Previously, fluctuations in the amount of the Sun’s energy that reaches the Earth have been put forward as a potential explanation for rising global temperatures. There have also been suggestions that when the Sun is particularly active, it blocks cosmic rays, thought to encourage the formation of clouds, which then reflect the Sun’s rays, leading to further temperature increases.

Professor Terry Sloan of the University of Lancaster and Professor Sir Arnold Wolfendale of the University of Durham compared global temperature records dating back to 1955 with fluctuations in cosmic ray activity – a proxy for solar activity. Although they found minor correlations between temperature changes and the rate at which cosmic rays entered the atmosphere every 22 years, the temperature changes took place a few years before the changes in the cosmic ray rate.

The study suggests that no more than ten per cent of 20th-century global warming could be attributed to solar activity. It also questioned a proposed link between cosmic rays and cloud cover, pointing to flaws in a recent study that made the link, where correlation occurred only in certain regions rather than over the globe.

This story was published in the January 2014 edition of Geographical Magazine