Tropospheric Aerosols

Between 1970 and 1990 the major advances in atmospheric chemistry were made in gas-phase photochemistry, except perhaps for a brief intermezzo of “nuclear winter” studies. This focus is now shifting, as it is recognised that natural and anthropogenic aerosols play a substantial role in the radiative properties of the atmosphere and Earth’s climate. In addition, studies on the causes of the Antarctic ozone hole have demonstrated the large role of reactions that take place on ice and particulate surfaces. If such reactions occur in the stratosphere, they must take place also in the troposphere, with its abundance of various types of aerosol. Considering these factors, and especially because of various break-throughs in experimental techniques, it is likely that aerosol research will be prominent in atmospheric chemistry in the coming decades. This research will involve process studies both in the atmosphere and in laboratories, studies on the sources and sinks of aerosols, chemical analyses of the particulate matter (PM), modelling, and especially regional (campaigns) and global (satellites) observations on the distribution of the atmospheric aerosol. This is all the more important because climate models, which in most cases currently consider only sulphur chemistry, cannot be tested sufficiently for want of data, despite the potentially great climate effects of aerosols. Aerosol particles may already be significantly counteracting the radiative forcing by the greenhouse gases (Ramaswamy et al. 2001).