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Global Warming Since 1997 Underestimated by Half

Filed under: — stefan @ 13 November 2013

A new study by British and Canadian researchers shows that the global temperature rise of the past 15 years has been greatly underestimated. The reason is the data gaps in the weather station network, especially in the Arctic. If you fill these data gaps using satellite measurements, the warming trend is more than doubled in the widely used HadCRUT4 data, and the much-discussed “warming pause” has virtually disappeared.

Obtaining the globally averaged temperature from weather station data has a well-known problem: there are some gaps in the data, especially in the polar regions and in parts of Africa. As long as the regions not covered warm up like the rest of the world, that does not change the global temperature curve.

But errors in global temperature trends arise if these areas evolve differently from the global mean. That’s been the case over the last 15 years in the Arctic, which has warmed exceptionally fast, as shown by satellite and reanalysis data and by the massive sea ice loss there. This problem was analysed for the first time by Rasmus in 2008 at RealClimate, and it was later confirmed by other authors in the scientific literature.

The “Arctic hole” is the main reason for the difference between the NASA GISS data and the other two data sets of near-surface temperature, HadCRUT and NOAA. I have always preferred the GISS data because NASA fills the data gaps by interpolation from the edges, which is certainly better than not filling them at all.

A new gap filler

Now Kevin Cowtan (University of York) and Robert Way (University of Ottawa) have developed a new method to fill the data gaps using satellite data.

It sounds obvious and simple, but it’s not. Firstly, the satellites cannot measure the near-surface temperatures but only those overhead at a certain altitude range in the troposphere. And secondly, there are a few question marks about the long-term stability of these measurements (temporal drift).

Cowtan and Way circumvent both problems by using an established geostatistical interpolation method called kriging – but they do not apply it to the temperature data itself (which would be similar to what GISS does), but to the difference between satellite and ground data. So they produce a hybrid temperature field. This consists of the surface data where they exist. But in the data gaps, it consists of satellite data that have been converted to near-surface temperatures, where the difference between the two is determined by a kriging interpolation from the edges. As this is redone for each new month, a possible drift of the satellite data is no longer an issue.

Prerequisite for success is, of course, that this difference is sufficiently smooth, i.e. has no strong small-scale structure. This can be tested on artificially generated data gaps, in places where one knows the actual surface temperature values but holds them back ​​in the calculation. Cowtan and Way perform extensive validation tests, which demonstrate that their hybrid method provides significantly better results than a normal interpolation on the surface data as done by GISS.

The surprising result

Cowtan and Way apply their method to the HadCRUT4 data, which are state-of-the-art except for their treatment of data gaps. For 1997-2012 these data show a relatively small warming trend of only 0.05 °C per decade – which has often been misleadingly called a “warming pause”. The new IPCC report writes:

Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends. As one example, the rate of warming over the past 15 years (1998–2012; 0.05 [–0.05 to +0.15] °C per decade), which begins with a strong El Niño, is smaller than the rate calculated since 1951 (1951–2012; 0.12 [0.08 to 0.14] °C per decade).

But after filling the data gaps this trend is 0.12 °C per decade and thus exactly equal to the long-term trend mentioned by the IPCC.


The corrected data (bold lines) are shown in the graph compared to the uncorrected ones (thin lines). The temperatures of the last three years have become a little warmer, the year 1998 a little cooler.

The trend of 0.12 °C is at first surprising, because one would have perhaps expected that the trend after gap filling has a value close to the GISS data, i.e. 0.08 °C per decade. Cowtan and Way also investigated that difference. It is due to the fact that NASA has not yet implemented an improvement of sea surface temperature data which was introduced last year in the HadCRUT data (that was the transition from the HadSST2 the HadSST3 data – the details can be found e.g. here and here). The authors explain this in more detail in their extensive background material. Applying the correction of ocean temperatures to the NASA data, their trend becomes 0.10 °C per decade, very close to the new optimal reconstruction.


The authors write in their introduction:

While short term trends are generally treated with a suitable level of caution by specialists in the field, they feature significantly in the public discourse on climate change.

This is all too true. A media analysis has shown that at least in the U.S., about half of all reports about the new IPCC report mention the issue of a “warming pause”, even though it plays a very minor role in the conclusions of the IPCC. Often the tenor was that the alleged “pause” raises some doubts about global warming and the warnings of the IPCC. We knew about the study of Cowtan & Way for a long time, and in the face of such media reporting it is sometimes not easy for researchers to keep such information to themselves. But I respect the attitude of the authors to only go public with their results once they’ve been published in the scientific literature. This is a good principle that I have followed with my own work as well.

The public debate about the alleged “warming pause” was misguided from the outset, because far too much was read into a cherry-picked short-term trend. Now this debate has become completely baseless, because the trend of the last 15 or 16 years is nothing unusual – even despite the record El Niño year at the beginning of the period. It is still a quarter less than the warming trend since 1980, which is 0.16 °C per decade. But that’s not surprising when one starts with an extreme El Niño and ends with persistent La Niña conditions, and is also running through a particularly deep and prolonged solar minimum in the second half. As we often said, all this is within the usual variability around the long-term global warming trend and no cause for excited over-interpretation.

263 Responses to “Global Warming Since 1997 Underestimated by Half”

  1. 101
    Hank Roberts says:

    ‘How it works’ should link to:

    Because As We All Know, The Green Party Runs the World.‎

  2. 102
    Tony Weddle says:


    Not a point by point rebuttal but I took a look, as a non-scientist. Like others, it’s hard to understand why you thought the article plausible. Here are a few points.

    as NASA GISS tries to do by infilling temperatures from stations far away with their smoothing algorithm

    Note the phrasing. Actually the NASA data set uses stations that are as close as possible (they can’t use stations that aren’t there).

    one should always be wary of trying to create data where there is none

    Eh? What exactly is the sattelite data, if not data?

    just two years ago he [Dana Nuccitelli] was trashing the UAH satellite data on SKS as “misinformation”

    Tries to rubbish Dana Nuccitelli by displaying a screen shot of part of an article by him, instead of linking to the article or just pasting from the article (which seems strange to me). There is a kind of link, but one which has to be copy and pasted, as though to deter a reader from exploring. In fact, I couldn’t find anything in the article that justifies the claim.

    There is no mention of the ways in which Cowtan and Wray have attempted to validate their method, either in Curry’s bit or Watts’ bit.

    There is no mention of the how the gaps might affect the apparent slowdown in surface temperature. So the meme that global warming has stopped continues even as they acknowledge that there are gaps – which may or may not be significant. Without a reliable way to fill the gaps, in their view, how can Curry or Watts keep spouting the pause nonsense?

    But I’m still puzzled over how you could regard the piece as plausible.

  3. 103
    Bouke says:

    Hi Steve,

    If you want to get informed on climate change, reading blogs might not be the way to go. You get to know a lot of fragments, but no coherent picture. A book by a good source will do better in that regard. I’d recommend this one, available online:

    The Discovery of Global Warming

    It’s written by a historian of science, about the development of climate science. It contains some real interesting nuggets, like that the heat-trapping properties of CO2 were first measured by the US army, in order to build heat-seeking missiles. It takes a long time to read, but fortunately it’s well written, and it gives you a good basis of the science.

    If you want to know what the debate is all about and are prepared to go to a library, this one is an eye-opener:

    Merchants of Doubt

    Again written by historians of science, this one is about the misuse of science to further political agendas, from the smoking and lung cancer link, acid rain, the ozon hole and lately climate change. Some people in the climate sceptic camp have been around denying all these problems. Unfortunately, the book itself is not available online.

    And finally, some fun:

    Caught greenhanded

    This is the definitive report on the climategate dustup from the sceptic side. It’s hilarious. Unless, of course, you are on The Team.

  4. 104
    wili says:

    This was posted on neven’s arctic ice blog under a similar story:

    from somewhere i got the idea to connect the atmospheric warming “hiatus” to the heat necessary to melt the 8000 km³ of perennial ice lost during the last 20 years or so.
    The calculations can be found here:
    What do You think of that?

    Posted by: dominik lenné | November 15, 2013 at 04:13″

    It is obviously a hugely simplified model since Arctic sea ice and the atmosphere aren’t the only two elements of the system. But are Dominik’s basic maths right for the energy balance involved?

  5. 105

    Steve: “Can somebody here respond point-by-point to Curry’s analysis (WUWT blog) of the Cowtan paper?”

    Maybe my preliminary thoughts on her comments are what you are looking for. On first reading, the her comments sounded valuable, but I start to have the feeling that on further investigation they will fall flat.

  6. 106
    Paul S says:

    #94 Robert Way – “One question, Tamino has noted that the satellite datasets tend to be affected by ENSO much more strongly than the terrestrial series. Have the authors considered this?”

    I believe that is probably related to the sensitivity of the remote sensing systems to precipitation and clouds in the atmosphere.

    There is a real reason (“real” meaning not measurement-dependent) why MSU/AMSU satellites show greater response to ENSO: The water vapor feedback response to El Nino warming enhances atmospheric temperatures more in the mid-troposphere than near the surface. The MSU/AMSU satellite channel used for TLT substantially samples in this mid-tropospheric region so it is expected that they should indicate greater response than observations at the surface. Radiosonde data sampling the same vertical space also shows this stronger ENSO response.

    However, this vertical response gradient is concentrated at lower latitudes and may even reverse in the Arctic.

  7. 107

    #89–“if the satellite data is robust enough to be usable to fill in holes in the surface data then is it not robust enough to be used and trusted in its own right?”

    It *is* used and trusted in its own right. All kinds of research has used and continues to use those data sets.

    But it is not a ‘drop in’ substitute for the instrumental record. The latter shows us something different than does the lower trop satellite data, which is spatially more diffuse (especially vertically.) Granted, the difference is ‘diluted’ somewhat by this hybridization process, but less so than if the lower trop values were dropped in directly.

    The procedure may not be perfect, but then in a perfect world we’d have thermometers all over the ice caps, wouldn’t we? If it can be shown create the best picture possible, then bring it on, I say.

  8. 108
    dne says:

    Jerry W @ #47,

    Have you not read the comments? They explain the peer review, as well as others who have commented on the expertise of the two in their fields and how it’s been of use to “fill” the gaps.

    I’m left dumbfounded when I read comments of people who acknowledge their complete lack of scientific knowledge, who then comment that they’ll check the credentials of the authors. Tell me, how are you going to do that? The fact that every respected research institute confirms the science isn’t enough, they’ll do their own “investigative” work. Did you bring your magnifying glass with you?

  9. 109
    flxible says:

    But I’m still puzzled over how you could regard the piece as plausible.

    Wattsopia peddles plausible deniability, much of what’s found there seems “plausible”, particularly if it’s a sciency-sounding piece by the likes of what’s-er-name.

  10. 110
    Hank Roberts says:

    Agreeing with Wili who points to the back-of-the-Excel-envelope calculations at that link above, I have also been wondering where all the higher amount of captured Arctic heat could be going as it goes somewhere in the climate system. Would it be expected to show a clear bump of something measurable somewhere?

    It needn’t show up right away as an increase in temperature, right? As that page points out it could show up as cold fresh water leaving the Arctic.

    If there is more hidden as melted fresh water — we don’t have great data that I know of on fresh meltwater flows from underneath the glaciers — would that show up anywhere in salinity changes? changes in overturning/sinking? Additional fresh water floating on top of seawater around where meltwater exits the glacier terminations at the ocean?

  11. 111
    tmb says:

    The paper is a really interesting piece of work. I had mistakenly assumed that that’s how the global temperature trends were already being calculated – score one for my laziness.

    But, while interesting, it’s not that consequential I don’t think. The underlying mechanism of AGW is unchanged and the heat is still being trapped. This highlights what should probably be a best practice perhaps for generating a temperature reconstruction, but a slight twitch in the warming rate doesn’t change the first principles of the story.

  12. 112
    Hank Roberts says:

    Steve — note that the real scientists here, identified as Contributors (link at top of every page) will often eventually add a response “inline” — right in the place you asked the question earlier. Watch that right hand sidebar. You have had some answers to your questions posted that way. Just in case you didn’t notice that, it’s sometimes missed.

  13. 113
    Flakmeister says:

    @Steve 74

    You can almost always judge the quality of a web site by the quality of the comments. Sure there is a lot of subtle snark here (less so at but it pales in comparison to WTFUWT :)

    Real scientists write very differently as well. They are trained to avoid weasel words and to recognize them. They are trained to spot manipulative figures, i.e. always be careful when two axis scales are present.

    When I first started “closely” following the Climate debate it was abundantly clear from the start that WUWT was not the real thing even before a closer reading of the actual articles revealed the paucity of intellectual honesty. Pielke very briefly fooled me but the comments gave it away…

  14. 114
    Esop says:

    #97 (Doug):
    You are quite right about the ”beginner”.
    I saw this coming from a mile away.
    The only thing missing from the usual ”help convince a newbie” recipe was a claim of being an engineer or a retired engineer.

  15. 115
    SecularAnimist says:

    Please stop referring to Anthony Watts, WUWT and similar purveyors of deliberate deceit as “skeptics”.

    The are not “skeptics”. They are propagandists who are paid to lie.

    Neither are their followers “skeptics”. They are, in fact, the diametric opposite of skeptics: they are gullible dupes who unquestioningly and slavishly believe whatever they are told by their “leaders”.

    Aside from granting them a respect that they do not deserve, calling them “skeptics” pollutes the English language with Orwellian gibberish.

    So please stop it.

  16. 116
    Jon says:

    @Steve (74)

    Perhaps some other responses, Victor Venema (105) for instance, will have given you some of what you want in the way of replies to some of the concerns raised at WUWT. I’d like, as a fellow non-scientist, to raise a point – you probably need to be patient and let the back and forth between the scientists sort itself out. Consider what Judith Curry wrote on her blog, reproduced at WUWT:

    “Let’s take a look at the 3 methods they use to fill in missing data, primarily in Africa, Arctic, and Antarctic.

    1. Kriging
    2. UAH satellite analyses of surface air temperature
    3. NCAR NCEP reanalysis
    The state that most of the difference in their reconstructed global average comes from the Arctic, so I focus on the Arctic (which is where I have special expertise in any event).

    First, Kriging. Kriging across land/ocean/sea ice boundaries makes no physical sense. While the paper cites Rigor et al. (2000) that shows ‘some’ correlation in winter between land and sea ice temps at up to 1000 km, I would expect no correlation in other seasons.

    Second, UAH satellite analyses. Not useful at high latitudes in the presence of temperature inversions and not useful over sea ice (which has a very complex spatially varying microwave emission signature). Hopefully John Christy will chime in on this.

    Third, re reanalyses in the Arctic. See Fig 1 from this paper, which gives you a sense of the magnitude of grid point errors for one point over an annual cycle. Some potential utility here, but reanalyses are not useful for trends owing to temporal inhomogeneities in the datasets that are assimilated.”

    Regarding use of Kriging, Dr. Curry says she “would expect no correlation in other seasons”. She doesn’t present of refer to any analysis done by herself or others to support this opinion.

    Regarding use of the UAH data, she says it’s “Not useful at high latitudes in the presence of temperature inversions and not useful over sea ice…”. Once again, no references to any evidence or any analysis she or anyone else has done to support this opinion. As Victor Venema observes on his blog, it’s a bit strange to ask John Christy to chime in to support her on this since he co-publishes the UAH data and apparently feels it is useful enough at high latitudes to be worth publishing.

    Regarding reanalyses in the Arctic, this is bizarre since by all accounts other than Dr. Curry’s, Cowtan and Way don’t use reanalysis data to infill where HADCRUT4 doesn’t have coverage. Looking at her blog post, where she quotes the abstract of the paper and various online commentary but, unlike with the other paper she discusses, doesn’t excerpt anything from the body of the paper, I can’t help getting the feeling that she wrote her blog post without actually reading the full Cowtan and Way paper.

    Now maybe I’m wrong on that last bit and she had read the paper before she dismissed it as not adding anything to our understanding of the global temperature field. In any case, the paper has only been published for a day or so so it’s understandable that at this point Dr. Curry is merely mentioning concerns she has with the methodology even if she has read the paper in full. However, as of now Cowtan and Way did a lot of data analysis in order to validate their approach and all Dr. Curry has clearly done in response is read their abstract, read some online commentary on their paper, watch their video describing their methodology and write a few paragraphs about it. She hasn’t done any number crunching to prove that kriging is useless in the Arctic or that it’s impossible to extract any useful information from UAH data at high latitudes. Based on my experience of watching her over the last couple of years, I’ll be astonished if she puts in the hard work to substantiate her expressed concerns but no doubt others will investigate further. As laypeople, we have little choice but to wait for them to do so, which is going to take time.

  17. 117
    Susan Anderson says:

    Steve response by Hank @~100

    Unfortunately, Hank muffed the link. His “How it works” was meant to link to this:

    It’s rather good on the topic, and includes this classic:

    Science is so powerful that it drags us kicking and screaming towards the truth despite our best efforts to avoid it. And it does that at least partly fueled by our pettiness and our rivalries. Science is alchemy: it turns shit into gold. Keep that in mind the next time some blogger decries the ill manners of a bunch of climate scientists under continual siege by forces with vastly deeper pockets and much louder megaphones.

    The chronic tone of frustration with the constant bringing up of WUWT is, well … chronic frustration. No matter how detailed and factual the response, the false claims keep bobbing up. Point by point rebuttals of the most recent phony logic are hard work, and they don’t change much.

    There are a few blogs that do this work, however:

    which has a specific response to this item, among others.

    Sou does some work on this too

    Some of Sou’s other posts are interesting on the subject as well.

    I know there are more, but this will do to go on with. Note these are responses, not provocations. The provocation is from WUWT, and never stops.

    If you actually read the various links provided, you will see that they provide point by point rebuttals. If you choose to show up in the top scientists’ own blog and insist that they personally answer your claims, and refuse to read the detailed responses provided for you, that says more about you than about them.

  18. 118
    Susan Anderson says:

    Hank, 100-101 – sorry about reinventing the wheel there. I see you had already corrected your link … the rest of what I had to say was for Steve.

    Perhaps the rest of you should get back to science.

  19. 119
    Ray Ladbury says:

    [edit – please try to limit the criticisms to issues that are specific to the topic at hand]

  20. 120
    wili says:

    This seems relevant to the conversation (sorry if it has already been linked–hard to see everything important through all the troll feeding):

    <discussed further and more recently here:

  21. 121
    Hank Roberts says:

    SA: how about we call’em catastrophes instead of skeptics?
    Oh, wait …

    Why not follow tradition, and call’em septics. That’s got legs.

  22. 122
    Richard Hawes says:

    Hank and Susan, re posts 100 et seq from the Rifter Article about the Green Party for Steve.
    I think you have missed the key quote, as follows with a modification:

    That’s how science works. It’s not a hippie love-in; it’s “Southern Hemisphere International Rugby, Springboks versus the All-Blacks at Port Elizabeth, the Original Home of the Punch-Up, in the rain”.
    Every time you put out a paper, the guy you pissed off at last year’s Houston conference is gonna be laying in wait.
    Every time you think you’ve made a breakthrough, that asshole supervisor who told you you needed more data will be standing ready to shoot it down.
    You want to know how the Human Genome Project finished so far ahead of schedule?
    Because it was the Human Genome projects, two competing teams locked in bitter rivalry, one led by J. Craig Venter, one by Francis Collins — and from what I hear, those guys did not like each other at all.

    This is how it works: you put your model out there in the coliseum, and a bunch of guys in white coats kick the shit out of it. If it’s still alive when the dust clears, your brainchild receives conditional acceptance. It does not get rejected. This time.

    I’m re-reading James Hansen’s “Storms of my Grandchildren”. He was too much of a gentleman with certain parties, and not enough of a Colin Meads or a Sebastien Chabal.
    Or a Thomas Huxley dealing with Soapy Sam Wilberforce with one deadly reposte.

  23. 123
    Chris Colose says:

    This is an interesting paper but I think a lot of the online discussion that this “issue” is not longer existent is misleading.

    The one point I think Judith Curry gets right is that the key issue is that the observed global warming trend over the last 15 years is still at the lower end of the CMIP5 historical ensemble range, and probably at the high end of the ensemble for the previous 15-year interval ending in 1998 (the figure from Ed Hawkins masks out the model data in comparison to HadCRUT4, and this general picture is true even if you look at the GISTEMP dataset, or the entire HAdCRUT4 100-member ensemble, and I don’t think too sensitive to whether you look at the 14 or 16 year trend or whatever). This is still sufficiently interesting to be thinking about whether or not the CMIP5 forcings are correct, the structure of ocean heat uptake, the spatial-temporal pattern of the hiatus (e.g., primarily a DJF phenomena, largely a Eurasian signal). There’s a lot of explanations surrounding the hiatus and they shouldn’t be seen as mutually exclusive, but it’s emphatically not a “non-issue” even if probably has little to do with broader questions of anthropogenic attribution or climate sensitivity.

  24. 124
    wili says:

    I’m glad to see the link to an attempt at a rough calculation of the heat balance met with approval by no less than hank. However, Chris Reynolds at neven’s forums has pointed out some problems with the assumptions there.


    (I learn a lot from watching my betters work through these things.)

  25. 125
    Steve says:

    Hi again everybody,

    Thanks to many of you who provided posts that were helpful to me, climate newbie. I found particularly good the discussion at these two blogs:

    There is only one thing that is nagging me. Maybe somebody can clarify. The WUWT blog, and I think Curry, say that the satellite data over the poles is not reliable. Watts gives a picture of the satellites’ trajectory implying that they kind of skirt the poles.

    It would seem that the validation methods of Crowtan and Way, using held-out data for other regions, might be suspect if those regions have reliable satellite data but the poles don’t.

    So, is the satellite data at the poles reliable enough to have been used in this study? (Presumably it is, because presumably these guys know what they are doing. But, it was a point raised in the skeptic blogs that I don’t think I have seen addressed).


  26. 126
    Peter Smith says:

    What a fascinating thread!

    I had a touch of the “but-but-but”s at one point there, but it should be preserved as an example of how to respond to difficult blog comments.

    Thanks everybody.

    [ Disclosure – I *am* a retired engineer :( ]

  27. 127
    Hank Roberts says:

    Steve, if you want to read a bit, there’s a site that’s reliably good on the basics– you have to set up a free account to look at it.

    Free, interactive, online training on a wide range of topics in meteorology, climatology, hydrology, oceanography, environmental science …

    Among much else you’ll find a good thorough explanation of how polar orbits work, why there’s a “hole” at the poles, what the “footprints” are and so forth. The relevant page is
    An animation showing that is at

  28. 128
    Hank Roberts says:

    Oh, and if you want to ‘oogle around, you could do worse than to start from this search, add additional search terms and remove others:

    Among much else, for example, remember the satellite’s data gives, after it’s worked with, different temperatures for different levels of the atmosphere and ground/ocean, for example.

    Kind of like taking one of those fancy multi-layered multi-colored drinks with a little umbrella in it, and a straw, and trying to get a taste of each layer and identify it.

    If you want just one page — this one covers it all:

    Why study the uncertainty?

    Without realistic uncertainty estimates we are not doing science!
    In the past, numerous conclusions have been drawn from MSU/AMSU data with little regard to the long term uncertainty in the data.
    Most previous error analyses for MSU/AMSU data sets have focused on decadal-scale trends in global-scale means, while in contrast, many applications are focused on shorter time scales and smaller spatial scales.
    Here we describe a comprehensive analysis of the uncertainty in the RSS MSU/AMSU products. The results can be used to evaluate the estimated uncertainty on all relevant temporal and spatial scales.


    Our MSU/AMSU products use data from 14 different satellites. The data need to be intercalibrated before being merged together. This is a complex process …

    … Available Uncertainty Information and Recommendations

    We have constructed a 100 realization uncertainty ensemble for each of the MSU/AMSU products we produce…. available in netCDF, with exactly the same form as the baseline temperature data. We recommend that researchers evalutate the uncertainty in any results they obtain using our MSU/AMSU data by re-running their analysis using each member of the uncertainty ensemble, and then evaluating the spread in the distribution of results obtained.

    Amateur recommendations, mind ya. I’m not a scientist. Others will have other suggestions.

  29. 129
    patrick says:

    Kevin Cowtan: “Like many scientists, I’m an obsessive problem solver. Sometimes you see a problem and think ‘That’s mine, I can make a contribution here.”

    And: “No difficult scientific problem is ever solved in a single paper. I don’t expect our paper to be the last word on this, but I hope we have advanced the discussion.”

    See the Guardian online: ClimateConsensus – The 97%, Abraham/Nuticellli on this topic, with animated version of data graphic in this post, narrated by Kevin Cowtan. Same animation is at SkepticalScience post on this topic, as well as on YouTube.

  30. 130
    patrick says:

    #25 “With the amount of open data available for anyone to analyse, this is not such a stretch.”

    Thanks for the key point. Thanks for the post. It’s a memorable moment.
    Someone could make a documentary thriller out of it. Shane Salerno, are you listening?

    A phase in the work of John Schellnhuber is relevant I think:

    “Tidal flats are ‘very peculiar ecosystems,’ he says. ‘[They are] a sort of fractal structure. It’s interesting how the water is transported and how nutrients are transported through these fractal structures, how algae start to settle there.’ Researchers from geology, biology, and chemistry came to ask him for advice about how to construct a mathematical model for their specialties. ‘So I started to become interested in ecosystems,’ he says,’not because I was a green activist, it was simply through sheer scientific curiosity.’

    “His own group focused on the stability of nonperiodic orbits, using Kolmogorov–Arnold–Moser theory. ‘That is probably the most complicated mathematical issue you can do in nonlinear dynamics,’ he says. Meanwhile, his colleagues in the Institute were considering how algae grew in the mud. ‘I found it refreshing.’ he says. ‘You cannot do 12 hours a day thinking of Kolmogorov–Arnold–Moser theory. There may be some people doing that but, in general, you do it a few hours a day. I found it more enjoyable to talk to people and even go out to the tidal flats to look at the structures.’ ”

    The PNAS profile is linked by a biographical footnote at Wikipedia:

    “From solid state physics and quantum mechanics, John Schellnhuber´s interest was drawn to complex systems and nonlinearity or chaos theory.[9]”

    Also relevant:

    “His background serves him well here. ‘Physicists have a pictorial understanding of very complex relationships,” Schellnhuber says. ‘Of course, you always need to do it in tongue-in-cheek. You never believe it’s a true picture.’ Werner Heisenberg, he says, always looked for a good picture or analogy, as did Richard Feynman, who invented ‘a sort of pictorial calculus.’ Even with an apt analogy in hand, Schellnhuber admits that with many leaders, ‘you cannot give a scientific lecture. But you try to do it in terms that can be felt intuitively, perceived by people. Sometimes you succeed and sometimes you fail.’ …

    “After his experience in the United Kingdom, Germany, and the United States, including several visits to Capitol Hill, Schellnhuber has faith that at least some leaders want to hear the truth. ‘I’m convinced that you simply have to provide the scientific evidence. If politicians ask “What is going on?” they will turn to the best scientific institutions and not to those who are shouting the loudest. So it’s very important that you remain credible.'”

    “The belief that his work is important and that his advice will be heeded by people in a position to implement change is what keeps Schellnhuber motivated.”

  31. 131
    patrick says:

    Correction: “With the amount of open data available for anyone to analyse, this is not such a stretch,” This is from response at #11, not #25. I like them all.

  32. 132
  33. 133
    Hank Roberts says:

    > approval by no less than hank
    I asked where the Arctic heat captured goes in the climate system — whether looking outside the Arctic would turn up support for the larger warming there, in some other measurement elsewhere. But I don’t understand that guy’s answer. Is he saying it’s not going into meltwater? Or that it’s trivial?
    Wili, do you follow the arithmetic? It’s beyond me. I’m looking for who to trust on these questions.

  34. 134
    Ray Ladbury says:

    Steve, regarding satellite trajectories. Most polar satellites do not in fact go directly over the poles. 98 degrees is a common inclination and corresponds to a Sun synchronous orbit, where the satellite passes over the same latitude at the same time of day. This has obvious advantages for measuring temperatures.

    As to the accuracy of the measurements–I rather doubt that the sensor only looks directly below the satellite. Clearly, the UAH and RSS groups do not share Aunt Judy’s pessimism about the accuracy of measurements over the poles, and the same suspects now questioning polar accuracy have for years been touting the satellites as superior because of their whole-Earth coverage. Methinks she doth protest too much.

    I’m still of two minds about the paper. I still find the results surprising, however, I think the methodology is promising.

  35. 135
    MARodger says:

    Chris Colose @123.
    Curry’s “bottom line” was to point out that Ed Hawkins masked the CMIP5 output and so to infill in the blank areas without temperature data would not invalidate the ‘masked’ Hawkins comparison. This is obviously correct.
    Ed Hawkins also compared GISS with the full global CMIP5 output and it is onto this second graph that Cowtan & Way would be plotted. It does looks like such a plot would remain below the 25-75% region.
    What I take away from the Hawkins graphs is that as a representation of ‘hiatus’ for the great unwashed they do cut the ‘hiatus’ in half. A 15-year-long pause is difficult to argue for if surface temperatures were in that 25-75% region as recently as 2006. While the ‘hiatus’ is worthy of full investigation, 2006 wasn’t 15 years ago.

  36. 136
    BillS says:

    Re: Hank Roberts @ 110:

    There is little readily accessible data on freshwater within the Arctic Basin and its exit from there.
    One paper by Rabe, et al. is available at Ocean Science Vol. 5, pages 219-233, 2009. Be prepared to brush up on your physical oceanography.
    Another more recent paper can be found here:

    There is growing evidence that a significant amount of cold, fresh water is entering the Greenland Sea and points south via polar surface waters on the East Greenland Shelf (western side of the Fram Strait). The Summary & Conclusions section of the Dodd paper is very readable.

  37. 137
    BillS says:

    The link to the Dodd, et al. JGR paper seems to be not working…

    On a search for: p.a.dodd,.b.rabe,e.hansen will bring up a working link…sorry….

  38. 138
    Susan Anderson says:

    Steve, though it’s not exactly on topic, you might enjoy looking at NASA’s material on the “A Train” about the various satellites out there which might provide information about the polar data hole. Going further afield, there is an issue now with our current satellites being on track to fade away leaving a gaping hole that the politicos are fighting about while one party works to defund anything that might increase scientific knowledge.* Though to be fair there were two launches that failed, and that may have been a design problem. Tricky business, launching and calibrating satellites!

    Being more of an amateur than you, I have to take most of this on others’ sayso, but I did start to try the NASA links and it looks like there’s more information there, for example:

    *ClimateCentral (for one) has some information on the funding/political clashes. Congress has been busy blaming the victim in classic fashion for potential satellite failures. You may have heard that we had to rely on the European model for information about Sandy and there’s more about that out there too. I’m providing the search rather than the results, but you can sort the information by date (shortfall Feb., funding March, blamefest September).

    And this on (weather not climate) forecast comparisons; Masters is excellent on this subject, though it appears to be focused on hurricanes:

  39. 139
    Roger Lambert says:

    Stefan, could you comment on the stoichiometry of the heat? Enough ‘hidden’ heat was accounted for in deeper ocean strata to explain the “pause”. Now this study interpolates enough missing heat somewhere else. Do we have too much heat floating around or not?

  40. 140
    Hank Roberts says:

    BillS, thank you! you pointed to

    Ocean Sci., 9, 91–109, 2013 doi:10.5194/os-9-91-2013
    Liquid export of Arctic freshwater components through the Fram Strait 1998–2011
    B. Rabe1, P. A. Dodd2, E. Hansen2, E. Falck3, U. Schauer1, A. Mackensen1, A. Beszczynska-Mo ̈ller1, G. Kattner1,
    E. J. Rohling4, and K. Cox4

    found that (full text and discussion)
    and much else relevant at Ocean Science
    “An Interactive Open Access Journal of the European Geosciences Union”

  41. 141
    Hank Roberts says:

    and Eli has a relevant topic on the IPCC’s underestimates now:

  42. 142
    Doug Bostrom says:

    Susan: Though to be fair there were two launches that failed, and that may have been a design problem.

    The kind of problem you’d expect when the launch organization is the relative equivalent of a primary school rocketry club. Same design problem, twice.

    Ipso facto drastically underfunded.

  43. 143
    BillS says:

    Polar holes in satellite data depend to some extent on the sensor and the satellite. here are just two examples.

    The ASTER sensor (Advance Spaceborne Thermal Emmission and Reflection Radiometer) is a push broom scanner (see wikipedia for a brief explanation on board the Terra satellite. Terra is designed to pass over the Equator at 1030 local time everyday on a descending orbit. Terra carries 4 other sensors in addition to ASTER — MODIS, MISR, CERES, & MOPITT. In theory, the ASTER sensor should not be able to “see” any farther North than about 82 degrees and about 80 degrees South. But, the ASTER telescopes can point up to 8.55 degrees either side of vertical so while you should not be able to get ASTER images of far northern Greenland (82-84 N) you can sometimes see the northern coast at 84N if the telescopes are pointing off-vertical (off-nadir). (It is possible to request such off-pointings if you can provide a good science reason.)

    The Landsat 7 and 8 sensors are whisk broom scanners on a satellite with the same orbit as Terra but designed to pass over the Equator every day at 1015 local time. Unlike the ASTER sensor however the Landsat sensors can not point any direction except straight down and you will never see any farther north or south than about 82 degrees.

    The Terra satellite can be re-positioned to get near-real time imagery of natural disasters; I don’t know whether any of the Landsats can be.

    NASA’s A-Train is a marvelous (Susan Anderson, above) idea; all satellites are designed to have 1330 local time Equator crossings.

    Finally, if you ever want the gory details of a satellite or sensor simply do a Google search on the satellite/sensor name, for example, “CALIPSO atbd”.

  44. 144
    JB Abbott says:

    There is a reason warming occurs at the poles faster than the rest of the planet. When Ice melts it absorbs energy, and when it freezes it releases energy. With liquid water temperature changes linearly with energy change. So, if you understand that ice warms significantly, while maintaining a constant temperature before melting that makes perfect sense.

  45. 145
    Hank Roberts says:

    There is a reason warming occurs at the poles faster than the rest of the planet. When Ice melts ….

    Er, that was the reason we thought so, long ago.

    After that, we thought it was the change in albedo.

    Then, people started modeling how energy moves in the climate system.

    That “habyhints” site is by a meteorologist. Keep watching. Presumably he updates his pages from time to time, as new science keeps being done.

    For example, this:

  46. 146

    Steve: “There is only one thing that is nagging me. Maybe somebody can clarify. The WUWT blog, and I think Curry, say that the satellite data over the poles is not reliable.”

    Yes the satellite retrievals of temperature over the poles are less reliable. That is why RSS does not provide any retrieved values at high latitudes. It is not a black and white issue, UAH has no problems providing data with a somewhat larger error and does provide data.

    If these measurement problems just make the data more noisy, that would be no problem. There is more than enough data to remove this. Also if the data has a bias, this would be no problem, such a bias would not affect the temperature trend. What would be a problem would be a change in the bias and thus change in the bias would only occur in the part where HadCRUT has no data. One reason for that could be the rapid melting of sea ice in the Arctic and the temperature retrievals need assumptions on the surface. I do not know how well that has been studied by the authors or whether that should be investigated in future. If it would be severe I would expect that they had seen a problem in their cross validation. (In a cross validation you leave out part of your data and investigate how well your method can reconstruct this again.) Still given that the temperature slowdown is such a minute effect, such details may matter.

    Steve: “Watts gives a picture of the satellites’ trajectory implying that they kind of skirt the poles.”

    As already noted above, polar orbiting satellites do not cross the poles exactly. Most have an offset of a few degrees, which they need to stay sun synchronous. This, however, leads to a minor gap of just a few degrees in the middle. This gap is so small that interpolation should be very save.

    In his post Anthony Watts was so careless to stray from the script of Judith Curry and showed this graph:
    and added: Note how the data near the poles starts to get spotty with coverage?

    He unfortunately did not note that the Antarctic is also very large on his figure. The figure has geographical coordinates, which near the poles means that points that are very close in reality (in km) are plotted as very distant (in degrees). In fact the effect goes the other way around, near the poles the sampling is much denser and near the equator. This can be seen in a figure Watts shows later:

    Even if the sampling near the poles would have been worse, this would have been no problem for this study. The points would be sufficiently near to be able to perform a very save interpolation. Furthermore, the plot Watts shows is for one day, over one month the sampling would be much better.

  47. 147
    Steve says:

    Thanks, everybody for all your replies.

    Victor@146 particular thanks to you. I don’t perfectly understand, but understand enough to feel reassured that the sat data was reasonable.

    There is one thing though I wonder if you can further comment on. It is about the validation. Imagine for a moment that the sat data for the poles is garbage. If so, then cross-validation in regions with good sat data would not demonstrate valid results where there is garbage sat data.

    I am not saying that the sat data is garbage, not at all. You dispelled that well. I am just asking an academic question about the validation. Basically, validation alone cannot show that the sat data is ok. You need to know it is prima facie, right?


  48. 148
    Hank Roberts says:

    > very large on his figure.

    Reminds me of some guy on the Internet a few years back who was foreseeing great opportunities to expand wheat farming into northern Canada. He figured the square miles available using the same kind of map projection.

  49. 149

    The cross-validation that was performed is quite strong. They did not just leave one point out and study how well they could reconstruct it, but the made the Arctic gap almost two times larger and studied how well they could reconstruct this edge region. That is a similar difficult extrapolation result. Also the removed region is probably already difficult to measure be satellite. That is most likely not a black and white issue.

    Maybe these edges are even more difficult as the center of the Arctic region. I am no expert for the Arctic, but I can imagine that these edges would be the region where the reduction in sea ice was strongest, whereas close to the North pole not much has happened yet to the ice cover and thus likely to the atmospheric profile. And I would guess that the changes in ice cover are the main reason to expect a trend in the bias, which is what could cause problems as argued above. Maybe someone more knowledgeable about sea ice can step in and say how well the regions and seasons match.

    To fully rule out such problems, an expert on the satellite retrievals should investigate how sensitive these retrievals are to changes in sea ice and the atmospheric profile and compare that to expected changes. The latter could be studied using radiosonde and dropsonde data. Black Board Lucia suggested studying this with model data. That would also be an option, but models are not that reliable for stable atmospheres, like we have in the Arctic. Thus I would prefer observations if we have enough of them.

  50. 150