Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation

Abstract

The covariation of carbon dioxide (CO₂) concentration and temperature in Antarctic ice-core records suggests a close link between CO₂ and climate during the Pleistocene ice ages. The role and relative importance of CO₂ in producing these climate changes remains unclear, however, in part because the ice-core deuterium record reflects local rather than global temperature. Here we construct a record of global surface temperature from 80 proxy records and show that temperature is correlated with and generally lags CO₂ during the last (that is, the most recent) deglaciation. Differences between the respective temperature changes of the Northern Hemisphere and Southern Hemisphere parallel variations in the strength of the Atlantic meridional overturning circulation recorded in marine sediments. These observations, together with transient global climate model simulations, support the conclusion that an antiphased hemispheric temperature response to ocean circulation changes superimposed on globally in-phase warming driven by increasing CO₂ concentrations is an explanation for much of the temperature change at the end of the most recent ice age.