Recent research paints an ominous picture of climate impacts on agriculture, in contrast to the relative optimism of research from the 1990s. Continued use of the earlier research findings, in economic models and policy analyses, contributes to an unwarranted complacency about the urgency of climate policy.
Earlier research concluded that the initial stages of climate change would bring net benefits to global agriculture, thanks to carbon fertilization and longer growing seasons in high-latitude regions. This conclusion has been challenged in at least three respects. First, newer experimental studies have sharply reduced older estimates of carbon fertilization effects. Second, the effect of temperature on many crops has been found to involve thresholds, above which yields rapidly decline; the number of hours above the threshold is typically more important than the average temperature. Third, climate change will bring significant changes in precipitation; in a number of important areas, decreases in precipitation may cause declines in agricultural production. Simple, aggregated economic analyses of climate change have often omitted these crucial effects of precipitation.
Adaptation to warmer and often drier conditions is necessary but not sufficient for agriculture. Within a few decades, business-as-usual climate change would reach levels at which adaptation is no longer possible. Emission reduction and climate stabilization are essential to any long-run solution for global agriculture.