THE United Nations climate science panel faces new controversy for wrongly linking global warming to an increase in the number and severity of natural disasters such as hurricanes and floods.
It based the claims on an unpublished report that had not been subjected to routine scientific scrutiny — and ignored warnings from scientific advisers that the evidence supporting the link too weak. The report's own authors later withdrew the claim because they felt the evidence was not strong enough.
The claim by the Intergovernmental Panel on Climate Change (IPCC), that global warming is already affecting the severity and frequency of global disasters, has since become embedded in political and public debate. It was central to discussions at last month's Copenhagen climate summit, including a demand by developing countries for compensation of $100 billion (£62 billion) from the rich nations blamed for creating the most emissions.
Ed Miliband, the energy and climate change minister, has suggested British and overseas floods — such as those in Bangladesh in 2007 — could be linked to global warming. Barack Obama, the US president, said last autumn: "More powerful storms and floods threaten every continent."
Last month Gordon Brown, the prime minister, told the Commons that the financial agreement at Copenhagen "must address the great injustice that . . . those hit first and hardest by climate change are those that have done least harm". The latest criticism of the IPCC comes a week after reports in The Sunday Times forced it to retract claims in its benchmark 2007 report that the Himalayan glaciers would be largely melted by 2035. It turned out that the bogus claim had been lifted from a news report published in 1999 by New Scientist magazine.
The new controversy also goes back to the IPCC's 2007 report in which a separate section warned that the world had "suffered rapidly rising costs due to extreme weather-related events since the 1970s". It suggested a part of this increase was due to global warming and cited the unpublished report, saying: "One study has found that while the dominant signal remains that of the significant increases in the values of exposure at risk, once losses are normalised for exposure, there still remains an underlying rising trend."
The Sunday Times has since found that the scientific paper on which the IPCC based its claim had not been peer reviewed, nor published, at the time the climate body issued its report.
When the paper was eventually published, in 2008, it had a new caveat. It said: "We find insufficient evidence to claim a statistical relationship between global temperature increase and catastrophe losses."
Despite this change the IPCC did not issue a clarification ahead of the Copenhagen climate summit last month. It has also emerged that at least two scientific reviewers who checked drafts of the IPCC report urged greater caution in proposing a link between climate change and disaster impacts — but were ignored.
The claim will now be re-examined and could be withdrawn. Professor Jean-Pascal van Ypersele, a climatologist at the Universite Catholique de Louvain in Belgium, who is vice-chair of the IPCC, said: "We are reassessing the evidence and will publish a report on natural disasters and extreme weather with the latest findings. Despite recent events the IPCC process is still very rigorous and scientific."