Everyone knows how the work week can take a toll¹ on employees, but new research suggests the five-day slog may have even broader impacts - on climate.

After examining more than 40 years of temperature data taken from roughly 10,000 surface stations, researchers from the National Oceanic and Atmospheric² 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 random³ variations and found neither to be at play. The only factor that could be causing the fluctuations⁴ was the Monday-through-Friday grind, they concluded in a recently published report in the Proceedings⁵ of the National Academy of Sciences.

"There is nothing in nature that should cause these data to be different," said Piers⁶ 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."

The meteorologists propose the differences in average temperatures between Saturdays as opposed to Thursdays, for example, may stem from workweek-induced pollution. Forster explains that during the workweek more people commute⁷ and more factories are in operation. Both contribute to the amount of particle pollution in the air.

Particles can influence cloud cover, but the kind of particles released into the atmosphere can lead to different changes, says Forster.

Lighter⁸ particles provide a surface for cloud droplets⁹ to form. This leads to an increase in cloud cover, which, in turn, can lead to an increase in temperature since clouds have an insulating effect.