Concern about the extent of global climate change and its potential consequences has increased dramatically in recent years. Many believe that unprecedented climate changes are – or soon will be – occurring as the result of man-made emissions of greenhouse gases. There remain large uncertainties, however, about the relationship between emissions of greenhouse gases and their atmospheric concentrations, about the link between atmospheric concentrations and global climate change, about whether extraordinary changes in climate are actually occurring, and about the impacts of climate changes on people and ecosystems.
The largest man-made source of greenhouse gases is carbon dioxide produced by the combustion of fossil fuels in utility and industrial boilers, and in internal combustion engines. Thus, any effort to reduce greenhouse gas emissions will start with efforts to restrict these activities. Therefore, it seems essential to develop a range of projections of the likely costs of alternative levels of control of carbon emissions from the energy sector.
A fundamental challenge facing policy makers is the need for all or most of the world’s largest countries to co-operate in restricting greenhouse gas emissions; greenhouse gas emissions anywhere affect atmospheric concentrations (and climate) everywhere. The 24 developed countries that are members of the Organization for Economic Cooperation and Development (OECD) currently produce slightly less than half of the world’s carbon dioxide emissions, and that percentage, even in the absence of emissions controls, is projected to decrease dramatically by the middle of the next century (to one third or so of the world total). Thus, if only the OCED countries control emissions, that may have only a very minor impact on world emissions and world climate. If only part of the OCED participates the impact would be even less.
The twelfth Energy Modeling Forum (EMF) working group met five times from September 1990 to May 1992 to compare alternative projections of the impacts of a number of greenhouse gas emission control scenarios. The working group specified thirteen control levels, as well as sensitivities on key standardized inputs. These scenarios were ultimately implemented by fourteen modeling teams employing a a wide variety of techno-economic models, although not every model could implement every scenario. In addition to these model comparisons, ten study groups were formed to analyze issues not being addressed by the fourteen models and thirteen scenarios. These groups used additional models and methods to analyze issues not addressed in the thirteen original scenarios.