{"id":501,"date":"2007-11-18T13:22:06","date_gmt":"2007-11-18T18:22:06","guid":{"rendered":"http:\/\/www.realclimate.org\/index.php\/archives\/2007\/11\/les-chevaliers-de-lordre-de-la-terre-plate-part-i-allgre-and-courtillot\/"},"modified":"2011-12-13T15:15:16","modified_gmt":"2011-12-13T20:15:16","slug":"les-chevaliers-de-lordre-de-la-terre-plate-part-i-allgre-and-courtillot","status":"publish","type":"post","link":"https:\/\/www.realclimate.org\/index.php\/archives\/2007\/11\/les-chevaliers-de-lordre-de-la-terre-plate-part-i-allgre-and-courtillot\/","title":{"rendered":"Les Chevaliers de l&#8217;Ordre de la Terre Plate, Part I: All&egrave;gre and Courtillot"},"content":{"rendered":"<div class=\"kcite-section\" kcite-section-id=\"501\">\n<p>France has a per capita carbon emission of 1.64 tonnes, compared to 2.67 tonnes for the U.K and 5.61 tonnes for the US. So, if anybody has earned the right to rest on their laurels and pontificate to the rest of the developed world about what they should be doing, you&#8217;d think it would be France. Far from it, under the leadership of Nicolas Sarkozy, France has embarked on an ambitious program of deeper carbon reductions. In introducing the measures, Sarkozy said &quot;The guiding principle is that the cost to the climate &#8212; the carbon cost &#8212; will be integrated into planning of all major public projects, and into all deliberations affecting the public.&quot; These measures include: a commitment that all new buildings would be net energy producers by 2020, incandescent lighting would be banned by 2010, buyers of efficient vehicles would be subsidized, drivers of inefficient vehicles would be penalized, and road construction would be severely curtailed in favor of expanded rail travel using state-of-the-art French TGV technology. A carbon tax is also being seriously contemplated. These proposals are the result of an intensive months-long series of discussions with scientists and stakeholders such as environmental nongovernmental organizations, industry representatives, and labor union representatives. The process, known as <a href=\"http:\/\/www.legrenelle-environnement.fr\/\">Le Grenelle de l&#8217;Environnement<\/a>, was described <a href=\"http:\/\/www.nature.com\/news\/2007\/071003\/full\/449518a.html\">here<\/a> by <i>Nature<\/i> (subscription required) and a summary of some of Sarkozy&#8217;s proposed actions was reported in the press <a href=\"http:\/\/ap.google.com\/article\/ALeqM5j-eG8z2TRaH_DClRfgRB3XFB4UDQ\">here<\/a>.<\/p>\n<p>All the same, there has been some pushback from a vocal pair of highly decorated French academicians, Claude All&egrave;gre being the most prominent and noisiest of the two. In recent years, Vincent Courtillot has emerged as a reliable sidekick to All&egrave;gre &#8212; a Dupont to his Dupond &#8212; helping to propagate All&egrave;gre&#8217;s claims and adding a few of his own. Both are members of the Acad&eacute;mie des Sciences, and All&egrave;gre has been awarded both the Crafoord Prize and Bowie Medal. All&egrave;gre has an impressive list of publications relating to the Earth&#8217;s interior, and besides that was Minister for Education, Research and Technology in the Jospin government. Courtillot &#8212; currently director of the Institut de Physique du Globe de Paris (IPGP) &#8212; has had a distinguished record of research on fundamental aspects of geomagnetism and is currently President of the Geomagnetism and Paleomagnetism Section of the American Geophysical Union. Their views were amply (some would say more than amply) represented at a symposium on the IPCC report, held last Spring at the Academie (See the issue &quot;Evolution des Climats&quot; of <i><a href=\"http:\/\/www.academie-sciences.fr\/publications\/lettre.htm\">La Lettre de l&#8217;Acad&eacute;mie des sciences<\/a><\/i>, and press reports in <a href=\"http:\/\/www.lefigaro.fr\/sciences\/20070314.FIG000000106_climat_polemique_entre_academiciens.html\">Le Figaro<\/a>, <a href=\"http:\/\/www.lemonde.fr\/journalelectronique\/donnees\/libre\/20070315\/QUO\/flash_pleinepage\/7.swf\">Le Monde<\/a>, and <a href=\"http:\/\/www.liberation.fr\/actualite\/sciences\/240724.FR.php\">Liberation)<\/a>. What does all this mean? Are the opinions of All&egrave;gre and Courtillot founded on some special profound insight that has escaped the notice of the community of scientists who have devoted entire careers to studying climate? Let&#8217;s take a look.<\/p>\n<p><lang_fr><br \/>\n[NDT&nbsp;: les passages en italique sont en fran&ccedil;ais dans le texte original]<\/p>\n<p>Les &eacute;missions de carbone en France s&#8217;&eacute;l&egrave;vent &agrave; 1,64 tonne par personne, contre 2,67 tonnes au Royaume Uni et 5,61 tonnes aux Etats Unis. Si un pays peut se targuer d&#8217;&ecirc;tre vertueux, et faire la le&ccedil;on aux autres pays d&eacute;velopp&eacute;s, vous pourriez penser que ce serait la France. Loin de l&agrave;, sous l&#8217;impulsion de Nicolas Sarkozy, la France s&#8217;est lanc&eacute;e dans un programme ambitieux de r&eacute;duction des &eacute;missions de carbone. En pr&eacute;sentant ces mesures, M. Sarkozy a d&eacute;clar&eacute;&nbsp;: &laquo;&nbsp;Premier principe&nbsp;: tous les grands projets publics, toutes les d&eacute;cisions publiques seront d&eacute;sormais arbitr&eacute;es en int&eacute;grant leur co&ucirc;t pour le climat, leur &#8216;co&ucirc;t en carbone&#8217;.&nbsp;&raquo; Ces mesures comprennent&nbsp;: l&#8217;engagement que tous les b&acirc;timents construits en 2020 soient des producteurs nets d&#8217;&eacute;nergie, l&#8217;interdiction des ampoules &agrave; incandescence &agrave; partir de 2010, des aides pour les acheteurs de v&eacute;hicules les moins polluants, les conducteurs de v&eacute;hicules les plus polluants &eacute;tant au contraire tax&eacute;s, et la construction de routes sera limit&eacute;e pour favoriser les transports ferroviaires avec la technologie de pointe fran&ccedil;aise du TGV&nbsp;! Une taxe carbone est &eacute;galement envisag&eacute;e. Ces propositions sont le fruit d&#8217;une intense s&eacute;rie de discussions entre scientifiques et repr&eacute;sentants de la soci&eacute;t&eacute; civile, dont des repr&eacute;sentants d&#8217;organisations non-gouvernementales &eacute;cologistes, d&#8217;organisations patronales et de syndicats. Ce processus, connu sous le nom de  <a href=\"http:\/\/www.legrenelle-environnement.fr\/\">Grenelle de l&#8217;Environnement<\/a>, a &eacute;t&eacute; d&eacute;crit bri&egrave;vement dans <i>Nature<\/i> <a href=\"http:\/\/www.nature.com\/news\/2007\/071003\/full\/449518a.html\">ici<\/a> (acc&egrave;s avec souscription), et un r&eacute;sum&eacute; par la presse des propositions d&#8217;actions de Sarkozy est <a href=\"http:\/\/ap.google.com\/article\/ALeqM5j-eG8z2TRaH_DClRfgRB3XFB4UDQ\">ici<\/a>.<\/p>\n<p>Cependant, il y a une certaine r&eacute;sistance de la part d&#8217;un tandem bruyant de deux membres tr&egrave;s d&eacute;cor&eacute;s de l&#8217;Acad&eacute;mie des Sciences fran&ccedil;aise, Claude All&egrave;gre &eacute;tant le plus m&eacute;diatis&eacute; et tapageur des deux. Au cours des derni&egrave;res ann&eacute;es, Vincent Courtillot est apparu comme le fid&egrave;le comp&egrave;re d&#8217;All&egrave;gre &#8211;le Dupont de Dupond&#8211;, l&#8217;aidant &agrave; diffuser ses th&egrave;ses, et en ajoutant aussi des personnelles. Tous deux sont membres de l&#8217;Acad&eacute;mie des Sciences, et All&egrave;gre a re&ccedil;u &agrave; la fois le prix Crafoord et la m&eacute;daille Bowie. All&egrave;gre a une liste impressionnante d&#8217;articles ayant sujet &agrave; la Terre interne, et fut de plus le Ministre de l&#8217;Education Nationale, de la Recherche et de la Technologie sous le gouvernement Jospin. Courtillot &#8211;actuellement directeur de l&#8217;Institut de Physique du Globe de Paris (IPGP)&#8211; a un pass&eacute; reconnu en recherche fondamentale sur le g&eacute;omagn&eacute;tisme, et est actuellement le pr&eacute;sident de la Section de G&eacute;omagn&eacute;tisme et Pal&eacute;omagn&eacute;tisme de l&#8217;American Geophysical Union. Leurs opinions ont &eacute;t&eacute; largement (certains diraient m&ecirc;me plus que largement) exprim&eacute;es lors d&#8217;un colloque sur le rapport du <a href=\"http:\/\/www.ipcc.ch\">GIEC<\/a> tenu au printemps dernier &agrave; l&#8217;Acad&eacute;mie (voir le num&eacute;ro sp&eacute;cial &#8220;Evolution des Climats&#8221; de la <i><a href=\"http:\/\/www.academie-sciences.fr\/publications\/lettre.htm\">Lettre de l&#8217;Acad&eacute;mie des Sciences<\/a><\/i>, ainsi que les rapports du <a href=\"http:\/\/www.lefigaro.fr\/sciences\/20070314.FIG000000106_climat_polemique_entre_academiciens.html\"><i>Figaro<\/i><\/a>, du <a href=\"http:\/\/www.lemonde.fr\/journalelectronique\/donnees\/libre\/20070315\/QUO\/flash_pleinepage\/7.swf\"><i>Monde<\/i><\/a> et de <a href=\"http:\/\/www.liberation.fr\/actualite\/sciences\/240724.FR.php\"><i>Lib&eacute;ration<\/i><\/a>). Qu&#8217;est-ce-que tout cela signifie&nbsp;? Est-ce que les opinions d&#8217;All&egrave;gre et Courtillot sont fond&eacute;es sur une profonde clairvoyance qui aurait &eacute;chapp&eacute; &agrave; la communaut&eacute; de scientifiques qui ont consacr&eacute; leur carri&egrave;re enti&egrave;re &agrave; &eacute;tudier le climat&nbsp;? Voyons cela.\n<\/p>\n<p><\/lang_fr><br \/>\n <!--more--><\/p>\n<p>When an active scientist of the distinction of All&egrave;gre or Courtillot speaks out, the voice has a special claim on our attention, no matter how implausible the claims may seem. It would be a mistake, however, to accept the proclamations of such luminaries on the basis of authority; one must examine the arguments on their merits. All&egrave;gre does not publish his arguments on climate in the peer-reviewed scientific literature, so we have to turn to his popular writings and public statements to get a glimpse of what these arguments are. A treasure trove of Allegrisms (Allegrories? Allegrations?) can be conveniently found in a little opus humbly entitled <i>Ma v&eacute;rit&eacute; sur la plan&egrave;te<\/i> (Plon\/Fayard:Paris 2007). Many of the things said here merely parrot standard discredited skeptics&#8217; arguments without adding anything new: For example, All&egrave;gre at several junctures repeats the old fallacy of confusing unpredictability of weather with the problem of determining how climate responds to changes in radiative forcing: &quot;I have difficulty believing that one could predict with precision the temperatures that will occur a century from now, when we can&#8217;t even predict what they will be one week from now.&quot; (p.89) He also repeats the fallacy that the lead-lag relation between CO<sub>2<\/sub> and temperature in Antarctic ice cores proves that temperature causes CO<sub>2<\/sub> variations rather than vice-versa &#8212; a tired and thoroughly discredited argument (look <a href=\"http:\/\/www.realclimate.org\/index.php\/archives\/2007\/04\/the-lag-between-temp-and-CO2\">here<\/a> for a summary of the rebuttals) . There is little more to say about such arguments, save that All&egrave;gre&#8217;s willingness to repeat them shows either a remarkable gullibility or a disturbing lack of scientific integrity.<\/p>\n<p>Elsewhere, though, All&egrave;gre breaks new ground with regard to passing off nonsense as scientific argument. Here are a few examples.<\/p>\n<ul>\n<li>All&egrave;gre claims that the disappearance of the glaciers on Kilimanjaro is due to moisture supply changes arising from tectonic uplift, and has nothing to do with global warming. This claim appeared over a year ago in All&egrave;gre&#8217;s column in <i>L&#8217;Express<\/i>, and was discussed in an <a href=\"http:\/\/www.realclimate.org\/index.php\/archives\/2006\/10\/con-All&egrave;gre-ma-non-troppo\/\">earlier RealClimate post on All&egrave;gre<\/a>. Essentially, All&egrave;gre failed to understand that the tectonic events referred to in the <i>Science<\/i> paper he cited affected the African climate millions of years ago, whereas the present Kilimanjaro glacier didn&#8217;t even come into existence until around 10,000 years ago.  The erroneous claim about Kilimanjaro is repeated in <i>Ma v&eacute;rit&eacute; sur la plan&egrave;te<\/i> (p.120), despite ample time and opportunity to correct the mistake. So much for <i>v&eacute;rit&eacute; <\/i>(&quot;his&quot; or otherwise).\n<\/li>\n<li>All&egrave;gre says that &quot;common sense&quot; casts doubt on the idea that CO<sub>2<\/sub> could have such a controlling effect on climate, because its concentration is only 300 parts per million (p.104). This &quot;common sense&quot; flies in the face of over a century of meticulous physics going back to the time of Tyndall, which shows precisely why certain trace gases have such a strong influence on infrared absorption by the Earth&#8217;s atmosphere.\n<\/li>\n<li>All&egrave;gre says we &quot;know nothing&quot; (p.109) about the Dansgaard-Oeschger events and other form of millennial variability appearing in the ice-core record. From this statement, I think you are supposed to infer that since we &quot;know nothing&quot; about the events it could well be that the current warming is just the latest warm phase of such a thing. To be sure, there&#8217;s a great deal still to be learned about millennial variability, but the phenomenon has been the subject of several hundred peer-reviewed scientific papers, dozens of conferences, and a major study by the US National Academy of Sciences. We know enough about the pattern of such events and the mechanisms involved to essentially rule out the possibility that the recent warming is a related form of natural variability. We also know enough to worry about the possibility that climate change due to greenhouse gas increases could trigger massive ocean circulation shifts of the sort that were involved in past millennial variability.\n<\/li>\n<li>All&egrave;gre says that under an increase of CO<sub>2<\/sub> there would be no warming at the equator, whereas the predicted warming at the equator is in fact only somewhat below the global mean warming. He states correctly that the warming is strongest at the poles, but states without support that a 10&#186;C warming would be no big deal (p.122). This is quite a startling statement, given that a much more moderate warming has already caused substantial loss of Arctic sea ice. Part of his misconception may come from the fact that he thinks that the temperatures at &quot;the poles&quot; range from &quot;-30 to -60&#186;C.&quot; (p.122) If that were really true, there would be no open water in the Arctic at the time of the sea ice minimum. It is easily verified that this is not the case, and indeed the Arctic commonly gets up to 0&#186;C in the summer, and sometimes more.\n<\/li>\n<li>Ignoring the numerous independent studies of the instrumental record of the past century, he says the Phil Jones analysis of this data has been &quot;put seriously in doubt&quot; (p.100). And by what means? A comparison of Jones&#8217; <i>global mean<\/i> data with an unpublished analysis of the average of a limited number of hand-picked European stations &#8212; presented as the epitome of the Geophysicists&#8217; incomparable expertise at time-series analysis! More on this when we come to discuss Courtillot.\n<\/li>\n<li>Helpfully, All&egrave;gre advises modellers that &quot;It is necessary to avoid basing predictions of future climate on a global mean whose status is vague.&quot; (p.106) Evidently he is unaware that general circulation models have been simulating geographical variations of future wind and temperature changes at least since the 1970&#8217;s, and that maps of such changes have been included in every IPCC report going back to the very first. Oh, but I forget. Elsewhere All&egrave;gre states that &quot;nobody reads&quot; the IPCC reports (p.115). Evidently, this statement applies to at least one person.\n<\/li>\n<li>Continuing his display of ignorance of the modelling enterprise, All&egrave;gre wonders why modellers put CO<sub>2<\/sub> in their models, and concludes that it is only because they happen to know how it has varied over the centuries. Could a century of meticulous laboratory and field work documenting the radiative effect of CO<sub>2<\/sub> perhaps have something to do with modellers&#8217; preoccupation with this gas? Evidently not in All&egrave;gre&#8217;s universe. But there&#8217;s more: &quot;Because one doesn&#8217;t well understand how clouds form, one neglects them! Because one has not mastered the role of aerosols and dust, one neglects them!&quot; (p.104) This is not at all true. Clouds, aerosols and dust (as well as solar irradiance variations and volcanic eruptions) are all included in modern models. Models that leave out the influence of the CO<sub>2<\/sub> rise fail to reproduce the warming of the past 30 years, and it is precisely for this reason that CO<sub>2<\/sub> is confirmed as the prime culprit in global warming.\n<\/li>\n<li>All&egrave;gre makes a number of false or misleading statements concerning the contents of the IPCC Fourth Assessment report. He claims that this report (contrary to French media coverage) &quot;considerably toned down&quot; its conclusions compared to previous reports (p.119). By way of evidence, All&egrave;gre states &quot;For a doubling of CO<sub>2<\/sub> emissions the temperature of the globe will rise between 2 and 4.5&#186;C in a century. The previous report said between 1.5 and 6&#186;C.&quot; (p.119) First of all, the IPCC statements on climate sensitivity refer to a doubling of CO<sub>2<\/sub> <i>concentration<\/i>, not CO<sub>2<\/sub> <i>emissions<\/i>, but let&#8217;s give All&egrave;gre the benefit of the doubt and assume this is just another instance of sloppy writing rather than true misunderstanding. Even so, All&egrave;gre is mixing up his apples with his <i>pommes de terre <\/i>in this statement. Though the climate sensitivity range narrowed from 1.5-4.5&#186;C previously to 2-4.5&#186;C now, reducing the likelihood of low climate sensitivity, the range of predictions for 2100 remain largely unchanged (and are moreover not strictly comparable between the reports given changes in the way &quot;likelihood&quot; is estimated).  In a similar vein, All&egrave;gre claims that the IPCC reduced its forecast of sea level rise, which is <a href=\"http:\/\/www.realclimate.org\/index.php\/archives\/2007\/03\/the-ipcc-sea-level-numbers\/\">not the case<\/a>.\n<\/li>\n<li>And there&#8217;s more. He says that IPCC has &quot;modified, though not completely abandoned, its argument concerning 20th century temperature rise.&quot; (p.119) This evidently refers to All&egrave;gre&#8217;s belief that one of IPCC&#8217;s main arguments has been that CO<sub>2<\/sub> must be responsible for temperature rise because (ben voil&agrave;!) they both go up! It&#8217;s hard for IPCC to abandon an argument it never made, and in any event the Fourth Assessment Report probably devotes more space to discussing the twentieth century temperature record, using more techniques, than any earlier report. And yes it does (pan to shot of Galileo here, speaking through clenched teeth as he bows before the inquisition) still <i>go up<\/i> (and by essentially the same amount as previously estimated). Continuing the theme of abandonment, All&egrave;gre says that the IPCC has &quot;abandoned&quot; its argument regarding the implications of ice-core CO<sub>2<\/sub> and temperature variations. Actually, not. There is no change in the way IPCC interpreted the Vostok isotope and CO<sub>2<\/sub> curve, which appears both in the 2001 and 2007 reports (the latter with Epica extensions into earlier times). The discussion appears in Chapter 6 of the Fourth Assessment Report (p 444 fig 6.3), but how could All&egrave;gre be expected to know that? Nobody reads the IPCC reports, right?<\/li>\n<\/ul>\n<p>Misconceptions and misrepresentations of the sort given above are liberally supplemented with the usual arsenal of innuendo and quote-mining. Because Christopher Landsea (extravagantly compared to Galileo!) chose to make a scene by resigning from the IPCC, the whole process is deemed to not allow dissent &#8212; conveniently ignoring that Lindzen happily stayed on the IPCC Third Assessment Report. An entirely reasonable and uncontroversial statement by Dennis Hartmann on modelling uncertainties is twisted to imply that modellers think we can&#8217;t simulate anything with sufficient precision to draw conclusions about future warming (p.105). Quotes on the possible necessity of adaptation measures from MIT&#8217;s Ron Prinn and Columbia&#8217;s Wally Broecker are used to imply that these two notables favor adaptation over CO<sub>2<\/sub> emissions reduction (p.126). And on the subject of adaptation vs. mitigation, some of All&egrave;gre&#8217;s statements are downright bizarre: He says that we have nothing to fear from global warming. After all, we adapted to the ozone hole, didn&#8217;t we? We adapted to acid rain, didn&#8217;t we? (p.127) Well, no actually, we did nothing of the sort. We &quot;adapted&quot; to the ozone hole by passing the Montreal Protocol to control CFC emissions. We &quot;adapted&quot; to acid rain by passing pollution control measures which reduced sulfate emissions. If this is &quot;adaptation,&quot; I guess I can just say: &#8216;d&#8217;accord!&#8217; Let&#8217;s just &quot;adapt&quot; to global warming by reducing CO<sub>2<\/sub> emissions!<\/p>\n<p>What is to be said of such claims? I couldn&#8217;t put it better than All&egrave;gre himself: &quot;&#8230; une imposture intellectuelle, une escroquerie!&quot; (p.107)<\/p>\n<p>Whatever agenda All&egrave;gre is pursuing in his public pronouncements on global warming, it would seem to be very little informed by his scientific expertise. Through his litany of errors, misconceptions and misrepresentations, he has abdicated any claim to be taken seriously as a scientist when he speaks about climate change. And lest Lomborg and similar eco-Pollyannas draw too much comfort from All&egrave;gre&#8217;s support, let us note that, at the end of the day, All&egrave;gre still calls for a 20% reduction in CO<sub>2<\/sub> emissions over the next 20 years. Many of us who wouldn&#8217;t touch All&egrave;gre&#8217;s arguments with a 10 foot baguette would be quite happy if such a plan were enacted in the United States, at least as a first step towards ultimate deeper reductions.<\/p>\n<p>So much for All&egrave;gre. Now what of M. Courtilllot? Fortunately, we need not go into nearly so much detail, since almost all of the arguments presented in the Academie debate (see his article in <i><a href=\"http:\/\/www.academie-sciences.fr\/publications\/lettre.htm\">La Lettre de l&#8217;Acad&eacute;mie des sciences<\/a><\/i>) mirror those given in All&egrave;gre&#8217;s book. Still, the man manages to add a few wrinkles of his own. For example he confidently declares that the glacial-interglacial CO<sub>2<\/sub> variations are &quot;simply&quot; explained by the effects of temperature on CO<sub>2<\/sub> solubility. He is evidently unaware that this simple mechanism was in fact quite simply evaluated years ago by Wally Broecker &#8212; like All&egrave;gre, a Crafoord prize winner &#8212; and found to be woefully insufficient (see <a href=\"http:\/\/dx.doi.org\/10.1029\/2003PA000914\">Martin, Archer and Lea, <i>Paleoceanography<\/i> 2005<\/a>, for a recent treatment of the subject).<\/p>\n<p>Remember the graph of European temperature in <i>Ma v&eacute;rit&eacute; <\/i>which was supposed to put Phil Jones&#8217; analysis of the instrumental record &quot;seriously in doubt?&quot; Well, it reappears in Courtillot amply decorated with a lot of new verbiage: climate scientists spend all their time modelling and hardly any looking at data; geophysicists are uniquely qualified to look at time series because they do it all the time and anyway they invented most of this stuff in the first place; nobody ever cross-checks or verifies Phil Jones&#8217; work. And patati, and patata, none of which holds a glimmer of truth. But, having declared all this the brave geophysicists of the IPGP decide to take a look for themselves by averaging together a few tens of European weather stations (with a few distant ones from the Urals thrown in for good measure) and ben voil&agrave;, how Courtillot is &quot;astonished&quot; that the curve doesn&#8217;t look at all like what they were taught it should look like! (Courtillot is evidently a man easily astonished, and equally easily surprised, since these words appear with stunning regularity in his article.)<\/p>\n<p>The analysis which evidently shocked Courtillot like a <i>coup de foudre<\/i> was presented at the Academie debate by Le Mou&euml;l (himself an Academician, and holder of the Fleming Medal). A video of his talk is <a href=\"http:\/\/www.academie-sciences.fr\/conferences\/seances_publiques\/html\/debat_13_03_07.htm\">here<\/a>. Dear reader, I urge you to take a look at this video for yourself and see if you can make any more sense of it than I could, amidst all the mislabeled graphs, bizarre choices of what to compare to what, and missing information about crucial aspects of the data handling. I have done my best to convey what I think is the essence of the argument Le Mou&euml;l is trying to make, but it isn&#8217;t easy. In the left panel below I reproduce the only graph in which Le Mou&euml;l attempts a direct comparison between his data and the Phil Jones analysis which appeared in the IPCC report; it was redrawn by tracing over a freeze-frame of Le Mou&euml;l&#8217;s presentation. The graph is labeled &quot;European Average&quot; in the presentation, but the data (thin black line) which Le Mou&euml;l compares to Jones&#8217; European analysis (red line) is actually from Denmark. Moreover, Le Mou&euml;l&#8217;s data seems to be monthly (or maybe daily) minima. Why one would want to compare Danish temperature minima with all-Europe temperature means is beyond me, but in the end what Le Mou&euml;l is making a big noise about is his claim that the yellow curve fit describes the data better than Phil Jones&#8217; curve. Given the variability, there is really no objective reason to prefer one over the other, but the distinction between the two fits is largely immaterial. What you can take home from Le Mou&euml;l&#8217;s analysis is that, in Europe, a marked temperature rise does not set in until the 1980&#8217;s. Sound familiar? It should, because that is more or less what the IPCC says, pointing out further that natural variability cannot explain the recent warming. This can be seen well in the right panel, taken from the Fourth Assessment report. The blue shaded region is the ensemble of simulations forced by natural variabiity, while the pink shaded region includes anthropogenic forcing. Only the latter reproduces the rise at the end of the record. <\/p>\n<p><img decoding=\"async\" data-src=\"\/images\/LeMouel.jpg\" alt=\"\" height=\"263\" width=\"573\" border=\"0\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" class=\"lazyload\" style=\"--smush-placeholder-width: 573px; --smush-placeholder-aspect-ratio: 573\/263;\" \/><\/p>\n<p>The point of a lot of this fiddling with temperature curves is that the Sun must be doing something to control all these fluctuations. That brings us to radiative forcing, and Courtillot and company have had some problems with this issue, since they have a hard time making it look like CO<sub>2<\/sub> is a small forcing and solar variability is a big forcing. One botched attempt at this was to claim that cloud fluctuations swamp CO<sub>2<\/sub>; Courtillot claims that clouds cause 80 Watts per square meter of radiative forcing, so that a mere 3% change in cloud cover would cause 2.4 Watts per square meter radiative forcing, which would be comparable to greenhouse gas forcing changes to date. To get this figure, though, Courtillot evidently assumed that all the Earth&#8217;s albedo is due to clouds, and moreover neglected the cloud greenhouse effect. When properly calculated, the net cloud radiative forcing is more like 20 Watts per square meter, so a 3% change gives you only 0.6 Watts per square meter, well below the greenhouse gas radiative forcing to date, to say nothing of what is in store for the future.<\/p>\n<p>This flub is nothing compared to the trouble Courtillot&#8217;s collaborator Le Mou&euml;l got into during the debates, when he was trying to show that the 1 Watt per square meter variation in the Solar irradiance over the solar cycle is fully half the greenhouse gas forcing. Well, there is the little matter that Le Mou&euml;l forgot to take into account the sphericity of the Earth (which means divide the solar irradiance by 4) or its reflectivity (which means take 70% of the result). As the <i>Le Monde<\/i> reporter archly noted, Le Mou&euml;l&#8217;s calculation assumes a black flat Earth, but, &quot;H&eacute;las! La Terre est ronde&quot; (zut alors!). Le Mou&euml;l seems eager to follow in All&egrave;gre&#8217;s geometrically-challenged footsteps: In a 1988 book (<i>12 cl&eacute;s pour la g&eacute;ologie<\/i>, Belin:Paris), All&egrave;gre confidently stated that the pole to equator temperature gradient was due to snow albedo and atmospheric absorption, making no mention of the role of the Earth&#8217;s spherical geometry, which is far and away the dominant factor (and the reason there&#8217;s ice at the poles to make a high albedo). Messieurs, here&#8217;s a little hint: What does the &quot;G&quot; stand for in &quot;IPGP?&quot;<\/p>\n<p>The round Earth having robbed him of his 1 Watt per square meter &#8211;which in any event is mostly averaged out over the relatively short solar cycle leaving a miniscule tenth of a Watt variation between cycles &#8212; Courtillot grasps at the possibility some unknown and unquantified nonlinear mechanism for turning the very high frequency solar variability into a century scale trend.<\/p>\n<p>There is also a bit of nattering about Moberg&#8217;s take on the Hockey stick, the supposed considerable warmth of the Medieval Warm Period, and some supposed millennial solar variability which supposedly accounts for why the present warming sort of looks like Moberg&#8217;s take on the Medieval Warm. Even leaving aside evidence that Moberg&#8217;s method exaggerates variability (see Mann, Rutherford, Wahl and Ammann 2005, available <a href=\"http:\/\/holocene.meteo.psu.edu\/Mann\/articles\/articles.html\">here<\/a>), the &quot;blame the Sun&quot; mantra falls apart because neither the Sun nor cosmic rays have been exhibiting any trend that could conceivably account for the recent warming, as we have discussed in many places on RealClimate (most recently <a href=\"http:\/\/www.realclimate.org\/index.php\/archives\/2007\/10\/cosmic-rays-don%e2%80%99t-die-so-easily\/\">here<\/a>).<\/p>\n<p>With regard to climate, Courtillot&#8217;s main claim to fame is not found in his article in <i><a href=\"http:\/\/www.academie-sciences.fr\/publications\/lettre.htm\">La Lettre<\/a><\/i>. For that we have to look to a paper recently published in <i>EPSL<\/i>, which claims that climate variations are closely tied to the geomagnetic field. How convincing is this work? That will be the subject of <a href=\"http:\/\/www.realclimate.org\/index.php\/archives\/2007\/12\/les-chevaliers-de-lordre-de-la-terre-plate-part-ii-courtillots-geomagnetic-excursion\/\">Part II<\/a>.<\/p>\n<p><lang_fr><\/p>\n<p>Quand un scientifique actif aussi distingu&eacute; qu&#8217;All&egrave;gre ou Courtillot s&#8217;exprime, sa parole capte notre attention, quelle que soit sa pertinence. Ce serait n&eacute;anmoins une erreur d&#8217;accepter les affirmations de tels phares uniquement &agrave; cause de leur renomm&eacute;e; on doit contr&ocirc;ler les arguments sur leurs m&eacute;rites. All&egrave;gre ne publie pas ses id&eacute;es sur le climat dans la litt&eacute;rature scientifique, de sorte que nous devons nous contenter de ses &eacute;crits de vulgarisation et d&eacute;clarations publiques afin d&#8217;avoir un aper&ccedil;u de ces arguments. Un tr&eacute;sor de ces all&egrave;greries (all&egrave;gritudes&nbsp;?, all&egrave;grations&nbsp;?) est facilement accessible dans un petit ouvrage humblement intitul&eacute; <i>Ma v&eacute;rit&eacute; sur la plan&egrave;te<\/i> (Plon\/Fayard, Paris, 2007). Beaucoup de choses que l&#8217;on y trouve ne sont que rab&acirc;chage d&#8217;arguments standard de sceptiques, arguments compl&eacute;tement discr&eacute;dit&eacute;s auxquels il n&#8217;apporte rien de neuf. Par exemple&nbsp;: il r&eacute;p&egrave;te &agrave; plusieurs endroits l&#8217;erreur classique de confondre le caract&egrave;re impr&eacute;visible de la m&eacute;t&eacute;orologie avec la d&eacute;termination de la r&eacute;ponse du climat au for&ccedil;age radiatif&nbsp;: &#171;&nbsp;J&#8217;ai peine &agrave; croire qu&#8217;on puisse pr&eacute;dire avec pr&eacute;cision le temps qu&#8217;il fera dans un si&egrave;cle alors qu&#8217;on ne peut pas pr&eacute;voir celui qu&#8217;il fera dans une semaine&nbsp;&#187; (p.89). Il r&eacute;p&egrave;te &eacute;galement le raisonnement faux que les relations de phase entre CO<sub>2<\/sub> et temp&eacute;rature mesur&eacute;s dans les carottes de glace de l&#8217;Antarctique prouvent que c&#8217;est la temp&eacute;rature qui est responsable des variations de CO<sub>2<\/sub> plut&ocirc;t que l&#8217;inverse &#8211; un raisonnement &eacute;cul&eacute; et largement discr&eacute;dit&eacute; (<a href=\"http:\/\/www.realclimate.org\/index.php\/archives\/2007\/04\/the-lag-between-temp-and-CO2\">lire ici<\/a> un r&eacute;sum&eacute; des contre-arguments). Il y a peu de choses &agrave; ajouter sur ces arguments, sauf que la capacit&eacute; d&#8217;All&egrave;gre &agrave; les r&eacute;p&eacute;ter indique soit une remaquable cr&eacute;dulit&eacute;, soit un inqui&eacute;tant manque d&#8217;int&eacute;grit&eacute; scientifique.<\/p>\n<p>Ailleurs, pourtant, All&egrave;gre excelle dans l&#8217;art de servir des balivernes comme arguments scientifiques. En voici quelques exemples.<\/p>\n<ul>\n<li>All&egrave;gre affirme que la disparition des glaciers du Kilimandjaro est due &agrave; un changement des apports de vapeur d&#8217;eau caus&eacute; par le soul&egrave;vement tectonique, et n&#8217;a rien &agrave; voir avec le r&eacute;chauffement global. Cette affirmation est apparue il y a un peu plus d&#8217;un an dans la chronique d&#8217;All&egrave;gre dans l&#8217;<i>Express<\/i>, et a &eacute;t&eacute; discut&eacute;e dans un <a href=\"http:\/\/www.realclimate.org\/index.php\/archives\/2006\/10\/con-All&egrave;gre-ma-non-troppo\/\">article pr&eacute;c&eacute;dent<\/a> de RealClimate au sujet d&#8217;All&egrave;gre. Pour l&#8217;essentiel, All&egrave;gre passe &agrave; c&ocirc;t&eacute; du fait que les &eacute;v&eacute;nements tectoniques dontil est question dans l&#8217;article cit&eacute; de <i>Science<\/i> ont modifi&eacute; le climat africain il y a plusieurs millions d&#8217;ann&eacute;es, alors m&ecirc;me que le glacier actuel du kilimandjaro est apparu il y a seulement 10&nbsp;000 ans. Cette affirmation erron&eacute;e au sujet du Kilimandjaro est r&eacute;p&eacute;t&eacute;e dans <i>Ma v&eacute;rit&eacute; sur la plan&egrave;te<\/i> (p.120), bien qu&#8217;il ait eu suffisamment de temps et d&#8217;opportunit&eacute;s pour corriger cette erreur. Autant pour la &#8216;<i>v&eacute;rit&eacute;<\/i>&#8216; (la sienne ou une autre).<\/li>\n<li>All&egrave;gre soutient que le &#8216;bon sens&#8217; permet de mettre en doute l&#8217;id&eacute;e que le CO<sub>2<\/sub> puisse autant contr&ocirc;ler le climat parce que sa concentration est seulement de 300 parties par million (p.104). Ce &#8216;bon sens&#8217; bouscule plus d&#8217;un si&egrave;cle de physique m&eacute;ticuleuse qui remonte &agrave; l&#8217;&eacute;poque de Tyndall et qui montre pr&eacute;cis&eacute;ment pourquoi certains gaz &agrave; l&#8217;&eacute;tat de trace influencent si fortement l&#8217;absorption des infra-rouges par l&#8217;atmosph&egrave;re.<\/li>\n<li>All&egrave;gre dit qu&#8217;on ne &#171;&nbsp;sait rien&nbsp;&#187; (p.109) sur les &eacute;v&eacute;nements de Dansgaard-Oeschger et autre type de variabilit&eacute; mill&eacute;naire existant dans les carottes de glace. De cette affirmation, je suppose que nous sommes cens&eacute;s d&eacute;duire que, comme on ne &#171;&nbsp;sait rien&nbsp;&#187; sur ces &eacute;v&eacute;nements, il se pourrait bien que le r&eacute;chauffement actuel soit juste la derni&egrave;re phase de l&#8217;un d&#8217;eux. Bien s&ucirc;r, il y a encore beaucoup de choses &agrave; apprendre sur la variabilit&eacute; mill&eacute;naire, mais ce ph&eacute;nom&egrave;ne a fait l&#8217;objet de plusieurs centaines de publications scientifiques, douzaines de conf&eacute;rences, ainsi qu&#8217;une synth&egrave;se majeure par l&#8217;Acad&eacute;mie des Sciences am&eacute;ricaine. Nous en savons assez sur la structure de ces &eacute;v&eacute;nements et leurs m&eacute;canismes pour tout &eacute;carter la possibilit&eacute; que le r&eacute;chauffement r&eacute;cent provienne simplement de ce type de variabilit&eacute; naturelle. Nous en savons &eacute;galement assez pour nous inqui&eacute;ter de la possibilit&eacute; que le changement climatique d&ucirc; &agrave; l&#8217;augmentation des gaz &agrave; effet de serre puisse d&eacute;clencher un de ces changements majeurs de la circulation oc&eacute;anique qui ont particip&eacute; &agrave; la variabilit&eacute; mill&eacute;naire dans le pass&eacute;.<\/li>\n<li>All&egrave;gre annonce qu&#8217;avec une augmentation du CO<sub>2<\/sub> il ne devrait pas y avoir de r&eacute;chauffement &agrave; l&#8217;&eacute;quateur, alors que le r&eacute;chauffement pr&eacute;dit &agrave; l&#8217;&eacute;quateur n&#8217;est que l&eacute;g&egrave;rement inf&eacute;rieur &agrave; la moyenne globale. Il affirme correctement que le r&eacute;chauffement est plus fort aux p&ocirc;les, mais aussi, et sans justification, qu&#8217;un r&eacute;chauffement de 10&#186;C serait sans importance (p.122). C&#8217;est une affirmation plut&ocirc;t surprenante puisqu&#8217;un r&eacute;chauffement bien plus faible est d&eacute;j&agrave; responsable d&#8217;une disparition notable de la glace de mer en Arctique. Cette conception erron&eacute;e pourrait provenir en partie du fait qu&#8217;il pense que la temp&eacute;rature &#171;&nbsp;aux p&ocirc;les&nbsp;&#187; varie entre &#171;&nbsp;-30 et -60&#186;C&nbsp;&#187; (p.122). Si c&#8217;&eacute;tait vrai, il n&#8217;y aurait pas d&#8217;eau libre en Arctique pendant le minimum de couverture de glace de mer. Il est facile de v&eacute;rifier que ce n&#8217;est pas le cas, et en fait l&#8217;Arctique monte souvent jusqu&#8217;&agrave; 0&#186;C, et parfois au-del&agrave;.<\/li>\n<li>Ignorant les nombreuses &eacute;tudes ind&eacute;pendantes des mesures sur le dernier si&egrave;cle, il soutient que l&#8217;analyse de Phil Jones de ces donn&eacute;es a &eacute;t&eacute; &#171;&nbsp;fortement mise en doute&nbsp;&#187; (p.100). Et par quel moyen&nbsp;? Par une comparaison entre les donn&eacute;es globales de Phil Jones et une analyse non publi&eacute;e des moyennes d&#8217;un petit nombre de stations europ&eacute;ennes &#8211; pr&eacute;sent&eacute;e comme l&#8217;arch&eacute;type de l&#8217;expertise incomparable des G&eacute;ophysiciens en analyse de s&eacute;ries temporelles&nbsp;! Nous y reviendrons &agrave; propos de Courtillot.<\/li>\n<li>Tr&egrave;s obligeamment, All&egrave;gre conseille aux mod&eacute;lisateurs&nbsp;: &#171;&nbsp;Il faut donc &eacute;viter de fonder les pr&eacute;dictions du climat futur sur une moyenne mondiale dont la situation est floue.&nbsp;&#187; (p.106). Visiblement il n&#8217;est pas au courant que, depuis au moins les ann&eacute;es 70, les mod&egrave;les de circulation g&eacute;n&eacute;rale simulent des champs spatialis&eacute;s des pr&eacute;visions de vent et de temp&eacute;rature, et que des cartes de ces changements ont &eacute;t&eacute; incluses dans tous les rapports du GIEC depuis le premier. Oh, mais j&#8217;oubliais. Ailleurs, All&egrave;gre ass&egrave;ne que &#171;&nbsp;personne ne lit&nbsp;&#187; (p.115) les rapports du GIEC. Visiblement, cette d&eacute;claration s&#8217;applique au moins &agrave; une personne.<\/li>\n<li>Continuant d&#8217;&eacute;taler son ignorance de la mod&eacute;lisation, All&egrave;gre se demande pourquoi les mod&eacute;lisateurs ont inclus le CO<sub>2<\/sub> dans leurs mod&egrave;les, et en conclut que c&#8217;est uniquement parce qu&#8217;ils connaissent ses variations sur les derniers si&egrave;cles. Est-ce-qu&#8217;un si&egrave;cle de travail m&eacute;ticuleux en laboratoire et sur le terrain pass&eacute; &agrave; documenter l&#8217;effet radiatif du CO<sub>2<\/sub> aurait peut-&ecirc;tre &agrave; voir avec l&#8217;attrait des mod&eacute;lisateurs pour ce gaz&nbsp;? Visiblement pas dans l&#8217;univers d&#8217;All&egrave;gre. Mais il y a mieux&nbsp;: &#171;&nbsp;Comme on ne sait pas bien comment se forment les nuages, on les n&eacute;glige&nbsp;! Comme on ma&icirc;trise mal le r&ocirc;le des a&eacute;rosols et des poussi&egrave;res, on les n&eacute;glige&nbsp;!&nbsp;&#187; (p.104) C&#8217;est compl&egrave;tement faux. Nuages, a&eacute;rosols et poussi&egrave;res (comme variations de l&#8217;irradiance solaire et &eacute;ruptions volcaniques) sont tous pris en compte par les mod&egrave;les actuels. Les mod&egrave;les qui n&eacute;gligent l&#8217;influence de l&#8217;augmentation du CO<sub>2<\/sub> n&#8217;arrivent pas &agrave; reproduire le r&eacute;chauffement des derniers trente ans, et c&#8217;est pr&eacute;cis&eacute;ment pour cette raison que le CO<sub>2<\/sub> a &eacute;t&eacute; confirm&eacute; comme le responsable principal du r&eacute;chauffement global.<\/li>\n<li>All&egrave;gre fait un certain nombre de d&eacute;clarations fausses ou fallacieuses sur le contenu du Quatri&egrave;me Rapport d&#8217;Evaluation du GIEC. Il assure, contrairement aux m&eacute;dias fran&ccedil;ais, que ce rapport &#171;&nbsp;est beaucoup plus mod&eacute;r&eacute; que les pr&eacute;c&eacute;dents.&nbsp;&#187; (p.119) Ainsi, All&egrave;gre assure que &#171;&nbsp;Pour un doublement des &eacute;missions de CO<sub>2<\/sub> , la temp&eacute;rature du globe augmenterait de 2 &agrave; 4,5&#186;C en un si&egrave;cle. Le pr&eacute;c&eacute;dent rapport disait entre 1,5 et 6&#186;C.&nbsp;&#187; (p.119) En premier lieu, les d&eacute;clarations du GIEC sur la sensibilit&eacute; climatique font r&eacute;f&eacute;rence &agrave; un doublement de la concentration en CO<sub>2<\/sub>, pas de ses &eacute;missions, mais laissons &agrave; All&egrave;gre le b&eacute;n&eacute;fice du doute et supposons qu&#8217;il ne s&#8217;agit que d&#8217;une autre coquille et pas d&#8217;une v&eacute;ritable incompr&eacute;hension. Tout de m&ecirc;me, All&egrave;gre m&eacute;lange ici des pommes et des frites. M&ecirc;me si la fourchette de la sensibilit&eacute; climatique a &eacute;t&eacute; r&eacute;duite, passant de 1,5&nbsp;&#8211;&nbsp;4,5&#186;C &agrave; 2&nbsp;&#8211;&nbsp;4,5&#186;C, ce qui diminue ainsi la probabilit&eacute; d&#8217;une faible sensibilit&eacute;, la fourchette des pr&eacute;visions pour l&#8217;ann&eacute;e 2100 n&#8217;a presque pas chang&eacute; (de plus la d&eacute;finition probabiliste de cette fourchette a vari&eacute; entre les rapports, elles ne sont donc pas directement comparables). Dans la m&ecirc;me veine, All&egrave;gre assure que le GIEC a r&eacute;duit ses pr&eacute;visions de hausse du niveau marin, ce qui n&#8217;est pas le cas (<a href=\"http:\/\/www.realclimate.org\/index.php\/archives\/2007\/03\/the-ipcc-sea-level-numbers\/\">voir ici<\/a>). <\/li>\n<li>Mais il y a mieux. Il dit que le GIEC &laquo;&nbsp;mod&egrave;re sans encore l&#8217;abandonner l&#8217;argument d&#8217;&eacute;volution de la temp&eacute;rature depuis le XIXe si&egrave;cle.&nbsp;&raquo; (p.119) Ceci correspond &eacute;videmment &agrave; la croyance d&#8217;All&egrave;gre que l&#8217;un des principaux arguments du GIEC est que le CO<sub>2<\/sub> doit &ecirc;tre responsable de l&#8217;augmentation de temp&eacute;rature parce que (<i>ben voil&agrave;<\/i>&nbsp;!) tous deux augmentent&nbsp;! Il est difficile au GIEC d&#8217;abandonner un argument qui n&#8217;a jamais &eacute;t&eacute; le sien, et en tout cas le Quatri&egrave;me Rapport d&#8217;Evaluation fait probablement plus de place &agrave; la discussion des enregistrements de temp&eacute;rature sur le 20e si&egrave;cle, en utilisant plus de techniques, qu&#8217;aucun des rapports pr&eacute;c&eacute;dents. Et pourtant (on pense ici &agrave; Galil&eacute;e, parlant en serrant les dents tout en s&#8217;inclinant devant l&#8217;Inquisition) elle augmente bien (et en suivant pratiquement les pr&eacute;visions). Poursuivant sur le th&egrave;me du renoncement suppos&eacute; du GIEC, All&egrave;gre assure que celui-ci a &#171;&nbsp;abandonn&eacute;&nbsp;&#187; son argumentation bas&eacute;e sur les variations de CO<sub>2<\/sub> et de temp&eacute;rature enregistr&eacute;es par les glace. Rien de tout cela. Il n&#8217;y a pas eu de changement d&#8217;interpr&eacute;tation par le GIEC des courbes isotopiques et du CO<sub>2<\/sub> de Vostok, interpr&eacute;tation qui apparait dans les deux rapports de 2001 et 2007 (avec, dans ce dernier, l&#8217;extension d&#8217;EPICA &agrave; des p&eacute;riodes plus anciennes). Cette discussion se trouve au chapitre 6 du Quatri&egrave;me Rapport d&#8217;Evaluation (p.444, figure 6.3), mais comment pourrait-on s&#8217;attendre &agrave; ce qu&#8217;All&egrave;gre sache cela, puisque personne ne lit le rapport du GIEC, n&#8217;est-ce-pas&nbsp;? <\/li>\n<\/ul>\n<p>De telles id&eacute;es fausses et d&eacute;formations de la r&eacute;alit&eacute; comme celles expos&eacute;es ci-dessus sont g&eacute;n&eacute;reusement accompagn&eacute;es de l&#8217;arsenal habituel d&#8217;insinuations et de citations abusives. Parce que Christopher Landsea (compar&eacute; de mani&egrave;re extravagante &agrave; Galil&eacute;e&nbsp;!) a choisi de faire toute une sc&egrave;ne de sa d&eacute;mission du GIEC, le processus dans son ensemble est jug&eacute; oppos&eacute; &agrave; toute dissidence &#8211; ignorant de mani&egrave;re opportune que Lindzen lui est rest&eacute; tranquillement tout au long du Troisi&egrave;me Rapport d&#8217;Evaluation du GIEC. Une affirmation de Dennis Hartmann, tout &agrave; fait justifi&eacute;e et incontestable, sur les incertitudes de la mod&eacute;lisation est d&eacute;tourn&eacute;e afin d&#8217;insinuer que les mod&eacute;lisateurs ne croient pas possible d&#8217;obtenir suffisamment de pr&eacute;cision pour tirer des conclusions sur le r&eacute;chauffement futur (p.105). Des citations sur la possible n&eacute;cessit&eacute; de mesures d&#8217;adaptation, venant de Ron Prinn du MIT et de Wally Broecker de Columbia, sont utilis&eacute;es afin d&#8217;insinuer que ces deux c&eacute;l&eacute;brit&eacute;s favorisent l&#8217;adaptation sur la r&eacute;duction des &eacute;missions de CO<sub>2<\/sub> (p.126). Et sur le sujet de l&#8217;adaptation par rapport &agrave; l&#8217;att&eacute;nuation, certaines affirmations d&#8217;All&egrave;gre sont franchement saugrenues&nbsp;: il soutient que nous n&#8217;avons rien &agrave; craindre du r&eacute;chauffement global. Apr&egrave;s tout, nous nous sommes adapt&eacute;s au trou d&#8217;ozone, n&#8217;est-ce pas&nbsp;? Nous nous sommes adapt&eacute;s aux pluies acides, n&#8217;est-ce pas&nbsp;? (p.127) Et bien, non en fait, nous n&#8217;avons rien fait de tout cela. Nous nous sommes &#8216;adapt&eacute;s&#8217; au trou d&#8217;ozone en adoptant le protocole de Montr&eacute;al pour contr&ocirc;ler les &eacute;missions de CFC. Nous nous sommes &#8216;adapt&eacute;s&#8217; aux pluies acides en adoptant des mesures de contr&ocirc;le des rejets soufr&eacute;s. Si c&#8217;est &ccedil;a &#8216;s&#8217;adapter&#8217;, je pense que je peux juste dire&nbsp;: &#171;&nbsp;<i>D&#8217;accord<\/i>&nbsp;! &#8216;Adaptons&#8217;-nous au r&eacute;chauffement global en r&eacute;duisant les &eacute;missions de CO<sub>2<\/sub>&nbsp;!&nbsp;&#187;<\/p>\n<p>Que peut-on dire de toutes ces affirmations&nbsp;? Je ne pourrais le faire mieux qu&#8217;All&egrave;gre lui-m&ecirc;me&nbsp;: &#171;&#8230;<i>une imposture intellectuelle, une escroquerie<\/i>&nbsp;!&nbsp;&#187; (p.107)<\/p>\n<p>Quel que soit le plan d&#8217;All&egrave;gre dans ses annonces publiques, celles-ci semblent peu fond&eacute;es sur son expertise scientifique. Avec sa litanie d&#8217;erreurs, d&#8217;id&eacute;es fausses et de d&eacute;formations de la r&eacute;alit&eacute;, il a renonc&eacute; &agrave; toute pr&eacute;tention d&#8217;&ecirc;tre consid&eacute;r&eacute; s&eacute;rieusement en tant que scientifique lorsqu&#8217;il parle du changement climatique. Et si m&ecirc;me Lomborg et autres <a href=\"http:\/\/www.nature.com\/nature\/journal\/v422\/n6929\/full\/422263a.html\">&eacute;co-polyannas<\/a> b&eacute;n&eacute;ficient trop du soutien d&#8217;All&egrave;gre, notons que, au final, All&egrave;gre appelle quand m&ecirc;me &agrave; une r&eacute;duction de 20% des &eacute;missions de CO<sub>2<\/sub> sur les vingt prochaines ann&eacute;es. Nombre d&#8217;entre nous qui se refuseraient &agrave; toucher aux arguments d&#8217;All&egrave;gre, m&ecirc;me avec un b&acirc;ton de 3 m, seraient tr&egrave;s heureux si un tel plan &eacute;tait mis en oeuvre aux Etats Unis, au moins comme un premier pas vers des r&eacute;ductions plus drastiques.<\/p>\n<p>Voici donc pour All&egrave;gre. Maintenant que dire au sujet de M. Courtillot&nbsp;? Heureusement il ne nous est pas n&eacute;cessaire d&#8217;aller si loin dans les d&eacute;tails, car pratiquement tous les arguments pr&eacute;sent&eacute;s au d&eacute;bat &agrave; l&#8217;Acad&eacute;mie (voir son article dans <i><a href=\"http:\/\/www.academie-sciences.fr\/publications\/lettre.htm\">La Lettre de l&#8217;Acad&eacute;mie des sciences<\/a><\/i>) refl&egrave;tent ceux du livre d&#8217;All&egrave;gre. Pourtant, notre homme parvient &agrave; ajouter quelques marques de son cru. Par exemple il d&eacute;clare, s&ucirc;r de lui, que les variations glaciaires-interglaciaires du CO<sub>2<\/sub> sont &#171;&nbsp;tout simplement&nbsp;&#187; dues &agrave; l&#8217;effet de la temp&eacute;rature sur la solubilit&eacute; du CO<sub>2<\/sub>. Il n&#8217;est donc pas au courant que ce m&eacute;canisme de base a &eacute;t&eacute; &eacute;valu&eacute; il y a bien des ann&eacute;es par Wally Broecker &#8211;comme All&egrave;gre, un d&eacute;tenteur du prix Crafoord&#8211; et a &eacute;t&eacute; estim&eacute; vraiment insuffisant (voir <a href=\"http:\/\/dx.doi.org\/10.1029\/2003PA000914\">Martin, Archer et Lea, Paleoceanography 2005<\/a>, pour un r&eacute;cent bilan sur ce sujet).<\/p>\n<p>Vous vous souvenez du graphe de la temp&eacute;rature europ&eacute;enne dans <i>Ma V&eacute;rit&eacute;<\/i>, qui devait remettre &#171;&nbsp;fortement en doute&nbsp;&#187; l&#8217;analyse de Phil Jones des enregistrements de temp&eacute;rature&nbsp;? Et bien il r&eacute;apparait avec Courtillot tr&egrave;s enrichi par de nouveaux verbiages&nbsp;: les scientifiques du climat passent tout leur temps &agrave; mod&eacute;liser et pratiquement pas &agrave; observer; les g&eacute;ophysiciens sont les seuls qualifi&eacute;s &agrave; &eacute;tudier les s&eacute;ries temporelles car ils le font sans arr&ecirc;t et de toute fa&ccedil;on ils ont pratiquement tout invent&eacute; en premier dans ce domaine; personne n&#8217;a jamais contr&ocirc;l&eacute; ou v&eacute;rifi&eacute; le travail de Phil Jones. Et patati, et patata, rien de tout cela n&#8217;ayant une once de v&eacute;rit&eacute;. Mais, apr&egrave;s avoir d&eacute;clar&eacute; tout cela, les braves g&eacute;ophysiciens de l&#8217;IPGP d&eacute;cid&egrave;rent de regarder par eux-m&ecirc;mes en moyennant quelques dizaines de stations m&eacute;t&eacute;orologiques europ&eacute;ennes (additionn&eacute;es de quelques stations &eacute;loign&eacute;es en Oural pour faire bonne mesure), et <i>ben voil&agrave;<\/i>, Courtillot est &#8220;&eacute;tonn&eacute;&#8221; que la courbe ne ressemble pas &agrave; ce qu&#8217;on leur avait appris&nbsp;! (Courtillot est visiblement quelqu&#8217;un de facilement &eacute;tonn&eacute;, et autant surpris, car ces mots apparaissent avec une r&eacute;gularit&eacute; stup&eacute;fiante dans son article).<\/p>\n<p>Cette analyse, qui frappa Courtillot d&#8217;un vrai &#8216;<i>coup de foudre<\/i>&#8216;, fut pr&eacute;sent&eacute;e lors du d&eacute;bat &agrave; l&#8217;Acad&eacute;mie par Le Mou&euml;l (lui-m&ecirc;me acad&eacute;micien, et d&eacute;tenteur de la m&eacute;daille Fleming). Une vid&eacute;o de cette pr&eacute;sentation se <a href=\"http:\/\/www.academie-sciences.fr\/conferences\/seances_publiques\/html\/debat_13_03_07.htm\">trouve ici<\/a>. Cher lecteur, je vous presse de regarder cette vid&eacute;o afin de voir si vous pouvez en tirer plus de sens que je ne l&#8217;ai pu, parmi tous les graphes mal annot&eacute;s, les choix &eacute;tranges des comparaisons, et les informations qui manquent sur certains aspects cruciaux du traitement des donn&eacute;es. J&#8217;ai fait de mon mieux pour pr&eacute;senter ce que je pense &ecirc;tre l&#8217;essence de l&#8217;argumentation de Le Mou&euml;l, mais ce n&#8217;est pas facile. Sur la partie gauche de l&#8217;image ci-dessous j&#8217;ai reproduit le seul graphe dans lequel Le Mou&euml;l tente une comparaison directe entre ses donn&eacute;es et l&#8217;analyse de Phil Jones parue dans le rapport du GIEC; ce graphe a &eacute;t&eacute; d&eacute;calqu&eacute; sur un des plans de la vid&eacute;o de la pr&eacute;sentation. Le graphe est titr&eacute; &#8220;Moyenne de l&#8217;Europe&#8221; dans la pr&eacute;sentation, mais les donn&eacute;es (courbe noire) que Le Mou&euml;l compare &agrave; l&#8217;analyse europ&eacute;enne de Phil Jones (trait rouge) sont en fait celles du Danemark. De plus, les donn&eacute;es de Le Mou&euml;l semblent correspondre &agrave; des minima mensuels (ou journaliers peut-&ecirc;tre). Pourquoi voudrait-on comparer les minima de temp&eacute;rature au Danemark avec la moyenne de temp&eacute;rature de toute l&#8217;Europe, cela me d&eacute;passe, mais finalement ce dont Le Mou&euml;l fait grand bruit c&#8217;est l&#8217;affirmation que la courbe jaune est une meilleure approximation des donn&eacute;es que la courbe de Phil Jones. En consid&eacute;rant la variabilit&eacute;, il n&#8217;y a vraiment pas de raison objective de pr&eacute;f&eacute;rer l&#8217;une &agrave; l&#8217;autre, la distinction entre les deux approximations est compl&egrave;tement irr&eacute;elle. Le message de l&#8217;analyse de Le Mou&euml;l est qu&#8217;en Europe une augmentation marqu&eacute;e de la temp&eacute;rature n&#8217;appara&icirc;t pas avant les ann&eacute;es 80. D&eacute;j&agrave; entendu quelque part&nbsp;? Vous devriez, car ceci correspond plus ou moins &agrave; ce que dit le GIEC, qui conclut de plus que la variabilit&eacute; naturelle ne peut expliquer le r&eacute;chauffement r&eacute;cent. Ceci est bien visible sur le graphe de droite tir&eacute; du Quatri&egrave;me Rapport d&#8217;Evaluation du GIEC. La zone ombr&eacute;e en bleu correspond &agrave; un ensemble de simulations forc&eacute;es par la variabilit&eacute; naturelle, tandis que celle en rose inclut aussi le for&ccedil;age anthropique. Seule cette derni&egrave;re reproduit l&#8217;augmentation de la fin de l&#8217;enregistrement. Bien loin de bousculer les conventions, Le Mou&euml;l a en fait montr&eacute; qu&#8217;une simple moyenne d&#8217;un jeu limit&eacute; de donn&eacute;es confirme largement l&#8217;analyse de Phil Jones &#8211; une &#8216;prouesse&#8217;, si l&#8217;on r&eacute;alise qu&#8217;en consid&eacute;rant une r&eacute;gion aussi petite que l&#8217;Europe, la tendance anthropog&eacute;nique est bien plus difficile &agrave; distinguer de la variabilit&eacute; naturelle due &agrave; la circulation.<\/p>\n<p><img decoding=\"async\" data-src=\"\/images\/LeMouel.jpg\" alt=\"\" height=\"263\" width=\"573\" border=\"0\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" class=\"lazyload\" style=\"--smush-placeholder-width: 573px; --smush-placeholder-aspect-ratio: 573\/263;\" \/><\/p>\n<p>Le but de tout ce trafic avec les courbes de temp&eacute;rature est que le soleil doit en &ecirc;tre pour quelque chose dans ces fluctuations. Ce qui nous am&egrave;ne au for&ccedil;age radiatif, o&ugrave; Courtillot et consorts ont eu quelques probl&egrave;mes sur ce point, car il leur a &eacute;t&eacute; tr&egrave;s difficile de faire passer le CO<sub>2<\/sub> pour un for&ccedil;age mineur et la variabilit&eacute; solaire pour un for&ccedil;age majeur. Un essai bacl&eacute; dans ce sens a &eacute;t&eacute; de pr&eacute;tendre que les variations des nuages surpassaient le CO<sub>2<\/sub>&nbsp;: Courtillot pr&eacute;tend que les nuages sont responsables d&#8217;un for&ccedil;age radiatif de 80 watts par m&egrave;tre carr&eacute;, de sorte qu&#8217;un changement aussi faible que 3% de la couverture nuageuse induirait un for&ccedil;age radiatif de 2,4 watts par m&egrave;tre carr&eacute;, comparable &agrave; celui actuel des gaz &agrave; effet de serre. Mais pour obtenir ce chiffre, Courtillot a &eacute;videmment suppos&eacute; que l&#8217;alb&eacute;do terrestre est enti&egrave;rement d&ucirc; aux nuages, et de plus il a n&eacute;glig&eacute; l&#8217;effet de serre des nuages. Calcul&eacute; correctement, le for&ccedil;age radiatif net des nuages est plut&ocirc;t de 20 watts par m&egrave;tre carr&eacute;, de sorte qu&#8217;une variation de 3% donne seulement 0,6 watts par m&egrave;tre carr&eacute;, tr&egrave;s inf&eacute;rieur au for&ccedil;age radiatif actuel des gaz &agrave; effet de serre, sans m&ecirc;me parler de celui qui nous attend.<\/p>\n<p>Cette gaffe n&#8217;est rien en comparaison de la difficult&eacute; &eacute;prouv&eacute;e pendant les d&eacute;bats par Le Mou&euml;l, qui collabore avec Courtillot, lorsqu&#8217;il essaya de montrer que la variation de 1 watt par m&egrave;tre carr&eacute; de l&#8217;irradiance solaire au cours d&#8217;un cycle solaire repr&eacute;sente vraiment la moiti&eacute; du for&ccedil;age des gaz &agrave; effet de serre. Bon, il y a un d&eacute;tail que Le Mou&euml;l oublie de prendre en compte, c&#8217;est la sph&eacute;ricit&eacute; de la Terre (ce qui implique de diviser l&#8217;irradiance solaire par 4) ou sa r&eacute;flectance (ce qui implique de prendre 70% du r&eacute;sultat). Comme le reporter du Monde le soulignait malicieusement, le calcul de Le Mou&euml;l suppose une Terre noire et plate, mais &#8220;<i>H&eacute;las! La Terre est ronde<\/i>&#8221; (<i>zut alors<\/i>&nbsp;!). Le Mou&euml;l semble ainsi suivre avec ferveur All&egrave;gre dans ses mauvais pas en g&eacute;om&eacute;trie&nbsp;: dans un livre de 1988 (<i>12 cl&eacute;s pour la g&eacute;ologie<\/i>, Belin\/Paris), All&egrave;gre affirme s&ucirc;r de lui que le gradient de temp&eacute;rature entre les p&ocirc;les et l&#8217;&eacute;quateur est d&ucirc; &agrave; l&#8217;alb&eacute;do de la neige et &agrave; l&#8217;absorption de l&#8217;atmosph&egrave;re, ne faisant aucune mention du r&ocirc;le de la g&eacute;om&eacute;trie sph&eacute;rique de la Terre, qui est de loin le facteur dominant (et la raison de la pr&eacute;sence aux p&ocirc;les de glace avec un alb&eacute;do &eacute;lev&eacute;). <i>Messieurs<\/i>, voici un indice&nbsp;: que veut dire le &#8216;G&#8217; de &#8216;IPGP&#8217;&nbsp;?<\/p>\n<p>La rotondit&eacute; de la Terre l&#8217;ayant priv&eacute; de son 1 watt par m&egrave;tre carr&eacute; &#8211;qui de toute fa&ccedil;on est pratiquement moyenn&eacute; au cours d&#8217;un cycle solaire et ne laisse qu&#8217;un dixi&egrave;me de watt par m&egrave;tre carr&eacute; entre les cycles&#8211; Courtillot se raccrocha &agrave; la possibilit&eacute; d&#8217;un m&eacute;canisme non lin&eacute;aire, inconnu et non quantifi&eacute;, pour transformer la variabilit&eacute; solaire haute fr&eacute;quence en une tendance sur un si&egrave;cle.<\/p>\n<p>Il y a &eacute;galement quelques bavardages sur la position de Moberg sur la &#8216;crosse de hockey&#8217;, la pr&eacute;tendue p&eacute;riode tr&egrave;s chaude de l&#8217;Optimum M&eacute;di&eacute;val, et une suppos&eacute;e variabilit&eacute; solaire mill&eacute;naire qui devrait expliquer pourquoi le r&eacute;chauffement r&eacute;cent correspond plus ou moins &agrave; l&#8217;explication de Moberg de l&#8217;Optimum M&eacute;di&eacute;val. Mises &agrave; part quelques indications que la m&eacute;thode utilis&eacute;e par Moberg surestime la variabilit&eacute; (voir Mann, Rutherford, Wahl et Ammann 2005, <a href=\"http:\/\/holocene.meteo.psu.edu\/Mann\/articles\/articles.html\">disponible ici<\/a>), le mantra du &#8220;C&#8217;est la faute au soleil&#8221; s&#8217;effondre puisque ni le soleil ni les rayons cosmiques ne montrent de tendance pouvant expliquer le r&eacute;chauffement des derni&egrave;res d&eacute;cennies, comme nous en avons discut&eacute; &agrave; plusieurs reprises sur RealClimate (le <a href=\"http:\/\/www.realclimate.org\/index.php\/archives\/2007\/10\/cosmic-rays-don%e2%80%99t-die-so-easily\/\">plus r&eacute;cemment ici<\/a>).<\/p>\n<p>Pour ce qui est du climat, les faits de gloire de Courtillot ne se trouvent pas dans son article de <i><a href=\"http:\/\/www.academie-sciences.fr\/publications\/lettre.htm\">La Lettre de l&#8217;Acad&eacute;mie<\/a><\/i>. Pour cela nous devons nous tourner vers un article r&eacute;cemment publi&eacute; dans EPSL, article qui pr&eacute;tend que les changements climatiques sont &eacute;troitement li&eacute;s au champ g&eacute;omagn&eacute;tique. Ce travail est-il convaincant&nbsp;? Ce sera le sujet de la <a href=\"http:\/\/www.realclimate.org\/index.php\/archives\/2007\/12\/les-chevaliers-de-l%e2%80%99ordre-de-la-terre-plate-part-ii-courtillots-geomagnetic-excursion\/\">seconde partie<\/a>.\n<\/p>\n<p><\/lang_fr><\/p>\n<!-- kcite active, but no citations found -->\n<\/div> <!-- kcite-section 501 -->","protected":false},"excerpt":{"rendered":"<p>France has a per capita carbon emission of 1.64 tonnes, compared to 2.67 tonnes for the U.K and 5.61 tonnes for the US. So, if anybody has earned the right to rest on their laurels and pontificate to the rest of the developed world about what they should be doing, you&#8217;d think it would be [&hellip;]<\/p>\n","protected":false},"author":43,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[1,34],"tags":[],"class_list":{"0":"post-501","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-climate-science","7":"category-skeptics","8":"entry"},"aioseo_notices":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts\/501","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/users\/43"}],"replies":[{"embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/comments?post=501"}],"version-history":[{"count":1,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts\/501\/revisions"}],"predecessor-version":[{"id":10232,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts\/501\/revisions\/10232"}],"wp:attachment":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/media?parent=501"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/categories?post=501"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/tags?post=501"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}