To translate these equilibrium results into a projection of future climate change requires a scenario for emissions and concentrations. Using rudimen- tary economic modeling, the Intergovernmental Panel on Climate Change (or IPCC), an international panel of distinguished scientists, projected that "busi- ness as usual" would produce a 3 to 6 degree C warming in 2100 (relative to
1900) with the best guess being 4 degrees C. The dashed lines in Figure 1 show the high, best, and low estimates from the IPCC.