Potential effects of anthropogenic trace gas emissions on atmospheric ozone and temperature structure and surface climate

Abstract

A coupled 1-D radiative-convective and photochemical diffusion model is used to assess the possible effects of past historical and projected future anthropogenic emissions of major trace gases on atmospheric ozone and temperature structure and surface climate. Two types of experiments are carried out. The first involves the calculation of equilibrium response of the atmosphere to a step-wise increase in trace gas emissions. The second experiment which also considers the major volcanic events that took place in the past, calculates the transient atmospheric response to a time varying trace gas concentrations. It is found that in both cases, the direct and indirect effects of non-CO 2 major trace gases (N 2O, CH 4 and CFCs) contribute substantially to the calculated temperature changes due to increase in CO 2 concentrations. The results in the first experiment indicate that by the year 2050 the calculated CO 2 surface wanning of about 1.5 K will be enhanced by more than 100% by the direct plus indirect heating contributions due to non-CO 2 trace gases. Based on the results in the second experiment, it is shown that for the time varying combined trace gas scenario (including CO 2) the surface temperature rises steadily to a value of 3.25 K by the year 2050 except during the major volcanic episodes when the heating is replaced by slight cooling temporarily. Also discussed are the calculated changes in atmospheric O 3 which contribute indirectly to the surface wanning and stratospheric cooling.