Global Surface Temperature Response to 11-Yr Solar Cycle Forcing Consistent with General Circulation Model Results

Abstract

The 11-year solar-cycle is associated with a roughly 1 W m-2 trough-to-peak variation in total solar irradiance and is expected to produce a global temperature response. The amplitude of this response is, however, contentious. Empirical estimates of global surface temperature sensitivity to solar forcing range up to 0.18 K [W m-2]-1. In comparison, best estimates from general circulation models forced by solar variability range between 0.03-0.07 K [W m-2]-1, prompting speculation that physical mechanisms not included in general circulation models may amplify responses to solar variability. Using a lagged multiple linear regression method, we find a sensitivity of global- average surface temperature ranging between 0.02-0.09 K [W m-2]-1, depending on which predictor and temperature datasets are used. On the basis of likelihood maximization, we give a best estimate of the sensitivity to solar variability of 0.05 K [W m-2]-1 (0.03-0.09 K [W m-2]-1, 95% c.i.). Furthermore, through updating a widely-used compositing approach to incorporate recent observations, we revise prior global temperature sensitivity estimates of 0.12 to 0.18 K [W m-2]-1 downwards to 0.07 to 0.10 K [W m-2]-1. The finding of a most likely global temperature response of 0.05 K [W m-2]-1 supports a relatively modest role for solar cycle variability in driving global surface temperature variations over the 20th century and removes the need to invoke processes that amplify the response relative to that exhibited in general circulation mod els.