Wednesday, April 26, 2006
Two new statistical studies that combine data sets cast doubt on soaring upper limits for projected climate change (of 9-11 degrees) during this century while eliminating any remaining doubt that there will be substantial warming. Climate modeler Gabriele Hegerl reports in this week's issue of Nature a 5% probability that climate change will be is less than 1.5 C and a 95% chance that it is less than 6.2 C. A similar study published by Annan and Hargreaves in Geophysical Research Letters found the same lower limit of 1.5 C and a 95% upper limit of 4.5 C. This matches the long-standing estimate of 1.5-4.5 C.
These studies should not be misinterpreted. They match the long-standing IPCC estimates of projected increase in mean global temperature. The studies also do not address another issue -- recent studies suggest that global ecosystems are reacting more abruptly to a given amount of climate change than we had anticipated.