Global warming, the scientists reported in Nature Geoscience, changes the molecular structure of organic matter in the soil, the university said in a news release.

"Soil contains more than twice the amount of carbon than does the atmosphere, yet, until now, scientists haven't examined this significant carbon pool closely," said Myrna Simpson, principal investigator and an environmental chemistry associate professor at the university, said. "Through our research, we've sought to determine what soils are made up of at the molecular level and whether this composition will change in a warmer world."

In their study, Simpson's team used an outdoor field experiment behind the university's campus. Electrodes warmed the test soil 3-6 degrees during a 14-month period.

"From the perspective of agriculture, we can't afford to lose carbon from the soil because it will change soil fertility and enhance erosion" says Simpson. "Alternatively, consider all the carbon locked up in permafrost in the Arctic. We also need to understand what will happen to the stored carbon when microbes become more active under warmer temperatures."