Why Global Warming Portends a Food Crisis

It can be difficult in the middle of winter — especially if you live in the frigid Northeastern U.S., as I do — to remain convinced that global warming will be such a bad thing. Beyond the fact that people prefer warmth to cold, there's a reason the world's population is clustered in the Tropics and subtropics: warmer climates usually mean longer and richer growing seasons. So it's easy to imagine that on a warmer globe, the damage inflicted by more frequent and severe heat waves would be balanced by the agricultural benefits of warmer temperatures.

comforting thought, except for one thing: it's not true. A study published in the Jan. 9 issue of Science shows that far from compensating for the damages associated with climate change (heavier and more frequent storms, increasing desertification, sea-level rise), hotter temperatures will seriously diminish the world's ability to feed itself. David Battisti, an atmospheric scientist at the University of Washington, and Rosamond Naylor, director of the Program for Food Security and the Environment at Stanford University, analyzed data from 23 climate models and found a more than 90% chance that by the end of the century, average growing-season temperatures would be hotter than the most extreme levels recorded in the past. (See the top 10 green stories of 2008.)

That means that barring a swift and sudden reduction in greenhouse-gas emissions, by the end of the century an average July day will almost certainly be hotter than the hottest heat waves we experience now. And the extreme heat will wilt our crops. Battisti and Naylor looked at the effect that major heat waves have had on agriculture in the past — like the ruthless heat in Western Europe during the summer of 2003 — and found that crop yields have suffered deeply. In Italy, maize yields fell 36% in 2003, compared with the previous year, and in France they fell 30%. Similar effects were seen during a major heat wave in 1972, which decimated farms in the former Soviet Union, helping push grain prices to worryingly high levels. If those trends hold in the future, the researchers estimate that half the world's population could face a climate-induced food crisis by 2100. "I'm very concerned," says Naylor. "How are we going to feed a world of 8 or 9 billion with the effects of climate change?"

more from Time