An Observational Estimate of the Pattern Effect on Climate Sensitivity

We estimate the contributions of the spatially varying temperature field to internal climate feedbacks through the statistical relationships between the observed global-mean radiative response R and the spatially-varying temperature field Ti. The results indicate regions where surface temperature covaries with R and thus provide a statistical analogue to the causal response functions derived from simulations forced with surface temperature “patches”. Notably, the results of the statistical analyses yield patterns in temperature that explain roughly the same fraction of the variability in R as that explained by patch experiments. Consistent with the results of those experiments, the observational analyses indicate large negative internal feedbacks due to temperature variability over the western Pacific. Unlike the results inferred from such experiments, the analyses indicate equally large positive internal feedbacks over the southeastern tropical Pacific and negative internal feedbacks over land areas. When estimated from observations, temperature variability over the land areas accounts for roughly 80% of the global-mean, negative internal feedback; and temperature variability over the southeastern tropical Pacific acts to attenuate the global-mean negative internal feedback by nearly 10%.