Climate Change – Past, Present and Future

Abstract

Local climate is a major determinant of both the composition and behavior of a region's ecosystems and of the infrastructure and culture of human society residing within the region. Hence, climatic statistics are an important factor in ecosystem management and planning for socioeconomic development. However, although decision makers often treat these statistics as a constant, there is clear evidence that climate has changed, is changing, and will change. Large natural changes have occurred in the geologic past. However, these have been relatively modest during the past few millennia. On the other hand, human interference with the climate system, primarily through land use change and changes in atmospheric composition, is now adding an unprecedented and increasingly dominant force for change. There is convincing evidence that this interference has already caused a substantial increase in global mean temperatures over the past 50 years. Projected changes for the next century will likely exceed anything yet experienced in human history and could rival the magnitude of very large changes during the past million years, but at a much more rapid rate. Such rapid change will have dramatic implications for, inter alia, the global hydrological cycle and the frequency and severity of extreme weather events.