The UN panel on climate change warning that Himalayan glaciers could melt to a fifth of current levels by 2035 is wildly inaccurate, an academic says.
J Graham Cogley, a professor at Ontario Trent University, says he believes the UN authors got the date from an earlier report wrong by more than 300 years.
He is astonished they "misread 2350 as 2035". The authors deny the claims.
Leading glaciologists say the report has caused confusion and "a catalogue of errors in Himalayan glaciology".
The Himalayas hold the planet's largest body of ice outside the polar caps - an estimated 12,000 cubic kilometres of water.
They feed many of the world's great rivers - the Ganges, the Indus, the Brahmaputra - on which hundreds of millions of people depend.
In its 2007 report, the Nobel Prize-winning Inter-governmental Panel on Climate Change (IPCC) said: "Glaciers in the Himalayas 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.
"Its total area will likely shrink from the present 500,000 to 100,000 square kilometres by the year 2035," the report said.
It suggested three quarters of a billion people who depend on glacier melt for water supplies in Asia could be affected.
But Professor Cogley has found a 1996 document by a leading hydrologist, VM Kotlyakov, that mentions 2350 as the year by which there will be massive and precipitate melting of glaciers.
"The extrapolar glaciation of the Earth will be decaying at rapid, catastrophic rates - its total area will shrink from 500,000 to 100,000 square kilometres by the year 2350," Mr Kotlyakov's report said.
Mr Cogley says it is astonishing that none of the 10 authors of the 2007 IPCC report could spot the error and "misread 2350 as 2035".
"I do suggest that the glaciological community might consider advising the IPCC about ways to avoid such egregious errors as the 2035 versus 2350 confusion in the future," says Mr Cogley.
He said the error might also have its origins in a 1999 news report on retreating glaciers in the New Scientist magazine.
The article quoted Syed I Hasnain, the then chairman of the International Commission for Snow and Ice's (ICSI) Working group on Himalayan glaciology, as saying that most glaciers in the Himalayan region "will vanish within 40 years as a result of global warming".
When asked how this "error" could have happened, RK Pachauri, the Indian scientist who heads the IPCC, said: "I don't have anything to add on glaciers."
The IPCC relied on three documents to arrive at 2035 as the "outer year" for shrinkage of glaciers.
They are: a 2005 World Wide Fund for Nature report on glaciers; a 1996 Unesco document on hydrology; and a 1999 news report in New Scientist.
Incidentally, none of these documents have been reviewed by peer professionals, which is what the IPCC is mandated to be doing.
Murari Lal, a climate expert who was one of the leading authors of the 2007 IPCC report, denied it had its facts wrong about melting Himalayan glaciers.
But he admitted the report relied on non-peer reviewed - or 'unpublished' - documents when assessing the status of the glaciers.
Recently India's Environment Minister Jairam Ramesh released a study on Himalayan glaciers that suggested that they may be not melting as much due to global warming as it is widely feared.
He accused the IPCC of being "alarmist".
Mr Pachauri dismissed the study as "voodoo science" and said the IPCC was a "sober body" whose work was verified by governments.
But in a joint statement some the world's leading glaciologists who are also participants to the IPCC have said: "This catalogue of errors in Himalayan glaciology... has caused much confusion that could have been avoided had the norms of scientific publication, including peer review and concentration upon peer-reviewed work, been respected."
Michael Zemp from the World Glacier Monitoring Service in Zurich also said the IPCC statement on Himalayan glaciers had caused "some major confusion in the media".
"Under strict consideration of the IPCC rules, it should actually not have been published as it is not based on a sound scientific reference.
"From a present state of knowledge it is not plausible that Himalayan glaciers are disappearing completely within the next few decades. I do not know of any scientific study that does support a complete vanishing of glaciers in the Himalayas within this century."
Pallava Bagla is science editor for New Delhi Television (NDTV) and author of Destination Moon - India's quest for Moon, Mars and Beyond.