The cause-and-effect relationship of solar cycle length and the Northern Hemisphere air surface temperature

It has previously been demonstrated that the mean land air temperature of t he Northern Hemisphere could adequately be associated with a long-term vari ation of solar activity as given by the length of the approximately Ii-year solar cycle. In this paper it is shown that the right cause-and-effect ord ering, in the sense of Granger causality, is present between the smoothed s olar cycle length and the cycle mean of Northern Hemisphere land air temper ature for the twentieth century, at the 99% significance level. This indica tes the existence of a physical mechanism linking solar activity to climate variations.