As it prepares to present its first report in six years to the world’s governments, the Intergovernmental Panel on Climate Change has lowered the range of predicted global warming by half a degree celsius, leading to accusations of a climb-down from earlier, more dire forecasts.
 
The subtle drop, which suggests a doubling of atmospheric carbon would increase mean global temperatures by between 1.5 and 4.5 degrees celsius, rather than the earlier range of between 2 and 4.5 degrees, is included in a confidential summary for policymakers obtained by the National Post.
 
There is a broad agreement among countries, derived largely from the IPCC, that warming must be kept lower than 2 degrees in order to avert the most serious consequences. This latest range is the first to suggest that threshold might not be crossed.

 The adjusted prediction follows a more drastic backtracking by the British Met Office, which this year lowered by 20% its previous prediction of how much hotter the coming few years will be than the long-term average since 1971. Both reflect efforts by climate scientists to reconcile the predictions of computer models with the observed so-called “pause” in global warming, which apparently stalled in 1998 and has yet to resume. This unexplained trend has been a headache for policymakers, many of whom came to the climate file during the era of clear-eyed alarmism driven largely by Al Gore’s film, An Inconvenient Truth.
 
(By Joseph Brean)