THE Intergovernmental Panel on Climate Change’s latest assessment reportedly admits its computer drastically overestimated rising temperatures, and over the past 60 years the world has in fact been warming at half the rate claimed in the previous IPCC report in 2007.
More importantly, according to reports in British and US media, the draft report appears to suggest global temperatures were less sensitive to rising levels of atmospheric carbon dioxide than was previously thought.
The 2007 assessment report said the planet was warming at a rate of 0.2C every decade, but according to Britain’s The Daily Mail the draft update report says the true figure since 1951 has been 0.12C.
Last week, the IPCC was forced to deny it was locked in crisis talks as reports intensified that scientists were preparing to revise down the speed at which climate change is happening and its likely impact.
It is believed the IPCC draft report will still conclude there is now greater confidence that climate change is real, humans are having a major impact and that the world will continue to warm catastrophically unless drastic action is taken to curb greenhouse gas emissions.
The impacts would include big rises in the sea level, floods, droughts and the disappearance of the Arctic icecap.
But claimed contradictions in the report have led to calls for the IPCC report process to be scrapped.
Professor Judith Curry, head of climate science at the Georgia Institute of Technology in Atlanta, told The Daily Mail the leaked summary showed “the science is clearly not settled, and is in a state of flux”.
The Wall Street Journal said the updated report, due out on September 27, would show “the temperature rise we can expect as a result of manmade emissions of carbon dioxide is lower than the IPCC thought in 2007”.
The WSJ report said the change was small but “it is significant because it points to the very real possibility that, over the next several generations, the overall effect of climate change will be positive for humankind and the planet”.
After several leaks and reports on how climate scientists would deal with a slowdown in the rate of average global surface temperatures over the past decade, the IPCC was last week forced to deny it had called for crisis talks.
“Contrary to the articles the IPCC is not holding any crisis meeting,” it said in a statement.
The IPCC said more than 1800 comments had been received on the final draft of the “summary for policymakers” to be considered at a meeting in Stockholm before the release of the final report. It did not comment on the latest report, which said scientists accepted their forecast computers may have exaggerated the effect of increased carbon emissions on world temperatures and not taken enough notice of natural variability.
According to The Daily Mail, the draft report recognised the global warming “pause”, with average temperatures not showing any statistically significant increase since 1997.
Scientists admitted large parts of the world had been as warm as they were now for decades at a time between 950 and 1250, centuries before the Industrial Revolution.
And, The Daily Mail said, a forecast in the 2007 report that hurricanes would become more intense had been dropped.
Writing in The Wall Street Journal, Matt Ridley said the draft report had revised downwards the “equilibrium climate sensitivity”, a measure of eventual warming induced by a doubling of carbon dioxide in the atmosphere. It had also revised down the Transient Climate Response, the actual climate change expected from a doubling of atmospheric carbon dioxide about 70 years from now.
Ridley said most experts believed that warming of less than 2C from pre-industrial levels would result in no net economic and ecological damage. “Therefore, the new report is effectively saying (based on the middle of the range of the IPCC’s emissions scenarios) that there is a better than 50-50 chance that by 2083 the benefits of climate change will still outweigh the harm,” he said.