A global assessment of the potential impact of climate change on world food supply suggests that doubling of atmospheric carbon dioxide concentration will lead to only a small decrease in global crop production. However, developing countries are likely to bear the brunt of the problem, and simulations of the effect of adaptive measures by farmers imply that these will do little to reduce the disparity between developed and developing countries. Recent research has focused on regional and national evaluations of the effects of climate change on agriculture. These studies have largely treated each region or nation in isolation. Recent work emphasizes the important role of international trade in adjusting the world food system to climate change-induced changes in crop yields. Crop growth models have been used in an international collaboration to determine the effect of various climate change scenarios on crop yields for individual countries and geographical regions. This study combines data from these individual studies to obtain a global picture of the simulated change in crop yield associated with different climate change scenarios. A world food trade model is then used to simulate the economic consequences of these potential changes in crop yields, estimating changes in world food prices and the number of people at risk of hunger in developing countries. The major finding of the study is that there is a large disparity in agricultural vulnerability to climate change between developed and developing countries. This occurs even though simulated global agricultural production of major grain crops declines are only small to moderate under the climate change conditions tested. The analysis included the combined effects of climate change and increasing CO₂ on crop yields and water use. Although projected temperature change in low latitudes tends to be lower than the global average in the general circulation model scenarios tested, modelled yield changes are primarily negative there, in contrast to predominantly positive yield changes in middle and high latitudes where many developed countries are located. This result has significant implications for potential future distributional aspects of the world food system. Studies such as this explore the sensitivity of important human systems (in this case, world food supply) to projected levels of global climate change. Such studies are initial demonstrations of the comprehensive, interdisciplinary research needed to improve understanding of the interactive biophysical and socio-economic effects that may result from global environmental change. The study used climate change scenarios developed from climate conditions predicted by three GCMs for doubled atmospheric CO₂ levels. The temperature changes of these GCM scenarios (4.0–5.2 °C) are near the upper end of the range (1.5–4.5 °C) projected for doubled CO₂ warming by the IPCC. Mean monthly changes in temperature, precipitation, and solar radiation from the appropriate GCM gridbox were applied to observed daily climate records to create climate change scenarios for each study site. The study estimated potential changes in national grain crop yields using compatible crop models and GCM scenarios at 112 sites. The crop model linkages were developed by the US Agency for International Development. Simulations were carried out in regions representing 70–75% of the current world production of wheat, maize,A global assessment of the potential impact of climate change on world food supply suggests that doubling of atmospheric carbon dioxide concentration will lead to only a small decrease in global crop production. However, developing countries are likely to bear the brunt of the problem, and simulations of the effect of adaptive measures by farmers imply that these will do little to reduce the disparity between developed and developing countries. Recent research has focused on regional and national evaluations of the effects of climate change on agriculture. These studies have largely treated each region or nation in isolation. Recent work emphasizes the important role of international trade in adjusting the world food system to climate change-induced changes in crop yields. Crop growth models have been used in an international collaboration to determine the effect of various climate change scenarios on crop yields for individual countries and geographical regions. This study combines data from these individual studies to obtain a global picture of the simulated change in crop yield associated with different climate change scenarios. A world food trade model is then used to simulate the economic consequences of these potential changes in crop yields, estimating changes in world food prices and the number of people at risk of hunger in developing countries. The major finding of the study is that there is a large disparity in agricultural vulnerability to climate change between developed and developing countries. This occurs even though simulated global agricultural production of major grain crops declines are only small to moderate under the climate change conditions tested. The analysis included the combined effects of climate change and increasing CO₂ on crop yields and water use. Although projected temperature change in low latitudes tends to be lower than the global average in the general circulation model scenarios tested, modelled yield changes are primarily negative there, in contrast to predominantly positive yield changes in middle and high latitudes where many developed countries are located. This result has significant implications for potential future distributional aspects of the world food system. Studies such as this explore the sensitivity of important human systems (in this case, world food supply) to projected levels of global climate change. Such studies are initial demonstrations of the comprehensive, interdisciplinary research needed to improve understanding of the interactive biophysical and socio-economic effects that may result from global environmental change. The study used climate change scenarios developed from climate conditions predicted by three GCMs for doubled atmospheric CO₂ levels. The temperature changes of these GCM scenarios (4.0–5.2 °C) are near the upper end of the range (1.5–4.5 °C) projected for doubled CO₂ warming by the IPCC. Mean monthly changes in temperature, precipitation, and solar radiation from the appropriate GCM gridbox were applied to observed daily climate records to create climate change scenarios for each study site. The study estimated potential changes in national grain crop yields using compatible crop models and GCM scenarios at 112 sites. The crop model linkages were developed by the US Agency for International Development. Simulations were carried out in regions representing 70–75% of the current world production of wheat, maize,