Potential Effects of Anthropogenic Trace Gas Emissions on the Atmospheric Ozone, Temperature, Structure and Surface Climate

A coupled one-dimensional 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 the atmospheric ozone, temperature structure, surface climate. Two types of experiments are carried out. The first involves the calculation of the atmospheric equilibrium response to step wise increases 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 time varying trace gas concentrations. It is found that in both cases, the direct and indirect effects of major trace gases other than CO₂ (N₂O, CH₄ and CFCs) contribute substantially to the calculated temperature changes due to increased CO₂ concentrations. The results of the first experiment indicate that by the year 2050, a calculated CO₂ surface warming of about 1.5 k will be enhanced by more than 100% by the direct plus indirect heating contributions due to trace gases other than CO₂. Based on the results in the second experiment, it is shown that for the time varying trace gas scenario ( including CO₂) the surface temperature increases steadily to a value of 3.25 K by the year 2050, except during major volcanic episodes when the heating is temporarily replaced by a slight cooling. Also discussed are the calculated changes in atmospheric ozone, which contribute indirectly to the surface warming and stratospheric cooling.