong from the University of North Dakota Department of Atmospheric Science, reported their findings in the Jan. 15 issue of the journal Nature.

Most evidence that increased levels of fossil fuel particles (aerosols) affects the reflectivity of clouds, thereby producing a cooling effect on the climate, has been indirect.