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Ocean Cooling. Not. Resfriamento Oceânico? Não. L’océan se refroidit. Pas.

Filed under: — gavin @ April 18th, 2007

A lot has been made of a paper (Lyman et al, 2006) that appeared last year that claimed that the oceans had, contrary to expectation, cooled over the period 2003-2005. At the time, we (correctly) pointed out that this result was going to be hard to reconcile with continued increases in sea level rise (driven in large part by thermal expansion effects), and that there may still be issues with way that the new ARGO floats were being incorporated into the ocean measurement network. Now it seems as if there is a problem in the data and in the latest analysis, the cooling has disappeared.

Ocean heat content changes are potentially a great way to evaluate climate model results that suggest that the planet is currently significantly out of equilibrium (i.e. it is absorbing more energy than it is emitting). However, the ocean is a very big place and the historical measurement networks are plagued with sampling issues in space and time. Large scale, long term compilations globally (such as by Levitus et al, 2001; Willis et al, 2004) and regionally (i.e. North Atlantic) have indicated that the oceans have warmed in recent decades at pretty much the rate the models expected.

Since 2000, though, ARGO – which is a network of floats that move up and down in the ocean and follow the currents – has offered the potential to dramatically increase the sampling density in the ocean and provide, pretty much for the first time, continuous, well spaced data from the least visited, but important parts of the world (such as the Southern Oceans). Data on ocean heat content from these floats had been therefore eagerly anticipated.

Initial ARGO measurements were incorporated into the Willis et al, 2004 analysis, but as the ARGO data started to dominate the data sources from around 2003, Lyman et al reported that the ocean seemed to be cooling. These were only short term changes, and while few would confuse one or two anomalous years with a long term trend, they were a little surprising, even if they didn’t change the long term picture very much.

The news this week though is that all of that ‘cooling’ was actually due to combination of a faulty pressure reading on a subset of the floats and a switch between differently-biased observing systems (Update: slight change in wording to better reflect the paper). The pressure error meant that the temperatures were being associated with a point higher in the ocean column than they should have been, and this (given that the ocean cools with depth) introduced a spurious cooling trend when compared to earlier data. This error may be fixable in some cases, but for the time being the suspect data has simply been removed from the analysis. The new results don’t show any cooling at all.

Are we done then? Unfortunately no. Because of the paucity of measurements, assessments of ocean heat content need to use a wide variety of sensors, each with their own quirks and problems. Combined with switches in data sources over the years, there is a significant potential for non-climatic trends to creep in. In particular, the eXpendable BathyThermographs (XBTs – sensors that are essentially just thrown off the side of the ship) have a known problem in that they didn’t fall as quickly as they were originally assumed to. This gives a warm bias (see this summary from Ingleby and Palmer or the paper by Gouretski and Koltermann) , particularly in data from the 1970s before corrections were fully implemented. We are still going to have to wait for the ‘definitive’ ocean heat content numbers, however, it is important to note that all analyses give long term increases in ocean heat content – particularly in the 1990s – whether they include the good ARGO data or exclude the XBTs or not).

There are a number of wider lessons here:

  • New papers need to stand the test of time before they are uncritically accepted.
  • The ARGO float data are available in near real-time, and while that is very useful, any such data stream is always preliminary.
  • The actual problem with these data was completely unknowable when Lyman et al wrote their paper. This is in fact very common given the number of steps required to create global data sets. Whether it’s an adjustment of the orbit of a satellite, a mis-calibration of a sensor, an unrecorded shift in station location, a corruption of the data logger or a human error, these problems often only get fixed after a lot of work.
  • Anomalous results are often the driver of fundamental shifts in scientific thinking. However, most anomalous results end up being resolved much more straightforwardly (as in the case, or the MSU satellite issue a couple of years back).

Scientists working in a field build up a certain intuition about how things ‘work’. This intuition can come from a gut instinct, deep theoretical understanding, robust model results, long experience with observations etc. New results that fall outside of that framework often have a tough time getting accepted, but if they are solid and get subsequent support they will generally be incorporated. But that intuition is also very good at detecting results that just don’t fit. When that happens, scientists spend a lot of time thinking about what might be wrong – with the data, the analysis, the model or the interpretation. It generally pays to withhold judgment until that process is finished.


Muito falou-se sobre um trabalho (Lyman et al, 2006) que foi publicado no ano passado que afirmava que os oceanos, ao contrário de todas as expectativas, haviam se resfriado no período de 2003 a 2005. Naquela época, nós (corretamente) apontamos que este resultado seria difícil de ser conciliado com as contínuas elevações do nível dos mares (ocasionados em grande parte por efeitos de expansão térmica), e que havia problemas na maneira como as novas bóias ARGO estavam sendo incorporadas na rede de medidas. Agora parece que de fato há um problema com os dados e nas
últimas análises, o resfriamento desapareceu.

Mudanças no conteúdo calórico dos oceanos são potencialmente uma ótima maneira de avaliar resultados de modelos climáticos que sugerem que o planeta está atualmente fora de equilíbrio (isto é, está absorvendo mais energia que emitindo). Entretanto, os oceanos são muito extensos e as redes de medidas históricas estão infestadas com problemas de amostragem no tempo e espaço. Compilações de longa duração e em grandes escalas globais (como as de Levitus et al, 2001; Willis et al, 2004) e regionais (i.e. Atlântico Norte) indicaram que os oceanos aqueceram-se em décadas recentes mais ou menos na taxa esperada pelos modelos.

Desde 2000, entretanto, ARGO – que é uma rede de bóias que se movem para cima e para baixo nos oceanos e seguem as correntes – ofereceram o potencial de aumentar dramaticamente a densidade de amostragem nos oceanos e de fornecer, pela primeira vez, dados contínuos e bem espaçados das regiões menos visitadas mas muito importantes do planeta (como os oceanos do sul). Dados sobre o conteúdo calórico dos oceanos eram conseqüentemente ansiosamente esperados.

Medidas iniciais ARGO foram incorporadas na análise de 2004 de Willis et al, mas a medida que os dados ARGO passaram a dominar as fontes de dados em torno de 2003, Lyman et al relataram que os oceanos pareciam estar se resfriando. Estas eram apenas mudanças de curto prazo, e enquanto poucos iriam confundir um ou dois anos anômalos com uma tendência de longo prazo, elas eram um pouco surpreendentes, mesmo considerando que o panorama de longo prazo era pouco modificado

A notícia esta semana é, no entanto, que todo aquele ‘resfriamento’ era na realidade devido à combinação de uma leitura de pressão defeituosa num subconjunto das bóias e a uma troca entre sistemas de observação com diferentes tendências. (Atualização:
leve mudança no palavreado para melhor refletir o paper). O erro na pressão significou que as temperaturas estavam sendo associadas com um ponto mais elevado na coluna oceânica do que deveria ser, e isto (dado que o oceano resfria-se com a profundidade) introduziu uma tendência de resfriamento espúria quando comparada com dados anteriores. Este erro pode ser corrigido em alguns casos, mas por enquanto os dados suspeitos foram simplesmente retirados da análise. Os novos resultados não mostram assim nenhum resfriamento.

Está tudo então no lugar novamente? Infelizmente não. Por causa da escassez de dados, levantamentos do conteúdo calórico dos oceanos devem utilizar uma ampla variedade de sensores, cada um com suas próprias peculiaridades e problemas. Tudo isto combinado com mudanças nas fontes de dados ao longo dos anos, há então um grande potencial para tendências não-climáticas aparecerem. Em particular, os eXpendable BathyThermographs (XBTs – sensores que são simplesmente jogados de um navio) têm um problema conhecido no fato de que estes não caem tão depressa quanto supostamente deveriam. Isto gera uma tendência de aquecimento (veja este resumo de Ingleby e Palmer ou o trabalho de Gouretski e Koltermann), particularmente nos dados dos anos 70, antes das correções terem sido plenamente implementadas. Nós teremos ainda que esperar pelos números ‘definitivos’ do conteúdo calórico dos oceanos, entretanto, é importante notar que todas as analises fornecem tendências de aquecimento no longo prazo – particularmente nos anos 90 – seja se elas incluem os dados ARGOS bons ou excluem as XBTs ou não).

Há aqui um número de importantes lições a serem tiradas:

  • Novos trabalhos científicos devem passar pelo teste do tempo antes de serem aceitos sem nenhuma crítica.
  • Os dados de bóias ARGO estão disponíveis em tempo quase real, e apesar disto ser extremamente útil, todo conjunto de dados deste tipo é sempre preliminar.
  • O problema real com estes dados era completamente desconhecido quando Lyman et al escreveram seu artigo. Este fato é muito comum dado o número de etapas necessárias para criar conjuntos de dados globais. Seja um ajuste na órbita de um satélite, a descalibração de um sensor, um desvio despercebido na localização de uma estação, a degradação de um armazenador de dados ou um erro humano, estes problemas são frequentemente corrigidos apenas após muito trabalho.
  • Resultados anômalos são frequentemente responsáveis por mudanças fundamentais no pensamento científico. Entretanto, a maior parte dos resultados anômalos terminam por serem explicados de uma maneira muito mais simples (como no caso em questão, ou o caso do satélite MSU há alguns anos).

Cientistas que trabalham num determinado campo de atividades desenvolvem uma certa intuição a respeito de como as coisas ‘funcionam’. Esta intuição vem de um certo faro, um profundo conhecimento teórico, resultados robustos de modelos, uma longa experiência com observações, etc. Novos resultados que caem fora dos padrões pré-estabelecidos freqüentemente enfrentam dificuldades para serem aceitos, mas se eles são sólidos e obtêm apoio subseqüente, eles geralmente são incorporados. Mas aquela intuição é também muito boa para detectar resultados que simplesmente não se encaixam. Quando isto acontece, cientistas gastam muito tempo pensando no que pode ter dado errado – com os dados, a análise, o modelo ou a interpretação. Geralmente é recompensador não emitir nenhum julgamento até que este processo tenha terminado.

traduzido por Fernando M. Ramos e Ivan B. T. Lima


Traduit par Etienne Pesnelle

On a fait tout un plat d’un article (Lyman et al, 2006) paru l’année dernière et qui prétendait que, contrairement aux attentes, les océans s’étaient refroidis sur la période 2003-2005. A l’époque, nous avions (fort justement) souligné que ce résultat allait être difficile à réconcilier avec l’augmentation continue du niveau des mers (provoquée en grande partie par la dilatation thermique), et qu’il pouvait y avoir des problèmes avec la façon dont les nouvelles bouées ARGO étaient insérées dans le réseau de mesure océanique. Il apparaît maintenant qu’il y avait un problème dans les données et dans la dernière analyse, le refroidissement a disparu.

L’analyse des variations de la quantité de chaleur océanique est potentiellement une méthode importante pour contrôler les résultats des modèles climatiques qui suggèrent que la planète n’est pas actuellement en état d’équilibre (c’est-à-dire qu’elle absorbe plus d’énergie qu’elle n’en émet). Toutefois, l’océan est un endroit très vaste et les anciens réseaux de mesure océanique sont la proie d’erreurs d’échantillonnage spatial et temporel. Les compilations à grande échelle et sur de longues périodes, qu’elles soient mondiales (comme celle de Levitus et al, 2001 ou Willis et al, 2004) ou régionales (par exemple dans l’Atlantique Nord) indiquent que les océans se sont réchauffés durant les dernières décennies, quasiment à la vitesse donnée par les modèles.

Depuis 2000, cependant, ARGO – un réseau de bouées qui montent et descendent dans les profondeurs océaniques et qui suivent les courants – a offert la possibilité d’augmenter spectaculairement la densité d’échantillonnage océanique et de fournir, quasiment pour la première fois, des données continues et bien espacées en provenance d’endroits parmi les moins visités mais néanmoins importants (comme le Sud des océans Atlantique et Pacifique). Les mesures de quantité de chaleur océanique en provenance de ces bouées étaient donc attendues avec impatience.

Les mesures initiales fournies par ARGO ont été intégrées dans l’analyse 2004 de Willis et al, mais comme ARGO a commencé à dominer les sources de données à partir de 2003 environ, Lyman et al ont constaté que l’océan semblait se refroidir. C’était seulement des évolutions à court terme, et même si peu de personnes confondent une ou deux années anormales avec une tendance à long terme, ces évolutions étaient un peu surprenantes, même si elles ne modifiaient pas beaucoup la vision à long terme.

Quant à la nouvelle de la semaine, c’est que tout ce “refroidissement” était en fait dû à la combinaison de mauvaises mesures de pression sur un sous-ensemble de bouées et d’un basculement entre deux systèmes de mesures présentant des distortions différentes (mise à jour : petite modification de forme pour mieux refléter l’article). L’erreur de pression signifiait que les températures mesurées étaient associées à un point situé plus haut qu’il n’aurait dû être dans la colonne d’eau, et que (comme l’océan se refroidit au fut et à mesure qu’on descend) cela a introduit une tendance fallacieuse au refroidissement quand on a comparé les mesures à des données plus anciennes. Cette erreur peut être réparée dans certains cas, mais pour l’instant les données suspectes ont été simplement retirées de l’analyse. Les nouveaux résultats ne montrent pas de refroidissement du tout.

Alors, c’est tout ? Malheureusement non. A cause du manque de mesures, l’évaluation de la quantité de chaleur océanique nécessite d’utiliser une large palette de capteurs, chacun ayant son lot de caprices et de problèmes. En y ajoutant des changements de sources de données au fil des ans, cela donne beaucoup de possibilités à des tendances non-climatiques d’entrer discrètement. En particulier, les bathythermographes extensibles (en anglais BathyThermographs ou XBT ; en gros ce sont des capteurs qui sont jetés par
dessus bord) présentent un défaut connu, à savoir qu’ils ne coulent pas aussi rapidement que prévu. Cela “réchauffe” les mesures (voir ce résumé d’Ingleby et Palmer, ou bien l’article de Gouretski et
Koltermann
), notamment celles des années 1970, avant que les corrections aient été effectuées. Nous sommes toujours à attendre les chiffres “définitifs” de la quantité de chaleur océanique, cependant il est important de noter que toutes les analyses donnent des augmentations à long terme de la quantité de chaleur océanique – notamment dans les années 1990 – qu’on inclut les bonnes données ARGO ou qu’on exclut les XBT ou non.

Il y a un certain nombre de leçons à tirer de cela :

  • les nouveaux articles doivent résister à l’épreuve du temps avant d’être acceptés sans critique ;
  • les données des bouées ARGO sont disponibles en quasi-temps réel, et bien que ce soit très pratique, un tel flux de données est toujours un préalable à l’analyse ;
  • il était impossible de s’apercevoir de ce qui entachait ces données quand Lyman et al ont écrit leur article. Cela est très courant, compte tenu du nombre d’étapes nécessaires pour créer une base de données mondiale. Que ce soit le mauvais ajustement de l’orbite d’un satellite, la mauvaise calibration d’un capteur, un décalage non identifié de la localisation d’une station, la corruption d’un journal de bord ou une erreur humaine, ces problèmes ne sont souvent corrigés qu’après beaucoup de travail.
  • Des résultats anormaux sont souvent les moteurs de changements fondamentaux de la rélflexion scientifique. Cependant, la plupart des résultats anormaux finissent par être résolus de façon beaucoup plus directe (comme c’est le cas ici, ou dans l’incident du satellite MSU il y a deux ans de cela)

Les scientifiques qui travaillent dans un domaine donné se construisent une certaine intuition sur la façon dont les choses “fonctionnent”. Cette intuition peut venir des tripes, d’une compréhension profonde de la théorie, de résultats robustes de modélisations, d’une longue expérience de l’observation, etc. De nouveaux résultats qui tombent en dehors du cadre mettent souvent beaucoup de temps à être acceptés, mais s’ils sont solides et s’ils obtiennent un soutien conséquent, ils finissent par être intégrés. Mais l’intuition est aussi excellente pour détecter les résultats qui ne collent pas. Quand cela arrive, les scientifiques passent beaucoup de temps à comprendre ce qui pourrait être faux – les données, l’analyse, le modèle ou l’interprétation. D’une manière générale, cela paie de retenir son jugement jusqu’à ce que ce processus soit achevé.


282 Responses to “Ocean Cooling. Not. Resfriamento Oceânico? Não. L’océan se refroidit. Pas.

  1. 51

    Mike-

    You are simply incorrect when you assert: “Emanuel (2005) shows that the warming SSTs are behind the increased TC intensity in the Atlantic. No impartial reading of that paper could come to any other conclusion.”

    [edited]

    [Response: Roger, we're not about cherry-picking sentences and out of context quotations here at RC, so you should take that somewhere else. Anybody who has studied the scientific issues involved well knows that SSTs in this context are a proxy for a more complex set of interconnected atmospheric environmental variables which tend to covary with it. We hardly need you to quote Emanuel for us. Figure 1 in Emanuel (2005) comparing SST and TC Power Dissipation in the tropical Atlantic speaks for itself, you might want to take another look. If we do an article on Hurricanes in the near future, you're free to engage in the discussion. But that's not the topic of this post, so we're going to close it out with this. -mike]

  2. 52
    mzed says:

    Re: Kuhn, paradigms, and the neutrality of scientists. Yes, I also see this as an example of paradigm-driven revolutionary science, and gavin (and co.) shouldn’t apologize for it. As he says, scientists are skeptics trying to make sense out of data. It is eminently satisfying when they do! That is an intellectual and emotional attachment to what they do. Scientists are not robots: they *enjoy it* when they solve a problem. They don’t simply spit out “fits theory” “doesn’t fit theory”. No scientist should apologize for this commitment. Just so, when a scientist or group of scientists think they have solved a problem, and then new data suggests they were wrong, there is nothing wrong with feeling frustrated about it! (In fact, there’s really nothing wrong with favoring one theory over another for whatever reason one wants; as long as you follow the data, you can think whatever you want about the theory.)

    Also I want to comment on this snippet from one of gavin’s replies to a comment on this thread:

    “But the level of confidence we do have (having passed a whole bunch of tests) is enough to allow to project pretty confidently a lot of what’s going to happen.”

    Yes–in fact I’m about to post on ClimateAudit on this very point to see how they react. This gets to the heart of the debate about “consensus”–Kuhn even writes on this subject in SSR (I forget exactly where: it’s at the very end of one of the middle chapters…I can look it up). When two paradigms are competing–or simply during a revolutionary period when one paradigm is supplanting an earlier normal science tradition (I get the sense that all this HPS/STS talk makes gavin a little nervous…) then it eventually becomes clear when one paradigm is becoming ascendant. You can almost always bet that it will ultimately be triumphant, i.e. its theory will eventually become accepted as fact, *without* appeal to consensus at all (because everyone will think that way; no proofs will be necessary, though there will be plenty on hand). The alternative paradigm (that anthro ggs play no significant role in current warming) is currently losing the battle; although they are still alive and kicking (and will probably continue to score points here and there) they are not making progress towards convincing the relevant community. It would take a seriously revolutionary set of data (a “counter-revolutionary” set of data?) to put a halt to agw theory right now–undeniable proof that cosmic rays are behind everything, for example, or maybe evidence that an immense cloud feedback is kicking in as we speak (though that latter might not really count as evidence against agw theory…hard to say). And, of course, it remains possible that even if agw theory ultimately triumphs and becomes accepted as fact, it could still be *wrong*–but again, it would take another revolutionary finding to show that.

    If agw is wrong, why does it keep succeeding among the scientific community? (As measured, for example, by the number of scientific organizations that support it:

    http://en.wikipedia.org/wiki/Scientific_opinion_on_climate_change

    I also bet that the citation index shows similiar levels of support, though to my knowledge no one has investigated this in detail.)

    Sorry for the windy lecture; I just wanted to weigh in. And of course, this could all be totally wrong :) But regardless, scientists still don’t need to apologize for having strong feelings about being wedded to one theory or another.

  3. 53
    John N says:

    I think it is now clear (after the warming of the oceans has now been proven) that if we do not stop adding GHGs to the atmosphere, the entire human race might go extinct along with thousands of other species wihtin a few decades.

    We must stop this catastophe from happening as soon as possible.

  4. 54
    Steve Latham says:

    I’d like to comment simply that I agree with the first part of #11 (Mosher) — it is important to be unbiased in our interrogation of observational data. Yes, data that don’t fit the common theory should be scrutized. Data that do fit should be scrutinized equally. Probably everyone could agree with that.

    On another matter, what have the ATOC results contributed to understanding oceanic heat content? http://en.wikipedia.org/wiki/Acoustic_Thermometry_of_Ocean_Climate
    It looks like “nothing” is the answer, but given a decade of data I’m surprised not to see a graph of some sort.

  5. 55
    DaveS says:

    And since the new analysis agrees with you, it should be taken the final word and not subjected to the same skepticism with which the previous study was treated, as per usual.

  6. 56
    Lynn Vincentnathan says:

    RE #53, “entire human race might go extinct along with thousands of other species wihtin a few decades”

    I think the possible danger is not so much that the worst will happen in a few decades or even in a hundred years, but that what we’re doing now may cause the earth system to rearch a point (maybe in years or decades, or we may have passed it already) at which it may be nearly impossible to slow or halt dangerous warming & great future harms, which could go on for hundreds, thousands, even hundreds of thousands, of years.

    And re #42, I can’t imagine anyone who would want AGW to happen (except some suicidal mass murders). That’s why so many good people are becoming climate scientists and environmentalists. Because they want to warn people and help us solve this problem.

    Seriously, are there GW believers on this site, who would be unhappy if tomorrow we found out that, oops, we forgot to square-root some calculation (or something) and GW is not happening afterall? Some may be red as beets for having claimed it was happening, they may be jumping hoops to show how any reasonable & smart scientist could have made that mistake, but surely their ecstasy in knowing it wasn’t happening, would far outweigh any embarrasment or even temporary unemployment (the guys here are smart, they’d get some other job; in fact I’ve read the many climate scientists started out in other fields). Many people have children and love them. Don’t you think they would be happy to know their children will have a good, sustainable world? Again, it is the denialists who are truly perplexing in their thinking and motives.

    And as for the environmentalists and do-gooders, there’s no shortage of other harms & evils in the world to combat, or one could just stop and smell the flowers along the way. Plenty of other things to do.

  7. 57
    Robin Johnson says:

    Measurement error, calculation error and reporting errors occur in every field – not just climate science. A significant portion of every professional’s time is spent investigating or fixing problems resulting from these kinds of errors. This is particularly painful in areas such as this – where decisions affecting potentially millions of lives is based on what can turn out to be faulty data or misapplication of data to theory. If it turns out that we can avoid the coming AGW disaster but we failed to act quickly enough because of faulty data – life in fubar. [NOTE: I think we're fubar already, but I'm hoping I'm really wrong about that.]

    Often I believe this drives the deniers – everyone knows that data is wrong, theories are wrong, etc and so they insist that its a data problem or theory problem. As long as the possibility exists that the data or theories are wrong – they reach for the elixir of “it could be bad data/theory” to avoid changing their reality. It’s natural. Human nature basically. In stable times, a high quality survival strategy. In unstable times, not so good.

  8. 58
    dhogaza says:

    DaveS the denialist says:

    And since the new analysis agrees with you, it should be taken the final word and not subjected to the same skepticism with which the previous study was treated, as per usual.

    The original post says:

    Are we done then? Unfortunately no.

    Seems that DaveS didn’t bother to read the post, which goes on to say:

    Because of the paucity of measurements, assessments of ocean heat content need to use a wide variety of sensors, each with their own quirks and problems. Combined with switches in data sources over the years, there is a significant potential for non-climatic trends to creep in. In particular, the eXpendable BathyThermographs (XBTs – sensors that are essentially just thrown off the side of the ship) have a known problem in that they didn’t fall as quickly as they were originally assumed to. This gives a warm bias

    In other words, that bias due to sensor problems has in one case been shown to run in the direction of warming.

    Gosh. Maybe it’s just about getting more accurate data and understanding the science after all, DaveS.

  9. 59
    Marian says:

    Can anyboy here please show me someone explaining the 800 year lag of co2? Any place where I can read about it?
    The explanation given on this site is not very intelligent.
    Thank you.

  10. 60
    pete best says:

    Re #56, As we came out of the last Ice Age there was a large amount of warming and as the oceans warmed there was a net large release of CO2 from them, however the warming attributed to this period lagged some 800 years behind the initial warming and did not cause it but it was responsible for its own warming and that is the point. It was not a driver for this ending of the ice age but it is a driver for warming as we are experiencing it today.

    I believe that some climate denialists have used the CO2 is not a driver for past climate argument which is incorrect.

  11. 61
    Craig Allen says:

    Re 56: explaining the 800 year lag of CO2

    There is a good explanation here. In a nutshell: 1) wobbles in the Earth’s orbit (the Milankovich cycles) have a warming and cooling effect. 2) Warming causes CO2 to be released – e.g. by thawing the permafrost and drying wetlands, soils and forests thereby allowing organic matter to breakdown, and warming the oceans which causes dissolved CO2 to outgas and methane (which breaks down to CO2) to be liberated from clathrates etc. 3) the extra CO2 (and methane) causes warming that is significantly greater than would otherwise result from the wobbles alone. 4) There is a delay because the various processes such as thawing of permafrost and breakdown of organic matter, warming of the oceans etc. take a certain amount of time to kick in after the wobble mediated warming starts.

    This time around we are not see a warming kick-started by a Milankovich wobble. Instead we are in an already warm period and are initiating extra warming by injecting even more CO2 into the atmosphere. The 64 million dollar question is: how much extra CO2 will now be liberated by those various CO2 liberating processes. And given that we seem to be kick-starting it all much faster than a wobble would, and are doing it on top of an already warm interglacial climate; how fast will that liberation occur, and how much CO2 will it add?.

  12. 62
    Tim says:

    Re: 85

    Thank you Dr. Schmidt. Both links were very helpful. I also read some of Hansen’s work on the subject.

    A few more questions for the forum on climate sensitivity to greenhouse gases:

    1. Doesn’t measurement of climate sensitivity rely on historic data?

    2. Are ice core temperature and gas composition data applicable to the entire globe or just Antartica?

    3. Hasn’t the climate changed dramatically over the last 400k years and thus how can we know how the earth will respond to forcings today if there are different processes at work?

    4. Hansen believes we can avert certain disaster if we keep warming under 1 degrees celsius. Isn’t this hypothesis built on the assumption that the earth will respond in a similar fashion to forcings that occured tens of thousand of years ago?

    Thanks again for taking the time to explain this to a non-scientist.

  13. 63

    [[I think it is now clear (after the warming of the oceans has now been proven) that if we do not stop adding GHGs to the atmosphere, the entire human race might go extinct along with thousands of other species wihtin a few decades.]]

    I doubt that. There will be great economic disruption and many people will suffer, but I don’t think the species is in danger of extinction. Let’s try to keep some perspective here.

  14. 64
    Marian says:

    So you say that the sun coming in at a different angle due to wobble of the earth is what previously caused global warming? But now it is the increase by 80 ppmv of CO2 that is the cause? Where in the Milankovic cycle are we now? Will that (M-cycle) have any effect on global warming this time?

    Trying my best to understand.
    Thanks for replying

  15. 65
    P. Lewis says:

    Re #64

    Where in the Milankovic cycle are we now?

    See Present Conditions on this linked page. You might well like to read the whole page, too.

  16. 66
    DaveS says:

    Can anyboy here please show me someone explaining the 800 year lag of co2?

    A natural 800-year lagging increase in atmospheric CO2 in response to rising temperatures does not somehow preclude an increase due to anthropogenic emissions… what’s to explain?

  17. 67
    DaveS says:

    Ha, I love that I’m a “denialist” because I point out the somewhat immature tone with which Gavin consistently addresses these things…. he’s made up his mind and has his biases as much as the “deniers” he derides. Even in this post, he said “[sea surface cooling] was going to be hard to reconcile with continued increases in sea level rise (driven in large part by thermal expansion effects)”. That’s called “begging the question”… if you presuppose that increases in measured sea-levels are due in large part to thermal expansion and that there is no “inertia” involved–whereby sea-level rise due to 350 years of warming may not necessarily stop on a dime with sea surface warming–then of course it’s difficult to reconcile. To a more objective observer, thermal expansion might be equally hard to reconcile with cooling waters.

    I’m no climate scientist, but I have a decent science background and I’m something of a lurker here… I’m just saying that it has been obvious to me from day one that Gavin is not exactly an objective source of information… he provides very good information from a perspective, and he does it in an intelligent–but slightly snarky–way. I like this blog and find it informative.

    Don’t project your biased, politicized view of this onto me, please.

  18. 68
    Lynn Vincentnathan says:

    #66, “Can anyboy here please show me someone explaining the 800 year lag of co2?

    A natural 800-year lagging increase in atmospheric CO2 in response to rising temperatures does not somehow preclude an increase due to anthropogenic emissions… what’s to explain?

    When you put these together, it’s a really bad scenario…much worse than simply CO2 causes warming.

    Watch out, world, for CO2 causes warming, which causes more CO2, which causes more warming, which causes more CO2, which cause a hellava lot more warming, which causes a hellava lot more CO2, which causes….(no one left to write about it).

  19. 69
    Fergus Brown says:

    Re #67: On ‘Gavin is not exactly an objective source of information’…
    On the list of people who I would trust to be a straight as possible on the subject and likely to know WTF they were talking about, Gavin is near the top of my list. Maybe this is because I, too, am prejudiced, or maybe it’s because I like the fact that he’s taking time , along with all the other experts here, to educate the likes of us.

    I like to pretend my judgement of other’s reliability is based on an assessment of their rationality and fairness, but who gives a damn about such archaic notions these days? I think there’s an important distinction to be made between being biased and having a clear point of view based on substantial knowledge and experience. But hey, that’s just me…

  20. 70
    Ingrid Tobar - Dept. Geosciences UMKC says:

    I think you make an important point regarding the “test of time” for research papers. In my studies I have found a number of papers which become widely accepted in a short period of time and shortly after we find stronger studies rebutting these initial findings. This applies to both sides of the controversy. After all, this is what science is all about, the problem is that some researchers, journalists and even the public get deeply attached to the first set of data they encounter and disregard subsequent arguments against those claims. That is why we should keep a critical eye on research papers concerning climate change, whether they support our personal beliefs or not.

    It is important to recognize that some data sources, such as the ARGO floats, can provide instantaneous data, but the overall trends may require more time to be determined. Some of the arguments I have encountered against global warming are based on a quick glance at these data, which may be displaying only short term trends, rather than continuous global cooling patterns. At the same time we also have some researchers supporting their claims on global warming in a similar fashion. This calls for caution on the part of the audience to which these claims may be directed. Neither proponents nor opponents should knowingly make strong claims based on faulty, incomplete or adjusted data due to the implications these factors may have on their conclusions.

    It is also alarming the fact that some of the probes may be producing anomalous data, and some researchers may be using it to back up previously construed arguments, instead of analyzing it, taking into consideration its flaws, to provide an objective study of climatic trends. With the increasing number of debates over this issue, my personal recommendation for the public is to understand data sources presented by both proponents and opponents before following either sideâ??s conclusion.

  21. 71
    Adrianne says:

    I am so happy that finally oceans get the attention they diserve, as I have strongly stated in varoius ways that we should consider more that the oceans are linked to the climate and influence the climate almos as much as the son does.

  22. 72

    Don’t project your biased, politicized view of this onto me, please

    Is anybody forcing you to participate here? Nobody is projecting anything on you here, if anything, by choosing to participate, you are projecting yourself onto us.

    This website belongs to its creators. They are free to project anything they want here, and you are free to ‘turn the channel’.

  23. 73
    Tim McDermott says:

    DaveS:

    As the Buddha said in a different context, “The pollution is in your mind.”

    Gavin’s statement that ocean cooling was going to be hard to reconcile with rising sea levels is simply fact, not attitude. Given that we know that sea level is rising several millimeters per year, the observed net contribution of melting glaciers and ice caps is not enough to explain current sea level rise, and water shrinks as it cools, how would you explain the current rate of sea level rise? You have to come up with a completely new source of water, a source of heat in the deap ocean, or show that water expands as it cools.

    If you don’t have an answer handy, then I submit that you demonstrate the simple truth of Gavin’s statement that such a reconciliation is hard.

  24. 74
    Ray Ladbury says:

    Dave S., Gavin does indeed have a perspective. We all do. The difference is that Gavin’s perspective is supported by the evidence and so reflects the scientific consensus on matters of climate. And lo and behold, because his perspective is consistent with the scientific consensus, he is, far more often than not, right.
    A scientist may support the scientific consensus. A scientist may be skeptical of the scientific consensus. In either case, they must do so based on the evidence. As soon as they lose sight of this fact, they leave the realm of science and, if they are experts, become contrarians (e.g. Lindzen), or if they are not experts, denialists, (e.g. you). In either case, you make yourself irrelevant to the process of science–quite unlike the true skeptic.
    Look, we know the climate is changing–that is beyond question. We have a very probable mechanism–anthropogenic greenhouse gas emissions. Those who say, “It’s natural” have absolutely no mechanism to propose to explain the changes we are seeing. As a physicist, I get uncomfortable when people seem to suggest that the energy in a system (e.g. the climate) can just increase with no cause. So until you have a mechanism to suggest, you are not part of the scientific process–skeptical or otherwise.

  25. 75
    Keith Rogstad says:

    RE# 68
    On the good side, we have 800 years to prepare before this supercharged co2 feedback begins?

  26. 76
    tamino says:

    Re: #75

    On the good side, we have 800 years to prepare before this supercharged co2 feedback begins?

    Not necessarily. One of the reasons the lag of CO2 behind temperature in deglaciations is so long is that warming during deglaciations is so slow. The rate of warming during a reasonably rapid deglaciation is about 0.1 deg.C/century, the rate today is about 1.8 deg.C/century.

    Also, the ice core records from Antarctica give a good measure of global CO2 concentration (it’s a well-mixed gas), but give a more local measure of temperature. Milankovitch cycles don’t actually cause warming globally, they redistribute incoming solar energy to more polar latitudes, so that they trigger ice melt. This causes the temperature in polar regions to warm even before the global temperature warms, but it’s the global warming that triggers CO2 release from the oceans. But the modern warming is global, so we can expect ocean-solubility influence to happen sooner.

    There is, however, the factor of CO2 released from melting ice masses, which one would expect to be “prompt” in relation to ice mass wasting. Anybody know the relative contribution to CO2 increase from oceans versus ice melt, during a deglaciation?

  27. 77
    DaveS says:

    Hmm, for whatever reason, my reply hasn’t showed up after two postings over the course of a couple of hours.

    I guess I’ll ask again and hope for the best…

    Gavin’s statement that ocean cooling was going to be hard to reconcile with rising sea levels is simply fact

    Since we know that the oceans expand and release CO2 over hundreds of years in response to surface warming, how is a few years of surface cooling hard to reconcile with continuing thermal expansion? The expansion is occurring in the depths of the oceans, in response to ongoing warming that has been occurring going back 300+ years, is it not?

    The “irreconcilability” seems to be an unfounded assertion. It seems to me that the thermal expansion wouldn’t stop on a dime in response to what amounts at this point to an insignificant blip of a few years of recent cooling (assuming, for the sake of argument, that cooling has occurred). If you take a longer-term moving average, any recent cooling wouldn’t even show up.

  28. 78
    Ray Ladbury says:

    Re 75. Actually, no. The feedback is temperature, rather than time dependent, so once we reach the temperature where the feedback kicks in, it will be too late–be that in 800 years or next year.

    That is one of the reasons why having working models is so important–it allows us to explore feedback mechanisms under various scenarios. This post is neither crowing over success, nor rejoicing at the demise of yet another denialist argument. Rather, it is saying that the models are working well, and that means that we will not be flying blind as we confront the likely effects of climate change.

  29. 79
    DaveS says:

    Look, we know the climate is changing–that is beyond question. We have a very probable mechanism–anthropogenic greenhouse gas emissions. Those who say, “It’s natural” have absolutely no mechanism to propose to explain the changes we are seeing. As a physicist, I get uncomfortable when people seem to suggest that the energy in a system (e.g. the climate) can just increase with no cause. So until you have a mechanism to suggest, you are not part of the scientific process–skeptical or otherwise.

    You are arguing with a straw man. You also seem to be unaware, incredibly, that noone denies that the climate varies naturally and always has… in other words, it is certainly true that “the energy in a system (e.g. the climate) can just increase with no cause”–of course, noone is arguing that there is “no cause” aside from your straw man. To claim such is nothing less than an intentional misrepresentation of people with whom you disagree.

    The difference is that Gavin’s perspective is supported by the evidence…

    What evidence is there that a few years of surface cooling would immediately stop the thermal expansion that is occurring in response to 300-400 years of warming? That was the statement I originally inquired about. There may be an answer, and that’s why I asked.

    I’m not a climate scientist, but common sense tells me that his assertion there was 100% unfounded. I’m simply asking, for the 4th time now, for someone to explain to me why it is founded. That’s all. What’s with the super-defensive reaction to a simple question?

    [Response: You are confusing surface warming (which can be checked directly with satellites) and upper ocean heat content (top 700m). Both the sea level change and the numbers reported here are sensitive to the latter, not the former. - gavin]

  30. 80
    DaveS says:

    So you’re saying that warming causes CO2 increases, which causes warming, which causes CO2 increases, etc? Why has this perpetual feedback cycle not caused our planet to be uninhabitable prior to this point?

    Once again, asking because I want an answer, not to be contrarian.

  31. 81

    It seems to me that the thermal expansion wouldn’t stop on a dime in response to what amounts at this point to an insignificant blip of a few years of recent cooling (assuming, for the sake of argument, that cooling has occurred)

    That just the point. Since sea level continues to rise, any observed cooling is likely to be insignificant in the long run. There are clear mechanisms for observed local cooling, which are not incompatible with local warming. A large volume of ocean is very cool. The ice sheets are melting into the oceans. Get the picture now?

    As long as sea level continues to rise, then there is no way to repudiate global warming. Sea level rise is clear evidence that warming is continuing, and there is no evidence to date to indicate that trend is reversing, or likely to reverse. Everything we see is in accord with our expectations. When the paper indicated anomalous cooling, we fully expected to see correction to the data to appear, because we understand sea level is rising via thermal expansion, and thermal expansion is nearly instantaneous on geological timescales. The analogy is neutrinos from the solar interior, they give us a nearly instantaneous picture of stellar processes which are otherwise obscured from our direct view.

  32. 82
    Marcus says:

    Re: 77: DaveS: Why wouldn’t thermal expansion stop on a dime? If there is no additional heat going into the ocean (and it is hard to imagine a way that additional heat could enter while the surface is cooling), then we are just moving heat around in the deep. And if we’re doing that… any increase of temperature and therefore expansion in one place will be balanced by a cooling and therefore contraction in another… There isn’t (as far as I understand it) “inertia” in thermal expansion: the water molecules respond pretty much instantly to the new temperature. The inertia comes in with the transfer of heat from atmosphere to ocean, and that’s why it takes hundreds of years to cause the expansion.

  33. 83
    Jeffrey Davis says:

    Re: the continuing saga of CO2-lagging indicator

    Going back 400,000 years, the maximum CO2 concentrations surrounding the warming and cooling pulses are all lower than current levels. (And the heating associated with those spikes is around +4C. )

  34. 84
    DaveS says:

    There isn’t (as far as I understand it) “inertia” in thermal expansion: the water molecules respond pretty much instantly to the new temperature.

    Hmm, that makes sense to me. However, the amount of expansion in response to new energy wouldn’t be uniform. That heat near the surface will move deeper over time, which will certainly have some sort of “lagging” effect. The density of the water is a function of temperature and pressure, right?

    Admittedly–off the top of my head–I suspect that this would actually exaggerate short-term sea-level changes, since the response would probably be smaller in colder, deeper waters under higher pressure. In other words, a complete halt in surface warming would probably cause a slow decline in sea levels, as surface heat mixed downward.

    That assumes, of course, that I’m remembering my physics correctly.

  35. 85
    David B. Benson says:

    Re #76: tamino — While but an amateur, it seems that the oceans store vast quantities of carbon in various forms and are much more extensive than the LGM ice sheets were. So I’ll hazard the guess that the contribution of carbon dioxide stored in the ice is negligible…

  36. 86
    Hank Roberts says:

    >thermal expansion
    I have no idea how pressure depth relates to thermal expansion — anyone got a pointer? I’m sure the submariners have charts for how density changes with temperature and with depth.

  37. 87
    Marcus says:

    Re: #83, DaveS: Huh. Yeah. The differences in density between deep water and surface water might mean that moving heat around could cause changes in sea level without new heat inputs. Also, the density to heat content relationship is probably non-linear, so that could also cause discrepancies.

    I’d still think that these would be 2nd order effects, and not large enough to account for the sea level changes being observed… but I acknowledge that I could be wrong.

  38. 88
    Tim says:

    RE: 62
    Still struggling with the concept of climate sensitivity. Questions above. Can anybody summarize the fundamental assumptions being made to estimate current climate sensitivity. I cannot seem to get past the idea that we can only make assumptions about today’s climate’s reaction to forcings based on the earth’s reaction to forcings from tens of thousands of years ago. Is it not reasonable to assume that many climate systems (ocean circulation patterns, cloud dynamics, etc.) are likely very different and thus past behavior cannot really give us an accurate sense of climate sensitivity today?

    Sorry if I am overlooking something obvious.

  39. 89
    Adrianne says:

    Lyman’s assert on observed ocean cooling last year was an interesting attempt on understanding ocean changes. Discussing therefore whether the ocean heat contents changes is a quiet sensible consequence. But wondering should be permitted. The oceans water masses are quite a massive body, with 1000 times the “heat capacity” of the entire atmosphere, and last not least are only +3,5 degree Celsius warm. Who will be able to tell that the ocean heat content has changed?

  40. 90
    Mark Hadfield says:

    Responding to 14 (I know this was a long way back, but I haven’t seen a specific response): “Also, how does this new information change the point made in the discussion from the original paper? This work has several implications. First, the updated time series of ocean heat content presented here (Figure 1) and the newly estimated confidence limits (Figure 3) support the significance of previously reported large inter annual variability in globally integrated upper-ocean heat content [Levitus et al., 2005]…”

    You’ve got to understand that none of the numbers here is known with a high degree of confidence, because the ocean is very poorly sampled. (Until ARGO, that is, but unfortunately that data is still new.) There have been suggestions for a while that the global ocean heat content has higher interannual variability than simulated by the models (ie by the ocean component of coupled climate models). With the latest revision the evidence for *really* high interannual variability has melted away. Still, it’s an interesting subject and one that should be revisited when we have, say, a decade of ARGO data.

    I wouldn’t be at all surprised if the ocean component of coupled climate models *did* show lower than observed levels of interannual heat flux variability. For one thing, the models in question have rather coarse spatial resolution and so the flow in them is very “syrupy”. (How that would affect interannual variability in heat content I don’t know, but you’ve got to wonder.) For another, there could be greater interannual variability in the radiative forcing at the ocean surface than we know about. But I don’t think any of this provides evidence of serious problems with the climate models, ones that would make their projections invalid.

  41. 91
    Rod B. says:

    re 69: I’m a skeptic and on opposite sides of the table from Gavin. I think he sometimes goes over the top and sometimes shows his bias too much (though bias is kinda O.K as opposed to prejudice). But, IMO, I’m very impressed with his efforts and scientific demeanor and consider him extremely reliable. I’ve critized him sometimes and questioned him a number of times but think he is top-notch and does a helluva job.

  42. 92
    Rod B. says:

    re 73 et al: This is a latent sandbox1 concern that’s been bugging me for some time. Beyond the spin and assertions of the sensor designers (designers always contend their design works exactly) how can we tell if ocean(s) rise a couple of millimeters? All the oceans? An average of all of the oceans? Particular oceanic “hot spots”? El Niño changes the surface about 500 mm; can we detect a variation of 1-2 mm “because of AGW”???

  43. 93
    Craig Allen says:

    No-one has answered 79 from DaveS yet: “So you’re saying that warming causes CO2 increases, which causes warming, which causes CO2 increases, etc? Why has this perpetual feedback cycle not caused our planet to be uninhabitable prior to this point?”

    I haven’t been able to found any good answers elsewhere yet. I assume that during the interglacials, various carbon sequestration processes kick in or are enhanced, and that these lower the CO2 concentration enough to bring the temperature back down. Does anyone have information on the specifics of this? What are the candidate processes and how well do we understand them? This explanation prompts the opposite question though. What prevents the CO2 concentration from continuing to drop until we freeze over?

  44. 94
    Chuck Booth says:

    Re 85 Hank,
    If I understood your question correctly:
    Water is nearly incompressible, so its density doesn’t change significantly with depth – any density differences are almost entirely due to differences in temperature and salinity. Any good oceanography textbook (e.g., Sverdrup, Johnson, and Fleming,1942, The Oceans Their Physics, Chemistry, and General Biology; see Chapter IV, http://ark.cdlib.org/ark:/13030/kt167nb66r/) have tables or nomagrams relating temperature/salinty/density, and tables or figures showing temperature and salinity as a function of depth. Another, more recent, source is:
    Emery, W.J. and L.J. Dewar, 1982: Mean temperature-salinity, salinity-depth and temperature-depth curves in the North Atlantic and North Pacific. Pergamon Press, Oxford, England, 91 pp.

  45. 95
  46. 96
    Joseph O'Sullivan says:

    This was a very informative post. The details of the ocean temperature data are important.The wider lessons at the end are even more important. One of the things that the general public needs to know when they are trying to understanding global warming is how science works.

    It also shows how politics have become a part of the public debate of the science. If someone submits a paper, like Lyman et al, that might cast doubt on AGW people wonder if there is a contrarian/political motive involved. In my own idealistic way, I think its unfortunate that that the clean scientific method is being drawn into the dirty world of politics.

  47. 97
    Tim says:

    re 92

    I agree that we seem to be extrapolating global trends from a limited number of data sets and therefore these global sea level rise figures have to be viewed with a healthy dose of skepticism. I think the same can be said of Antartic ice core data and their utility for determining temperature for the rest of the planet.

    Still learning a lot reading the contributions at this exceptional site, but it is my impression that the scientists still lack sufficient knowledge to be able to categorically state that the earth is on the verge of catatrophe.

  48. 98
    Henry Molvar says:

    Re: #87: Marcus-*The differences in density between deep water and surface water might mean that moving heat around could cause changes in sea level without new heat inputs. Also, the density to heat content relationship is probably non-linear, so that could also cause discrepancies.*

    When a water molecule warms it vibrates more. This causes it to occupy more space amongst the molecules surrounding it. As it mixes with cooler molecules it warms them and they cool it, causing the extra space that it occupied on warming to diminish; however, the original extra space is not lost but merely acquired by the molecules that it warmed.

    The net effect is no additional thermal expansion or contraction due to mixing with other molecules. Additional heat must be added to the water molecules to cause more expansion.

  49. 99
    tamino says:

    Re: #92, #97 (sea level trend)

    Indeed the rate of sea level rise is slow by comparison to changes brought about by tide and wind. I don’t know whether or not there is a limited number of data sets, but let’s assume, for the sake of argument, that indeed it’s true.

    The limited amount of data does not invalidate in any way the detection of a trend. When we study data looking for a trend, we apply statistical tests which are tried-and-true, confirmed by literally millions of cases, and more important, can be *proved* in the only way that true proof exists: mathematically. If the statistical test shows overwhelming likelihood of a trend, then it’s overwhelmingly likely to be there — regardless of whether we have a limited number of data sets.

    Of course, more data sets are better, because that increases the sensitivity of the trend analysis; it enables us to separate ever-smaller trends from the noise with statistical confidence. So, more is better.

    The “catch” is that statistical tests can detect and quantify trends in the data. But if the data don’t match the physical system, as is the case for the Argo floats, then we’ve only detected a trend in a bunch of numbers, not in the physical quantity we tried — and failed — to measure.

    Therefore a larger number of data sets is doubly helpful: not only does it increase the sensitivity of statistical tests, to identify even smaller trends if present, it also decreases the likelihood that we’ll be fooled by bad data, since it’s unlikely that multiple data sets will all be affected by errors that go in the same direction, giving false detection of a trend (opposite errors will cancel in a trend analysis, and give the false impression of the absence of a trend).

  50. 100

    [[if you presuppose that increases in measured sea-levels are due in large part to thermal expansion and that there is no "inertia" involved--whereby sea-level rise due to 350 years of warming may not necessarily stop on a dime with sea surface warming--then of course it's difficult to reconcile.]]

    How in God’s name does inertia tie into it? You’re saying the ocean had momentum upward which took decades to dissipate? I don’t think that ties in with what we’ve known about physics for the last 300 years or so.

    As the ocean warms, it has to expand. Period. Do you want the equations? You can probably look the figures up in the CRC Handbook. If they don’t have the values for seawater, the NOAA might. But previous expansion will have no effect at all. There is something called “thermal inertia,” but it has nothing to do with expansion.


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