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.
It is not plausible that Himalayan glaciers are disappearing completely within the next few decades
"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".