PAGE95 is a computer simulation model developed in 1992 for policy analysis of the global warming problem. This paper surveys key developments in understanding the global warming problem that have occurred since 1992. For example, anthropogenic sulphates have been found to have a significant cooling effect. Halocarbons, once thought to be the most potent greenhouse gases, are now believed to have only a slight global warming effect because they destroy ozone, itself a strong greenhouse gas. Furthermore, case studies in various regions of the world have improved our ability to predict future damages from global warming. These developments have strong implications for the economic consequences of the greenhouse effect and motivated an update of the PAGE95 model. This paper discusses the new model version, PAGE95 , and conclusions for global warming policy analysis.