According to the Helmholtz Association of German Research Centres, even small fluctuations in soloar activity can have large influence on climate.  What is most telling in this report is that climate models, to date, have not been able to adequately represent the sun's impact.  (and yet, we are to believe that we have been able to model the effects of man on climate and predict all manner of dire consequences if we don't all drive the Prius! 

Read report here