Climate Change and its Consequences

Abstract

Most General Circulation Models (GCMs) realistically simulate large-scale circulation patterns, particularly monsoonal winds over the Asian and Australian regions and their related rainfall patterns, but they underestimate observed magnitudes of these variables. The consistency between model-predicted and observed changes in surface temperature during the last 100 years is good, particularly when these models include the combined effects of increases in carbon dioxide (CO2), sulfate aerosols and solar influences. However, these models underestimate the degree of variability in daily weather phenomena that are associated with local- and meso-scale circulation patterns and daily rainfall. Cyclones and storms which produce heavy rain events, and droughts and floods associated with the El Nino-Southern Oscillation phenomenon, are not well simulated. Observational studies indicate an increasing trend in heavy rainfall intensity and frequency in Australia, Japan and the United States, but the results are mixed (increasing and decreasing trends or no trends) in the former Soviet Union and China. All GCMs simulate an increase in global mean temperature for increased greenhouse gas concentrations, and minimum temperatures tend to increase more than maximum temperatures, leading to a reduction in diurnal temperature range. All GCMs simulate an increase in global mean rainfall but decreases and increases occur on a regional scale, with little agreement between models. In regions which become wetter, some models indicate an increase in heavy rainfall events and a decrease in light rainfall events under enhanced greenhouse conditions. Links between climate change, agriculture, industry and socio-economic factors are very complex in nature. There will be winners and losers, and adaptation to climate change associated with an approximate doubling of present CO2 concentrations will be unavoidable.