Endless World Reconnaissance

Emily Sohn, Discovery News

Jan. 21, 2009 -- By the end of the century, the hottest temperatures in recent history will become typical, and the world's food supply will be in deep trouble as a result.

Those grim predictions come from a new study that looked at heat waves of the past as well as climate projections for the future to paint a frightening picture of what's to come: severe food shortages and rising malnutrition, especially in places where people are already poor and hungry.

"The changes are so big and in the wrong direction in places where it really matters," said agricultural economist David Bittisti, of the University of Washington, Seattle. He led the study, which appeared recently in the journal Science.

Battisti urges immediate reductions in fossil fuel emissions and agricultural preparations for a warmer world.

"If we don't adapt, we will have really serious problems," he told Discovery News. "People will need to either migrate or die."

Battisti and colleagues used 23 global climate models to forecast average growing season temperatures through the end of the century. All the models agreed: With our current rate of greenhouse gas emissions, there is a greater than 90 percent chance that by 2100, summers in the tropics and subtropics will be hotter than the hottest summers recorded between 1900 and 2006.





In temperate regions, last century's most extreme summers will be the norm.

To predict how such temperature changes might affect crop growth, the scientists looked at several past examples of extreme heat, including Western Europe's record hot summer of 2003. During that three-month heat wave, some 52,000 people died from heat-related stress, and corn yields dropped by more than 30 percent in Italy and France.

With time, growers can usually recover from events like these. But if temperatures get excessively hot and stay that way -- and not just locally but everywhere, the situation could be disastrous.

"We're looking at reductions in crop yield of 20, 30, or 40 percent in some cases," Battisti said. "The fact that this is a global impact all at the same time means that there [will be] no where to turn for food."

The tropics and subtropics include Africa, central Europe, Asia, the Middle East, Australia, Central America, the southern United States, and northern South America. More than 3 billion people live in those regions. One third of them are already malnourished, Battisti said. And the population will only continue to grow.

"They've given us an early glimpse into territory beyond charted human experience," said geographer Bill Easterling, of Pennsylvania State University in University Park. "We could be up against challenges for which we have no historical experience."

The study drives home the need to research and develop new agricultural strategies, Easterling added, such as more heat-resistant and drought-resistant crops, and production techniques that consume fewer fossil fuels.

"What was learned in this study was that we need to act now, not later," Easterling said. "We can't delay."