Palaeoclimatology: the record for marine isotopic stage 11.

The marine isotopic stage 11 (MIS 11) is an extraordinarily long interglacial period in the Earth's history that occurred some 400,000 years ago and lasted for about 30,000 years. During this period there were weak, astronomically induced changes in the distribution of solar energy reaching the Earth. The conditions of this orbital climate forcing are similar to those of today's interglacial period, and they rendered the climate susceptible to other forcing--for example, to changes in the level of atmospheric carbon dioxide. Here we use ice-core data from the Antarctic Vostok core to reconstruct a complete atmospheric carbon dioxide record for MIS 11. The record indicates that values for carbon dioxide throughout the interglacial period were close to the Earth's pre-industrial levels and that both solar energy and carbon dioxide may have helped to make MIS 11 exceptionally long. Anomalies in the oceanic carbonate system recorded in marine sediments at the time, for example while coral reefs were forming, apparently left no signature on atmospheric carbon dioxide concentrations.