Contribution of Greenhouse Gas Radiative Forcing and Atlantic Multidecadal Oscillation to Surface Air Temperature Trends

I. I. Mokhov and D. A. Smirnov

The contributions of radiative forcing of greenhouse gases (GHG) and Atlantic Multi- decadal Oscillation (AMO) to the trends in global surface air temperature (GST) and surface air tempera- ture for different latitude bands are estimated. Instrumental observational data obtained since the middle of the 19th century and three-component autoregressive models are used. Characteristics of influences of both factors on GST (Wiener–Granger causality) are obtained. The contribution of AMO over the length intervals of 15–30 years appears comparable in absolute value to the contribution of GHG and sometimes even exceeds it, while its contribution over 60-year and longer periods is insignificant. During the recent decades, GHG contribute stronger to the trends of GST and tropical surface air temperature, while their contribution to the trends in surface air temperature in the middle and high latitudes is smaller.