Comet Enthusiast

Overall solar activity has been increasing over the past century, so the researchers believe it is possible that during this period, the Sun has been contributing a small cooling effect, rather than a small warming effect as had previously been thought. A new study, by researchers from Imperial College London and the University of Colorado, shows that a decline in the Sun's activity does not always mean that Earth becomes cooler.

It is well established that the Sun's activity waxes and wanes over an 11-year cycle and that as its activity wanes, the overall amount of radiation reaching Earth decreases. This latest study looked at the Sun's activity over the period 2004-2007, when it was in a declining part of its 11-year activity cycle.