Solar Forcing of Global Temperature Change Since AD 1400

It is well known that the magnetic field imbedded in the solar wind modulates the production of cosmogenic isotopes by galactic cosmic rays. Power spectral analysis yields evidence for fundamental periods relevant to this study including the Suess, Gleissberg, Hale and Schwabe cycles of ca. 210, 88, 22 and 11 years lengths. There is increasing evidence for an irradiance component accompanying each of these cycles. Assuming this is valid, we model the magnitude of irradiance change associated with these cycles that is compatible with the paleoclimate record. We conclude that the resultant model fit requires less than ±0.8 change in solar irradiance for each of these cycles even if we assume low climate sensitivity (0.5 °C(Wm^–2)). Our solar irradiance model accounts for about 18% of 20th century global warming to 1997 and also predicts that the next maximum would occur in ad 2040 and contribute 0.2 °C to 21st century Northern Hemisphere warming.