{"id":94,"date":"2005-01-14T05:31:19","date_gmt":"2005-01-14T09:31:19","guid":{"rendered":"\/?p=94"},"modified":"2007-08-02T08:29:27","modified_gmt":"2007-08-02T13:29:27","slug":"the-global-cooling-myth","status":"publish","type":"post","link":"https:\/\/www.realclimate.org\/index.php\/archives\/2005\/01\/the-global-cooling-myth\/","title":{"rendered":"The global cooling myth Le mythe du refroidissement global<\/lang_fr>"},"content":{"rendered":"
\n

Every now and again, the myth that “we shouldn’t believe global warming predictions now, because in the 1970’s they were predicting an ice age and\/or cooling” surfaces. Recently, George Will mentioned it in his column (see Will-full ignorance<\/a>) and the egregious Crichton manages to say “in the 1970’s all the climate scientists believed an ice age was coming” (see Michael Crichton\u2019s State of Confusion<\/a> ). You can find it in various other places too [here<\/a>, mildly here<\/a>, etc]. But its not an argument used by respectable and knowledgeable skeptics, because it crumbles under analysis. That doesn’t stop it repeatedly cropping up in newsgroups<\/a> though.
\n
\nPar William Connolley (Traduit par Pierre Allemand)<\/small><\/p>\n

De temps en temps, le mythe selon lequel “nous n\u2019allons pas croire aujourd\u2019hui les pr\u00e9dictions concernant le r\u00e9chauffement global car dans les ann\u00e9es 70, on pr\u00e9disait un nouvel \u00e2ge glaciaire et\/ou un refroidissement”, refait surface. R\u00e9cemment, George Will le mentionnait dans son \u00e9ditorial (voir Will-full ignorance<\/a>) et le fameux Crichton s\u2019arrange pour dire “dans les ann\u00e9es 70, tous les chercheurs dans le domaine climatique pensaient qu\u2019un nouvel \u00e2ge glaciaire allait arriver” (voir Michael Crichton\u2019s State of Confusion<\/a> ). Vous pouvez le trouver \u00e9galement dans divers autres endroits [ici<\/a>, ici<\/a> (en termes plus nuanc\u00e9s), etc]. Cependant, cet argument n\u2019en est pas un pour les sceptiques respectables et bien inform\u00e9s, car il ne r\u00e9siste pas \u00e0 l\u2019analyse. Cela n\u2019emp\u00eache pas, n\u00e9anmoins, qu\u2019il soit r\u00e9guli\u00e8rement repris dans les groupes de discussion<\/a>.<\/p>\n

(suite…)<\/a>
\n<\/lang_fr>
\n<\/p>\n

I should clarify that I’m talking about predictions in the scientific press<\/i>. There were some regrettable things published in the popular press (e.g. Newsweek<\/a>; though National Geographic<\/a> did better). But we’re only responsible for the scientific press. If you want to look at an analysis of various papers that mention the subject, then try http:\/\/www.wmconnolley.org.uk\/sci\/iceage\/.<\/p>\n

Where does the myth come from? Naturally enough, there is a kernel of truth behind it all. Firstly, there was a trend of cooling from the 40’s to the 70’s (although that needs to be qualified, as hemispheric or global temperature datasets were only just beginning to be assembled then). But people were well aware that extrapolating such a short trend was a mistake (Mason, 1976<\/a>) . Secondly, it was becoming clear that ice ages followed a regular pattern and that interglacials (such as we are now in) were much shorter that the full glacial periods in between. Somehow this seems to have morphed (perhaps more in the popular mind than elsewhere) into the idea that the next ice age was predicatable<\/i> and imminent<\/i>. Thirdly, there were concerns about the relative magnitudes of aerosol forcing (cooling) and CO2 forcing (warming), although this latter strand seems to have been short lived.<\/p>\n

The state of the science at the time (say, the mid 1970’s), based on reading the papers is, in summary: “…we do not have a good quantitative understanding of our climate machine and what determines its course. Without the fundamental understanding, it does not seem possible to predict climate…” (which is taken directly from NAS, 1975<\/a>). In a bit more detail, people were aware of various forcing mechanisms – the ice age cycle; CO2 warming; aerosol cooling – but didn’t know which would be dominant in the near future. By the end of the 1970’s, though, it had become clear that CO2 warming would probably be dominant; that conclusion has subsequently strengthened.<\/p>\n

George Will asserts that Science magazine (Dec. 10, 1976) warned about “extensive Northern Hemisphere glaciation.”<\/i>. The quote is from Hays et al<\/a>. But the quote is taken grossly out of context. Here, in full, is the small section dealing with prediction:<\/p>\n

\nFuture climate. Having presented evidence that major changes in past climate were associated with variations in the geometry of the earth’s orbit, we should be able to predict the trend of future climate. Such forecasts must be qualified in two ways. First, they apply only to the natural component of future climatic trends – and not to anthropogenic effects such as those due to the burning of fossil fuels. Second, they describe only the long-term trends, because they are linked to orbital variations with periods of 20,000 years and longer. Climatic oscillations at higher frequencies are not predicted.<\/p>\n

One approach to forecasting the natural long-term climate trend is to estimate the time constants of response necessary to explain the observed phase relationships between orbital variation and climatic change, and then to use those time constants in the exponential-response model. When such a model is applied to Vernekar’s (39) astronomical projections, the results indicate that the long-term trend over the next 20,000 years is towards extensive Northern Hemisphere glaciation and cooler climate (80).<\/i>\n<\/p><\/blockquote>\n

The point about timescales is worth noticing: predicting an ice age (even in the absence of human forcing) is almost impossible within a timescale that you could call “imminent” (perhaps a century: comparable to the scales typically used in global warming projections) because ice ages are slow, when caused by orbital forcing type mechanisms.<\/p>\n

Will also quotes “a full-blown 10,000-year ice age” (Science, March 1, 1975)<\/i>. The quote is accurate, but the source isn’t. The piece isn’t<\/b> from “Science”; it’s from “Science News”. There is a major difference: Science is (jointly with Nature) the most prestigous journal for natural science; Science News is not a peer-reviewed journal at all, though it is still respectable. In this case, its process went a bit wrong: the desire for a good story overwhelmed its reading of the NAS report which was presumably too boring to present directly.<\/p>\n

The Hays paper above is the most notable example of the “ice age” strand. Indeed, its a very important paper in the history of climate, linking observed cycles in ocean sediment cores to orbital forcing periodicities. Of the other strand, aerosol cooling, Rasool and Schneider, Science, July 1971, p 138, “Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate<\/a>” is the best exemplar. This contains the quote that quadrupling aerosols could decrease the mean surface temperature (of Earth) by as much as 3.5 degrees K. If sustained over a period of several years, such a temperature decrease could be sufficient to trigger an ice age!<\/i>. But even this paper qualifies its predictions (whether or not aerosols would so increase was unknown) and speculates that nuclear power may have largely replaced fossil fuels as a means of energy production<\/i> (thereby, presumably, removing the aerosol problem). There are, incidentally, other scientific problems with the paper: notably that the model used was only suitable for small perturbations but the results are for rather large perturbations; and that the estimate of CO2 sensitivity was too low by a factor of about 3.<\/p>\n

Probably the best summary of the time was the 1975 NAS\/NRC report<\/a>. This is a serious sober assessment of what was known at the time, and their conclusion was that they didn’t know enough to make predictions. From the “Summary of principal conclusions and recommendations”, we find that they said we should:<\/p>\n

    \n
  1. Establish National climatic research program\n<\/li>\n
  2. Establish Climatic data analysis program, and new facilities, and studies of impact of climate on man\n<\/li>\n
  3. Develope Climatic index monitoring program\n<\/li>\n
  4. Establish Climatic modelling and applications program, and exploration of possible future climates using coupled GCMs\n<\/li>\n
  5. Adoption and development of International climatic research program\n<\/li>\n
  6. Development of International Palaeoclimatic data network\n<\/li>\n<\/ol>\n

    Which is to say, they recommended more research, not action. Which was entirely appropriate to the state of the science at the time. In the last 30 years, of course, enormous progress has been made in the field of climate science.<\/p>\n

    Most of this post has been about the science of 30 years ago. From the point of view of todays science, and with extra data available:<\/p>\n

      \n
    1. The cooling trend from the 40’s to the 70’s now looks more like a slight interruption of an upward trend (e.g. here<\/a>). It turns out that the northern hemisphere cooling was larger than the southern (consistent with the nowadays accepted interpreation that the cooling was largely caused by sulphate aerosols); at first, only NH records were available.\n<\/li>\n
    2. Sulphate aerosols have not increased as much as once feared (partly through efforts to combat acid rain); CO2 forcing is greater. Indeed IPCC projections of future temperature inceases went up from the 1995 SAR to the 2001 TAR because estimates of future sulphate aerosol levels were lowered (SPM<\/a>).\n<\/li>\n
    3. Interpretations of future changes in the Earth’s orbit have changed somewhat. It now seems likely (Loutre and Berger, Climatic Change, 46: (1-2) 61-90 2000) that the current interglacial, based purely on natural forcing, would last for an exceptionally long time: perhaps 50,000 years.\n<\/li>\n<\/ol>\n

      Finally, its clear that there were<\/i> concerns, perhaps quite strong, in the minds of a number of scientists of the time. And yet, the papers of the time present a clear consensus that future climate change could not be predicted with the knowledge then available. Apparently, the peer review and editing process involved in scientific publication was sufficient to provide a sober view. This episode shows the scientific press in a very good light; and a clear contrast to the lack of any such process in the popular press, then and now.<\/p>\n

      Further Reading<\/strong>:<\/p>\n

      Imbrie & Imbrie “Ice Ages: solving the mystery” (1979) is an interesting general book on the discovery of the ice ages and their mechanisms; chapter 16<\/a> deals with “The coming ice age”.<\/p>\n

      Spencer Weart’s History of Global Warming<\/a> has a chapter on Past Cycles: Ice Age Speculations<\/a>.<\/p>\n

      An analysis of various papers that mention the subject is at www.wmconnolley.org.uk\/sci\/iceage\/.
      \nJe me dois de pr\u00e9ciser que je parle de pr\u00e9dictions dans la litt\u00e9rature scientifique<\/i>. Il y a eu des choses regrettables publi\u00e9es dans la presse populaire (par exemple,       Newsweek<\/a>; mais National Geographic a encore fait mieux<\/a>). Mais nous ne sommes responsables que de la presse scientifique. Si vous voulez consulter une analyse des diff\u00e9rents articles qui parlent du sujet, essayez http:\/\/www.wmconnolley.org.uk\/sci\/iceage\/<\/a>.<\/p>\n

      D\u2019o\u00f9 vient donc le mythe ? Naturellement, il y a un fond de v\u00e9rit\u00e9 derri\u00e8re tout cela.<\/p>\n

      Premi\u00e8rement, il y a eu une tendance au refroidissement des ann\u00e9es 40 aux ann\u00e9es 70 (encore que cela demande \u00e0 \u00eatre bien \u00e9tabli, car les s\u00e9ries de donn\u00e9es de temp\u00e9ratures des h\u00e9misph\u00e8res ou du globe commen\u00e7aient \u00e0 peine \u00e0 \u00eatre rassembl\u00e9es). Cependant, on savait bien qu\u2019extrapoler sur une aussi courte p\u00e9riode \u00e9tait une erreur (Mason, 1976<\/a>) .<\/p>\n

      Deuxi\u00e8mement, il devenait clair que les \u00e2ges glaciaires se succ\u00e9daient selon un rythme r\u00e9gulier, et que les p\u00e9riodes interglaciaires (comme celle d\u2019aujourd\u2019hui) \u00e9taient beaucoup plus courtes que les p\u00e9riodes glaciaires qui les encadraient. D\u2019une certaine fa\u00e7on, il semble que cela ait conduit (peut-\u00eatre plus dans le milieu populaire qu\u2019ailleurs) \u00e0 l\u2019id\u00e9e que le prochain \u00e2ge glaciaire \u00e9tait pr\u00e9visible et imminent.<\/p>\n

      Troisi\u00e8mement, on se posait des questions concernant la magnitude relative du for\u00e7age par les a\u00e9rosols (refroidissement) et par le CO2 (r\u00e9chauffement), bien que cela n\u2019ait, semble-t-il, pas dur\u00e9 tr\u00e8s longtemps.<\/p>\n

      L\u2019attitude de la science, \u00e0 cette \u00e9poque (disons au milieu des ann\u00e9es 70), \u00e9tait, en se fondant sur les articles publi\u00e9s, en r\u00e9sum\u00e9 : “\u2026nous ne comprenons pas bien quantitativement la fa\u00e7on dont la machine climatique fonctionne et ce qui d\u00e9termine son cours. En l\u2019absence de cette compr\u00e9hension fondamentale, il ne semble pas possible de pr\u00e9dire le climat\u2026” (repris directement de NAS, 1975<\/a>). D\u2019une fa\u00e7on un peu plus d\u00e9taill\u00e9e, on connaissait les diff\u00e9rents m\u00e9canismes de for\u00e7age \u2013 le cycle des p\u00e9riodes glaciaires ; le r\u00e9chauffement par le CO2 ; le refroidissement par les a\u00e9rosols \u2013 mais on ne savait pas ce qui serait dominant dans le futur proche. A la fin des ann\u00e9es 70, n\u00e9anmoins, il \u00e9tait devenu clair que le r\u00e9chauffement par le CO2 serait probablement dominant ; cette conclusion s\u2019est, depuis, renforc\u00e9e.<\/p>\n

      George Will affirme que Science magazine (10 d\u00e9c. 1976) pr\u00e9venait d\u2019une “glaciation extensive de l\u2019h\u00e9misph\u00e8re nord”. La citation vient de Hays et al.<\/a> Mais cette citation est grossi\u00e8rement extraite de son contexte. Voici in extenso la section qui traite de cette pr\u00e9diction :<\/p>\n

      \nClimat futur. Ayant montr\u00e9 l\u2019\u00e9vidence que les changements climatiques majeurs du pass\u00e9 \u00e9taient associ\u00e9s \u00e0 la g\u00e9om\u00e9trie de l\u2019orbite de la terre, nous devrions \u00eatre capables de pr\u00e9dire l\u2019orientation du climat futur. De telles pr\u00e9visions doivent \u00eatre examin\u00e9es de deux mani\u00e8res. D\u2019abord, elles s\u2019appliquent uniquement aux composantes naturelles du climat futur \u2013 et non aux effets anthropog\u00e9niques comme ceux r\u00e9sultant de l\u2019utilisation des combustibles fossiles. Ensuite, elles d\u00e9crivent uniquement les tendances \u00e0 long terme, car elles sont li\u00e9es \u00e0 des variations orbitales dont les p\u00e9riodes sont de 20 000 ans et plus. Les oscillations climatiques de fr\u00e9quence plus \u00e9lev\u00e9e ne sont pas comprises dans les pr\u00e9visions.<\/p>\n

      Une des approches possibles pour les pr\u00e9visions des tendances climatiques naturelles \u00e0 long terme consiste \u00e0 estimer les constantes temps de r\u00e9ponse n\u00e9cessaires pour expliquer les relations de phase observ\u00e9es entre les variations orbitales et les changements climatiques, puis d\u2019utiliser ces constantes de temps dans des mod\u00e8les \u00e0 r\u00e9ponse exponentielle. Quand un tel mod\u00e8le est appliqu\u00e9 aux projections astronomiques de Venekar (39), le r\u00e9sultat montre que la tendance \u00e0 long terme pour les prochaines 20 000 ann\u00e9es va vers une glaciation extensive de l\u2019h\u00e9misph\u00e8re nord, et un climat plus froid (80).\n<\/p><\/blockquote>\n

      La question des \u00e9chelles de temps doit \u00eatre not\u00e9e : pr\u00e9dire une p\u00e9riode glaciaire (m\u00eame en l\u2019absence de for\u00e7age humain) est presque impossible \u00e0 l\u2019\u00e9chelle que vous pourriez appeler “imminente” (peut-\u00eatre d\u2019un si\u00e8cle : comparable aux \u00e9chelles typiquement utilis\u00e9es dans les projections du r\u00e9chauffement global) parce que les p\u00e9riodes glaciaires sont lentes, \u00e0 cause du type de m\u00e9canisme de for\u00e7age orbital.<\/p>\n

      Will cite aussi “une pleine p\u00e9riode glaciaire de 10 000 ans\u201d (Science, 1 mars 1975).<\/p>\n

      La citation est exacte, la source non. La citation ne vient pas de “Science” ; elle vient de “Science News”. Il y a une diff\u00e9rence majeure : Science est (avec Nature) le journal le plus prestigieux concernant les sciences naturelles ; Science News n\u2019est pas du tout un journal \u00e0 relecture par des pairs, bien qu\u2019il reste un journal respectable. Dans ce cas, les choses ont un peu d\u00e9riv\u00e9 : le souci de pr\u00e9senter une histoire passionnante a d\u00e9pass\u00e9 la simple lecture du rapport de la NAS [NdT : National Academy of Sciences], consid\u00e9r\u00e9 comme trop ennuyeux pour \u00eatre pr\u00e9sent\u00e9 directement. <\/p>\n

      L\u2019article de Hays ci-dessus est l\u2019exemple le plus notable de l\u2019aboutissement \u00e0 l\u2019\u00e2ge glaciaire. Encore une fois, c\u2019est un article tr\u00e8s important dans l\u2019histoire du climat, faisant le lien entre les s\u00e9diments oc\u00e9aniques et la p\u00e9riodicit\u00e9 des for\u00e7ages orbitaux. Rasool and Schneider, Science, July 1971, p 138, “Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate<\/a>” repr\u00e9sente le meilleur exemple de l\u2019autre aboutissement, le refroidissement par les a\u00e9rosols.<\/p>\n

      L\u2019article mentionne que le quadruplement des a\u00e9rosols pourrait faire descendre la temp\u00e9rature moyenne (du globe) d\u2019au moins 3,5 degr\u00e9s K. Si elle se prolongeait sur plusieurs ann\u00e9es, une telle chute de temp\u00e9rature pourrait \u00eatre suffisante pour d\u00e9clencher une p\u00e9riode glaciaire !<\/p>\n

      Mais, m\u00eame cet article temp\u00e8re ses pr\u00e9dictions (on ne savait pas si les a\u00e9rosols allaient augmenter ou non) et sp\u00e9culait que l\u2019\u00e9nergie nucl\u00e9aire pourrait avoir largement remplac\u00e9 les combustibles fossiles comme moyens de production d\u2019\u00e9nergie (supprimant par l\u00e0 m\u00eame le probl\u00e8me des a\u00e9rosols).<\/p>\n

      Il y a incidemment d\u2019autres probl\u00e8mes scientifiques dans cet article : notamment que le mod\u00e8le utilise \u00e9tait valable seulement pour de petites perturbations, alors que le r\u00e9sultat portait sur d\u2019assez larges perturbations ; ensuite, l\u2019estimation de la sensibilit\u00e9 du CO2 \u00e9tait sous estim\u00e9e d\u2019un facteur de 4.<\/p>\n

      C\u2019est dans le 1975 NAS\/NRC report<\/a> que la question \u00e9tait la mieux r\u00e9sum\u00e9e \u00e0 cette \u00e9poque. Ce rapport \u00e9tait une pr\u00e9sentation s\u00e9rieuse et sobre de ce qui \u00e9tait connu \u00e0 cette \u00e9poque, et les conclusions en \u00e9taient qu\u2019on en connaissait pas assez pour faire des pr\u00e9dictions. Le “r\u00e9sum\u00e9 des principales conclusions et recommandations” disait qu\u2019on pourrait :<\/p>\n

      1. Etablir un Programme National de recherche sur le climat.<\/p>\n

      2. Mettre en place un programme d\u2019analyse des donn\u00e9es climatiques, de nouveaux laboratoires, et des \u00e9tudes sur l\u2019impact humain du climat.<\/p>\n

      3. D\u00e9velopper un programme de surveillance d\u2019indices climatiques.<\/p>\n

      4. Etablir un programme de mod\u00e9lisation et d\u2019applications, et d\u2019exploration de futurs climats possibles en utilisant des GCM coupl\u00e9s [NdT<\/i> : “General Circulation Models”, mod\u00e8les de circulation g\u00e9n\u00e9rale].<\/p>\n

      5. Adopter et d\u00e9velopper un programme international de recherche sur le climat.<\/p>\n

      6. D\u00e9velopper un r\u00e9seau de donn\u00e9es pal\u00e9oclimatique international.<\/p>\n

      En d\u2019autres termes, ils recommandaient plus de recherche, mais pas d\u2019action. Ce qui \u00e9tait enti\u00e8rement appropri\u00e9 \u00e0 l\u2019\u00e9tat de la science \u00e0 cette \u00e9poque. Au cours des 30 derni\u00e8res ann\u00e9es, \u00e9videmment, d\u2019\u00e9normes progr\u00e8s ont \u00e9t\u00e9 r\u00e9alis\u00e9s dans le domaine de la science climatique.<\/p>\n

      La plupart de ces lignes concerne la science d\u2019il y a 30 ans. En ce qui concerne la science d\u2019aujourd\u2019hui, et en tenant compte des donn\u00e9es suppl\u00e9mentaires disponibles :<\/p>\n

      1. La tendance au refroidissement des ann\u00e9es 40 aux ann\u00e9es 70 ressemble plus \u00e0 une interruption d\u2019une tendance inverse (voir ici<\/a>). Il ressort que le refroidissement de l\u2019h\u00e9misph\u00e8re nord \u00e9tait plus important que celui du sud (conform\u00e9ment \u00e0 l\u2019interpr\u00e9tation accept\u00e9e aujourd\u2019hui que le refroidissement \u00e9tait largement caus\u00e9 par les a\u00e9rosols sulfuriques) ; au d\u00e9but, les chiffres nord-h\u00e9misph\u00e9riques \u00e9taient les seuls connus.<\/p>\n

      2. Les a\u00e9rosols sulfuriques n\u2019ont pas augment\u00e9 autant que redout\u00e9 (partiellement \u00e0 cause des efforts pour combattre les pluies acides) ; le for\u00e7age par le CO2 est plus important. Evidemment, les chiffres des projections du GIEC concernant les augmentations futures de la temp\u00e9rature ont augment\u00e9 entre le Deuxi\u00e8me (1995) et le Troisi\u00e8me (2001) Rapport d\u2019Evaluation puisque les estimations concernant les futurs niveaux d\u2019a\u00e9rosols sulfuriques ont \u00e9t\u00e9 abaiss\u00e9es (SPM<\/a> [NdT : M\u00e9mento pour les D\u00e9cideurs] ).<\/p>\n

      3. Les interpr\u00e9tations des changements futurs dans l\u2019orbite de la Terre ont quelque peu chang\u00e9. Il semble maintenant (Loutre et Berger, Climatic Change, 46: (1-2) 61-90 2000) que la p\u00e9riode interglaciaire, fond\u00e9e uniquement sur le for\u00e7age naturel, durerait pendant un temps exceptionnellement long : peut-\u00eatre 50 000 ans.<\/p>\n

      Finalement, il est clair qu\u2019un certain nombre de scientifiques \u00e9taient inquiets, peut-\u00eatre m\u00eame assez fortement, \u00e0 cette \u00e9poque. Les articles de l\u2019\u00e9poque refl\u00e8tent un consensus clair sur le fait que le climat futur ne pouvait pas \u00eatre pr\u00e9dit avec les connaissances disponibles.<\/p>\n

      Apparemment, la relecture par les pairs, et le processus d\u2019\u00e9dition mis en \u0153uvre pour une publication scientifique apportait une garantie suffisante de s\u00e9rieux. Cet \u00e9pisode met tr\u00e8s clairement en lumi\u00e8re la presse scientifique ; et aussi le contraste tr\u00e8s clair concernant l\u2019absence d\u2019un tel processus dans la presse populaire, d\u2019alors et d\u2019aujourd\u2019hui. <\/p>\n

      A lire :<\/p>\n

      Imbrie & Imbrie “Ice Ages: solving the mystery” [NdT : “Les p\u00e9riodes glaciaires : r\u00e9soudre le myst\u00e8re”] (1979) livre g\u00e9n\u00e9ral int\u00e9ressant sur la d\u00e9couverte des p\u00e9riodes glaciaires et leurs m\u00e9canismes ; le chapitre 16 concerne “The coming ice age” [NdT : ” la p\u00e9riode glaciaire qui arrive”].<\/p>\n

      Spencer Weart’s History of Global Warming<\/a> [NdT : “Histoire du r\u00e9chauffement global”] il y a un chapitre sur Past Cycles: Ice Age Speculations<\/a> [NdT : Les cycles pass\u00e9s : sp\u00e9culations sur les p\u00e9riodes glaciaires].<\/p>\n

      On peut trouver une analyse des diff\u00e9rents articles qui mentionnent ce sujet sur : www.wmconnolley.org.uk\/sci\/iceage\/<\/a>. <\/lang_fr><\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

      Every now and again, the myth that “we shouldn’t believe global warming predictions now, because in the 1970’s they were predicting an ice age and\/or cooling” surfaces. Recently, George Will mentioned it in his column (see Will-full ignorance) and the egregious Crichton manages to say “in the 1970’s all the climate scientists believed an ice […]<\/p>\n","protected":false},"author":12,"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":[1,13,3,9,2],"tags":[],"class_list":{"0":"post-94","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-climate-science","7":"category-faq","8":"category-greenhouse-gases","9":"category-instrumental-record","10":"category-paleoclimate","11":"entry"},"aioseo_notices":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts\/94","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\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/comments?post=94"}],"version-history":[{"count":0,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts\/94\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/media?parent=94"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/categories?post=94"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/tags?post=94"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}