Corn farmers in the U.S. have seen a fivefold increase in crop yields since the 1940s. Advances in farm technology have largely been credited for the production boost, but a study published this week in Proceedings of the National Academy of Sciences by UCI, University of Minnesota and Harvard University researchers shows that climate change has also played a major role. Warmer temperatures have lengthened the growing season, allowing seeds to be planted earlier each year – by three days per decade, on average. A second, more surprising finding is that even though temperatures have gone up over the past century, fields in the U.S. corn belt have experienced localized cooling. “Increasingly productive and densely planted crops can evaporate more water from leaves and soils during hot days,” said study co-author Nathaniel Mueller, UCI assistant professor of Earth system science, formerly a postdoctoral research fellow at the Harvard University Center for the Environment. “Widespread increases in rates of evaporation apparently help shield maize from extreme heat, cooling the surrounding area and helping to boost yields.” In the paper, the researchers stress that while climate change may be optimizing crop yields today, there’s no guarantee that future warming will deliver similar benefits. The study was supported, in part, by the David & Lucile Packard Foundation and the National Science Foundation.