This paper uses the Ricardian approach to examine how farmers in 11 countries in Africa have adapted to existing climatic conditions. It then estimates the effects of predicted changes in climate while accounting for whatever farmer adaptation might occur. This study differs from earlier ones by using farmers' own perceptions of the value of their land. Previous research, by contrast, has relied on either observed sale prices or net revenues, sometimes aggregated over geographically large tracts of terrain. The study also makes use of high resolution data describing soil quality and runoff. Furthermore, it tackles the challenges involved in modeling the effect of climate on agriculture in a study that includes countries in the northern and southern hemispheres, as well as the tropics. The study confirms that African agriculture is particularly vulnerable to climate change. Even with perfect adaptation, regional climate change by 2050 is predicted to entail production losses of 19.9 percent for Burkina Faso and 30.5 percent for Niger. By contrast, countries such as Ethiopia and South Africa are hardly affected at all, suffering productivity losses of only 1.3 percent and 3 percent, respectively. The study also confirms the importance of water supplies as measured by runoff, which, being affected by both temperature and precipitation, may itself be highly sensitive to climate change.