LOW-LATITUDE GLACIAL COOLING IN THE SOUTHERN-HEMISPHERE FROM AMINO-ACID RACEMIZATION IN EMU EGGSHELLS

The record of natural climate variability over glacial-interglacial ti mescales provides a framework from which a better mechanistic understa nding of the climate system may be derived, But this approach is limit ed by the number and distribution of well-dated and reliable palaeoenv ironmental archives, Particularly vexing is the conflicting evidence f or low-latitude cooling during the Last Glacial Maximum, and the appar ent synchrony in glacial activity between the hemispheres despite out- of-phase insolation forcing(1-4). Here we utilize the temperature-depe ndent amino acid racemization reaction in radiocarbon-dated emu eggshe ll fragments from the continental interior of Australia to reconstruct low-altitude subtropical temperatures for the past 45 kyr, Racemizati on rate-changes indicate that millennial-scale average air temperature s were at least 9 degrees C lower between 45 and 16 kyr BP than since 16 kyr sp. A temperature change of this magnitude, coupled with other low-latitude palaeotemperature records that indicate substantial cooli ng(3,4), must reflect global processes, which, we speculate, involved glacial-age reduction in atmospheric water vapour content.