Optimistic views of climate impacts on agriculture, drawing on 1990s research, have helped to justify relatively complacent approaches to climate policy. Newer research has identified more ominous climate threats to agriculture—calling for a revised perspective on climate policy. This chapter reviews three categories of climate impacts on agriculture. First, carbon fertilization, although still seen as a benefit to most crops, is now estimated to be smaller than in earlier research. Second, the effect of temperature increases is now recognized to involve thresholds, beyond which yields per hectare will rapidly decline. Finally, changes in precipitation can be crucial—not only in cases of drought, but also in subtler shifts in timing and intensity of rainfall. Response to the climate crisis in agriculture will require adaptation, via the creation of heat-resistant and drought-resistant crops and cultivars, and reduction in greenhouse gas emissions as rapidly as possible, to limit future climate-related damages.