Climate implications of greenhouse gas emissions scenarios

Global-mean temperature and sea-level implications are calculated for four preliminary emissions scenarios presented elsewhere in this issue. Total an thropogenic temperature change in the year 2100 ranges from 1.3-4.0 degrees C using the four scenarios for upper and lower bounds on emissions and high and low values for the climate sensitivity. The lower bound is higher than that given in the IPCC Second Assessment Report, due mainly to lower futur e sulfur dioxide emissions. These lower emissions also have the effect of r educing uncertainties associated with sulfate aerosol forcing. Significant future climate changes occur in all scenarios, indicating that adaptation p olicies need to be considered as an important component of climate-change p olicy. (C) 2000 Elsevier Science Inc.