While the rest of the world is warming, the northern and midwestern United States are getting colder.

Known as the US Corn Belt, the area is seeing summer temperatures drop by up to 1°C (1.8°F) while rainfall increases by up to 35 percent – the largest spike in the world.

This time around greenhouse gas emissions aren't the culprit. Rather, according to new research published in the journal Geophysical Research Letters, agricultural production is to blame.

It shows how climate systems can be impacted at the regional level. 

There’s a reason this area is named after produce: it grows a lot of corn. In 2016-17 the US grew over 385 million tonnes (424 million US tons) of corn that was exported to more than 100 countries. 

Researchers say this cooling trend has to do with how these crops use photosynthesis. A plant photosynthesizes when its pores open to allow carbon dioxide in, which simultaneously lets water out. This process increases the amount of water going into the air and returning as rain, causing more rainfall.

“We believe that our results show the importance of accounting for agricultural intensification and land use changes in future climate model development and attribution studies so that we can improve our understanding of the climate system,” Ross Alter, lead author of the study and now a meteorologist with the US Army Corps of Engineers, told IFLScience in an interview.

It offers a deeper look at how agricultural production may be impacting our weather systems and climate at a regional level, compared to greenhouse gas emissions.

Using data from 1982 to 2011, researchers at Massachusetts Institute of Technology modeled five different 30-year climate situations to see how intense agricultural production might affect regional weather. When compared to situations without agricultural influence, the simulations showed different results.

They then took it to a global level. The researchers compared their results to global stimulations from the World Climate Research Programme (WCRP), an organization that predicts weather and climate changes around the world, taking into account greenhouse gas emissions and other natural and manmade influences, but not agricultural production.

Excluding agricultural production brought about different results as well: temperature and humidity levels increased and rainfall rose up to 4 percent. Sea surface temperature variations didn’t match either.

It shows that the effects of agricultural production are independent of gas emissions, and it's affecting regional climates around the world.

However, Alter thinks this might not be a long-term trend.

“Large increases in crop production and yield in the central United States during the 20th century are unlikely to continue during the rest of the 21st century,” he said. “Therefore, the cooling influence of agricultural intensification may diminish over time, especially as regional and global temperatures rise due to increasing greenhouse gas emissions.”