Most climatologists believe that global warming is a real and accelerating process and that the build up in the atmosphere of CO2 (along with methane and nitrous oxide) is, at least in part, a direct result of human activities. Predictions of the extent and rate of global warming vary widely but based on 1990 figures, increases in air temperatures of between 1.4 and 5.8 1C by 2100 are suggested. Of course, increases in air temperatures lead to increases in land temperatures and the melting of ice sheets and glaciers and the raising of sea levels. Precipitation patterns are also likely to change, with a general intensification of the hydrological cycle. Thus, along with global warming comes global flooding and more frequent extremes in climate.