Blame the Sun for Climate Change

One of the arguments global warming folk employ is that man-caused (anthropogenic) greenhouse gas emissions are causing greater cloud cover in the atmosphere resulting in higher temperatures as those clouds trap more heat near the earth's surface. One counter-argument has been that anthropogenic greenhouse gasses are a relatively insignificant cause of cloud formation and that other factors such as volcanism and solar activity play a much greater role.

Andrew Orlowsky at The Register reports on a study conducted by CERN scientists and just published in the journal Nature which offers substantial support to the view that any global climate change presently occurring is the result of factors beyond our control and that the human contribution is relatively minor. Orlowsky writes:

CERN's 8,000 scientists may not be able to find the hypothetical Higgs boson, but they have made an important contribution to climate physics, prompting climate models to be revised.

The first results from the lab's CLOUD ("Cosmics Leaving OUtdoor Droplets") experiment published in Nature today confirm that cosmic rays spur the formation of clouds through ion-induced nucleation. Current thinking posits that half of the Earth's clouds are formed through nucleation.

This has significant implications for climate science because water vapour and clouds play a large role in determining global temperatures. Tiny changes in overall cloud cover can result in relatively large temperature changes.

Unsurprisingly, it's a politically sensitive topic, as it provides support for a "heliocentric" rather than "anthropogenic" approach to climate change: the sun plays a large role in modulating the quantity of cosmic rays reaching the upper atmosphere of the Earth.

CLOUD's lead physicist Jasper Kirkby is quoted in the accompanying CERN press release:

"We've found that cosmic rays significantly enhance the formation of aerosol particles in the mid troposphere and above. These aerosols can eventually grow into the seeds for clouds. However, we've found that the vapours previously thought to account for all aerosol formation in the lower atmosphere can only account for a small fraction of the observations – even with the enhancement of cosmic rays."

[Test] results confirm that cosmic rays increase the formation of cloud-nuclei by a factor of 10 in the troposphere, but additional trace gasses are needed nearer the surface.

CERN's supporting literature states that:

"[I]t is clear that the treatment of aerosol formation in climate models will need to be substantially revised, since all models assume that nucleation is caused by these vapours [sulphuric acid and ammonia] and water alone.

Orlowsky concludes:

[T]he father of the theory [of solar genesis of condensation nuclei] Henrik Svensmark says he believes the solar-cosmic ray factor is just one of four factors in climate. The other three are: volcanoes, a "regime shift" that took place in 1977, and residual anthropogenic components.

When Dr. Kirkby first described the theory in 1998, he suggested cosmic rays "will probably be able to account for somewhere between a half and the whole of the increase in the Earth's temperature that we have seen in the last century."

In short, if the findings of this research are accurate, by far the most significant factor in global warming is not the CO2 and other emissions we're pumping into the atmosphere but rather ionizing radiation produced by the sun and the rest of the galaxy. The earth may be warming, but, pace Al Gore, the extent to which humans are responsible is far from a settled matter.

There are lots of links at The Register.