After examining more than 40 years of temperature data taken from roughly 10,000 surface stations, researchers from the National Oceanic and Atmospheric Administration and from the University of Reading in the U.K. found that temperature differences between day and night appear to follow distinct five-days-on, two-days-off patterns.

The scientists checked the data for all possible natural influences such as the lunar cycle as well as random variations and found neither to be at play. The only factor that could be causing the fluctuations was the Monday-through-Friday grind, they concluded in a recently published report in the Proceedings of the National Academy of Sciences.

"There is nothing in nature that should cause these data to be different," said Piers M de F. Forster, a meteorologist based at the University of Reading, England, who co-authored the study with NOAA's Susan Solomon. "So whatever the cause we find has to be something that we're changing, ourselves."… ..