Greenhouse Gases and Climate Change

At current growth rates in the emissions of greenhouse gases, we can expect increases in concentrations equivalent to a doubling of the pre-industrial concentration of CO₂ by about 2030. Most of the general circulation models show an equilibrium heating, an increase of annual average global temperature, in the neighborhood of 3 to 5 degrees Celsius for a doubling of CO₂ concentration. The effects of climatic change are probably nonlinear. Some of the physical impact, sea level rise, for example, may be a linear function of average warming over some range, but the impact of the sea level rise will be highly nonlinear. About 60 percent of the greenhouse gases appear to come from fossil fuels, the rest from a number of other sources. Both the ocean's and the biosphere's capacity to fix carbon are dependent upon complex processes that are affected by temperature and carbon dioxide concentration.