Monday, 3 June 2002: 9:45 AM
East Asia Source Region Aerosols (EASRA): An Ideal Testbed for Studying the Direct and Indirect Climate Effects of Natural and Anthropogenic Aerosols
The importance of aerosols in the work of the Earth's climate system is being increasingly realized, but it remains a daunting task to fully understand and unravel the complex effects. To tackle the problem readily with significant scientific impact, we shall direct a major effort to special regions where not only are aerosols laden and unique but also the climate is exceptionally sensitive to their influences. One ideal region is East Asia with its heart located in China. Aerosols in China have so many unique properties that warrant much attention. First, China is one of the major aerosol sources in the world and has exhibited apparent increasing trend over the last two decades. Mean aerosol optical depth in China is about twice the world mean value. Second, three major types of aerosols co-exist in China, namely, sulfate and carbonaceous aerosols and dust aerosol, some of which (e.g. dust) can travel a long distance (e.g. US) affecting a much bigger area. In general, aerosols observed in China are much more absorbing than those found in most parts of the world, rendering strong radiative forcing at the top, inside, and bottom of the atmosphere. Strong direct radiative forcing seems to have caused significant cooling over a considerable portion of the country in the south. Third, there is likely a strong indirect effect on the hydrological cycle that may threaten the well-being of over a billion people. Since the country's modernization beginning in the late 1970s, there are apparently strong regional correlations between aerosol loading, surface temperature, and precipitation. It is argued that the ever-increasing climate pattern of "north draught and south flooding" is caused at least partially by increasing aerosol loading. Several potential aerosol-related mechanisms are yet to be explored to explain the trend ranging from the conventional direct and indirect effects to complex feedbacks involving dynamic, physical and chemical processes. These are some of the major goals of a newly proposed international initiative to be presented at the conference.