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The warm Glacier-temperature-reconstruction of Oerlemans 2005

Posted by Frank Lansner (frank) on 4th March, 2010
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Oerlemans “glacier-temperature-proxy” shows a strong rise in temperature 1970-90 where the 1990 level even exceeds 1940 level and everything seen since year 1600.

This is how glacier retreat speed can be converted into a temperature estimate – according to Oerlemans:

fig 1.

But how was Oerlemans “glacier-temperature-proxy” created? Fortunately Oerlemans presents the data fundament from 169 glaciers:

fig 2.

Left: The number of records  - Right: The speed of glacier retreat.

The long period around 1930-50 of fast glacier retreat is evident. In recent years it seems a shorter period 1995-2000 shows fast glacier retreat. However, exactly these years have a very little number of records to back it up. And more, without data majority from the Alps, NO glacier retreat is seen world wide after 1995. The Alps is obviously a tiny tiny area when counting glaciers on earth, so obviously, a data majority from the Alps should definetely not dominate a global result. And if we look at the world without Alp dominance, the glacier retreat simply stops in 1995 - for the first time in hindred years.

This is getting weird.

Oerlemans has then placed the Alps-dominated graf on top of the rest-of-world graph.

Lets take a closer look at the Oerlemans “glacier-temperature-proxy”:

fig 3.

So, it seems, that Oerlemans - on the few years after 1995 with scarce data and also dominated by the Alps - can produce a global glacier-based temperature graph, where tempeature rise already from year 1970? And where year 1990 happens to reach faster glacier retreat speed than year 1940. Amazing.

Heres Oerlemans explanation of how to produce this graph:

“Because glaciers need time to react and the number of records drops sharply after 1995, the warming seen in the instrumental record over the past 15 years is not yet reflected in the reconstruction.”

The best clue we have is that “Glaciers need time”. 1970-90 rising glacier proxy-temperature MUST be due to later retreat-blib after 1995 based on the Alps and scarce data.

A quite unusual feature for science writings: It seems that Oerlemans last actual data point on his glacier-temperature-recunstruction graph, fig 1, is around 1985. Why does he then continue his solid line to almost 1990? 99% of all viewers will just see the graph and not notice that there is a missing datapoint to support it. And this is the very data point that exceeds the 1940 level. If there is no data to support this datapoint, there is no excuse for including it in his graph.

If we compare trends taken from WGMS fig 5.9 we find that the slowest retreat period 1970-80 appears to happen simultaneously with the 1970´ies cooling generally accepted for the period:

fig 4.

So, in this case at least it is not really easy to se a very long delay of temperature effect on glaciers for decades. Also, the 1945-50 strong trend does happen just after the gennerally accepted warm period around 1930-1940-1950.

In short:

The rise in Oerlemans glacier temperature proxy 1970-90 where 1990 exceeds anything seen since year 1600 seems to rely on:

1) Scarce data after 1995 ( Station dropout )   

- and -

2) Allowing data from the Alps to dominate data from the rest of the worlds glaciers.

- and -

3) the claim, that missing glacier retreat is caused by a very long delay of temperature effect on glacier retreat.


In 2005, the world climate report analysed the Oerleman paper, and reached the conlusion, that there was no basis in data for a global glacier-temperature proxy graph, at most a Northern hemisphere. WCR then calculated a version I find much more in harmony with the data from the 169 glaciers:

Now we see a prolonged strong temperature decline 1940-1980.

WCR 2005

Oerlemans 2005


The IPCC is refering to this Oerleman 2005-writing several times in their AR4 report, but it seems that they does not quote the dodgy parts of this wrting?

** Post Scriptum ....

If you compare the speed of retreat of 169 glaciers for [1900-1925] against [1965-1990] the 1 colder periods of the twentieth century:


Data from the 169 glaciers shows, that glaciers in the cold period 1900-25 where loosing lenght around twice the speed as the cold period 1965-90.

Here the CRU global temperatures for the 2 periods:

Oerlemans writes that sometimes glacier movement can rely on temperatures 100 years back etc. But stil, there where no warm period for a very long time before year 1900 to explain why the glaciers retreat 200% as fast in 1900-25 than 1965-90.

Colder in 1965-90 than 1900-25? Or does it simply take more and more heat to melt glaciers back today than earlier? An equilibrium length of glaciers is approaching?

 If so, what does this tell about the predictions of the melting ice everywhere on the globe?



Last changed: 5th March, 2010 at 23:56:14



Dig this, the alps and more: By Frank Lansner on 21st February, 2011 at 22:24:39

K.R. Frank
glacier retreat By Unknown on 21st February, 2011 at 21:20:10
I have hiked and skiid in the Alps for several decades, and I am certain that the speed of retreat has little to do with temperature per se. The biggest temp. change is at night and in winter, when it is usually freezing anyway at the altitudes concerned. Also if temperature was the factor, we would expect a continuous slowing as the altitude of the ice face increased. Actually retreat slows when cloud cover and precipitation increase, and vice-versa. The 70s were very cloudy in the Alps in winter, with lots of snow, the 90s were sunny with much less snow.

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