THE NORTH TEMPERATE CLIMATE ON LONG-TERM TIMESCALES. CONNECTION TO SOLAR VARIABILITY

The Earth's climate is influenced by solar variability in multiple ways: the well-known effect of changes in the solar irradiance and also via the interaction of the solar wind with Earth's magnetosphere resulting in the so-called geomagnetic activity. In this study we analyze the possible long-term effects of the solar variability as external natural forcing over the North temperate climate (35-65 degrees N band) using near surface air temperature data from NCEP/NCAR Reanalysis database. The database has a global coverage by 2.5 degrees latitude x 2.5 degrees longitude and a temporal one from 1948 to present. The reanalyzed time series have been compared to the observed surface air temperature for several locations over the Northern Hemisphere, and the differences between them are discussed. In order to obtain the interdecadal and centennial trends in data, time series have been treated by means of successive 11 and 22 year running averages. The solar signals at time scales of Schwabe (11 year) and Hale (22 year) solar cycles have been computed as differences between the initial data and the interdecadal trend, and between the interdecadal and the centennial trends, respectively. The corresponding trends and the 11 and the 22 year signals in SAT are discussed.