From the “science is still settling” department, the question still seems up in the air to me.
On one hand we have Dr. Jasper Kirkby, Head of the CLOUD Experiment, CERN Geneva giving a thorough review showing strong correlations between cosmic rays, solar cycles and earth’s climate. He projects a possible mini ice age by 2015 similar to the Dalton or Maunder minimum.
On the other hand, we have RealClimate fanboy Rasmus Benestad with a new paper that says “no, absolutely not, except maybe Northern Europe, but I don’t know why, more study is needed”.
First Jasper Kirkby:
Then we have Rasmus:
An analysis of more than 50 years’ worth of climate data has found scant evidence for a controversial theory that attempts to link cosmic rays and global warming. The theory suggests that solar variations can affect the number of cosmic rays reaching the Earth, which in turn influences climate by impacting on cloud formation. The latest study was done by Rasmus Benestad of the Norwegian Meteorological Institute and he concludes that changes to the Sun cannot explain global warming.
Benestad compared variations in the 1951–2006 annual mean galactic cosmic-ray-flux data with annual variations in temperature, mean sea-level barometric pressure and precipitation. The cosmic-ray data were obtained using a high-altitude neutron monitor located in Climax, Colorado.
He looked for meteorological responses to cosmic rays over timescales of more than a year, and for “fingerprint” patterns in both time and space. He also checked for responses to greenhouse-gas concentrations and the El Niño Southern Oscillation.
“The significance of the findings was that the results were negative – I found little evidence of the cosmic rays having a discernible affect on a range of common meteorological elements: temperature, the barometric pressure or precipitation,” says Benestad. “Not for the global mean at least. One possible exception may have been for parts of Europe, however.”
The galactic cosmic-ray flux was associated with lower temperatures in parts of Eastern Europe. Benestad is intrigued whether these results were a coincidence or do indeed show a connection between cosmic rays and both temperature and sea-level pressure. He plans to investigate further. “Why would a solar effect be seen only in a limited region?” he wonders. “This region is affected by the North Atlantic Oscillation, and this phenomenon is a bit special – a variation in the sea-level pressure over timescales of up to several years. The persistence in these variations may match the variations in the Sun by accident, but it could also be sensitive to variations in the Sun.” If there is a real connection between changes to the Sun and the North Atlantic Oscillation, Benestad believes that this knowledge could benefit decadal predictions.
On a larger scale, the analysis indicated that the weak global mean-temperature response associated with cosmic-ray flux could easily be down to chance. What is more, there has been no long-term trend in cosmic-ray flux. “Hence, there is little empirical evidence that links galactic cosmic-ray flux to recent global warming,” wrote Benestad in Environmental Research Letters.
It is unfortunate that this was published by Rasmus Benestad, I’d give more credence to sombody not joined at the hip with James Hansen, Mick Mann, and Gavin Schmidt.