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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. 201
    Sean says:

    I would also suggest, given the ‘pattern’ shown already, that Judith Curry is “playing them” with a thin veneer of ‘genuineness’… which sends them off (especially Cowtan) chasing more and more info down the rabbit hole.

  2. 202
    Sean says:

    Similarly, there is a significant gap between public perception of scientific consensus and the 97% reality. A 2012 survey found that 57% of Americans either disagreed with or were unaware of the fact that most scientists agree global warming is happening. This matters because perceived consensus is a strong predictor of support for climate policy. When people think the scientists agree, they are more likely to support climate action.

    Unfortunately, mainstream media outlets are perpetuating the misconceptions. One way they achieve this is by granting outlier voices disproportionate visibility in the public arena, creating misleading and counterproductive debates.

    In the survey of surveys was Q. “Warming is extremely important personally (and is likely to influence voting)”.

    Here are the results for some the states, more or less at random. Nevada 12%, Florida 14%, Louisiana 9%, Alabama 7%, Montana 5%, New Jersey 12%, West Virginia 6%, New York 11%, Rhode Island, Delaware 8%, Michigan 8%. I could have looked at more but a pattern is emerging. (It looks like the green vote.)

    Something is going on in the survey, I suspect that respondents are trotting out the “right” answers to the “motherhood questions like “Global warming has been happening” and giving some more thought to those questions that require a measured response.

    This can be seen in the huge disparity (disconnection) between the strong agreement with, say, the question “Warming will be a serious problem for the world” and the massive disagreement with the “Warming is extremely important personally”.

  3. 203
    Steven Sullivan says:

    Sean has good points. As a scientist myself, it pains me to see how the likes of Curry and her acolytes are controlling the narrative. Scientists need to be *much* more forceful than this in public fora. This isn’t academia. Come on, scientists, *engage*! Be *aware* of the distortions and ‘incorrect assertions’ being made, and counter them specifically — if someone mocks your work in the title of their blog post, make sure you ADDRESS THAT. If it’s another *scientist*, an authority figure like Judith Curry, misrepresenting your work, give it to her with *both barrels*. And when you engage on sites like hers, think about who is reading what you write, and with what intent — they *will* take your measured, context-dependent sentences out of context if you don’t think first and *anticipate* before you write. And those quotes will get propagated over and over.

  4. 204
    Radge Havers says:

    Re the whole hiatus thing, I think you’re more on point here, Sean. The response to these sorts of attacks tends to be desultory from the outset. The broader lay audience (the vast, pacified middle) is left unattended with an impression of dithering that only reinforces confusion.

  5. 205
    Sean says:

    Steven and Radge, thank you very much for commenting.

  6. 206
    Dave123 says:

    But is it true that the likes of Curry control the narrative? Where have those blogosphere thoughts been picked up by any mainstream media? (I’ve been on vacation since the 22nd and haven’t been paying close attention.)

    C&W provides ammunition in some public forums, and Sean’s points are useful in facing flying monkeys. But I’m not alarmed yet.

  7. 207
    Sean says:

    Dave123 says re “But is it true that THE LIKES of Curry control the narrative?”

    Absolutely true Dave, imho. Why did the head of the IPCC need to specifically make a public announcement comment about the “pause/hiatus” before the WGI itself did in writing – unless they were reacting to what is?

    Curry, WUWT ala Mocnkton, ala heartland ala Murdoch, a whole of activists, journalists, ala Corporations CEOs, radicalised scientists who are deniers and more have overwhelmed the narrative for the last 4 years very aggressively, with co-ordinated ‘action teams’ controlling (influencing) and sharing of “methodologies” MOs, topics, weak points to attack, and the “phraseology” & “slogans” used – you bettcha they control it.

    Why do you doubt such a thing? Is the IPCC controling the narrative? Is the EU controlling the narrative? Is China or India, or Real Climate or the hundreds of scieitific bodies on earth controlling it? Are any Politicians or Political Parties controlling the narrative, outside of the USA?

    Why are Cowtan and Way posting on Curry’s Blog? Not because they admire her scientific work and attitude. THAT’s control, when you get someone to REACT or ACT in a way which otherwise they would NEVER do .. that is effective “controlling” of others. Did a bit of myself from time to time, when necessary. :)
    and those were genuine questions. If you feel I am wrong above, please explain why this is so in your view. Thx Sean

  8. 208
    Sean says:

    Now my prior reply is my normal MO. This is my head kicking MO – It’s a choice. This time you have the opportunity to see them both together, and note the difference style from the very same person. Which would you prefer RC Moderators? Nobody operates in a vacuum here. Moderators can make a difference, but when they are little better than those that consistently insult others, well, what’s the point in participating or asking a straight question on the science?

    “Sean’s points are useful in facing flying monkeys.”

    The ‘default’ respect shown for others on this site, when someone presents a view new or different than one’s own is telling and meaningful.

    Which is why I have intentionally couched my words in some posts the way I have (not all posts) to see what the response would be from those who seem to love giving out and how well they would be able to take it. It’s been a good experiment. Lot’s of data collected. TY all.

    Yes I am confronting and speak truth to power who don;t want to listen yet, but I am NOT abusive, far from it. Sean

  9. 209
    Radge Havers says:


    I don’t know about cause for alarm, but the ‘pause’ business made it into the MSM briefly. Unlike climategate where denialists behaving like jerks was treated as somehow being news, there seems to be genuine confusion about the hiatus. The flap may be a minor issue to those immersed in climatology, but for others the take-away may differ. After “hiatus” has slipped from memory, the impression left will be the uncertain, unsettled, controversy about AGW.

    Which do you think carries more weight for a distracted citizen, a subtle point of science made in a noisy dispute or the thought that, meh, maybe it’s not worth it for me to worry about this now?

    Sharp messaging.

  10. 210

    First, sorry for jumping into this discussion late. Something really begs the question here, and I wonder if it’s well addressed: What about the ~70y warming cycle in the Arctic? If we pick the longest series in GISS station data and plot 30y moving average graphs, most stations in the Arctic or subarctic show a large multidecadal temperature cycle, and I believe there is some agreement that this cycle also seems to extend into the 19th century and earlier, and the causes are still not yet perfectly understood. We are currently near the top of that cycle and the satellite era largely coincide with the rising edge of the cycle. You probably see where I’m going.

    So if we’re mainly interested in the global warming signal, not the effects of a local multidecadal phenomenon, isn’t the “Arctic hole” sort of addressing, though somewhat crudely, that problem, at least until the cycle in the Arctic is properly understood? Filling the whole for the satellite era would then create a different bias unless the cycle is somehow addressed.

  11. 211
  12. 212
    Sean says:

    @209 Dear Dave, we seem to see this differently. Which is fine by me. neither of us have the power to change or influence a thing anyway.

    Where you say: “but the ‘pause’ business made it into the MSM briefly.” I can’t know whose MSM you are referring to, or have been observing the last 4 years, but it’s clearly not the same one’s I have been watching. Especially via the Murdoch press globally, and their ideological cohorts.
    One simple example may be the following ‘speech’ made the week immediately after the AR5 WGI was publicly released.
    Recalling that amid the IPCC announcement a concerted global campaign was put out through the MSM globally by the deniers industry every day for the week beforehand. That PR push emphasised nothing BUT the 15 years “hiatus/pause” disinformation. PLUS quoting the IPCC directly supposedly claiming it has CONFIRMED this ‘pause’.

    Nov 05, 2013 – ex-PM Howard made major MSM news in UK, Canada, Australia for week over this speech. Every nation has it;s own ‘talking heads” that have th power to break into the news cycles and get prominence on the nightly TV news and newspaper front pages.

    He said: “And the most recent IPCC Report has produced a grudging admission that the warming process has been at a standstill for the past 15 years. ”

    He also said far worse than that regarding the science, the scientists, and the IPCC system. Repeatedly quoted professional climate science deniers.

    I am not sure how this fits in the big picture that you see. Perhaps we are both right, depending on where we might live, and how far afield we have looked at the issue in the Media and common public perceptions and why they are what they are. Thanks very much for your reply Dave, I hope the proceeding is useful. Sean

  13. 213

    > This may give you a start:

    Not really. The first page is a discussion not about this study, nor air surface temperatures directly, but about Arctic ice extent. While your second link takes me discussions on realclimate about the ~70y temperature oscillation, which most seem to think is real, my concern is more about that they study a period which coincides with the rising edge of this oscillation, discuss that in the context of the longer global warming trend, yet I don’t see the oscillation mentioned anywhere (the discussion could be behind the paywall, though). I think it’s important to realise and be clear about that the recent Arctic warming likely is a combination of a ~70y cycle and the longer warming trend seen elsewhere during the 20th century.

  14. 214
    Hank Roberts says:

    Stendar, read through the Tamino link again; the claimed 70-year cycle doesn’t show up in the data. The claim about a cycle in sea ice is directly related to the claim you asked about of a 70 year cycle in temperature. Point is, it’s a major talking point much repeated but without data to support the claim.

    Try Google Scholar for the same search terms and compare the result to what Google gives you. (Remember to clear cache and cookies as Google tries very hard to give you more and more of whatever you like to see, which can lead people very far into notions lacking a basis in the science; there’s always more to find, but not more good info.)

  15. 215
    Hank Roberts says:

    ps, try this: analyzing the data looking at a similar claim of a cycle in temperature

  16. 216


    > The claim about a cycle in sea ice is directly related to the claim you asked about of a 70 year cycle in temperature.

    Ice extent is not a direct way to measure air temperature. Why do you want to use a temperature reconstruction based on scattered and incomplete ice observations involving the complexities of currents in air and sea as well as air-ocean interaction, when direct measurements exist and are more complete?

    > Point is, it’s a major talking point much repeated but without data to support the claim.

    I suggest that you go to and pick the stations with the longest records, say, 90+ years to get at least one cycle and three normal periods, and plot the 30y to find climatic trends. I agree that there is little data in the sense that there are few stations with that long history, but I don’t believe that much in coincidence in what exists. And I agree that there are even less data to say for sure that the oscillation goes back centuries. Nor can we say for sure whether the period is fixed or not. Still, let’s not pretend that the direct evidence that exists isn’t there. If you can direct me to papers (rather than apologetical blogs) giving good evidence that the instrument records showing this pattern are flawed, I would be interested.

    As a start, I made some 30y plots for you (from GISS):

    While the shapes will differ if you go on, they generally agree that last turn happens to coincide with the start of the satellite measurements, and it seems obvious that the 30y average will continue to rise for a decade or more unless you believe in an imminent and very rapid Arctic cooling.

  17. 217


    > ps, try this: analyzing the data looking at a similar claim of a cycle in temperature

    I’m not sure what the argument here is. So, one cycle does not perfectly model the data, and a fit of any cycles can model any dataset (obviously) – then, having proven that both extremes fail to predict anything, we can conclude that it applies to the general case: cycles can not exist in temperature data?

    Anyway, altogether denying the existence of this ~70y oscillation (whether it has existed a long time or only for a short time) seems to place you outside both camps in the climate debate. In mutually derogative terms, a couple of papers from the “alarmist” and “denialist” camps respectively aknowledge the cycles:

  18. 218
    CptWayne says:

    I found this article by David Rose: Global warming ‘pause’ may last for 20 more years

    “The 17-year pause in global warming is likely to last into the 2030s and the Arctic sea ice has already started to recover, according to new research.

    A paper in the peer-reviewed journal Climate Dynamics – by Professor Judith Curry of the Georgia Institute of Technology and Dr Marcia Wyatt – amounts to a stunning challenge to climate science orthodoxy.

    Not only does it explain the unexpected pause, it suggests that the scientific majority – whose views are represented by the UN Intergovernmental Panel on Climate Change (IPCC) – have underestimated the role of natural cycles and exaggerated that of greenhouse gases.

    Read more:

    Pause: How the Earth’s average temperature defied scientists’ predictions by remaining almost the same

    Pause: How the Earth’s average temperature defied scientists’ predictions by remaining almost the same

    The research comes amid mounting evidence that the computer models on which the IPCC based the gloomy forecasts of a rapidly warming planet in its latest report, published in September, are diverging widely from reality.

    The graph shown above, based on a version published by Dr Ed Hawkins of Reading University on his blog, Climate Lab Book, reveals that actual temperatures are now below the predictions made by almost all the 138 models on which the IPCC relies.

    The pause means there has been no statistically significant increase in world average surface temperatures since the beginning of 1997, despite the models’ projection of a steeply rising trend.

    According to Dr Hawkins, the divergence is now so great that the world’s climate is cooler than what the models collectively predicted with ‘five to 95 per cent certainty’.

    Curry and Wyatt say they have identified a climatic ‘stadium wave’ – the phenomenon known in Britain as a Mexican wave, in which the crowd at a stadium stand and sit so that a wave seems to circle the audience.

    Recovery: A new study suggests global warming is at a halt and Arctic seas are starting to recover

    In similar fashion, a number of cycles in the temperature of air and oceans, and the level of Arctic ice, take place across the Northern hemisphere over decades. Curry and Wyatt say there is evidence of this going back at least 300 years.

    According to Curry and Wyatt, the theory may explain both the warming pause and why the computer models did not forecast it.

    It also means that a large proportion of the warming that did occur in the years before the pause was due not to greenhouse gas emissions, but to the same cyclical wave.

    ‘The stadium wave signal predicts that the current pause in global warming could extend into the 2030s,’ said Wyatt. This is in sharp contrast with the IPCC’s report, which predicts warming of between 0.3 and 0.7C by 2035.

    Wyatt added: ‘The stadium wave forecasts that sea ice will recover from its recent minimum.’ The record low seen in 2012, followed by the large increase in 2013, is consistent with the theory, she said.

    Even IPCC report co-authors such as Dr Hawkins admit some of the models are ‘too hot’.

    He said: ‘The upper end of the latest climate model projections is inconsistent’ with observed temperatures, though he added even the lower predictions could have ‘negative impacts’ if true.

    But if the pause lasted another ten years, and there were no large volcanic eruptions, ‘then global surface temperatures would be outside the IPCC’s indicative likely range’.

    Professor Curry went much further. ‘The growing divergence between climate model simulations and observations raises the prospect that climate models are inadequate in fundamental ways,’ she said.

    If the pause continued, this would suggest that the models were not ‘fit for purpose’.”

  19. 219
    Hank Roberts says:

    You should check the claims you read in the newspapers, and the reputation of the people making them. You’re rebunking claims that were shown to be bogus months ago. You know how to look this stuff up.

    See, for example, what Ed Hawkins has to say about David Rose’s claims.


    From the first page of results (yours may vary, search is like that, read carefully what you get):

    Philip Plait

    Columbia Journalism Review

    … (Ed Hawkins of the IPCC took to Twitter to affirm that none of this actually happened)

    Copypasting stuff from other blogs without checking their claims often merely repeats misstatements that their authors knew they were making up; they fooled you.

    No shame being fooled once.
    Don’t be fooled again.

  20. 220
    Ray Ladbury says:

    OK, time to break out my example again. Consider the following set of ordered pairs.


    Does this represent a periodic function, and if so predict the next y value (the 11th). If you said 1 or 2, you are wrong. It is in fact 4. The y values are merely the digits of the base of napierian logarithms, e, and the x values are their ordinal position. The number e is transcendental, and so cannot be periodic, and yet it appears as if we have 5 periods.

    What this says is that you have to be very, very careful when positing a periodic behavior. You have to either have many, many periods or you have to have physics that suggests behavior will be periodic. Your “oscillation” has neither. Beware.

  21. 221
    Hank Roberts says:

    For CptWayne:

    Reading say just the 2013 papers, if not more, will make clearer what variety of observed changes over time have been called “AMO” — there’s no clear and definite cycle. the more data looked at the less clear and less definite the variation seems to have been.

    Quaternary Science Reviews
    Volume 69, 1 June 2013, Pages 142–154
    Evolution of NAO and AMO strength and cyclicity derived from a 3-ka varve-thickness record from Iceland

    … Spectral analyses from three sediment cores recovered from the lake show essentially the same periods of 2.8–3.4, 13, 35–40 and 85–93, for the overlapping ∼900-year period. Additionally, cycles of 55, 130 and 290 years are found in the spectrum for the 3000-year record that do not show up in the spectra for the shorter cores. Some of these cycles show similar variability to those of the North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO). This relationship is supported by a significant correlation between varve thickness and both the NAO (precipitation) and AMO (summer temperature) indices over the 180-year instrumental period. NAO cyclicities (2–15 years) are weakly expressed in the first half of the record, increase between 600 and 1000 AD, decrease in strength during medieval time, and are most strongly expressed between 1300 AD and the early 20th century. AMO cyclicities (50 to 130 years) are also relatively weak in the first half of the record, becoming quite strong between 600 and 1000 AD and again between 1100 and 1500 AD, but are essentially absent through the peak of the LIA, between 1500 and 1900 AD, a time when strong cyclicities of about 35 years appear.

    Using just the past couple of hundred years of data you can fit any kind of curve you want; using all the data available tells you whether there’s one clear cycle: Not.

  22. 222

    I’m gonna have to go with CptWayne on this one, he sounds official and look at all the effort he put into his post and his thesis! All you’ve got is a bunch of googly papers by a bunch of smarty pants.

  23. 223


    I did stress in my first post both that the data showing the pattern going centuries back are not very complete (an inherent feature of paleoclimatology) and that the causes are not perfectly understood (some attempts to explain the physics have been presented, but I think it will take time for these to ripe or rot). We don’t really know for sure. The uncertainty goes both ways. You can’t argue that something doesn’t exist because the evidence is incomplete. You need more complete contradicting evidence to do that. Or your position can simply be that there is not sufficient evidence either way.

    We know from the instruments that there was a temperature change in the Arctic in the 20′s and 30′s comparable to the current temperature change so far (I write “comparable”, since the current change might still be ongoing and by cherrypicking smoothing or average windows one can easily make either temperature change look larger than the other). Regardless of whether one believes this is a cycle, it tells us that such changes can happen in the Arctic without the modern CO2 boom, and if we are to accept that CO2 is the cause now, and that something else was the cause previously, I think that some clarification would be due. I’m not saying that it can’t be. I’m just suggesting that it’s hardly a wild idea that something that has happened before, once for sure and probably several times before to a lesser or greater extent, can happen again. And that the question becomes relevant because the satellite period overlaps very well with the expected rise if the change indeed has repeated.

  24. 224
    Steve Fish says:

    Re- Comment by Steinar Midtskogen — 3 Dec 2013 @ 4:44 PM

    “We don’t really know for sure. The uncertainty goes both ways.”

    No it doesn’t. Statistical curve fitting to a noisy signal without any physical explanation is not science. There are known possible physical explanations for the ups and downs it is just hard to determine what was working in the past. During the instrumental period it is known, for example, that the period of decreasing and flat temperatures after WWII were due, in part, to industrial sulfates and the occasional volcano.


  25. 225
    dhogaza says:

    “We know from the instruments that there was a temperature change in the Arctic in the 20′s and 30′s comparable to the current temperature change so far”

    We know this how? Without satellites? How?

  26. 226
  27. 227
    KR says:

    “We know from the instruments that there was a temperature change in the Arctic in the 20′s and 30′s comparable to the current temperature change so far” – No, no we don’t. In fact, the evidence shows the contrary.

    Ice extents are currently far below those of the 20′s and 30′s, as shown in Rayner et al 2003, and in fact are demonstrating a ‘hockey-stick’ decline compared to the last 1450 years, as in Kinnard et al. 2011, Fig. 3a. And that ice extent means that Arctic temperatures were just not as high as they are now.

  28. 228


    > Statistical curve fitting to a noisy signal without any physical explanation is not science. There are known possible physical explanations for the ups and downs it is just hard to determine what was working in the past.

    I agree on that, but just because it’s hard doesn’t prove that the signal doesn’t exist.

    What is your best physical explanation for the rapid warming seen at Arctic stations, in particular on the North Atlantic side, in the 20′s and 30′s?

    I find the large variability (compared to the rest of the world) of the Arctic climate interesting (as a side effect of an interest in the Arctic in general). Understanding the 20′s and 30′s warming may prove important, since we have little data before this, and later the global warming trend is disturbing the scene.


    > We know this how? Without satellites? How?

    With meteorological stations that been operational for ~100 years. You can look up the station data on the internet.

  29. 229
    dhogaza says:

    “With meteorological stations that been operational for ~100 years. You can look up the station data on the internet.”

    They do not cover the entire arctic. As others have pointed out above, sea ice extent is far, far less overall in the arctic now than then.

    Your claim is one of those common denialist claims which the arctic climatology community has been aware of for a long time, and which has long been debunked. You’re not likely to impress anyone here by repeating it.

  30. 230

    On sea ice–Yes, while data is sparser than we’d like for the 20s and 30s, I think it is still quite ample enough to rule out out any extent crash such as that observed today. Hank’s link is good in that respect, and you can find contemporaneous ice edge maps online for the Atlantic sector–DMI, perhaps? And the AR5 Technical Summary (p. 8) says that current extent is “unprecedented” within the last 2 millennia (medium confidence.)

  31. 231
    Steve Fish says:

    Re- Comment by Steinar Midtskogen — 4 Dec 2013 @ 4:50 AM

    “I agree on that, but just because it’s hard doesn’t prove that the signal doesn’t exist.”

    Consider that the signal indicating the reality of the sirens on Titan is also absent. If it isn’t science then it isn’t science and I hope that you agree with this.


  32. 232

    “> Statistical curve fitting to a noisy signal without any physical explanation is not science. There are known possible physical explanations for the ups and downs it is just hard to determine what was working in the past.”

    I am trying to see how far one can take the curve fitting by applying a variational approach. If one assumes that aggregated energy on the scale of the earth does not fluctuate spontaneously, and must be the result of real physical forcing changes, one can try to apportion each change in temperature to a contributing factor.

    This does not go over well at blogs such as Lucia’s Blackboard because it uses all the skeptical arguments to substantiate warming attribution to CO2. All the fluctuation terms such as Curry’s Stadium Wave, and Scafetta’s gravitational terms, and Bob Carter’s SOI cancel out and we are left with what is called the secular trend, the ln(CO2) control knob signal. Even the long pauses are explained.

    Needless to say, the skeptics do not like seeing the tables turned and using their own ideas against them.

  33. 233
    Ray Ladbury says:

    Steinar Midtskogen: “I agree on that, but just because it’s hard doesn’t prove that the signal doesn’t exist.”

    Wait, are we talking about the weather or the Loch Ness Monster? Science concerns itself with what DOES exist. I do not have to come up with an explanation of how invisible, pink unicorns got into the trunk of my car until I at least find some unicorn crap in the trunk.

  34. 234


    “They do not cover the entire arctic. As others have pointed out above, sea ice extent is far, far less overall in the arctic now than then. Your claim is one of those common denialist claims which the arctic climatology community has been aware of for a long time, and which has long been debunked. You’re not likely to impress anyone here by repeating it.”

    1. Few regions on earth are well covered by stations. With such an argument you can just as well deny any global warming before the satellite era on the basis that stations only cover a small fraction of the globe. I don’t know who that would impress, if that’s an objective for anyone here.

    2. I’m not here to impress or get impressed, but I’m here for an open discussion.

    3. You confuse change with level. Less ice today does not contradict a similarly sized shift 70 years ago if the starting point was lower (check the data). I have nowhere compared absolute levels, because it’s irrelevant here. I have only spoken of change. Besides, if you’ve ever seen sea ice in action, you must know that wind and sea currents influence coverage a lot in addition to temperature, so you’re not only using sparse observations, but also an oversimplification and that misunderstanding of change vs level to debunk direct instrumental observations.

  35. 235
    Hank Roberts says:

    for Steinar, from JC quoting from Watts:

    … Dr Walt Meier of The National Snow and Ice Data Center in Boulder:

    “Analysis of the temperatures does not support a cyclic explanation for the recent warming. The warming during the 1920s and 1930s was more regional in nature and focused on the Atlantic side of the Arctic (though there was warming in some other regions as well) and was most pronounced during winter. In contrast, the current warming as observed is amplified over almost the entire Arctic and is seen in all seasons. Another thing that is clear is that, the warming during the 1920s and 1930s was limited to the Arctic and lower latitude temperatures were not unusually warm.”

    Seriously, as dhogaza wrote above, you’ve found and posted a fresh copy of an old, long-debunked story about the Arctic.

  36. 236

    “Loch Ness monster”, “sirens on Titan”, etc.

    I’m saying that there is something between solid evidence and nothing. In this case the evidence is sufficient to have it identified as a possible cycle in the literature. Are you saying that scientists writing that are also inclined to believe in pink unicorns? Then you must direct much science to the junkyard.

  37. 237
    Hank Roberts says:

    Steinar, read the linked page at JC’s quoting Watts. The ‘nialists have given up on that idea, pretty much. Walt Meier did a good patient job of talking this through.

    Yes, ice and temperature highs and lows changed as weather conditions moved back and forth across the Arctic; once the picture was put together, it became clear that averaged out.

  38. 238

    #232–Yes, that’s the quantified version of the contemporary denialist contradiction: after years of berating the scientific mainstream for (allegedly) supposing that *only* CO2 affects temperature, they are all agog about the ‘hiatus’, since that proves the mainstream wrong–provided you assume that *only* CO2 affects temperature, that is.

  39. 239
    Steve Fish says:

    Re- Comment by Steinar Midtskogen — 4 Dec 2013 @ 4:27 PM

    There is a big difference between proposing a hypothesis based on interesting statistical data and then suggesting it is anything more than that. For the hypothesis to progress would require support in the form of a reasonable physical mechanism that would cause 60 year temperature oscillations and then some kind of test of its veracity. Until this is accomplished we just have a proposal equivalent to the belief in the Great Spaghetti Monster. This hypothesis hangs in the no-man’s-land along with many others, such as the influence of cosmic rays or planet alignment on weather.


  40. 240
    dhogaza says:

    Steve Fish:

    “This hypothesis hangs in the no-man’s-land along with many others, such as the influence of cosmic rays or planet alignment on weather.”

    Or, in shorter form, “anything but CO2!”.

    As if the radiative properties of CO2 don’t exist, sigh …

  41. 241


    I read Tony Brown’s post at JC a while ago and his others on the topic, since the topic interests me. I have nowhere stated that the entire recent warming can be explained by a cycle, but made it clear that I consider the global trend a significant factor as well. And since a cycle might not have a consistent amplitude, nor period, as I stated right away, separating the signals is not trivial. Which is precisely why being dead sure is dangerous.

    Look, why are you trying to polarise this discussion so much? Is it all either all CO2 or all nonsense to you, all black and white? You know better, of course. While some claim to have found a match with planetary alignment, it does no job at explaining the phenomenon since it totally lacks a physical basis. That doesn’t mean that everyone who see a possible cycle is into astrology. I don’t think solar activity and cosmic rays are relevant here, either. It doesn’t seem very cyclic to me anyway, and if anything, the influence seems weak or it would show up clear in the data. While I wont rule out a detectable influence in Europe (nor other explanations for the little ice age), there is nothing to suggest, as far as I know, that the Arctic was particularly cold during the little ice age. On the contrary, if the Arctic were much colder than last century, few would have gone through the trouble of going there, some even overwintering, and even less return, during the little ice age, but they did.

    Anyway, another 30 years of data should shed some more light on this. I plan to stay around to see what that tells us.

  42. 242
    dhogaza says:


    “Look, why are you trying to polarise this discussion so much? Is it all either all CO2 or all nonsense to you, all black and white? ”

    No, it is not “all CO2 or all nonsense”. Quit putting words into people’s mouths.

    You made a claim about arctic temps being as warm in the 1920s and 1930s as now, a claim made by denialists for quite a long time, and thoroughly debunked by professionals in the field. You begin your argument from a false premise. Therefore your argument has no legs to stand on. The rest is noise flowing from your original misconception.

  43. 243
    Ray Ladbury says:

    The frustration you are sensing is due the the fact that you aren’t paying attention to what people are saying. Yes, it is POSSIBLE there could be an oscillation. It’s possible there could be hundreds of oscillations. And even if there are not, we can reproduce any time series (except, perhaps near the endpoints) of data if we use enough sinusoidal functions, since these form a complete set of functions. It is for this latter reason that it is prudent to either require compelling evidence of such an oscillatory behavior or to have a compelling evidence of an oscillatory driver of the proper frequency. Without this, you are engaging in Mathturbation–to borrow Tamino’s term.

    It is very easy to fool oneself into thinking there is oscillatory behavior when there is not, and if you are so fooled, the misinformation will distort your understanding of all other aspects of your model. So take a hint from William of Occam: Don’t add complexity to your model until you have definitive evidence you need it.

  44. 244
    Hank Roberts says:

    > a cycle might not have
    > a consistent amplitude, nor period

    What else does a cycle have, if not repeatability over time?

    Do you mean noise is a cycle? natural variability is a cycle?

    “Analysis of the temperatures does not support a cyclic explanation for the recent warming.” == Meier, op. cit.

    Where is this cycle you claim you find?

  45. 245
    Steve Fish says:

    Re- Comment by Steinar Midtskogen — 5 Dec 2013 @ 8:14 AM

    You appear to be objecting to the usual and appropriate progression of science. With apologies, you are beginning to sound like a concern troll because of the combination of claims that objections to your ideas are “polarizing” and the assertion that those critical of you claim that it is “all either CO2 or all nonsense.” This latter claim is a straw man argument. Further, you admit that some hypotheses (cosmic rays, planetary alignment) that are, as yet, unsupported, are not relevant, while your own unsupported pet hypothesis is.

    Please admit that an interesting statistical fit to a noisy signal, with no underlying physical explanation, is just an unsupported hypothesis with no reason, as yet, for concern. I hope that your blogging behavior improves.


  46. 246

    #241–Steinar, I don’t think that there’s any intent to polarize the discussion. What folks are saying is that one (purported) cycle really has very low evidentiary value.

  47. 247
    Hank Roberts says:

    Steinar, here’s where that’s been discussed, at considerable length. Seriously, it’s an old story:

    …the pattern of warming of the 1930s was very different from the recent warming. In the 1930s, warming was localised to the high latitudes, consistent with this warming being the result of a natural oscillation (the so-called “Atlantic Multidecadal Oscillation”). Very similar natural oscillations are also found in climate models. The recent warming, in contrast, encompasses most of the planet; this is consistent with it being the result of a global forcing.

    If that natural variability is what you’re thinking about — that thread explains the difference between then and now.

  48. 248
    Hank Roberts says:

    Unprecedented recent summer warmth in Arctic Canada
    Gifford H. Miller et al.
    4 NOV 2013
    DOI: 10.1002/2013GL057188

    … the extent to which recent Arctic warming has been anomalous with respect to long-term natural climate variability remains uncertain. Here we use 145 radiocarbon dates on rooted tundra plants revealed by receding cold-based ice caps in the eastern Canadian Arctic to show that 5000 years of regional summertime cooling has been reversed, with average summer temperatures of the last ~100 years now higher than during any century in more than 44,000 years, including the peak warmth of the early Holocene when high-latitude summer insolation was 9% greater than present. Reconstructed changes in snowline elevation suggest that summers cooled ~2.7°C over the past 5000 years, approximately twice the response predicted by Coupled Model Intercomparison Project Phase 5 climate models. Our results indicate that anthropogenic increases in greenhouse gases have led to unprecedented regional warmth.

  49. 249

    I’ll touch the key points briefly.

    20′s warming debunked. I can only ask, have you actually checked the station data or have you just read somewhere on the Internet that the warming is debunked? You can easily access GISS station data. If you pick stations going back at least 90 years, plot a 30y moving average, the warming is easy to spot. In some places very striking, a few not so much, which could be due to short history (110+ years would be best) or simply that the station was the exception, but the pattern is beyond coincidence. Sure, there could be errors and the correctness was already questioned in the 20′s because the warming was unheard of, but I don’t think errors happen many places independently. What I did was to get those 30y trends. This was version 2 data and I see today that there is a version 3 dataset, but both are available. If we can’t agree on whether the station data are real, our premises are just too different to make the other discussion points relevant.

    Consistent period/amplitude. Again, it’s not either a perfect sine or noise. Sunspot cycles have variation in period and amplitude (this is just an example, not suggesting that it has anything to do with an Arctic cycle). Yet most people call it a cycle. By the argument given here, however, it’s to be considered random noise. Also note that when the discovery of the sunspot cycles was published, it was initially only done so on the basis of two periods and no satisfactory physical explanation. It provided a testable prediction, and I see no reason why still couldn’t be called a scientific hypothesis, but here it would apparently have been likened with pink unicorns.

    Straw man: Yes, I thought the same thing when cosmic rays, astrology, etc came up. I didn’t bring up this discussion to prove the “hiatus”. I don’t even find it or the lack of it very interesting for the question on global warming because 15-20 years is a short time frame in the respect in my opinion, but that’s a different discussion.

  50. 250
    MARodger says:

    Steinar Midskogen @249.
    Why do you insist on examining individual station data. This cycle you hypothesize about is in the Arctic? GISS do provide Arctic temperatures here. Unless you want to do GISS’s job for them, why reinvent the wheel? If you plot out the GISS Arctic temperature you get the red trace here (may require two clicks to ‘download your attachment’).
    Bar a 25 year period 1940-65, the Arctic temperatures are rising over the entire record. Is this your basis for arguing for a hypothetical 70-year Arctic cycle?

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