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[span class=articletext]The leader of Sun-climate research at the Danish National Space Center, Henrik Svensmark, puts together the findings reported by him and his colleagues in a dozen scientific papers, to tell how the climate is governed by atomic particles coming from exploded stars. These cosmic rays help to make ordinary clouds. High levels of cosmic rays and cloudiness cool the world, while milder intervals occur when cosmic rays and cloud cover diminish.
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Cosmic radiation entering the Earth's atmosphere.  Credit:  Danish National Space Center

The review paper en. . .

not a very new theory and has been generally regarded with scepticism in the past by the climate change crowd. we'll see if it will get more attention now.

While is not new, it makes as much sense as many of the other theory's I have read about. It would be nice to see a graph, to see just how closely clouds have followed variations in cosmic rays, and to compare the time frame to things like major volcanic eruptions and great floods.

I view the work of Svensmark skeptically.  I don't believe the GCR is that variant, i.e. its been relatively constant.

Now the GCR contribution does change according to the local solar activity.  When the solar wind is strong, it interacts with the GCR more strongly, and when the solar wind in minimal, the GCR is relatively stronger.  I think it more the case that clouds and earth's terrestrial weather is more strongly influenced by the sun's activity, but also by the chemical composition of the earth's atmosphere.

The big question these days is - are so-called greenhouse gases responsible for the apparent general warming of the earth's atmosphere during the last several decades?  And if so, what must we do to mitigate the potentially negative effects?

In the modern era (since 1954)

( 1 ) The galactic cosmic ray intensity near earth has been one of the lowest in the past 1150 years.

( 2 ) The frequency of occurrence of large solar particle events has been low compared to the long term average.

For a period similar to 1889 - 1901

( 3 ) The galactic cosmic ray intensity was higher compared to the modern
era by factors of:

 - 7.0 at 100mev
 - 3.5 at 300mev
 - 2.25 at 1.0gev.

( 4 ) The frequency of occurrence of large spe was a factor of ~5 times greater compared to the modern era.

from - http://hesperia.gsfc.nasa.gov/sspvse/oral/Ken_McCracken/wintergreen1.pdf