| Summary: | The strong correlation between atmospheric greenhouse-gas concentrations and Antarctic temperature, previously described by Barnola et al. (1987), is confirmed by the extension of the Vostok ice-core record (Petit et al. 1999). From the extended Vostok record, Petit et al. (1999) concluded that present-day atmospheric burdens of carbon dioxide and methane seem to have been unprecedented during the past 420,000 years. Temperature variations estimated from deuterium were similar for the last two glacial periods (Jouzel et al. 1996), and the detailed δDice record confirms the main features of the third and fourth climate cycles described by Petit et al. (1997). The records also indicate both similarities and differences between successive interglacial periods. Although the third and fourth climate cycles are of shorter duration than the first two cycles in the Vostok record, all four climate cycles show a similar sequence of a warm interglacial, followed by colder glacial events, and ending with a rapid return to an interglacial period. Minimum temperatures are within 1 degree C for the four climate cycles. The overall amplitude of the glacial-interglacial temperature change is ~8 degrees C for the temperature above the inversion level and ~12 degrees C for surface temperatures. Climate cycles deduced from the Vostok ice core appear to be more uniform than those in deep-sea core records (Petit et al. 1999).
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