Wheat, corn and barley yields have suffered a loss of 44 million ton loss per year from 1981-2002 due to increasing global temperatures, according to a study printed in the journal Environmental Research Letters.
Annual global temperatures increased by about 0.7 degrees from 1980 to 2002, with some regions experiencing even larger changes. The study estimates that this rise in temperature causes losses of around $5 billion for major cereal crops.
"There is clearly a negative response of global yields to increased temperatures," says David Lobell, a Lawrence Livermore National Laboratory researcher and lead author of the study. "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," says Christopher Field, co-author on the study and director of Carnegie Institution's Department of Global Ecology.
Lobell and Field studied the world's six most widely grown crops - wheat, rice, corn, soybeans, barley and sorghum. Using global yield figures for 1961-2002 from the Food and Agriculture Organization, Lobell and Field compared yields with average temperatures and precipitation over the major growing regions.
The authors say this study can help show a relationship between yield losses and temperature increases, with this study putting that figure around a 3-5% drop for each degree Fahrenheit increase.
"A key moving forward is how well cropping systems can adapt to a warmer world," Lobell says. "Investments in this area could potentially save billions of dollars and millions of lives."