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The Sun's Magnetic Field May Influence Earth's Climate
Solanki, S.K., Schussler, M. and Fligge, M.  2000.  Evolution of the sun's large-scale magnetic field since the Maunder minimum.  Nature 408: 445-447.

What was done
The authors developed a model of the long-term evolution of the sun's large-scale magnetic field and compared its predictions against two proxy measures of this parameter.

What was learned
The model was successful in reproducing the observed century-long doubling of the strength of the part of the sun's magnetic field that reaches out from the sun's surface into interplanetary space.  It also indicated that there is a direct connection between the length of the 11-year sunspot cycle and secular variations in solar activity that occur on timescales of centuries, such as the Maunder minimum of the latter part of the 17th century, when sunspots were few in number and earth was in the midst of the Little Ice Age.

What it means
In the words of the authors, their modeled reconstruction of the solar magnetic field "provides the major parameter needed to reconstruct the secular variation of the cosmic ray flux impinging on the terrestrial atmosphere," as a stronger solar magnetic field "more efficiently shields the earth from cosmic rays."  The significance of this accomplishment, they say, is indicated by the fact that it has been suggested that "cosmic rays affect the total cloud cover of the earth and thus drive the terrestrial climate."  Their work should thus enable this proposed sun-climate link to be more thoroughly and rigorously examined.  Such work will be of great worth in helping to determine the relative importance of solar variability and atmospheric CO2 concentration increases in driving climate change since the "beginning of the end" of the Little Ice Age.

Reviewed 20 December 2000