Does the sun affect the earth's climate?

In this study, we deal with the question whether the solar activity affects the earth's climate or not. For this reason, we have chosen two parameters to check a possible relation, the total size of Ca plage areas on the sun and terrestrial air temperatures above the ground at more than 1300 stations covering the northern latitude belt between 30 and 60 degrees. Data include the time period between 1940 and 1984. We found a strong positive correlation between the two parameters up to 1966, but after this time an anti-correlation was seen. In the investigated period the mean value of temperature was 10.56+/-0.32degreesC. Our investigation shows that an effect of the sun upon the earth's atmosphere seems to exist, but increasing amounts of greenhouse gases (GHGs) dominate the solar influence