Ozone Depletion and Global Warming

Abstract

Abstract This thesis examines global warming and the possible contribution that ozone depletion provides to this warming. An examination is performed to determine the extent of any warming/cooling events within the Earth-atmosphere system. The change in energy corresponding to this warning of the Earth- atmosphere system is estimated as being equivilent to an increase of mean solar input of 0.22W/m2. This is compared to the predicted changes of solar input for the two most common global warming scenarios: greenhouse gases and solar irradiance variance; and for a less well explored scenario, snow-ice albedo change. Examination of ozone depletion data shows that an absence of ozone in the stratosphere produces an increase in UV-B radiation at the surface of the Earth. This increase in UV-B light has not previously been thourougly examined in any of the global warming scenarios. This is presented as a fourth scenario for global warming. An analytical three layer model of the Earth-atmosphere, based on an earlier two layer model, is developed. Using this model it is determined that greenhouse gases, solar irradiance, snow-ice albedo feedback and ozone depletion can cause warming of the Earth's atmosphere. After comparison with other models, a snow-ice albedo mechanism is incorporated into the three layer model. This produces an amplification effect of any warming that occurs. Compared to the observed increase of surface temperature between 1975-2000 of 0.55 K, the model using a snow-ice albedo feedback, produced an increase of temperature of 1.4 K for greenhouse gases, 0.294 K for a solar irradiance increase and 0.119 K caused by a decrease in the ozone layer. Of the greenhouse gas, solar irradiance and ozone depletion scenarios, ozone depletion demonstrates the most realistic relative changes with a cooling of the stratosphere and a warming of the troposphere and Earth's surface as has been observed. It is concluded that ozone depletion is likely for a reasonable part of observed global warming.