"There are indications that the results and effects of global warming, and especially the recent acceleration of global warming, are already visible as a signal," Matteo Zampieri, an Italian climatologist and irrigation expert working for the European Union, told HuffPost Tuesday. "They are emerging in a statistically significant way."

The findings were published last month in the journal Environmental Research Letters, and the researchers are now expanding the study to examine corn and rice. Climate has an even bigger effect on corn, accounting for as much as 50 percent of its yield variability, they found.

Rice requires a more sophisticated analysis, Zampieri said. The grain is often grown in deliberately flooded paddies, making it less sensitive to weather fluctuations. But water scarcity ― yet another impact of global climate change ― would likely decrease rice production as well.

As food production drops, prices will go up. Studies have already found that manmade global warming has driven up the cost of food by as much as 20 percent over the past few decades. Beef prices alone skyrocketed 34 percent from 2010 to 2014 amid historic droughts in cattle-ranching states like California and Texas.

Another factor will be the world's growing population. More people will mean more competition for water and other resources ― making it more important than ever for crop yields to reach their potential, Zampieri said.