WASHINGTON — Climate change has stunted the worldwide increase in corn and wheat yields since 1980 by 3.8 and 5.5 percent respectively, according to a new study in the journal Science.

Without global warming, total harvests of both crops would have been significantly larger than they were, the statistical analysis found.

The shortfall equals the annual yield of corn in Mexico, some 23 metric tonnes, and wheat in France, about 33 metric tonnes.

One of the country's with the largest crop loss was Russia, where wheat production fell some 15 percent.

The study estimates that the global drop-off in production may have caused a six percent hike in consumer food prices since 1980, some $60 billion per year.

Net impact on rice and soybean was insignificant, with gains in some countries balancing losses in others, according to the study.

The researchers, led by David Lobell of Stanford University, noted one "startling exception": the United States isn't getting hotter, nor are its crop yields less than they might have been without climate change.

"The results are a reminder that while the relationship between crop production and climate change is obvious on a global scale, models that zoom in... on a country-by-country basis won't necessarily see the same effects," the researchers said in a press release.

To carry out the study, Lobell and colleagues compared two mathematical models, one tracking actual increases in temperatures and the other projecting 1980 temperatures over the next three decades.

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