Solar variability has a small effect on climate change

Ed Suominen

The Earth wouldn't have much of a climate if it weren't for the Sun. But it's a different thing entirely to conclude that because of its essential role the Sun contributes significantly to climate change. To alter the climate, the amount of energy sent our way by the Sun would have to vary significantly. And most studies have found that, while the Sun's output does vary, it hasn't seemed to have changed enough to have left a mark on the recent climate record.

But a few studies have suggested that the Sun's influence may be much larger. In fact, the range of estimates differ by an order of magnitude. One of the high-end estimates attempted to infer historic solar activity based on an examination of the details of the Sun that we can currently observe. And that, as its title suggests, "leads to large historical solar forcing."

A team from the University of Edinburgh decided to figure out if that actually made any sense. So, they compared a climate model's output with reconstructions of the Northern Hemisphere's temperatures for the last 1,200 years (Northern Hemisphere data is much more complete than Southern). Within the climate model, they set both large and small values for the influence of solar activity on the climate.