Listen up, naysayers. Still think balmy temps will be good for the world food supply? Think again.
In the first study estimating how much global food production is already affected by climate change, researchers from Lawrence Livermore National Laboratory and the Carnegie Institution's Department of Global Ecology report that warming since 1981 has caused annual losses of roughly $5 billion to the major cereal crops. This during a time when annual global temperatures increased by about 0.7 degrees Fahrenheit, with even larger changes observed in some regions.
From 1981-2002, fields of wheat, corn and barley throughout the world produced a combined 40 million metric tons of food less per year because of increasing temperatures caused by human activities. From Lawrence Livermore
"There is clearly a negative response of global yields to increased temperatures," said David Lobell, a Lawrence Livermore National Laboratory researcher and lead author of the study that appears online March 16 in Environmental Research Letters. "Though the impacts are relatively small compared to the technological yield gains over the same period, the results demonstrate that negative impacts of climate trends on crop yields at the global scale are already occurring."
"Most people tend to think of climate change as something that will impact the future, but this study shows that warming over the past two decades already has had real effects on global food supply," said Christopher Field, co-author on the study and director of Carnegie Institution's Department of Global Ecology.
Using global yield data from the Food and Agriculture Organization for 1961-2002, Lobell and Field compared average temperatures and precipitation with yields over the major growing regions. On average, they found, several food crops responded negatively to warmer temperatures. They then used these relationships to estimate the effect of observed warming trends.
"To do this, we assumed that farmers have not yet adapted to climate change, for example by selecting new crop varieties to deal with climate change," Lobell said. "If they have been adapting something that is very difficult to measure then the effects of warming may have been lower."
Most experts believe that adaptation would lag several years behind climate trends, because of the difficulty of distinguishing climate trends from natural variability. The importance of this study, the authors said, was that it demonstrates a clear and simple relationship at the global scale, with yields dropping by approximately 3-5 percent for a one-degree Fahrenheit increase. "A key to moving forward is how well cropping systems can adapt to a warmer world," Lobell said. "Investments in this area could potentially save billions of dollars and millions of lives."
So what happens if, as some predict, change comes too fast for even intelligent agriculture to keep up?