Towards regional scenarios for a CO2-warmed Earth

Abstract

Measured and projected increases in carbon dioxide content of the atmosphere point towards a significant global warming. The regional effects of such a warming will be of primary importance in determining the social and economic consequences. Four methods of arriving at tentative regional scenarios are discussed and illustrated by application to Australia and New Zealand. Methods used include numerical modelling, extreme warm and cold year ensembles, dynamical/empirical reasoning and palaeoclimatic reconstructions from the Hypsithermal. A surprising degree of consistency is revealed between the various approaches to a scenario for a CO2-warmed Earth and the climatic conditions which prevailed during the Hypsithermal. The best overall analogy to a CO2-warmed Earth seems to be this epoch, especially as recent evidence suggests it to be one of higher CO2 concentrations. High priority should be given to further investigations using numerical models which include an interactive dynamic ocean and hydrologic cycle including variable cloudiness, as well as more detailed reconstruction of climatic conditions during the Hypsithermal in areas sensitive to any circulation changes.