One more denier talking point has been debunked by scientists using actual observations. You can read the Science News article here, which explains, “New research has dealt a blow to the skeptics who argue that climate change is all due to cosmic rays rather than to man-made greenhouse gases.”

You can read the original article, just published by the Institute of Physics’ Environmental Research Letters, “Testing the proposed causal link between cosmic rays and cloud cover,” online here. The major finding:

[N]o evidence could be found of changes in the cloud cover from known changes in the cosmic ray ionization rate.

Here is the full abstract:

A decrease in the globally averaged low level cloud cover, deduced from the ISCCP infrared data, as the cosmic ray intensity decreased during the solar cycle 22 was observed by two groups. The groups went on to hypothesize that the decrease in ionization due to cosmic rays causes the decrease in cloud cover, thereby explaining a large part of the currently observed global warming. We have examined this hypothesis to look for evidence to corroborate it. None has been found and so our conclusions are to doubt it. From the absence of corroborative evidence, we estimate that less than 23 percent, at the 95 percent confidence level, of the 11 year cycle change in the globally averaged cloud cover observed in solar cycle 22 is due to the change in the rate of ionization from the solar modulation of cosmic rays.

You can read more debunking here.

Yes, I know, the whole idea should have died last year with the study in Proceedings of the Royal Society A, “Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature” that I blogged about here. That study found:

There is considerable evidence for solar influence on the Earth’s pre-industrial climate and the Sun may well have been a factor in post-industrial climate change in the first half of the last century. Here we show that over the past 20 years, all the trends in the Sun that could have had an influence on the Earth’s climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures.

The authors specifically looked at trends in cosmic ray intensity as part of their analysis. As Britain’s Royal Society said in an accompanying statement at the time:

At present there is a small minority which is seeking to deliberately confuse the public on the causes of climate change. They are often misrepresenting the science, when the reality is that the evidence is getting stronger every day.

Can we finally bury this myth once and for all?

This post was created for, a project of the Center for American Progress Action Fund.