The increase in atmospheric concentrations of man-made aerosols—tiny particles suspended in the air—from such sources as transportation, industry, agriculture, and urban land use not only poses serious problems to human health, but also has an effect on weather and climate. Recent studies suggest that increased aerosol loading may have changed the energy balance in the atmosphere and at the Earth's surface, and altered the global water cycle in ways that make the climate system more prone to precipitation extremes.
It appears that aerosol effects on clouds can induce large changes in precipitation patterns, which in turn may change not only regional water resources, but also may change the regional and global circulation systems that constitute the Earth's climate.
The proposed framework improves scientists' ability to simulate present and future climates by integrating, for the first time, the radiative and microphysical effects of aerosols on clouds. The radiative effects of aerosols on clouds mostly act to suppress precipitation, because they decrease the amount of solar radiation that reaches the land surface, and therefore cause less heat to be available for evaporating water and energizing convective rain clouds. Microphysical effects of aerosols can slow down the conversion of cloud drops into raindrops, which shuts off precipitation from very shallow and short-lived clouds….Cloud wall associated with fast moving cold front, NOAA, Wikimedia Commons