Leaders of the Intergovernmental Panel on Climate Change (IPCC) "regret the poor application of well-established IPCC procedures in this instance", they said in a statement on the flaw in a paragraph of a 938-page scientific report.
They noted that the projection of a thaw by 2035 did not make it to the final summary for policymakers in its latest report in 2007. The summary projected a faster thaw in the coming years for glaciers from the Andes to the Alps.
India and some climate researchers have criticised the IPCC in recent days for over-stating the shrinking of Himalayan glaciers, whose seasonal thaw helps to supply water to nations including China and India.
A disappearance of the glaciers would badly disrupt flows in Asia that are vital for irrigation. The IPCC leaders said they were strongly committed to ensuring a high standard for the reports.
The offending paragraph says: "Glaciers in the Himalaya are receding faster than in any other part of the world and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate."
On Monday, Indian Environment Minister Jairam Ramesh said that "glaciers are receding, but the report that glaciers will vanish by 2035 is not based on an iota of scientific evidence".
The IPCC statement said that the 2035 projection was based on "poorly substantiated estimates of rate of recession" and that proper checks were not made.
The IPCC's core finding in 2007 was that it was more than 90 percent sure that mankind is the main cause of global warming, mainly by using fossil fuels.