Are reconstructed pre‐instrumental hemispheric temperatures consistent with instrumental hemispheric temperatures?

Abstract

Reconstructions of Northern Hemisphere near‐surface temperatures from climate ‘proxy’ data such as tree rings, ice cores, and corals, suggest that late 20th century Northern Hemisphere mean warmth is anomalous in the context of the past several centuries and likely at least the past two millennia. Though substantial uncertainties in the paleoclimate reconstructions exist, these findings add to the evidence for a discernible human influence on climate. Here we use our simple climate model with six radiative‐forcing reconstructions and climate sensitivity determined from instrumental temperatures over 1861 to 1997 to simulate the forced pre‐instrumental hemispheric‐average temperatures from 1500 to 1895. The model‐simulated pre‐instrumental temperatures indicate that the proxy temperature reconstructions are consistent with the instrumental temperatures in the Northern Hemisphere, but are too warm in the Southern Hemisphere.