Overestimating global warming?

There is a new Nature Climate Change commentary called Overestimating global warming over the past 20 years. It’s by John Fyfe, Nathan Gillet, and Francis Zwiers. I’ve been trying to find out what the criteria are for a commentary in Nature Climate Change, but can’t seem to find much about this. I don’t know if the paper is peer-reviewed or not and if it was solicited or not.

Anyway, I find it a slightly strange paper for a number of reasons. It is a comparison between surface temperature trends from CMIP5 models and HadCRUT4 data. It considers the period 1993-2012 and the period 1998-2012. The basic conclusion is that the observed warming trend is significantly different to that expected based on CMIP5 models. Indeed, that is – as far as I’m aware – quite well know.

Comparison between HadCRUT4 trends  and model trends for the periods 1993-2012 and 1998-2012 from Fyfe et al. (2013)

Comparison between HadCRUT4 trends and model trends for the periods 1993-2012 and 1998-2012 from Fyfe et al. (2013)

The are a number of immediate issues I have with the paper. One is that it’s not obvious why comparing trends (rather than simply comparing temperature anomalies) is that appropriate. This seems a little like cherry-picking start years. It can make the mismatch seem much worse than it maybe is. Another is that I can’t see where the errors are coming from. The paper suggests that for the period 1998-2012, the observed trend is 0.05 +- 0.08oC per decade. The Skeptical Science Trend Calculator gives 0.052 +- 0.155oC per decade. Both of these are meant to be 95% confidence intervals, so why is the value in this paper half that from the Skeptical Science Trend Calculator? It could be that they’ve used un-correlated errors, but that would be wrong as far as I’m aware. For the CMIP5 models, the paper claims that the trend for 1998-2012 is 0.021+-0.03oC per decade. Again, I don’t see how these can be 2σ uncertainties. Certainly the distribution of model trends seems to have a standard deviation that is bigger than 0.015oC per decade.

So, I don’t dispute the basic result, I’m just surprised by the confidence intervals and am, hence, not convinced that they have actually compared the appropriate distributions. Admittedly, I am no expert at this so maybe I just don’t understand this well enough to really know if they have made some kind of silly mistake or not. I do, however, have a bigger issue with the paper. The title refers to global warming. The paper itself says

The inconsistency between observed and simulated global warming is even more striking for temperature trends computed over the past fifteen years (1998–2012).


The evidence, therefore, indicates that the current generation of climate models (when run as a group, with the CMIP5 prescribed forcings) do not reproduce the observed global warming over the past 20 years, or the slowdown in global warming over the past fifteen years.

Why is this an issue? Well, the paper is actually comparing simulated and observed warming of the surface, not global warming. Global warming is about the increase in energy in the climate system. This paper considers, only, the trends in surface warming. I appreciate that many have associated surface warming with global warming, but this seems to stem from an era when the most reliable dataset was the surface temperature dataset. Today we have evidence (ocean heat content for example) indicating that global warming continues despite the “slowdown” in surface warming. It’s now fairly clear that the surface temperature alone is not necessarily particularly representative of overall global warming, and it’s also not a particularly good indicator (over short time periods) of global warming.

Given that it now seems widely accepted that the ocean heat content is a much better indicator of overall global warming, I find it surprising that something published in Nature Climate Change is still referring to surface warming as global warming. It would seem that climate scientist would want to distinguish between overall global warming and surface warming so as to avoid their work being mis-interpreted. Even if the authors weren’t bothered I would expect either the referees or the editor would like to avoid such confusion. Again, I’m not a climate scientists so I can’t really say why there are still papers that use “global warming” when referring to “surface warming”. Maybe there is a perfectly valid reason. I also appreciate that climate scientists have a sufficiently hard time without me also criticising what they’re doing. I just find it surprising that this is still happening despite the ongoing debate about the significance (or lack thereof) of the “hiatus” in surface warming.

This entry was posted in Climate change, Global warming and tagged , , , , , . Bookmark the permalink.

124 Responses to Overestimating global warming?

  1. BBD says:

    The world-weary cynic in me keeps insisting that garnering attention is good for the career. I do my best to ignore this dry whispering, but it just won’t go away.

  2. wotts,
    I know you’ve been pushing this for a while, but ‘global warming’ is not the ‘increase of energy in the system.

  3. Yes Shub, it is. What else can it be?

  4. BBD says:

    Me too! (Sorry Wotts).

    I’m going to sit and wait for this one!


  5. BBD says:

    A less cynical but still troubling alternative is that some climate scientists are using the term “global warming” in formal publications as it is (mis)understood by the media and wider public. Which would be a negative feeback.

  6. Yes, I had wondered that. It’s certainly how people perceive global warming but it still doesn’t really make sense for scientists to continue using it in this context. They could just be not really thinking about this because its the terminology that they’ve been using for so long, but even that doesn’t really make sense. It would seem fairly straightforward to adapt.

  7. Sou says:

    Me too. A crowd (of three) is gathering with bated breath…

  8. Show me a definition from a suitably official and reasonably old source that says global warming is ‘increase of energy in system’

  9. Reich.Eschhaus says:

    No Shub. You are trying to deflect. It is you saying that “global warming is not the increase of energy in the system.” Now tell the increasing crowd what, according to you, global warming is instead.

  10. Firstly, you could read the wikipedia page. Secondly, I’m not here to be a resource for you. Do some reading of your own. I don’t really care if you’re convinced or not. It’s not important or relevant.

    However, what are you actually asking? There clearly are sites that associate global warming with surface temperatures. These are, however, misleading. Are you actually disputing that enhanced greenhouse gas concentrations in the atmosphere are leading to rising ocean heat content and reduced arctic sea ice? These are both indicators of global warming. Furthermore, the rate of increase of ocean heat content indicates that 90% or more of the energy associated with global warming is going into the oceans. That’s really the point. Our climate system continues to gain energy despite the “slowdown” in surface warming. Therefore the slowdown in surface warming does not indicate that global warming has stopped. If you want to believe that all we should be considering are surface temperatures, that’s fine. You go right on and do that if that’s what you want to do. I think you’ll be in for a big surprise in a few years though.

  11. Sou says:

    Ha! Copping out I see.

  12. BBD says:

    The bated breath thing only works for so long. I’m starting to turn blue.

  13. I cannot see anything wrong with using the term “global warming” the way it has been used for a long time as in increase in the global mean surface temperature.

    You are right, that in the current pause it makes sense to distinguish between increases in the atmospheric surface temperature and the heat of the climate system. Consequently, you would expect that nowadays people would clearly define what they mean with global warming.

    Instead of try to change the meaning of a traditional term, maybe it would be easier to introduce a new term. How about using “global heating” for an increase in the global mean heat content of the climate system?

    Global warming in the traditional sense still is important. Because of the dense station network, we can homogenize station temperature data much better as ocean data. Maybe it is my bias, but I trust trends in the surface temperature a lot more. Furthermore, the climate record is much longer for station temperature.

    In addition, if a larger part of the energy goes into the oceans and the atmosphere heats less, you also have a smaller moisture feedback, which would give you smaller estimates for the transient climate sensitivity. Also humans being a land animal of about 1.5 to 2 meter means that many impacts of climate change will be due to the surface temperature. Thus it is worthwhile to have a term for increases in the surface temperature. Maybe “global warming” would be a good one for traditional reasons.

  14. BBD says:

    Oh Hell’s teeth, I’ve died of anoxia.

    That Shub! He’s got a lot to answer for!


  15. BBD says:

    In addition, if a larger part of the energy goes into the oceans and the atmosphere heats less, you also have a smaller moisture feedback, which would give you smaller estimates for the transient climate sensitivity.

    A good point, but as I understand it, the current increase in ocean heat uptake is likely to be short-lived, so its effect on TCR (the definition is important) is likely to be cancelled by future warming since the radiative forcing seems likely to increase with time.

  16. I was wondering about this myself. Certainly we could simply decide to define “global warming” as meaning “surface warming” and it does seem clear that many do see it this way. What is missing is the clear distinction between surface warming and overall warming and so people clearly interpret the “slowdown in global warming” as meaning it’s stopped completely, which it clearly hasn’t. So, if we could make this clear and if people could realise the difference between overall warming (global heating) and surface warming (global warming) then I, obviously, have no issue with whatever term is used. The issue is more that some are clearly interpreting papers like this as indicating that overall warming has stalled and it does seem important to clarify this issue.

    You also make a valid point in your last paragraph. The TCR may well be lower because of increased energy going into the oceans and clearly we (as humans) are interested in what will happen where we live, so surface temperatures are important. My issue really is just that it seems that there would be some merit in making it clear that a “hiatus” in surface warming does not indicate that overall global warming has stopped.

    I suspect that in my case an issue is that I don’t think I have ever perceived global warming as only applying to surface warming, but that’s more because I haven’t been directly involved in this for as long as others so I’m just not as influenced by how the terminology may have evolved.

  17. BBD says:

    @ Shub

    Show me a definition from a suitably official and reasonably old source that says global warming is ‘increase of energy in system’

    You know we’ve been through this before! I have quoted this to you at BH. Surely you remember?

    From the preface to the “Charney Report” back in 1979:

    The conclusions of this brief but intense investigation may be comforting to scientists but disturbing to policymakers. If carbon dioxide continues to increase, the study group finds no reason to doubt that climate changes will result and no reason to believe that these changes will be negligible. The conclusions of prior studies have been generally reaffirmed. However, the study group points out that the ocean, the great and ponderous flywheel of the global climate system, may be expected to slow the course of observable climatic change. A wait-and-see policy may mean waiting until it is too late.

    Read the words; there it is.

  18. Tom Curtis says:

    First, picking 15 and 20 year intervals terminating in the most recent complete year of data is hardly cherry picking. That is particularly the case given that the authors show the running 15 and 20 year trends from 1980 in Figure 2. It would be interesting to know (I haven’t purchased the paper) if in their discussion they note that if the primary cause of the discrepancy was the 97/98 El Nino, we would expect 15 year trends to decline until 2006 (dating the trend from its median year), and then start rising; and 20 year trends to decline until 2008.

    Second, from the abstract and figures I think Fig 3 is probably the most interesting in the paper. It shows estimated impacts on trends of ENSO, COWL (?), Volcanic, and a residual. Interestingly in the residual the 2.5-97.5% confidence interval of observations lie just inside that of the models, showing that on this analysis the models are not yet falsified. I would be interested in knowing how they determined the relevant impacts. That is particularly the case for ENSO, where the apparent impact for the 15 year trend looks dubious. They show a -0.025 C/decade impact on the 15 year trend, compared to Foster and Rahmstorf’s 0.09 C/decade (for HadCRUT3). Using Foster and Rahmstorf equivalent adjustments would have reduce the difference in residual trends between observed and models to about 0.05 C/decade.

    Finally, as always in these cases, it would be interesting to know if they compared the HadCRUT4 observations to the model predictions with a HadCRUT4 mask. Absent that, by omitting some of the most rapidly warming areas from HadCRUT4 but not from the model predictions, they bias the result towards a low observed trend relative to the model trend. They also bias the result by inflating the relative impact of ENSO.

  19. Mircea says:

    It is strange to find a discussion of what means “global warming” in a blog in year 2013. Here are some definitions for global warming (Google is my friend):

    “Global warming refers to the recent and ongoing rise in global average temperature near Earth’s surface. ”

    “an increase in the earth’s atmospheric and oceanic temperatures widely predicted to occur due to an increase in the greenhouse effect resulting especially from pollution”

    “Global warming refers to climate change that causes an increase in the average temperature of the lower atmosphere. ”

    The energy imbalance is interesting to the public exactly because of the potential “global warming”. Few care if the deep oceans warm a little or the stratosphere cools a little.

    As such, when papers about “97% consensus that increase CO2 increases the surface temperatures” are promoted ad nauseum it becomes then very difficult to explain why the “hiatus”.

    I find your blog really good and I enjoy reading the articles and the comments.

  20. In the early 80s, growing out of environmental movement and newer developments, was a unique problem: acid rain. Germany and Sweden blamed UK for its coal burning causing acid rain and forest die-off. Environmental consequences of industrial activity affected people far away from the origin of the polluting source. Tied with the kind of awareness that widespread dissemination of minute amounts of polluting substances (such as DDT) were thought to cause, a new paradigm in environmental/ecologic thought took root: it was billed “global change”. The first publicly prominent bonafide global change agents were the halogenated compounds thought to produce the ozone ‘hole’. Substances produced as a by-product of industrial activity, would become well-,mixed in the atmosphere and caused effects that affected everyone. Even such issues as acid rain and fertilizer pollution behaved like point-source problems although at a vaster scale. ‘Global change’ agents, on the other hand, exerted effects via diffuse distribution via the atmospheric commons, and affected planet-scale processes. If you refer to the environmental literature you’ll see emergence of the term ‘global change’, simply something that changes over planetary scale regions, or the whole earth, as opposed to classical point-source pollution issues.

    The “Global change” concept captured several dimensions hitherto unstudied – the increasing omnipotence of humankind, its ubiquitous nature and the novelty of the litigation and legislation domains it opened up.

    Following closely on its heels, arising in parallel almost, was the issue of global climate change. It was a subset of global change. Global climate change shared several features with the ozone problem. Greenhouse gases at once inherited several of the paradigmatic properties of the halogenated carbons: present everywhere, causing diffusely distributed effects. CO2 doesn’t precipate out from the atmosphere, unlike H20, and exerts effects constantly.

    As the greenhouse effect increase was proposed, several questions arose. One of the major themes was the non-uniformity of the rate and magnitude of temperature rise in the observed record. Patterns of regional temperature evolution showed differences, and there wasn’t enough good data. Maybe the forcing agent wasn’t well-distributed enough. In response, a major, pioneering effort to collect actual thermometer data and produce an instrumental proxy (as opposed to educated guesses) was undertaken in the UK. If ‘natural causes’ and other unknown factors would influence global temperatures, they wouldn’t produce global change. One part would be warm while the other cold and this would vary, and so on and so forth. As time passed, and through the 90’s, a powerful answer to this question built up: the average temperature curve showed a distinctive, synchronized-appearing, monotonous temperature rise manifested in almost all regional reconstructions. They matched the global pattern. The Keeling graph had established the well-mixed nature of CO2. Now, its planetary-scale, uniform effects were visible. Indeed, when the Steig et al Antarctic paper came, it was hailed for demonstrating a continent-scale warming over the second half of the 20th century. The last place on earth showed effects of the trace gas increase. “This warming trend is difficult to explain without the radiative forcing associated with increasing greenhouse-gas concentrations.”, wrote authors Steig, Mann and others in their Nature paper on Antarctic warming.

    Perhaps, more importantly, greenhouse gases produce their effect of ‘enhancement’ of warming via increased surface warming. As long as the surface temperatures showed a only a rising trend (which was true over the entire period of the instrumental record, see below), increasing forcing agents could be explained to cause increased surface temperatures to restore radiative balance. The uniform, surface warming observed in the 20th century, especially in its second half, is thus distinctly greenhouse-induced. Even in the mid-century cool period, it is actually warming, which is superimposed with and counteracted by other temporary global change agents of the same anthropogenic source, fossil fuels.

    It is in this way, that ‘global climate change’ and ‘global warming’ are descriptors. Not by referring to different parts of the earth, nor with reference to ‘energy’, in the ‘system’, though these may be technically correct (and useful, as the time arises!). They are post-hoc novel rewritings of terms whose etymology is different. The ‘globe’ refers to scale, uniformity and diffuseness.

    Global energy content, may increase, for example, as is being contended now, without producing significant temperature change. To my knowledge, no description of the greenhouse effect provides such explanation. Secondly, energy may well increase in the system, diffusely, with no appreciable temperature change and disssipate, say via storminess, or windiness, or rain etc. But even such phenomena are affected only via the mediation of surface temperatures.. But these are additional issues and questions.

    So, let us go easy on the cobweb spinning.

  21. Tom, COWL is acronym for Cold Ocean Warm Land and accounts for dynamically induced atmospheric variability. The ENSO is calculated following Fyfes 2010 paper. It is estimated using a simple ocean mixed layer model. If I’m not wrong, it is doing that for the entire instrumental period. No surprise the ENSO impact is very small. I never found their approach (see also Thompson et all. 2009) particularly compelling. Had they used FR11, they probably wouldn’t have had anything to publish 🙂

  22. Thanks, but don’t your very links illustrate why discussing the meaning of global warming is relevant. I looked last night and found a wide range of definitions that weren’t all consistent. Some mentioned surface temperatures, some mentioned atmospheric temperatures, and others discussed oceans, arctic ice and surface temperatures. If you look at the video I posted yesterday they discuss that there’s been no slowdown in global warming because of the arctic ice and rising ocean heat content. There doesn’t seem to be a consistent definition.

    I’m slightly confused about your comment with regards to the 97% paper. It’s wasn’t intended, I didn’t think, to explain anything other than there is a consensus in the literature. I’m not sure why you’re “blaming” it for the inability to explain the “hiatus”.

  23. Tom, I’ll have another read of the paper later and see what they say about the 97/98 El Nino. I can’t seem to access it from home. Maybe you could clarify the issue with the errors. The errors they use seem smaller (by a factor of 2) than the errors from the Skeptical Science Trend Calculator and their model errors also seem lower than I would have expected looking at the figures. Do you understand how they got their errors and are they correct?

  24. I had a brief Twitter exchange with Gavin Schmidt about this paper yesterday. Gavin was being a little opaque :-), but I got the impression that he was implying that there was some link between this and how Canadian science is being influenced by government policies. Do you have any insights into this? I may well, of course, have completely misunderstood what was being implied.

  25. Shub, a short comment. Numerous bits of evidence indicate that the energy in the climate system continues to rise. The only viable explanation for this is the enhanced concentration of CO2 in the atmosphere. If we continue to add CO2 to the atmosphere then this “global heating” will continue until surface temperatures have risen so that the amount of energy being radiated back into space matches the amount of energy our climate system is receiving. Hence the implications of continued “global heating” are fairly clear and no, this energy can’t simply increase without an eventual increase in surface temperatures.

    Seriously, you write the above comment and suggest I go easy on the cobweb spinning. I may have asked you this before, but do you have any self-awareness?

  26. chris says:

    It’s not easy to see the point you’re trying to make Shub, unless your investing heavily in a purely semantic argument (something like “global warming/climate change has largely been discussed in relation to surface/atmospheric temperature changes in response to greenhouse forcing, and so it’s wrong/deceitful to change the focus towards net energy accumulation in the climate system to rescue a situation where there has been little change in surface temperature for a while”).

    Something like that?

    But this assertion of yours is surely wrong:

    “Global energy content, may increase, for example, as is being contended now, without producing significant temperature change. To my knowledge, no description of the greenhouse effect provides such explanation.”

    That has to be untrue. The greenhouse effect refers to accumulation of energy in the climate system as a response to greenhouse forcing, and the progression of the Earth surface/atmospheric temperature towards a new equilibrium with fluctuations due to natural variability. This must happen for the TOA radiation of LWIR to space to return eventually to equilibrium with respect to incoming solar radiation.

    The present “hiatus”, if you wish to call it that, is reasonably well understood and is fully in accordance with our understanding of the greenhouse effect. The present so-called “hiatus” is a brief juncture on the progression of the Earth’s surface/atmospheric temperature towards a new equilibrium. If one were to use the NASA GISS temperature (which is more inclusive of areas that we know are warming most quickly), the so-called “hiatus” is hardly apparent (one might say that “global warming stopped in 2010”!). We know that we are in a period where solar output is a little low and we know that natural variability has given a temporary enhanced transfer of forced energy accumulation into the deeper oceans where it has little effect on surface temperature (but does contribute to sea level rise etc.).

    You can’t negate our scientific understanding by using semantic arguments about terminology!

  27. chris says:

    Personally I don’t have too much of an issue with this commentary since it does address an obvious point (surface warming hasn’t progressed recently anywhere near the rate found in many climate simulations), and does seek to address some of the factors relevant to this discrepancy, especially the effects of natural variability in modulating the progression of surface/atmospheric warming (and, for example, the contribution of stratospheric aerosols which seem to have been rather significant during the past two decades and generally haven’t been included in models).

    However I do agree with your top point that the descriptions and terminologies are lazy and this is poor for a scientific commentary in a Nature journal. If the authors had substituted “surface warming” for “global warming” throughout, and discussed this essential distinction it would have made their commentary much more useful and truthful in the sense of being a more faithful representation of the real world at this present time and out understanding of this…

  28. Chris, agreed it does address some of the issues so I really just wasn’t sure what to make of it. One thing I still haven’t established (and maybe you can help) is whether or not their 95% confidence intervals are correct. They seem smaller than I was expecting. The other issue I had was quite what the point was. It seems to show something that is quite well known and the discussion seemed to mainly repeat what also seems to be quite well known. I just wasn’t sure what it was adding that was new. I think I expected more from something in a Nature Climate Change journal. Then again, I could just simply be missing something important 🙂

  29. Yes you are right and the difference in the water vapour feedback would probably be a minor correction anyway. As Wotts writes below, the direct effect of more heat going into the ocean for estimates of the TCR is likely larger.

  30. If a scientist writes an article about the hiatus without mentioning the evidence that the energy went into the ocean, he would lose a lot of credibility with me, then you lose your honest broker status, which every good scientist should have. (I hope the authors of the paper you discus did, I did not check.)

  31. As far as I can see all they talk about is the difference between the observed and simulated surface temperatures. Their discussion of why there is a difference seems okay (they mention El Ninos, aerosols, forced and internal variability) but I can’t find any explicit statement about the continued rise in ocean heat content, despite the slowdown in surface warming. One might argue that it is implicit in their discussion, but it does not appear to be mentioned explicitly. I could have missed something, but the paper is quite short and I think I’ve read it all.

  32. BBD says:

    They are post-hoc novel rewritings of terms whose etymology is different.

    Classic Shub!

    Runs away when scuppered. Comes back *hours and hours* later and posts obfuscatory waffle way down the thread not up with the original exchange where it belongs…

    And will keep this nonsense up forever if permitted!

  33. chris says:

    The TCR seems to me to be an artificial/idealised parameter anyway and it needs to be discussed with a few strings attached. It’s defined as (Wikipedia) “..the average temperature response over a twenty-year period centered at CO2 doubling in a transient simulation with CO2 increasing at 1% per year”, but in the real world must be a massively moveable feast. Either it could be discussed in an idealised manner according to its definition (this would have to be with reference to a model Earth response to forcing without internal variability), or if it was being used in relation to real world observations in would be a number that would change according to the effects of natural and anthropogenic variability.

  34. Chris, I think I would largely agree. What is probably roughly correct is that internal variability and energy going into the deep oceans cannot actually change the ECS, but it could influence the lag time. It would take longer to reach an equilibrium. Admittedly, even this is a bit of a moving target if we keep increasing atmospheric CO2 concentrations. So it seems to me that understanding internal variability can give us some indication of what sort of time scale we will be dealing with, but doesn’t really change what will ultimately happen (i.e., we don’t really need to know the details of the internal variability to have a good indication of how much warming we are likely to undergo).

  35. In fairness, Shub isn’t alone is adopting this kind of strategy.

  36. chris says:

    It’s worth thinking about this (even if only qualitatively) in terms of response times: The surface/atmosphere has a rapid response to forcing, whereas the oceans have a very slow response. So the progression towards a new temperature equilibrium in response to TOA forcing has slow and fast response elements (a spectrum of response times in fact). The full climate sensitivity is realized when everything (oceans and surface and atmosphere) approaches its equilibrium.

    Right now one of the slow response elements (the oceans) is being “filled up” rather more quickly than its long term average rate of heat accumulation and this is suppressing the surface response for now. However it’s not obvious that this has much of an effect on the timescale of warming on (say) the multidecadal time scale.

    In fact one could argue that the present “hiatus” due to deep ocean warming will increase the rate at which we approach equilibrium (if it were to continue). After all since the TOA radiative imbalance isn’t being dissipated by surface warming at the moment, the rate of accumulation of heat into the Earth system is particularly fast right now. This is a little like the fact that ocean heat uptake is faster during La Nina periods and slower during El Nino’s.

    The oceans have to accumulate heat (lots and lots of it!) in order for the Earth system to equilibrate eventually with greenhouse forcing. In fact it’s probably most likely that the current “hiatus” has rather little to say about the overall rate of warming as the Earth responds to radiative imbalance on multidecadal timescales.

  37. BBD says:

    Life isn’t fair, Wotts! As you know.

  38. You call Gavin answering your question with this link opaque?

  39. I was wondering a bit about this last night. As you say, the full climate sensitivity is reached when everything is in equilibrium. As far as I see it, if previous estimates of climate sensitivity have ignored the deep ocean then presumably they’ve over-estimated how much energy is available to heat the land and atmosphere and would under-estimate the timescale over which equilibrium is reached. On the other hand, if previous estimates have included that the entire ocean would need to reach a new equilibrium then their estimates would probably be more correct and – as you say – we’re simply seeing a phase where the oceans are being heated faster than their long-term average.

  40. I did acknowledge that I was probably being a bit dense, and probably still am 🙂

    I did read that and it did seem remarkably concerning. I may have missed something obvious, but I couldn’t quite work out how that article related to the paper I was discussing in this post. I have some suspicions but am always a little concerned about invoking conspiracy theories.

  41. BBD says:


    My understanding is that this is a *temporary* phenomenon. Likely to be insignificant on the multi-decadal to centennial scale. Also that the strong warming trend will resume once the rate of ocean heat uptake falls slightly. There is no assumption that any of the stored energy needs to emerge from the oceans for strong warming to resume. Although stored energy will emerge, of course, contributing to future warming.

  42. You probably also do not need a government order or conspiracy to explain this paper.

    I do not know Francis Zwiers that well, but I can imagine that he likes writing such papers. He is one of the organizers of the International Meeting on Statistical Climatology, together with Hans von Storch amongst others. This is a great conference and I can encourage every climatologist to go there, but informally it is called the climate sceptics conference (without the scare quotes, there is no deception WUWT-style).

  43. BBD says:


    Do read the Bowen book Censoring Science that I recommended. Gavin features, here and there. You will perhaps be more… open to the idea that governments can and do muzzle “inconvenient” scientists while encouraging those more “on-message”, as it were. I didn’t read your twitter exchange with GS, but if that is what he is indeed implying, he has an insider’s perspective and is hardly known for wild-eyed ranting.


  44. Yes, I wasn’t suggesting that the energy would need to re-emerge, simply that if more energy is required, than expected, to bring the oceans to equilibrium with the climate system, the timescale may be longer. I agree that it is most likely that strong surface warming will resume when the rate of ocean heat uptake reduces. Also, as Chris was mentioning, the longer this takes the larger the energy imbalance will get and the faster the subsequent surface warming is likely to be.

  45. Thanks Victor and BBD. That makes things clearer. I shall endeavor to read the book you recommend.

  46. “The present “hiatus”, if you wish to call it that, is reasonably well understood…”

    Why was it not predicted?

  47. Shub, can you explain the relevance of your question? Why should the lack of a prediction undermine how we understand it today? What if the likely inherent chaos of the internal variability makes such predictions virtually impossible to make (at least in the sense of predicting precisely when, rather than predicting if)? Do you really believe that we should continue to distrust our understanding of the “hiatus” simply because it wasn’t precisely predicted?

  48. BBD says:

    Why was it not predicted?

    Groundhog Day.

    Have fun, Wotts. Hope you haven’t got anything pressing on for the next couple of weeks.

  49. BBD says:

    @ Wotts

    simply that if more energy is required, than expected, to bring the oceans to equilibrium with the climate system,

    Why might more energy be required than expected? I think I’ve missed a bit here. I agree with chris above btw, to save repeating things.

  50. Paul Matthews says:

    “I don’t know if the paper is peer-reviewed or not”

    “We thank Greg Flato, Bill Merryfield and Slava Kharin for their comments on an early draft”

  51. I’ve probably explained myself badly or shown my lack of experience in this. I was simply suggesting that equilibrium requires an increase in energy in all parts of the climate system. Given that it seems that some were surprised by the possibility that energy has been going into the deep ocean I was simply wondering if earlier work had underestimated the amount of energy required to bring the system as a whole to equilibrium and, hence, if these early estimates were under-estimating the time it would take to reach equilibrium. It is quite possible that my musing are not making much sense 🙂

  52. And that tells me what? As you probably know, when I used the term “peer-reviewed” I was implying formally by someone selected by the journal, rather than by people the authors asked to read the paper. Of course, if one wants to be pedantic you could indeed claim that it has undergone some form of peer-review, but I think most would agree that the term does not normally simply mean “by your mates”.

  53. “Global warming” will have a definition. But, in terms of communicating to laymen, such as myself, I’d prefer it if the words made intuitive sense. For me, global is all the surface, atmosphere and oceans – decidedly three dimensional. Warming, of course, is tougher – most people think thermometers – but they only measure an aspect of heat capacity. Still, something in 3D that I can measure is what would seem to count for those, like me, who approach the topic more casually.

  54. In a sense, I’m in the same position as you. I can see merit in the scientific community deciding to define the term “global warming” as meaning surface warming and using something else – “global heating” – to refer to the whole system. My concern would be (similar to you I think) that – to the casual observer – the distinction would still not be obvious and so it’s not clear how this would solve the communication problems that seem to exist at the moment.

  55. BBD says:

    Ah, I see. Thanks for the clarification. Blogs is ‘orrible for discussing serious stuff, really. Although I believe Twitter might be even worse!


  56. JCF says:

    From the Lead Author of ” Overestimated global warming over the past 20 years”:

    1. Reviews
    Our commentary was reviewed by 4 anonymous peers selected by the journal and underwent 2 major revisions and one minor revision over the course of 6 months. It was also internally reviewed by 3 colleagues in my Centre. It was not solicited by the journal.

    2. Originality
    To my mind there’s a difference between what people think they know through popular discourse (which is perfectly fine), and what they actually know after weighing the evidence provided in original peer review literature (which is better). Some aspects of our commentary were known by some, and other aspects were known by few or none.

    3. Uncertainty
    Several sources of uncertainty in several contexts are considered in our commentary. These a laid out in detail in the Supplementary Information file that accompanies our commentary. Our specific estimate of the observed GMST trend and uncertainty for the period 1998-2012 is based on monthly-mean data and takes into account serial correlation (as described in my co-authors book titled “Statistical Analysis in Climate Research”). I can’t vouch for the Skeptical Science Trend Calculator, but I do note that with it one obtains identical trends and uncertainties regardless of whether monthly-averaged or running-averaged data is used.

    4. Cherry-picking
    This is not issue with our commentary having considered all start years from 1980 to 1998, and having explicitly accounted for several known signals of natural climate variability (e.g. ENSO and volcanic eruptions).

    5. Global warming
    On second thought perhaps we should have titled our commentary “Overestimated global surface warming over the past 20 years”, although perfection can only be an aspiration.

    6. Spatial coverage
    The models were sampled only where observations exist.

  57. Sou says:

    If you want to know if it was peer reviewed, just send an email to the editor. I did that once with a paper that was in a category that may or may not have been peer reviewed and got a response within hours. I told them I write a blog, which may have helped. (In that case I was told that the paper was peer reviewed.)

  58. t_p_hamilton says:

    Natural climate variability has a huge effect. Note that for 1993-2012 (20 years) the rate is 0.15 degrees C per decade, only 0.05 degrees C per decade for the 15 year period. However if you look at the 20 year observations (red, 0.15), they are near the middle of the 20 year model distribution.

  59. Mircea, the consensus opinion in climatology is that the global mean temperature has been increasing since the industrial revolution and that humans are the main cause of this. Even if the atmospheric surface temperature (you should be careful what you write on this blog 🙂 ) stays at the current high level for several more decades, that statement remains true. The temperature will have to have an unexplained drop towards previous levels in the coming decades before one would conclude that additional CO2 and other greenhouse gasses does not cause warming.

    Depending on what the causes of the pause are, it may influence our projections. Let’s see what the science will tell us the coming years. We have some first indications, but finding the cause of such a minor fluctuation of one or two tenth of a degree, will be difficult.

    The projections are not part of any consensus. There is much uncertainty there. And uncertainty can go both ways, I may have to add. I am sure we will see some surprises, such as the current unexpected rapid decline of the Arctic ice cap or consequences we simply did not think of.

    As someone working on the quality of station data, I am naturally wondering whether the increased used of ventilated automatic weather stations could explain part of an explanation of the pause. Will be a large project to find out, unfortunately.

  60. andrew adams says:

    I kind of agree with Victor here. Obviously there’s no “official” definition of “Global Warming” and logically it makes sense to refer to the earth as a whole rather than just a particular part of it, but in general discussions in the past around the subject have tended to concentrate on the surface temperature, whether it’s current temperature trends, the future (ie the IPCC global temperature projections) or the past (paleo reconstructions).
    So when people point out that surface temperatures have been relatively flat in recent years it’s fair to point out that this does not mean that the earth has stopped warming but it’s also right IMHO to accept that the warming has not manifested itself as anticipated, otherwise it can appear that we are just moving the goalposts.
    And while I don’t see any obvious reason to think that surface warming won’t pick up again in the near future I guess it is possible that our understanding of where all that extra energy in the climate system will end up may be lacking and we will see more going into the oceans in the long term, with correspondingly less impact on surface temperatures, and that will obviously have an impact on the likely impacts.
    Having said that, it would also be fair to point out that the combined land/ocean temperature record is a bit of a mish-mash (to use the technical scientific expression) itself and that land surface temperatures have actually continued to rise at a faster rate, which is hardly a casue for comfort.

  61. andrew adams says:

    but it’s also right IMHO to accept that the warming has not manifested itself as anticipated

    Sorry, I meant to add a caveat here to the effect that it’s also right to point out that over such short periods this is not particularly meaningful.

  62. Thanks for the comment and clarifications. I appreciate you taking the time to make a comment, and it’s certainly clarified some of my confusion.

    As far as the uncertainties go what confused me a little is that a particular claim being bandied around in the media and on various blogs is that the HadCRUT4 (and other anomaly datasets) has a trend since 1998 that is not statistically significant (i.e., the 2σ errors are larger in magnitude than the trend). From your figure 1 it seems that you’ve managed to determine trends that are statistically significant for this time period. Is there an easy way to explain this difference?

    As far as cherry-picking goes, I’m happy to concede that I didn’t maybe give that as much thought as I should have (I don’t have the advantage of multiple stages of peer-review :-)). I hadn’t appreciated that your Figure 2 (as Tom Curtis has already pointed out) covers the period from 1980 onwards and considers 15 and 20 year trends.

    I certainly agree that distinguishing between global warming global surface warming would be valuable but I also appreciate that the terminology has been in use for quite some time and so it may not necessarily be obvious that such a distinction should be made. I’ve been looking at this from the outside and seen how papers can often be mis-interpreted and so can see the value in making the distinction, but this is more to avoid confusion with those who wish to sow confusion, than because I think the papers are making some kind of fundamental mistake.

  63. Mircea says:

    “I’m slightly confused about your comment with regards to the 97% paper.” – My comment is not clear on this and now that I rethink about it actually is wrong. Thank you for your patience!

  64. Thanks Andrew. Although I’ve been critical of the use of “global warming” when used to refer only to surface warming, I can see why it’s been used in that way and why we might choose to continue to do so. It’s really just about defining the terminology and making people understand the distinction between surface warming and overall warming. I completely agree that this shouldn’t be used to hide that surface warming has not occurred as expected. Having said that, overall warming has continued (as far as I’m aware) as expected and so it is fair to claim that at a fundamental level the models are still correct. They may not be correctly modelling how the energy is distributed throughout the system, but they are modelling how it’s increasing overall (at least I think this is roughly correct).

    I suspect we mostly agree that whatever terms we choose to use, the important thing is to understand all that we can about what’s happening without getting too pedantic about terminology (although I will acknowledge an irony in my saying this after writing this particular post :-))

  65. I’m a little confused by your comment. Are you referring to the figure I included here? For the period 1993-2012 the observations still seem quite different to the model trends, or am I missing something obvious?

  66. rumor has that Francis Zwiers is an old friend of Richard Tol

  67. A rumour you could presumably confirm if you chose to do so 🙂

  68. wotts, you make as though you disagree with me and yet, spread out over several ‘yes yes’ and nods to your buddies on this thread, you agree with several points.

    The ‘global’ in global warming does not refer to parts of the earth. It refers to involving all portions of the globe. If you try the bait-and-switch, just as Chris already has in his comment above, where you try to say: “Well, we always meant different parts of the earth, deep sea, mountaintop, etc and it was only the skeptics who expected the surface to warm up”, and interpret surface warming, surface-no change and surface cooling as evidence of global warming, there would be few weasely defenders of the orthodox position who could beat that. It is impossible to have a sane discussion when global surface temperature can go up, remain flat, or go down for significant periods of time in anthropogenic global warming.

    Imagine however if CO2 had precisely such an effect overall. We know the effect of CO2 is not evident at daily scales. What if it were swamped by system variability at the decadal scale and multidecadal scale as well, as it appears to be the case now. It wouldn’t mean that it has no effect. On the contrary, it would mean CO2 is a powerful driver capable of producing inexorable change, but its short-time scale effects would be small. In other words, the so-called ‘sensitivity’ would be low. CO2 cannot dominate or overpower other forces and swamp out their effects. But its own long term effects will nevertheless be present. CO2 cannot force a rate change in the system: the warming rates observed in the first half of the 20th century will be the same in the second, and will probably be the same when the next bout of warming comes along.

    The ocean heat story originates and evolves in response to the question: “well, why isn’t the surface warming up?’ Work is done by scientists to figure out the answer. If “global warming” the definition included such phenomena as deep ocean heat by virtue of the deep ocean being a part of the ‘globe’, why would anyone even study it?

    One of these days we’ll know who the real deniers are.

  69. To be honest, Shub, I’m not really following what you’re trying to get it with your comment. Indeed I have disagreed with you, but that’s because I’ve disagreed with you. I agree with others because I agree with them. I can’t really do much about that.

    Can you please explain this part of your comment

    The ‘global’ in global warming does not refer to parts of the earth. It refers to involving all portions of the globe.

    That is essentially what I’ve been suggesting all the time. We should consider everything (oceans, polar ice, land, atmosphere) rather than simply one portion of the climate system (surface). If that’s what you’re also suggesting, then I indeed agree with you. If that’s not what you’re suggesting, can you clarify?

  70. JCF says:

    The uncertainty that you see here, 0.05 +- 0.08 C per decade, and the uncertainty that you see in the red-hatching in our Figure 1 represent different uncertainties. The former is what you find if you take one realization of the observations and estimate it’s trend and uncertainty taking into account serial correlation. With these numbers we conclude that the observed trend over this period is not significantly different from zero. The latter is what you find if you compute trends for each of the 100 observational realizations and plot their 5-95% range. These numbers tell you that there is some “observational” uncertainty in the observed trend but it is small. I hope this helps.

  71. “wotts, you make as though you disagree with me and yet, spread out over several ‘yes yes’ and nods to your buddies on this thread, you agree with several points.”

    I hate to have to admit it, but on the topic that the term “global warming” is typically used to signify the warming of the surface, I agree with Shub Niggurath.

    That people respond respectfully when I write that and get annoyed when Shub Niggurath writes that, is not fair, but a fact of life. The way you formulate things, the arguments you use, and your reputation are important factors in human communication.

    This makes it ever weirder that WUWT and Co. so casually destroy their reputations by spreading misinformation every day.

  72. Thanks, I think that is roughly what I had thought might be the case, but am still uncertain as to what this means. Does what you’ve done imply that you can constrain the trend more accurately than a single realisation would indicate, or is it simply a mechanism you’ve used so as to compare the model realisations with observational realisations?

  73. Okay, let’s go back a few steps then. If what Shub means is that global warming is typically used to refer to surface warming, but that there is still an overall warming of the climate system despite the “slowdown” in surface warming, then I will openly acknowledge that I have treated Shub unfairly in this discussion.

    Having said that, in all the occasions where I have acknowledged what others have said it has been in discussions in which they have been willing to make the distinction between overall warming and surface warming (even if they do refer to surface warming as global warming). So Shub could have put some effort into making this distinction, and the discussion would have gone much more smoothly.

  74. BBD says:

    What if it were swamped by system variability at the decadal scale and multidecadal scale as well, as it appears to be the case now.

    But it isn’t “swamped”. The combined effects of all the putative cooling influences have merely slowed down the rate of surface warming. The surface is not cooling. OHC continues to rise.

    it would mean CO2 is a powerful driver capable of producing inexorable change, but its short-time scale effects would be small. In other words, the so-called ‘sensitivity’ would be low.

    No. It would mean that natural variability periodically overprints the long-term forced trend. Effects on TCR probably minimal, on ECS likewise.

    CO2 cannot force a rate change in the system: the warming rates observed in the first half of the 20th century will be the same in the second, and will probably be the same when the next bout of warming comes along.

    Obviously wrong at a very basic level. The radiative forcing from an increasing atmospheric fraction of CO2 is itself increasing over time. The forced trend will increase over time.

    One of these days we’ll know who the real deniers are.

    That is already evident. See above.

  75. wotts, I know you’ve been pushing this for a while, but ‘global warming’ is not the ‘increase of energy in the system.

    That is formally the same statement as global warming designates warming of the surface.

    But it set a completely other tone. I already wrote above that I would expect a scientist that talks about the pause to acknowledge the work on natural variability and the increase in the heat content. That part was also missing here and it is natural that people respond unfriendly to such an unbalanced statement, even if formally not wrong.

  76. My comment landed at the wrong place. Here it is again.

    wotts, I know you’ve been pushing this for a while, but ‘global warming’ is not the ‘increase of energy in the system.

    That is formally the same statement as global warming designates warming of the surface.

    But it set a completely other tone. I already wrote above that I would expect a scientist that talks about the pause to acknowledge the work on natural variability and the increase in the heat content. That part was also missing here and it is natural that people respond unfriendly to such an unbalanced statement, even if formally not wrong.

  77. Indeed, at face value the statement is the same as those made by others, so formally not wrong (or, at least, consistent with how some define it). It was indeed the tone I responded to, so if Shub would like to clarify I’d be more than happy to accept that I interpreted the initial comment unfairly.

  78. I responded too soon 🙂

  79. Paul says:

    Re: What is global warming
    If I am understanding the basic argument here, I believe it is:
    1) Satellites show that more energy is entering the earths atmosphere than is leaving
    2) That energy imbalance must be producing an increase in potential or kinetic energy of the earth system.
    3) There don’t seem to be significant potential energy stores that are currently building up (coal deposits, oil deposits, etc.) that could be acting to absorb this energy imbalance (in fact if anything we are converting earlier potential energy stores back into kinetic eneryg) so the vast majority of this energy imbalance must be increasing the kinetic energy of the earth system.
    4) General increases in kinetic energy in a system are measured as increases in temperature.
    5) Therefore we conclude that the globe must be warming even if not all parts are in equilibrium with the average.
    Based on this analysis, regardless of what any single measure is reporting, unless one of these previous statements is proven to be wrong we must conclude that global warming is increasing in direct relationship to the measured energy imbalance.

  80. Essentially yes. I would add that ocean heat content data also tells us that the total energy is increasing (I also believe that the errors in the measured TOA energy imbalance are constrained using ocean heat content data). There are some subtleties to this discussion that I myself am only starting to learn. There are some arguments for why it is acceptable to use the term “global warming” when referring to surface warming. I think this is partly because this is the context in which it has often been used and partly because surface warming is (in some sense) what’s of interest to us as humans.

    That, however, doesn’t change the fundamental point that a “slowdown” in warming in one part of the system does not necessarily indicate that overall warming has stopped. So I agree with your final comment; there is indeed evidence to suggest that overall global warming continues and that it is consistent with the measured energy imbalance

  81. I understand Shub’s question, and yet I did not predict it.

    Fancy that.

  82. JCF says:

    Perhaps we can look at in this way:

    We have 100 hundred realizations of the HadCRUT4 observations, and for each of those realizations we can compute a trend and its 95% confidence interval. All of those 100 trends, but one, are no different than zero when judged at this significance level. This though is not the focus of our paper. Rather, the focus of our paper is to test the null hypothesis that the model-average trend is equal to the observed trend, and this is where the individual observed (all 100 of them) and simulated realizations (all 117 of them) come into play.

  83. ‘Global’ refers to all surface, NH vs SH, Europe vs Asia vs North America versus the whole globe.’Global’ refers to ‘everywhere’, not ‘all parts of the earth.’

    This is a simple historical fact of the evolution of the term and the global is used exactly in the same sense in other areas I can remember as examples. Even in lay usage, ‘Global’ refers to the whole world, as opposed to ‘focal’, for example, which refers to limited, fixed areas. The term has a clear origin by its use in the environmental sciences: you can trace its evolution in books and papers. You don’t have believe or disbelieve me because I am ‘Shub Niggurath’, etc. Just look at the literature yourself.

    In global warming from CO2, per the orthodox theory, ‘energy’ may increase in the ‘system’, and it may hide in different parts of the earth, but that’s not what’s captured, or meant by the term ‘global warming’.

    Interestingly enough, I found this on one of your favourite sources: Skepticalscience.

    “Global warming involves warming of the whole globe (the clue is in the name), but it does not necessarily affect every part of the globe at the same rate”

  84. Sure, but you’ve added the word “surface” into your description. Let’s go back a step though. There are those who argue that it is reasonable to use the term “global warming” to refer to surface warming. Let’s accept that this is a reasonable use of the term (I’m not suggesting that I necessarily agree, but I can see that it has been used in this way). This then means that the term “global warming” does not refer to the entire climate system. So if surface warming has stalled and we then say “global warming has stalled”, that does not mean that heat has stopped accumulating in the system. The evidence indicates that there is still a TOA energy imbalance and, hence, that the ocean heat content continues to rise.

    Hence, if we choose to use the term “global warming” to refer to surface warming, the statement “global warming has stalled” simply means surface warming has stalled and does not indicate that greenhouse gases have stopped acting to accumulate heat in the climate system. In my opinion, using the term “global warming” in this way then requires that we make this distinction clear. Do you agree with this or not?

  85. Paul says:

    Thanks for the reply. Like you I am a professional scientist well outside the area of discussion. Despite your attempts to clarify things, I am clearly missing the reason why anyone would use the term “global warming” to mean something other than the increase in system kinetic energy, Obviously there are some historical reasons this is being done, but I would think for professionals lack of clarity would be a problem, But perhaps they all know what each other is talking about so they don’t even notice the lack of clarity. It seems clear, however, that this lack of clarity is sewing confusion outside the professional ranks.
    Also I am confused as to why global air surface warming is “what’s of interest to us as humans” as opposed to what I will call true global warming. I had thought that thermal expansion of the oceans was one of the bigger problems with global warming, not just that I might have to run my air conditioner longer. Indeed, I would have thought that the effects of warming on climate was largely driven by ocean warming rather than surface air temperatures. But, perhaps I am missing something again.
    P.S. I have enjoyed your blog quite a bit. Thanks for putting in all the work. I wouldn’t be able to keep my job if I tried to do what you have been able to do.

  86. Wotts writes: “The paper suggests that for the period 1998-2012, the observed trend is 0.05 +- 0.08°C per decade. The Skeptical Science Trend Calculator gives 0.052 +- 0.155°C per decade. Both of these are meant to be 95% confidence intervals, so why is the value in this paper half that from the Skeptical Science Trend Calculator?”

    The discrepancy may be even larger. The SkS Trend Calculator states:

    “Data: (For definitions and equations see the methods section of Foster and Rahmstorf, 2011)”

    The method of Foster and Rahmstorf removes the ENSO signal from the global mean temperature and thus finds much clearer trends and smaller uncertainty intervals.

    I do not have access to Nature Climate Change. Does “Overestimated global warming over the past 20 years” also subtract the ENSO signal? Otherwise the difference in uncertainty estimates would be even larger.

  87. Thanks, I’m going to have to give this a little more thought. It’s not clear to me how you can have 100 realisations of the HadCRUT4 observations but that’s probably just me not really understanding how the observational trends are computed.

  88. BBD says:

    Shub, you are quibbling to distract. Let’s break this down:

    – Energy is accumulating in the climate system as a consequence of increased RF from GHGs, mainly CO2. This is evident from the observed and ongoing increase in OHC 0 – 2000m.

    – The term “global warming” is arguably synonymous with global surface temperature/tropospheric temperature increase, particularly in informal usage.

    – This is a matter of semantics and does not affect the physics underpinning the GHE or the observed increase in OHC during the recent hiatus in surface/tropospheric warming.

    – Therefore arguing about it is somewhat besides the point.

    Can we agree these statements?

  89. BBD says:

    Sorry Wotts. Crossed again.

  90. I don’t think that the paper does. According to the paper the models include natural variability associated with ENSO cycles. You’ve maybe noticed that the lead author has commented here to clarify certain things. Something that has confused me is that the observed trends are determined by 100 reconstructions of the HadCRUT4 dataset. I don’t really understand what this means. Could this effectively remove the ENSO signal and hence produce a smaller uncertainty?

  91. Paul, I am working on the quality of the surface climate stations. So in the literature I read there is no confusion. Global warming refers to an increase of the surface temperature. For communication to the public and for broad reviews, such as the IPCC reports, it may actually make sense to have more terms to make sure that everyone knows in which way a term is used.

    The expansion of the oceans, that is sea level rise, is just one of the impacts of global warming. Even some contributions to sea level rise such as the melting of glaciers depend on the surface temperature.

    Changes to land eco-system, including agricultural systems and vector borne deceases, depend on the land temperatures. Not everyone can afford a house with air-conditioning. 😉 Heat waves can cost the lives of thousands, partially because people do not realise how dangerous they are.

    And for the (land) surface temperature we have a much longer record and can thus estimate the statistical significance of changes much more reliably. Because of the dense station network, we can homogenize station temperature data much better as ocean data. Maybe it is my bias, but I trust trends in the surface temperature a lot more.

    These would all be reasons to find the land temperature also important and not just the heat content of the climate system or the ocean. I would not want to do away with a word for the increase of the surface temperature and would prefer to keep global warming for this based on convention. Then it might be a good idea to have a new word to the increase of the heat content of either the ocean or the full climate system. Above I proposed “global heating”, but there may be better options.

  92. ” Despite your attempts to clarify things, I am clearly missing the reason why anyone would use the term “global warming” to mean something other than the increase in system kinetic energy”

    Look at the usage of the term. Don’t impose your self-intuited meaning onto the term and read things into it. It is as simple. Use the term for what it was used for, instead of retrospectively adding meanings to it.

  93. I noticed. Without the paper it is hard for me to chime in. As I am not anonymous, I would hate to comment about colleagues without being sure.

    I imagine you could compute the trends in 100 stations or grid points of the HadCRUT4 dataset. However, they would not be independent realisations. Even if the correlation of the daily or yearly mean temperatures would not be high, the larger the averaging scale the stronger the correlations become. Thus the trend estimates, even over just 20 years, would not be independent.

  94. Paul, like you I had assumed that global warming referred to the whole system. It’s also clear that some do use it in this way (see the video I included in the previous post). There are, however, commenters here who are more experienced than me and who seem to accept that global warming can be used when referring to surface warming. However, most accept that it’s still important to distinguish between surface warming and overall warming. I must admit that I’m still not convinced that global warming should be used when referring to surface warming but it’s clear that some do use it this way.

    When it comes to surface warming and us, I think the suggestion was simply that we are more aware of the temperature of the surface than anything else. I don’t think anyone is suggesting, however, that ocean warming is not important.

    I’m pleased you enjoy the blog. Are you able to elaborate on why you wouldn’t be able to keep your job if you did this. I’m assuming that I can do this without risking my job, but I haven’t actually checked.

  95. JCF says:

    This from the Hadley Centre website:

    “The dataset is presented as an ensemble of 100 dataset realisations that sample the distribution of uncertainty in the global temperature record given current understanding of non-climatic factors affecting near-surface temperature observations. This ensemble approach allows characterisation of spatially and temporally correlated uncertainty structure in the gridded data, for example arising from uncertainties in methods used to account for changes in SST measurement practices, homogenisation of land station records and the potential impacts of urbanisation.”

  96. I see, thanks. That clarifies that. Learn something new every day 🙂

  97. Paul says:

    Re: Victor and Shub
    My confusion on the issue has little to do with the relative value of knowing surface temperatures to understand many of the effect of “global warming”, and certainly I may be wrong about the importance of the ocean temperatures relative to land surface temps for any specific effect of “global warming.” As I said its not my area of research. My confusion has to do with the correct term that should be used when referring to ” the increase in kinetic energy of the entire earth system” if it is not going to be “global warming” then what is the correct term to use. If we don’t have a useful term where everyone knows what we are talking about then things certainly do get confusing. Also I should add that the previous post on this blog was “There’s been no pause in global warming!” so I am certainly not alone.

  98. Paul says:

    Re: Are you able to elaborate on why you wouldn’t be able to keep your job if you did this. I’m assuming that I can do this without risking my job, but I haven’t actually checked.

    I am referring to the evident time commitment required to assimilate what is going on in a completely different field, as well as the para-field (all the associated commentary) and then make reasoned comments while also respond in a timely manner to your own blog comments. In my own life, between keeping up with the literature, writing grants, writing papers, teaching, serving on committees, and raising a family seems like enough. Indeed all these time commitments makes even following a handful of blogs and posting a few comments now and then hard enough.

  99. I see, yes that is a good point. I have rather been committing a little bit too much time to this. I’m busy preparing lecture notes and trying to write a chapter of a book, so this is a nice distraction. I suspect that once the semester starts in earnest, I may have to cut back quite substantially 🙂

  100. dbostrom says:

    Yet again, what’s said is less informative than by whom, and when. Of late there seems to finally be a dawning recognition that describing global warming to the public purely as a surface temperature phenomenon is a public communications error. Those keen on fostering error would prefer that this particular one not be corrected because it’s been so useful, let alone a gift. Hence the appearance here and semantic/epistimological experimentation by the fecund black goat.

    Prototyping and testing.

  101. “Also I should add that the previous post on this blog was “There’s been no pause in global warming!” so I am certainly not alone.”

    Yes, our civil local host has this habit. 🙂 I have the feeling that this attempt to change the meaning of the term “global warming” is rather recent. If only because accurate measurements of the ocean heat content are only available since a few years.

    This indeed now causes a confusion.

    I admit that it might be nice to have a word for an increases in the heat content in the climate system. When our host made the above claim, I expect that he showed a figure with the increase in the ocean heat content. Thus until we have a better term, we could use the title: “These’s been no pause in the increase of the ocean heat content”. A little less sexy, I am afraid.

  102. BBD says:


    One thing:

    the fecund black goat

    Since not everyone will get the Lovecraftian subtext, here’s some background.


  103. Tom Curtis says:

    As I understand it, the SkS trend calculator always uses monthly values in calculating error. The adjustable length of the moving average is only for the display graphed with each calculation (the monthly values also being shown). The major difference may be that the SkS trend calculator follows Foster and Rahmstorf (2011) in using an ARMA (1,1) model of autocorrelation rather than the more typical AR(n) model. I do not know how much of the difference in confidence intervals that accounts for.

    I am more interested in the narrow confidence intervals for the CMIP5 models, quoted as +/-0.03 C for the 1998-2012 trend above. In the graphs presented above, each bin of CMIP5 model trends is approximately 0.03 C in width. Therefore with a +/-0.03 C confidence interval, 95% of results should lie within 2 bins of the the central value of 0.21 C/decade. That is clearly not the case. How do the authors reconcile such a narrow confidence interval with so large a scatter of model trends?

  104. Tom Curtis says:

    JCF, thankyou for taking the time to clarify here. I note, however, that you do not comment on your very low ENSO correction relative to that of Foster and Rahmstorf (2011). Is there any reason you arrived at so low a value for that correction, considering the near record size of both the 97/98 El Nino and the 2008 La Nina?

  105. Tom Curtis says:

    Victor, the trend as calculated for Foster and Rahmstorf HadCRUT3 data from Jan 1998-Dec 2012 is 0.176 +/- 0.099 C/decade (2 sigma confidence interval). Using the “raw: data, ie, the data from the Hadley center as adjusted by them for UHI etc, it is 0.071 +/- 0.344 C/decade. You can find this in the second SkS trend caculator (linked from the page describing the main calculator). It does not allow calculation of HadCRUT4 trends. The main calculator uses unadjusted HadCRUT4 data.

    The discrepancy between the paper and the calculator is probably due to the use of different noise models. It is possible also that Fyfe et al quote only 1 sigma confidence intervals (otherwise the discrepancy between their narrow confidence interval for the models and the spread of trends in the models becomes even harder to explain). It may also derive from Fyfe et al quoting a confidence interval derived from p values rather than directly from the standard deviation.

  106. Tom Curtis says:

    I think it is more accurate to say they used the full dataset, but “bootstrapped” the adjustments for biases in the data. Of the land data, they say,

    “Given distributions of likely measurement biases, feasible biases can be drawn from the distribution and a gridded temperature data set can be created by applying the derived bias adjustments. By repeating this procedure multiple times, drawing different bias realizations each time, an ensemble of gridded data sets is created, which together
    capture the complex spatial and temporal structure of uncertainties that arose from uncertainties in the required bias adjustments.”

    For ocean temperatures, they say:

    “The interdependencies of uncertainty in the HadSST3 data set are represented by creating multiple realizations of the data set, each using different realizations of bucket, ERI and drifting buoy bias adjustments. These bias adjustment
    realizations are created through a combination of adjustments for each measurement type, weighted by the fractions of measurements in each grid box (which are uncertain)
    obtained using each of the observation techniques. These realizations are then added to the gridded temperature anomalies to create multiple realizations of the SST data set
    representing uncertainty in the required bias adjustments. Together these realizations span the distribution of uncertainties in the bias adjustments, encoding spatial and temporal interdependencies resulting from differing geographic distributions of measurement methods and changes in the makeup of the measurement network over time.”

  107. Dang, a lot of comments on this post!

    Surface warming has traditionally been referred to as “global warming” in climate science literature. Personally I think that was obviously a mistake, and imprecise language. Now deniers tend to use that imprecision to score points (they much prefer ‘point scoring’ to actual intelligent discourse), saying ‘AH-HA! You called surface warming ‘global warming’ and now surface warming is slowed, hence you must admit that global warming has slowed!’.

    The issue is that we didn’t used to have good measurements of ocean temps/heat content, so climate scientists mainly relied on the much more accurate surface temp record. Now we do have better ocean measurements, so it makes sense to consider them. I’m no traditionalist and have no problem defining ‘global warming’ as the amount of warming happening across the whole ‘globe’ (including oceans), though I know some who consider this inaccurate because of the historical ‘definition’ of ‘global warming’.

    Personally I think climate scientists should at the very least refer to global surface warming as exactly that. Use the precise term. When you say ‘global warming’, other climate scientists know what you’re talking about, but you’re misleading everyone else.

    It’s a problem that scientists aren’t great communicators. They don’t think “how will the press interpret this?”, they just put it in terms other scientists (who are normally the folks you’d expect to be reading peer-reviewed climate papers) will understand. But that leads to misunderstandings like this.

  108. KR says:

    The SkS trend calculator (based upon the F&R 2011 paper) is described as using an ARMA(1,1) noise model (autoregressive moving average), rather higher uncertainty than the more commonly used AR(1) models.

  109. KR says:

    The more accurate, but noisier, surface temperature record… Where periods (too short for statistical significance) of low or even negative trend are only to be expected.

  110. toby52 says:

    ‘Global’ refers to all surface, NH vs SH, Europe vs Asia vs North America versus the whole globe.

    is that so? When we talk about “global warfare”, we do not exclude submarine warfare. When we talk about “global communications infrastructure”, we do not exclude submarine cables. When we talk about “global biota”, we do not exclude marine life. The energy balance at the top of the atmosphere, and the affects of ocean acidification on marine life, have always been part of the climate change discussion.

    A search for synonyms for the word “global” turned up examples like “planetary”, “earthly”, “cosmic”, “thorough”, “total”, “universal”, “comprehensive”, “general” and “exhaustive”, most of which would encompass the deep oceans if you added the words “warming” and the climate change context.

    The climate change discussion cannot be reduced to a semantic wrangle over the word “global” in “global warming”. There is a superficial connection with the surface only (ha ha!), but this is just a continuation of the inane semantic wars over words like “significance” waged by deniers in the past.

  111. Wow, what a ‘civil’ discussion. Where one side comes to discuss scientific points but at the same time gets to equate their opponents to Holocaust deniers.

  112. Who’s equated their opponents to Holocaust deniers? If I search for the term “deniers” it appears in a few places, but noone has actually accused any individual involved in this debate of being a denier (and certainly noone has used the term “Holocaust denier”). By the way, one of those who’s used the term, Shub, is you. Please develop some self-awareness, because this really is getting tiresome.

  113. More of what I found at skepticalscience:

    “It’s called “global warming” for a reason, and one of the principal reasons is that climate change takes into account not only the approximately 29 percent of the Earth’s surface that consists of land, our continents, but also the 71 percent comprised of oceans.”

    How interesting.

  114. Shub, as many have acknowledged (and which I even acknowledged in my post) the term “global warming” has indeed been used to refer to surface warming. So, there’s an acknowledgement for you. Global warming has been used to refer to surface warming. However, in using it in this way the term then fails to incorporate all the other anthropogenic warming (arctic ice, ocean heat content) that is taking place. So I don’t really care what term we use but implying that AGW has stopped because surface warming has stalled (because the term global warming has been used to refer to surface warming only) is wrong. Do you disagree?

  115. “By the way, one of those who’s used the term, Shub, is you.”

    Yeah, I used it against no one person in particular either.

  116. I know, I wasn’t claiming that you did. I don’t think anyone else aimed the term at anyone in particular (or, at least, I can’t find where if someone did). Hence my suggestion that you develop some self-awareness.

  117. BBD says:

    Instead of sniping away from the shadows, why not answer direct questions?

    I am still waiting for a response to these.

  118. I don’t disagree. My point is clear: you don’t improve or evolve your understanding (or decision!) on how ‘global warming’ should be characterized and then declare all that was already inherent or implied in the phrase.

    And anyway, the evidence for deep ocean heating etc is quite sketchy. You don’t want to base your case on it. Moreover, if you switch to ocean heating and the surface starts going up again, you’d have to switch back to the instrumental record and that would be embarrassing.

  119. BBD says:

    And anyway, the evidence for deep ocean heating etc is quite sketchy. You don’t want to base your case on it.

    Unreferenced argument by assertion. Also a misrepresentation bordering on dishonesty, Shub. Tut, tut!

  120. BBD says:

    I don’t disagree. My point is clear: you don’t improve or evolve your understanding (or decision!) on how ‘global warming’ should be characterized

    I think this is quibbling to misdirect.

    Still waiting, Shub…

  121. Tom Curtis says:

    Again with the tiresome ploy of pretending that any use of the word “denier” is a subtle comparison to “holocaust deniers”. As it happens, in the English language for most of its history, (and for most European languages over the last 1600 years) the term “denier” or its equivalent was most frequently used of Peter the denier, or of denier’s of Jesus in general. Indeed, only in the late 1980’s did “Holocaust denier” become a more frequent usage, and “Peter the denier” continues to be used more frequently than “holocaust denier”.

    If Shub’s linguistic absurdity had any merit, then the long usage of the phrase “Peter the denier” would have fixed the meaning of “denier” simpliciter to mean “like Saint Peter”, or at worst “not a Christian”. These of course would not cause sufficient offense. Consequently deniers seek to trade on the memory of the Holocaust victims by making the false association between “AGW denier” and “Holocaust denier” so that they will not be described accurately.

  122. Shub, well at least we agree on something. However, you don’t need to switch back again. The ocean heat content data is reasonably new and is clearly a better indicator (and more representative) of overall warming. Why would we “switch-back” to surface warming in the future? If we want to understand overall warming and the long-term trends then all the data would be considered. That’s not to say that surface temperatures aren’t important, just that there’s no reason why would we suddenly start ignoring data in the future.

  123. Pingback: “Global warming” vs “Global heating” | Wotts Up With That Blog

Comments are closed.