Solar activity not a significant factor in global warming

As the sun approaches the peak of its 11-year activity cycle, British scientists say they've confirmed that activity plays a minimal roll in global warming. Researchers at the University of Lancaster and the University of Durham said their studies show changes in solar activity have contributed no more than 10 per cent to global warming in the 20th century. Changes in the amount of energy from the sun reaching Earth have previously been proposed as a driver of increasing global temperatures, as has the sun's ability to block cosmic rays, which may have a role in cooling Earth by encouraging formation of clouds. York scientist Terry Sloan and Durham researcher Arnold Wolfendale compared data on the rate of cosmic rays entering the atmosphere, which can be used as a proxy for solar activity, with the record of global temperatures going back to 1955. Their results, they said, show neither changes in the activity of the sun, nor its impact in blocking cosmic rays, can be a significant contributor to global warming. Sloan and Wolfendale have published the results of their study in the journal Environmental Research Letters.