Attributing observed changes in physical and biological systems to anthropogenic climate influences

Professor David Karoly, Univ. of Melbourne, Melbourne, Australia

The IPCC Working Group II Fourth Assessment Report (AR4) found, with very high confidence, that observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases. Observed changes related to regional warming has been found primarily in terrestrial biological systems, the cryosphere, and hydrologic systems. The IPCC Working Group I AR4 concluded that most of the observed increase in global average surface temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. For the first time, the IPCC extended its attribution to the continental scale, stating that it is likely that there has been a substantial anthropogenic contribution to surface temperature increases in every continent except Antarctica since the middle of the 20th century.

Here we describe a joint attribution study across multiple physical and biological systems at both global and continental scales by 1) demonstrating consistency of observed changes in natural systems with warming; and 2) conducting spatial analyses that show that the co-location of observed changes in natural systems and areas of warming is highly unlikely to be due to natural variability of the climate or the systems themselves and is consistent with the responses to anthropogenic climate change. We show that changes in natural systems since at least 1970 are occurring in regions of observed temperature increases and conclude that anthropogenic climate change is having a significant impact on physical and biological systems at continental and global scales.

10:30am Thursday 20 March 2008

Main Conference Room, NIWA Wellington

For further information, please contact Dr J. Renwick, (04) 386-0343 or (021) 178-5550