The U.N. Intergovernmental Panel on Climate Change (IPCC) was widely criticized after admitting its 2007 global warming report wrongly said Himalayan glaciers would vanish by 2035 and that it overstated how much of the Netherlands is below sea level.

Such firm forecasts should be made "only when there is sufficient evidence," said a review group supported by the academies of science from the United States, Netherlands, Britain and around 100 other countries.

Critics of the idea of mandatory limits on so-called greenhouse gas emissions have said the IPCC errors show the science behind global warming is questionable.

The United Nations has been concerned that focusing only on errors by the panel, which shared the 2007 Nobel Peace Prize with former U.S. Vice President Al Gore for work on global warming, could undermine the broader U.N. message that climate change is a real phenomenon requiring urgent action.

The report said the IPCC's mandate calls for it to be "policy relevant" without advocating specific policies. But some senior IPCC officials have been criticized for remarks that appeared to support specific policy approaches.