A retired meteorologist working on global warming has discovered from an analysis of satellite data going back to 1979 that weekends really are colder than weekdays.
He attributes the significant difference between weekday temperatures, which peak on Wednesdays, and those at the weekend to increased industrial activity which produces a short-lived worsening of global warming.
Adrian Gordon, a former Meteorological Office scientist who is now a researcher with the Flinders Institute for Atmospheric and Marine Sciences in Adelaide, Australia, discovered the weekly cycles in global temperatures after analysing satellite records over the past 14 years.
In a letter to the journal Nature, Dr Gordon says Wednesdays tend to be warmer than Thursdays or Fridays, which would expect to suffer a greater build-up of direct heating from industrial sources, because the research was based on Greenwich Mean Time and Friday is a holiday in the Muslim world.
'Thus at midday on Thursday, Friday is already starting to move over the eastern half of the world. This argument favours a possible Wednesday maximum in the northern hemisphere, where the Muslim faith is more predominant east of the Greenwich Meridian,' he says.
'A further argument to explain the Wednesday peak could be that various holidays in the Western world tend to congregate between Wednesday and Tuesday. For example at least 2 per cent of Thursdays are Thanksgiving holidays in the United States, while the effect of Fridays is even more pronounced.'
Dr Gordon said yesterday that although the average temperature of a typical Wednesday is only a fraction of a degree above that of a typical Sunday, the rate of change he discovered over seven days is 70 times greater than the temperature change expected as a result of man-made global warming over the coming decades.
However, whether the differences in weekday and weekend temperatures are enough to cause significant perturbations in the weather is still a matter of conjecture.