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.
Figures at a glance
- Figure 1: Proxy temperature records.
a, Location map. CBT, cyclization ratio of branched tetraethers; MBT, methylation index of branched tetraethers; TEX86, tetraether index of tetraethers consisting of 86 carbon atoms; , alkenone unsaturation index. b, Distribution of the records by latitude (grey histogram) and areal fraction of the planet in 5° steps (blue line).
- Figure 2: CO2 concentration and temperature.
a, The global proxy temperature stack (blue) as deviations from the early Holocene (11.5–6.5 kyr ago) mean, an Antarctic ice-core composite temperature record42 (red), and atmospheric CO2 concentration (refs 12, 13; yellow dots). The Holocene, Younger Dryas (YD), Bølling–Allerød (B–A), Oldest Dryas (OD) and Last Glacial Maximum (LGM) intervals are indicated. Error bars, 1σ (Methods); p.p.m.v., parts per million by volume. b, The phasing of CO2 concentration and temperature for the global (grey), Northern Hemisphere (NH; blue) and Southern Hemisphere (SH; red) proxy stacks based on lag correlations from 20–10 kyr ago in 1,000 Monte Carlo simulations (Methods). The mean and 1σ of the histograms are given. CO2 concentration leads the global temperature stack in 90% of the simulations and lags it in 6%.
- Figure 3: Global temperature and climate forcings.
a, Relative sea level26 (diamonds). b, Northern Hemisphere ice-sheet area (line) derived from summing the extents of the Laurentide43, Cordilleran43 and Scandinavian (R. Gyllencreutz and J. Mangerud, personal communication) ice sheets through time. c, Atmospheric CO2 concentration. d, Global proxy temperature stack. e, Modelled global temperature stacks from the ALL (blue), CO2 (red) and ORB (green) simulations. Dashed lines show global mean temperatures in the simulations, using sea surface temperatures over ocean and surface air temperatures over land. f, Insolation forcing for latitudes 65° N (purple) and 65° S (orange) at the local summer solstice, and global mean annual insolation (dashed black)44. Error bars, 1σ.
- Figure 4: Hemispheric temperatures.
a, Atmospheric CO2 concentration. b, Northern Hemisphere (blue) and Southern Hemisphere (red) proxy temperature stacks. c, Modelled Northern Hemisphere (blue) and Southern Hemisphere (red) temperature stacks from the ALL simulation. d, Northern Hemisphere minus Southern Hemisphere proxy temperature stacks (dark purple). North Atlantic minus South Atlantic region proxy temperature stacks (light purple). e, Modelled Northern Hemisphere minus Southern Hemisphere temperature stacks in the ALL (blue), CO2 (red) and ORB (green) simulations. f, Modelled AMOC strength in the ALL (blue), CO2 (red) and ORB (green) simulations. g, North Atlantic sediment core OCE326-GGC5 231Pa/230Th (ref. 24). Temperatures are given as deviations from the early Holocene (11.5–6.5 kyr ago) mean. Error bars, 1σ.
- Figure 5: Temperature change before increase in CO2 concentration.
a, Linear temperature trends in the proxy records from 21.5–19 kyr ago (red) and 19–17.5 kyr ago (blue) averaged in 10° latitude bins with 1σ uncertainties. b, Proxy temperature stacks for 30° latitude bands with 1σ uncertainties. The stacks have been normalized by the glacial–interglacial (G–IG) range in each time series to facilitate comparison.
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