Solar Activity increasing

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.

The Sun's activity has recently affected the Earth's atmosphere and climate in unexpected ways, according to a new study published in the journal Nature. 


The 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 the 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 the Earth decreases. The 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.

Although the Sun's activity declined over this period, the new research shows that it may have actually caused the Earth to become warmer. Contrary to expectations, the amount of energy reaching the Earth at visible wavelengths increased rather than decreased as the Sun's activity declined, causing this warming effect.

Following this surprising finding, the researchers behind the study believe it is possible that the inverse is also true and that in periods when the Sun's activity increases, it tends to cool, rather than warm, the Earth.

This is based on what is already known about the relationship between the Sun's activity and its total energy output.

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.