Global warming losers: why developing world agriculture stands to suffer big time.

• Author: Cline, William R.

Fifteen years ago the Institute for International Economics published my book, The Economics of Global Warming. In that study I made rough estimates of the damages that could be expected for the U.S. economy from long-term global warming. Agriculture was an important category in my list of expected losses, not surprisingly for anyone who has read John Steinbeck's Grapes of Wrath with its account of 1930s dust bowl conditions in Oklahoma and Arkansas. My estimates were based on EPA studies of agricultural impacts.

In recent years there has been a certain revisionism toward more benign diagnoses of prospective effects of global warming on agriculture. Some have argued that up to an additional 2[degrees]C or even 3[degrees]C in global mean surface temperatures would lead to global benefits rather than losses, because of improved growing conditions in cold regions and because of "carbon fertilization" from increased atmospheric concentrations of carbon dioxide (which is an input into the process of photosynthesis). At the same time, there has been a growing body of research indicating that the developing countries will be the ones to suffer most and earliest, because their predominantly low-latitude location makes their temperatures already close to or above levels at which additional warming reduces productivity.

[ILLUSTRATION OMITTED]

Research findings in recent years have provided a growing base of model estimates that can offer the basis for a more comprehensive and systematic analysis of the impact of global warming on world agriculture than previously available. My new book makes such estimates for late in this century (the 2080s) at a geographically detailed level, with calculations for more than one hundred countries, regions, and sub-regions within the largest countries. This essay summarizes my findings and considers their implications for international policy.

The first question is whether the world as a whole faces devastating agricultural losses. The answer turns out to be no, at least in the central estimate: there would be aggregate losses on net, but they would be modest to moderate. The second question is whether the developing countries would be at risk. The answer is a definite yes, especially in South Asia, Africa, and Latin America. Yet even here it turns out that there is a major caveat: the most important developing country of all for global warming policy, China, is about neutrally affected overall (despite potentially...