A study spanning sixty years has shown that overnight temperatures in Ohio have gradually risen, and experts are left wondering what it means. Ohio State University researcher Jeffrey Rogers is now looking into whether the warmer Ohio nights may be a sign of global warming.

Rogers figures indicate that the difference between average summer nighttime low and average nighttime high temperatures in Cleveland is 1.5 degrees. In Columbus the difference is much greater, with nighttime temperatures having increased by 3 degrees. Day time temperatures have remained largely constant.

What Rogers and his fellow researchers currently believe is that increasing clouds and humidity are making heat retention more likely, thus the higher nighttime temps. This theory falls in line with other global studies, says the National Center for Atmospheric Research.