In a critical assessment of the results regarding a possible association between solar activity variations and climate by Friis-Christensen and Lassen  and Lassen and Friis-Christensen , Laut and Gundermann [this issue] conclude that the correlation between the solar cycle length parameter and the Northern Hemisphere land temperature is weak. In this short reply we confirm our earlier conclusion, on the basis of new and independent temperature data, that during 400 years, from 1570 to 1970, there is a significant statistical correlation between these parameters, indicating that solar forcing constitutes an important contribution to the natural temperature fluctuations. This does not exclude, as also stated previously, that other climate forcings may have an effect on global temperature, including the effect of man-made greenhouse gases, in particular, after 1970.
Lassen, K., & Friis-Christensen, E. (2000). Solar cycle lengths and climate: A reference revisited - Reply. Journal of Geophysical Research-space Physics, 105(A12), 27493-27495. https://doi.org/10.1029/2000JA900067