Anthropogenic global warming hypothesis: testing its robustness by Granger causality analysis

In research into the main causes of recent global warming, the Granger causal link from anthropogenic forcings to global temperature has often been analyzed in a bivariate system, with an evidence of a causal effect of greenhouse gases on temperature as the final result. In the present paper, the robustness of these results are investigated by considering an auxiliary variable in the system. In particular, we include natural forcings and some patterns of natural variability, separately, as the third variable. Previous bivariate Granger results are shown to be robust.