Solar variability and global warming: a statistical comparison since 1850

The magnitude of the Sun’s influence on climate has been a subject of intense debate. Estimates of this magnitude are generally based on assumptions regarding the forcing due to solar irradiance variations entering climate modelling. Given the complexity of the climate system, however, such modelling is perforce based on simplifying assumptions, which leaves it open to criticism. We take a complementary approach. We assume that the Sun has been responsible for climate change prior to 1970 and that their interrelation remained unchanged afterwards. Then, employing reconstructions and measured records of relevant solar quantities as well as of the cosmic-ray flux, we estimate statistically which fraction of the dramatic temperature rise after that date could be due to the influence of the Sun. We show that at least in the most recent past (since about 1970) the solar influence on climate cannot have been significant. 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.