Previous studies of a solar influence on climate variations have often suffered from the relatively short length of continuous direct solar observations of less than 400 years. We use two recently reconstructed series of the sunspot number and the cosmic ray flux to study this question over time intervals of up to nearly 1800 years. Comparison of the Sun-related data sets with various reconstructions of terrestrial Northern Hemisphere mean surface temperatures reveals consistently positive correlation coefficients for the sunspot numbers and consistently negative correlation coefficients for the cosmic rays. The significance levels reach up to 99% but vary strongly for the different data sets. The major part of the correlation is due to the similarity of the long-term trends in the data sets. The trend of the cosmic ray flux correlates somewhat better with the terrestrial temperature than the sunspot numbers derived from the same cosmogenic isotope data.