Con Allègre, ma non troppo

Guest Commentary by Georg Hoffmann (LSCE)

Climate change denial is not necessarily a speciality of Washington DC think tanks – sometimes it can also be found in old Europe. Right now there is a little media storm passing by in France evoked by an article from Claude Allègre in L’Express. Who is Claude Allègre? He is one of the most decorated french geophysicists specializing in geochemistry and the use of paleomagnetism. Being a longtime friend of the former prime minister, Lionel Jospin, he even became Minister of Education and Research in the former Socialist government. He still plays an active role within the Socialist party and though he has never published anything directly related to anthropogenic climate change, one would assume that he has some understanding of the scientific matter. But this assumption would be wrong.

In the French weekly journal l’Express he exposed his “sceptical” views in an article entitled “The snows of Kilimanjaro”. In the short editorial, he somehow became lost when following Ernest Hemingway to East Africa. Allègre mentions two scientific examples to demonstrate that there is something fundamentally wrong in the IPCC statements on the reality of climate change. First, he commented on the disappearing glaciers of the Kilimanjaro, sometimes treated as the “Panda” of anthropogenic climate change. Citing a “Nature” study (which was in fact published in Science) by Pierre Sepulchre and colleagues from my laboratory, he claimed that this modelling study demonstrated that Kilimanjaro’s glaciers are controlled by tectonic activity. In fact, the article describes the impact of tectonics of the East African Highlands on Indian ocean moisture transport —- on a time scale of millions of years! This confuses glacier variability over the last ~100 years with rainfall trends extending back to the time of the early hominids (such as Lucy).

In fact, there are good reasons to believe that the situation on the Kilimanjaro is a bit more complicated than a simple “atmosphere gets warmer/ glaciers are melting” equation (for instance, see this previous post on tropical glacier retreat). Furthermore, the real link to climate change does not come from the retreat of one single tropical glacier, but from the fact that, to my knowledge, all studied tropical glaciers have retreated over the 20th century, and the retreat rates have generally increased in recent decades.

Allègre’s misunderstanding was immediately followed by another one. Citing a recent study on relatively stable Antarctic snowfall over the last 30 years (Monaghan et al, 2006, discussed here) , he highlighted what he thought was a clear contradiction to future climate simulations of global circulation models (melting of the Antarctic ice sheet). However, that’s not what they predict. All models predict a comparably stable Antarctic ice sheet for the 21th century in which comparably moderate temperature changes in Antarctica are compensated by slight increase in snowfall. The Monaghan et al study does not contradict these model scenarios.

The French climate research community was of course not very pleased about this short sequence of misrepresentations and personal attacks (“les Cassandres”) and corrected Allègre in an open letter published here on the website of the Institute Pierre Simon Laplace (which includes links to the ongoing back and forth, for those that speak French).

Curiously enough, twenty years ago Allègre wrote in “Clés pour la géologie”, (éd. Belin/France Culture):

“En brûlant des combustibles fossiles, l’homme a augmenté le taux de gaz carbonique dans l’atmosphère, ce qui fait, par exemple, que depuis un siècle la température moyenne du globe a augmenté d’un demi-degré.”


“By burning fossil fuels man enhanced the concentration of carbon dioxide in the atmosphere which has raised the global mean temperature by half a degree in the last century”.

But at that time he used this argument against the anti-nuclear energy movement. It might be that there is simply a bit too much politics in Allègre’s life…

57 comments on this post.
  1. Maurizio Morabito:

    Re: 50


    Regarding regurgitations, please do read a comment before replying

    The “great unwashed” was about people like me

  2. Barton Paul Levenson:

    Re #49 and “Dan: Whatever Al Gore is doing to be carbon-neutral (and the amounts to offset do vary from website to website), it is not part of any article I have ever read about his movie…Wonder if the great unwashed are supposed to be googling about the Man?…ClimateCrisis clear states “Fly less”: the air-travel offset is supposed to be an alternative, if one really cannot fly less, not the main message. Has Mr Gore organized the launch of the movie in different countries so he would minimise the amount of miles, one wonders…And most of all, why oh why could he not ram in the clear-and-present-danger of climate change by presenting the movie via internet conferencing?”

    I take it this poster would ignore a doctor’s advice to quit smoking if the doctor was a smoker himself. That’s a logical fallacy, buddy. Try talking about the issue instead of the people presenting the issue.


  3. Dan:

    re: 51. “Wonder if the great unwashed are supposed to be googling about the Man?” and “The “great unwashed” was about people like me”.

    It certainly does not read that way.

  4. Maurizio Morabito:

    RE: 52

    BPL: I didn’t say _we_ should not follow Gore’s advice because he’s more of a global warming “sinner” than most of us.

    I wrote that “it would help” if _he_ would follow his own advice

    I am sure “Gore pledges not to travel by air” would be headline news for days

    Re 53:

    Dan: Apologies for not having been clearer. You had suggested to google about Gore. My point was that most people reading all the commentaries about the movie should not “have to” google.

    Somehow the message about him being carbon neutral is not filtering through to the newspapers, the vast majority of whose articles I have read talk positively about Gore’s efforts

    And in any case the question remains: what’s so wrong with internet conferencing, nowadays? Especially in a circumstance where its usage would underly the message so effectively

  5. William H. Calvin:

    In 1994, I happened to be sitting next to Carl Sagan at a conference table when Claude Allegre came in and sat down across the table from us. Sagan immediately started criticizing Allegre for something he had written about early planetary atmospheres. I have never witnessed such a hard-edged scientific critique in my life. Sagan was really mad at Allegre for continuing to push something that had been shown to be wrong (or so I remember, not knowlng the subject material myself). This went on for perhaps ten minutes, with Allegre having trouble getting a word in edgewise.

  6. Stephen Berg:

    “Greenland Ice Sheet on a Downward Slide”:

  7. RAC:

    Allegre makes a defense of his scepticism in Le Monde of 26th October.Article entitled ‘Le droit au doute scientifique‘ in Opinion section… The scientist’s right to scepticism.