Saying the glaciers could be gone in 35 years is more accurate than denying that they are melting and denying that there are water problems as a result.

First, “could be gone in 35 years” is not what the disputed quote claimed. It claimed that “the likelihood … is very high” [elsewhere defined as >90%] that all would be gone by 2035 (27 years from the date of publication.) Despite IPCC AR4 claiming that this was from a peer-reviewed source, the total number of professional glaciologists who actually believed that date either then or now — including IPCCs own glaciologists — is none whatsoever. Even Syed Hasnain (the original source of the quote, in a telephone interview to a magazine) does not believe it; at the time he actually said it was an outside possibility in the worst case scenario, but has since concluded that even that speculation was too pessimistic.

It is not too difficult to see why this figure is not just wrong but obviously absurd. The mean rate of measured retreat was about 15 m per year. That might sound a lot but when you are looking at structures 5,000 to 30,000 metres long, 15 m/yr is clearly not going to totally or even largely consume that structure in 25 years, or even in 100 years. In fact the earliest date that has actually been accepted in peer-reviewed journals, is more than three centuries away – even under the assumption that not only does nothing get better, but that things continue to get worse at the current rate.

Secondly, there is nothing wrong with denying that they are melting, because most of them aren’t. Glaciers retreat and advance all the time, in extremely complex patterns only distantly related to current weather conditions. From the 1970s to the early 2000s, there was a period when the balance was definitely on the side of overall retreat, and during the 1990s the fraction retreating exceeded 90% – nearly all of them were retreating at once, in some cases relatively quite quickly. This was claimed, superficially reasonably but on the basis of no scientific evidence whatsoever, to be caused by global warming.

However even by the time AR4 was published in 2007, that phase had already passed. In fact most Himalayan glaciers are currently either retreating at a very low and sustainable rate, stable, or even growing again, and have been for a decade. To take an example at random, simply because it is one of the most studied (being the source of the Ganges River), between 1971 and 1996 Gangotri retreated at 32 to 34 metres per year; from 1996 to 2001, some parts kept up 30 m/yr but most of the “snout” slowed to about 10 m/yr; and since then it slowed even further, averaging 4 m/yr with some parts not retreating at all. Gangotri is what they usually mean when they talk about glacial meltwater provinding water for “millions” as against a few thousand villagers, because Gangotri is the source of the Ganges. And it is 30,200 m long. Even at 30 m/yr, it will clearly last many centuries; at 4 m/yr, millennia.

Further, detailed research by Indian glaciologists had shown that the cause of “negative annual mass balance” was almost entirely due to reduced precipitation in the monsoon season, not due to increased melting in summer. This might be indirectly caused by climate change, but there is no evidence for it. Moreover, it means that the retreat will not speed up with time, it will gradually slow down, even if nothing else changes. The glaciers will not melt away completely, they will asymptotically approach a new “equilibrium line”, and probably take over a thousand years to get there.

There is an exception to this: in the Eastern Himalaya, there are glaciers that are still retreating fast, and that is due to increased surface melt, caused by soot deposits from Chinese coal-fired power stations. This is still related to reduced precipitation (one good snowfall can cover up decades worth of soot accumulation), but at least it may also be a much easier problem to fix.

This post was mentioned on Twitter by polq26: @F_Cardinal IPCC cites boot clning guide http://climatequotes.com/2010/02/01/ipcc-cites-boot-cleaning-guide-for-antarctica-tour-operators/...