Global Surface Temperatures and Sunspot Cycle Length
. Variations in the air temperature over land in the Northern Hemisphere (solid line) closely fit changes in the length of the sunspot cycle (dashed line). Shorter sunspot cycles are associated with increased temperatures and more intense solar activity. This suggests that solar activity is at least partly responsible for the rise in global temperatures over the last century, and that the Sun can substantially moderate or enhance global warming brought about by human increases of carbon dioxide and other greenhouse gases in the atmosphere.
Copyright 2010, Professor Kenneth R. Lang, Tufts University