Introduction and overview

Global population is projected to rise from today's 5.3 billion to more than 8.3 billion by 2025, with about 85% of that population living in developing countries (World Bank 1992). If that population is to be fed and if standards of nutrition are to improve, production of food will need to be increased several times from present levels. Cropland expansion and technological progress in farm production and in the processing sectors will help in meeting this goal. However, there are concerns that we may be running short on land suitable for cultivation and that further improvements in yields may be harder to achieve. Another factor that has recently attracted attention is the likelihood of change in climatic conditions. Climate change is an ongoing process, and global or local climates have changed in the past. Much of the present concern over climate change stems from the perceived negative consequences that might result from an enhanced greenhouse effect.

Some climatologists have long argued that the accumulation of carbon dioxide (CO2) and other greenhouse gases would give rise to global warming and other climatic changes. However, they are not able to predict the exact timing and severity of this greenhouse effect. The best that can be done is to perform simulations with general circulation models (GCMs) that incorporate current knowledge of climatic phenomena and produce internally consistent climate scenarios.