Russel Norman

Solar activity and climate change

by Russel Norman

The climate change denial industry has rested some of its argument on the link between solar activity and climate change. They argue that increased solar activity is driving the heating of the Earth, or they argue that decreased cosmic rays coming from the sun causes heating because cosmic rays generate clouds that cool the Earth. They say that rather than use computer modelling of the climate, we should look at these simple factors.

However a new study in the Proceedings of the Royal Society shows that the simple evidence does not support this conclusion, regardless of the computer modelling. Since 1985 temperatures on Earth have risen rapidly but solar activity has declined, as measured by sunspots or brightness. And since 1985 cosmic rays have increased (the Earth’s magnetic field protects us from cosmic rays and it peaked in 1987) but the temperature has increased, whereas more cosmic rays should have resulted in a cooling planet if the skeptics were right.

Thus whichever skeptics theory you subscribe to, the evidence is pointing the other way. Which isn’t to say that the sun’s activity does not influence the climate, it does. It’s just that current warming is not due to variable sun activity, it’s due to us releasing greenhouse gases. Here is their summary:

There are many interesting palaeoclimate studies that suggest that solar variability had an influence on pre-industrial climate. There are also some detection–attribution studies using global climate models that suggest there was a detectable influence of solar variability in the first half of the twentieth century and that the solar radiative forcing variations were amplified by some mechanism that is, as yet, unknown. However, these findings are not relevant to any debates about modern climate change. Our results show that the observed rapid rise in global mean temperatures seen after 1985 cannot be ascribed to solar variability, whichever of the mechanisms is invoked and no matter how much the solar variation is amplified.

Published in Environment & Resource Management by Russel Norman on Thu, July 12th, 2007   

Tags:

More posts by Russel Norman | more about Russel Norman