Busting the myth buster 1: Climate’s changed before

A number of commenters seem genuinely confused about what to believe when it comes to climate change, climate science and energy policy. Members of the public seem inclined to believe the scientific consensus and certain commenters on Energy Matters are clearly disturbed by the fact that myself and Roger Andrews should have the audacity to challenge what is presented as settled science that 97% of scientists evidently agree upon.

A number of comments point to John Cook’s blog called Skeptical Science that sets out to straighten the record made crooked by sceptical blogs like WUWT, Roy Spencer, Judy Curry and, I dare say, Energy Matters. It was pointed out that no one has presented a systematic rebuttal to John Cook, and while writing this type of post is not the most favoured use of my time, I think it is potentially useful to try and straighten out some of the issues. At the moment I plan 10 posts to address each of John Cook’s alleged climate myths, but we will see how things go.

The first myth, is attributed to MIT Professor of Meteorology, Richard Linzen. Myth 1: Climate’s changed before:

Climate is always changing. We have had ice ages and warmer periods when alligators were found in Spitzbergen. Ice ages have occurred in a hundred thousand year cycle for the last 700 thousand years, and there have been previous periods that appear to have been warmer than the present despite CO2 levels being lower than they are now. More recently, we have had the medieval warm period and the little ice age. (Richard Lindzen)

Cook does not refute the point that climate has changed before but instead constructs an argument around the pace of climate change, implying that climate today is changing more rapidly than in the past although he presents little hard data to back up this argument. High latitude climate has changed rapidly about 50 times in the last 3 million years associated with the glacial episodes and interglacials of the ice age that we remain in.

He compares today’s burning of fossil fuels to past natural disasters in the form of large scale volcanic eruptions or meteor impacts. And while he recognises that other gasses such as SO2 may also be implicated in extinction events he tends to lay the blame at the door of elevated CO2. This is presented under the banner “what the science really says”.

But all this is moot since Cook misses completely the essence of the sceptic argument bound in Lindzen’s quote. This boils down to attribution of observed temperature changes. The climate science community has tended to attribute all of the temperature rise seen between 1975 and 1998 to human activity, especially rising CO2 (Figure 1). The sceptics say hey wait a minute, Earth’s climate is still seeking equilibrium from the last glaciation and from the Little Ice Age that ended a mere 150 years ago. Warming in the period 1910 to 1945 is attributed to natural warming by most workers. If that warming was natural what evidence is there to suggest that late twentieth century warming was not natural too (Figure 1)?

Figure 1 The HadCRUT4 global temperature reconstruction as graphed by Roger Andrews, my additions in colour. The 20th century has two marked global warming periods, one in the first half and the other in the second half. The warming 1910 to 1945 is attributed by most to natural causes but that from 1970 to 1998 to an increase in atmospheric CO2. How do we know? Note that the gradients of the arrows are identical.

This is important since that late 20th Century warming trend tends to be projected to the year 2100 by many GCMs (climate models) with a rate of 0.6˚C in 40 years = 1.5˚C per century. This underpins many climate models, many of which are now running hot compared to observations. Now, let us imagine that a component of late 20th Century warming is down to natural causes, the climate change that happened before to which Lindzen refers. This significantly deleverages the Human caused component. Introducing a natural warming component to the late 20th century trend provides a way of reducing the CO2 (human) contribution that may be used to bring the hot-running models in line with observations. In essence, the data as it stands seem more consistent with a climate sensitivity in the region 1.5˚C±0.5˚C . The response of society to that outcome should be entirely different to the risks posed by 3˚± 1.5˚C climate sensitivity.

This, in my opinion, lies at the heart of the whole climate debate. How should politicians react to the spread in climate sensitivities to CO2 presented to them by the IPCC in AR5 that have a range form 1.5 to 4.5˚C?

The temperature data in Figure 1 can be placed in an entirely different context using proxy temperatures from the GISP2 (Greenland) ice core that provides a geological record of temperature change in the N Atlantic area that matches what is known from human historical records. That 1˚C of 20th Century warming does not look at all out of place in this context which rather worryingly shows the high latitude N hemisphere continuing to cool. We seem merely to be on the latest warming up leg that may come to an end in about 100 years time.

Figure 2 Proxy temperature reconstruction and forecast from the GISP2 ice core, Greenland. The current temperature rise attributed to the modern warm period does not look out of place set in the context of past climatic fluctuations referred to by Richard Lindzen. We strongly suspect that a component of recent warming is down to CO2 but we do NOT know what that proportion is compared with the natural warming cycle.

The summary rebuttal to John Cook is that Earth’s climate is always changing by natural causes. The glacial – interglacial cycles are subject to large swings in temperature and climate. The climate science community needs to present the evidence for the split between natural and manmade warming for the period 1975 to 1998. Simply attributing it all to CO2 is not scientific.

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45 Responses to Busting the myth buster 1: Climate’s changed before

  1. Bernd Palmer says:

    Thanks for helping to disentangle Cook’s crooked arguments for “his” cause.

  2. Hugh sharman says:

    On this issue I am 100% content that you are right! On the other hand. I have never heard of john cook. Who is he?

    • Graeme No.3 says:

      You don’t really have to know. Ex-cartoonist, not that I’ve ever seen anything from him, associate of Lewandowsky whom he has reputedly followed to Bristol University, and mainstay of the Skeptical Science site.

      Noted for 2 things, photographed posing in Nazi uniform with like types (said photos available to the curious on his site until publicised) and converting me to scepticism. Well, not so much for the latter. While seeking information I read an article on his site “proving” the medieval warm period didn’t happen, which appeared reasonable unless you had some knowledge of history and grape growing. The lies, omissions and the outright distortions were more than enough for me to abandon any belief in AGW.

      And I never thanked him. Would it be too late to send him a bottle of wine (I have one with weeping cork that looks cloudy)?

      • Euan Mearns says:

        Graeme, thanks for this. A few enjoyable moments on Google led me straight to posts at WUWT and Joe Nova. Readers can by all means amuse themselves with Google but please keep links to this off this site.

    • Streetcred says:

      He’s a cartoonist from the University of Queensland, Australia. Yes, a cartoonist!!

  3. Sam Taylor says:

    I’m just going to quote Richard Alley from this story: http://dotearth.blogs.nytimes.com/2010/02/08/richard-alley-on-old-ice-climate-and-co2/

    “First off, no single temperature record from anywhere can prove or disprove global warming, because the temperature is a local record, and one site is not the whole world. One of the lessons drawn from comparing Greenland to Antarctica and many other places is that some of the temperature changes (the ice-age cycling) are very widespread and shared among most records, but other of the temperature changes (sometimes called millennial, or abrupt, or Younger-Dryas-type) are antiphased between Greenland and the south, and still other temperature changes may be unrelated between different places (one anomalously cold year in Greenland does not tell you the temperature anomaly in Australia or Peru)”


    “So, using GISP2 data to argue against global warming is, well, stupid, or misguided, or misled, or something, but surely not scientifically sensible. And, using GISP2 data within the larger picture of climate science demonstrates that our scientific understanding is good, supports our expectation of global warming, but raises the small-chance-of-big-problem issue that in turn influences the discussion of optimal human response.”

    • Euan Mearns says:

      The temperature data in Figure 1 can be placed in an entirely different context using proxy temperatures from the GISP2 (Greenland) ice core that provides a geological record of temperature change in the N Atlantic area that matches what is known from human historical records.

      Sam I am getting mighty tired of you misrepresenting what I say. You are on verge of joining William in the wilderness.

      Its also noted that here you argue in favour of “polarised” hemispherical climate change. And yet you raise no objection to GISS showing identical temperature evolution in N and S hemispheres.

      • Sam Taylor says:


        For a global past temperature series why not use Marcott et al, (http://www.sciencemag.org/content/339/6124/1198.abstract).

        My argument is not inconsistent. I don’t deny that the distribution of energy can shift around the earth, leading to warming in one area and cooling in another. However when you change the whole system forcings, by say changing the composition of the atmosphere causing a net increase in the energy of the global system, then I’d say a reasonable first order approximation is that you’d see roughly the same trends in either hemisphere.

        As for what caused what Meehl et al (http://journals.ametsoc.org/doi/pdf/10.1175/1520-0442%282004%29017%3C3721%3ACONAAF%3E2.0.CO%3B2) found that early century warming could largely be accounted for by solar forcings, but later in the century those forcings couldn’t explain it. Again, something like the ENSO is just a shifting around of energy in the system, what “natural warming” mechanism then explains the net energy gain?

        • Hans Erren says:

          The big problem with Marcott’s “wheelchair”cartoon of temperature history is that the there is a frequency bias in the recontruction which lessens the peak to peak signal in the earlier warm periods as is clearly proven with the high resolution greenland icecore.

        • Hmm, Marcott el all was savagely dissected and found wanting by fellow Canadians Steve McIntyre and Ross McKittrick some time ago.

      • donb says:

        Because oxygen and hydrogen isotopes fractionate at several stages from evaporation at sea to precipitation as snow, any absolute temperature constructed from them does depend to some degree on the sea temperature, as well as temperature over the ice core site.
        However, with the reasonably assumption that the sea source of this moisture remained relatively constant, then changes in temperature as shown in the graph depend only on conditions over the ice core site. Absolute temperature for earlier times are often extrapolated from comparisons of directly measured core site temperatures with the isotopic fractionation of recent snow.

  4. Yvan Dutil says:

    This is for the central Greenland only and the last data point is 1855. According to BEST, Greenland is roughly 2 °C hotter now than the last data point.


    Off course, this steep jump is not present on the graph.

    • Euan Mearns says:

      Applying the first rule of Green Thinking, if its published in peer reviewed literature then it must be correct. Using BEST to support an argument suggests that even you Yvan are scraping at the bottom of the barrel.

      Neither you nor Sam actually address the main question. How much of late 20th Century warming is natural and how much is man made. This comment and Sam’s are just diversionary noise.

      • Euan Mearns says:

        I just checked the chart Yvan. ALL of your 2˚C warming occurred around 1920. And so I don’t even understand the point of your comment.

        • Yvan Dutil says:

          The graph you show stop even before CO2 had an effect. add 150 years of data and you will show a strong uptic.

          If you really mind about science, Shauwn Lovejoy has done a nice analysis ont the natural fluctation.


          • A C Osborn says:

            I would love to know where he got that Temperature Graph from as it doesn’t look like anything I recognise.
            He specifically does not state any sources of data, a classic Science FAIL as is the paper.
            As a Physics Professor I would be ashamed to put my name on it.

          • Yvan Dutil says:

            You should read the original paper. Everything you complain is explained.

          • He specifically does not state any sources of data, a classic Science FAIL as is the paper.
            As a Physics Professor I would be ashamed to put my name on it.

            Good job he hasn’t failed then, since his paper cites exactly what data was used. If you’re sceptical, go off and read the original source. In this case, it appears to be open access so no excuses.

            Lovejoy, S., 2014. Scaling fluctuation analysis and statistical hypothesis testing
            of anthropogenic warming

            …in this analysis, we used data over the period 1880–2008 from three sources: the NOAA NCDC (National Climatic Data Center) merged land, air and sea surface temperature dataset (abbreviated NOAA NCDC below), on a 5 x 5 grid (Smith et al. 2008), the NASA GISS (Goddard Institute for Space Studies) dataset (Hansen et al. 2010) (from 1880 on a 2 x 2) and the HadCRUT3 dataset (Rayner et al. 2006) (on a 5 x 5 grid)…

          • duwayne says:

            I wonder why Lovejoy in 2014 would cherry-pick 1870 to 2004 for his graph? 1850 to 2014 would nullify his conclusions.

          • Yvan Dutil says:

            1880 is the start of 2 of 3 dataset. He also present other from multiproxies also.

    • JerryC says:

      And we are supposed to be alarmed because it’s -17C in central Greenland rather than -19C? Who decides that -19C is an appropriate temperature for central Greenland, but -17C is just too darn hot?

  5. Euan Mearns says:

    As is often the case with our posts, there is an opportunity for those on both sides of the debate to offer informed opinion on the subject and links to data that backs up that informed opinion. The two key questions with this post are:

    1) Is John Cook’s myth busting effort on the money? Or does he miss the point completely?
    2) What proportion of late 20th Century warming is down to natural causes and what proportion is down to manmade causes?

    I will open the bidding.

    On Q1 John Cook has either deliberately misrepresented the sceptic argument OR he doesn’t understand the sceptic argument and its importance.

    On Q2 I’ll guess 50% natural and 50% manmade. Those levels are consistent with a low value for climate sensitivity, one where theoretical feedbacks are nothing like as potent as many models suggest. Without CO2 we may have in fact been entering a slow natural cooling phase. The switching from natural warming to natural cooling explains the pause – pre 1998 natural warming was reinforced by CO2, post 1998 natural cooling cancels greenhouse warming.

    Natural climate variability that has now entered the warmist vocabulary cannot be selectively applied to explain only the bits of data that don’t fit the theory.

    • Yvan Dutil says:

      You should really read the work of Lovejoy.

      • Euan Mearns says:

        Thanks for the paper Yvan. I’ve had a quick look and will admit that some the physics etc is a bit beyond me. But I whole heartedly approve of the general methodology. I will defer more detailed comment and let others go first – but folks had better be ware that they properly understand what is being said. From the paper would you care to say where Lovejoy sees the natural : anthropogenic split?

        You may recall an old post of mine:

        UK temperatures since 1956 – physical models and interpretation of temperature change


        Going into that I really hoped that we could explain all by natural fluctuations in clouds, but we couldn’t. We had to call on CO2 to explain some of the warming in the UK.

        Here’s a chart that Roger made. It looks a bit raged, been meaning to get the data and algos to check it. If I read Lovejoy correctly he sees CS at 3.08±0.58K. So posting Roger’s cahrt as a discussion point. I’m cooking dinner tonight – yes bloggers need to eat 😉

        • A C Osborn says:

          Euan, see my earlier response, the second paper is probably better for you to read.
          There is a lot of maths and physics in both papers, but they are also full of assumptions and proxies.
          The main Assumption of course is that CO2 causes CAGW. in that respect it is very IPCC-esque.

          • A C Osborn says:

            Sorry, my response was at the same time as yours , but for some reason went to the bottom of the comments.

    • Graeme No.3 says:

      Q1: deliberately misrepresented. It is what he does. See response to Hugh sharman above.
      Q2: If man-made includes the adjustments to the records then at least 75% man made. If you remove the adjustments etc. then the remainder is due to natural causes.

    • donb says:

      A recent peer-reviewed paper also came to your conclusion:
      On Q2 I’ll guess 50% natural and 50% manmade.

  6. Doug Brodie says:

    John Cook and his cronies have never given a convincing rebuttal of Bob Tisdale’s analysis which shows that most of not all of the warming since about 1980 has been due to natural El Nino events, as shown clearly by this graph: https://bobtisdale.files.wordpress.com/2014/08/04-s-atl-ind-w-pac.png

    The point about this graph is that it is based on the sea surface temperatures which are most affected by El Nino events. It is physically impossible for atmospheric greenhouse gases to cause such sudden steps in sea surface temperatures.

    The SkepticalScience attempted rebuttal (The Escalator) uses a more diffused global surface (sea + land) temperature series which blurs the clear-cut El Niño/La Niña characteristics, a cherry picked start date (cooling in 1970) and very unconvincingly drawn steps, see http://www.skepticalscience.com/graphics.php?g=47

    • Yvan Dutil says:

      Tisdale analysis is just a form of numerology. Without clear statistical criteria you can maintain anything.

      • Doug Brodie says:

        Numerology is any belief in divine, mystical or other special relationship between a number and some coinciding events.

        Your rebuttal is not credible. What have statistics got to do with it?

  7. A C Osborn says:

    Yes I can see why you would be impressed, especially as there is such a good fit between the log CO2 Trend and the Temperature Trend.
    Except of course I know that the GISS data has been Adjusted so that it’s final temperature trend matches that of of CO2. in fact the “Adjustments” have an almost perfect corellation to CO2 increases.

    However the historical reconstruction of CO2 increases supposedly generated by man made CO2 output and the temperature data have a few problems. The major one being that there is no massive increase in CO2 during WW2 when practically the whole world geared up for war.
    There is also a problem with the temperatures after the war decreasing when the the world was being rebuilt and Consumer spending was taking off.
    The other problem of course with the temperature trend is the 1970s drop in temperature that prompted the “Ice Age” scare at that time which has magically disappeared.
    And then there is the small fact that the graphs end at around 2010 and do not show the pause which should have started at the end of the 1990s
    There is nothing like making the data fit the theory.

    This paper is also very good

    But note with this one they do not superimpose the CO2 trend on the Temperature data because this one does show the 2000s Temperature pause which would rather destroy the symmetry of the trends.
    I especially like the graph on page 28 and their interpreation of it.
    Note that it shows a 0.4 degree drop after the 1940s down to the 1970s, that was originally a 0.7 degree drop in records prior to 1990.
    But the “averaged data in the first paper you pointed to has further reduced it to less than 0.2 degree.
    Interestingly they only quote the temperature decreases as neing natural and ignore the temperature increases.

    And just to put it all in to perspective it all uses multi proxies.

    The very best bit which Euan will really appreciate is the work on page 30 which conclusively proves that Sceptics will have to wait until 2020 to show that the “pause” is meaningful.
    It wa sof course originally 15 years and then it was 17 years and now with 18 years 3 months it has been moved out another 6 years.
    Euan will also love page 32 where it states this
    “atmospheric data and models (GCM’s) are now of high enough quality “

    • Bernd Palmer says:

      Funny way of arguing.
      “which conclusively proves that Sceptics will have to wait until 2020 to show that the “pause” is meaningful” And of cours you will have to wait until then, to prove that the pause was not meaningful. But whatever 2020 will “prove”, it will certainly not answer Euan’s question 2: To what extent temperature fluctuations are caused by CO2..

  8. duwayne says:

    The chart from the link below compares the detrended Hadcrut4 temperature record with the “natural” Atlantic Meridional Oscillation (AMO).


    There clearly is a natural ocean current oscillation which correlates closely with fluctuations in the global temperature record with a cycle of about 60 years.

    When the AMO is negative, temperatures trends are flat for 30 years. Climate sensitivity calculations are highly dependent on the selection of the starting and ending year for the calculation. If the AMO correlation with temperatures continues, in another 15 years a 30 year climate sensitivity will be zero indicating that natural variations are as great or greater than CO2-caused variations in temperatures.

  9. Euan, you say: Cook does not refute the point that climate has changed before but instead constructs an argument around the pace of climate change, implying that climate today is changing more rapidly than in the past although he presents little hard data to back up this argument.

    In fact he presents no hard data whatever (the articles he links to are pure speculation). All he presents is an argument:

    Greenhouse gasses – mainly CO2, but also methane – were involved in most of the climate changes in Earth’s past. When they were reduced, the global climate became colder. When they were increased, the global climate became warmer. When CO2 levels jumped rapidly, the global warming that resulted was highly disruptive and sometimes caused mass extinctions. Humans today are emitting prodigious quantities of CO2, at a rate faster than even the most destructive climate changes in earth’s past.

    Or in other words, CO2 controls climate and CO2 is changing faster than it ever has before, therefore climate is changing faster than it ever has before.

    One has to wonder whether this claim is even worth rebutting.

    • Euan Mearns says:

      One has to wonder whether this guy is even worth rebutting.

      I agree in part, if Kit has time to check back through my comments he’ll see that I referred to this site as junk, and the more I read there the more I agree with what I said in the past. I think it was William who learned his climate science there and who was surprised at my allegation. If it is influencing the views of the “layman” them I think its worthwhile gathering a series of rebuttals that will reside on the menu bar up top.

      If nothing else the posts provide a good venue for discussion, though I’m still waiting for someone to stick their head above the parapet and tell me how they see Lovejoy’s spilt between natural and anthropogenic warming. Maybe you’d care to have a stab at that? 🙂

      Myth 2 is The Sun – where his myth busting is a joke 🙂

      • I started to go through Lovejoy’s paper. I soon came across this:

        Today, GCM’s are so much the dominant tool for investigating the climate that debate centers on the climate sensitivity to a doubling of the CO2 concentration which—whether ‘‘equilibrium’’ or ‘‘transient’’—is defined as a purely theoretical quantity being accessible only through models …. An unfortunate side effect of this reliance on models is that it allows GCM skeptics to bring into question the anthropogenic causation of the warming.

        I think that answers your question.

      • I will add one more thing. Lovejoy uses the HadCRUT4, GISS LOTI and NCDC combined land-ocean series to estimate CS. Like so many others he doesn’t realize that these series are apples-and-oranges averages of land air temps and SSTs and that they don’t give you meaningful results when used for CS estimates. Had he analyzed HadCRUT4’s component series separately, for example, he would have estimated a 37% higher CS value from CRUTEM3 and a 16% lower CS value from HadSST3. Which one should he have used? CS is defined as the response of surface air temperatures to a doubling of CO2 so he should have used CRUTEM3, which by proration would have given him a CS somewhere around 4.2, not the 3.08 he quotes.

  10. Phil Chapman says:

    What needs to be understood is the importance of Fig. SPM 5 in the AR5 (2013) Summary for Policy Makers, which compares the magnitude of various forcings. The ONLY natural forcing recognized by the IPCC is a possible tiny change since 1750 in the Total Solar Irradiance (TSI) reaching the Earth. This is critically important, because it is the justification for the conclusion that observed warming MUST be anthropogenic, since there is nothing else. Since CO2 and other anthropogenic sins are insufficient by themselves to explain the warming, the effect MUST be amplified by positive feedbacks in the climate system, with water vapor feedback as the most obvious choice. Water vapor feedback MUST be positive — i.e., evaporation from the oceans cannot form clouds, which might have a cooling effect — because there is no other explanation.

    This is the entire basis for the warmist position; everything else, including most computer modeling, is mere smoke and mirrors. This is also the reason for the stubborn opposition to common sense. The whole argument collapses if there is any possibility that there night be some significant natural forcing, because then it would be necessary to undertake real research, instead of merely arguing that AGW MUST be correct because there is no other alternative. So don’t expect rational discussion.

    • Euan Mearns says:

      Its an important point Phil. Climate Science remains locked in the myth that natural climate change doesn’t take place, rooted in the hokey stick, and embodied in this chart that effectively sets all natural forcing to zero.

      John Cook’s myth 2 is the Sun which is next on the menu.

  11. Euan Mearns says:

    We have had a form of response to the requested clarification over at Real Climate. I posted this comment a couple of days ago and Gavin Schmidt provides the response below:


    Roger Andrews has a post on my (our) blog that summarises 800 raw (un homogenised) temperature records.

    How Hemispheric Homogenization Hikes Global Warming

    This painstaking work has been done over many years. Roger finds that in N hemisphere his selected subset of raw records matches GISS very well. But in the S hemisphere that match is not there at all. There seems to be a large number of S hemisphere records where the distant past has been cooled or the recent past warmed relative to the raw records.

    Furthermore Roger finds that the temperature gradient through GISS N hemisphere is IDENTICAL to the gradient through the S hemisphere which I find highly suspicious / bordering on physical impossible I’d expect N and S hemispheres to respond quite differently to both natural and Man forced warming.

    I sent email to Gavin Schmidt yesterday asking for an explanation, awaiting a reply. We are simply seeking truth and will readily accept an acceptable explanation 😉

    PS cross posted this comment to my own blog.

    And Gavin’s reply is edited into another of my comments:


    M A Rodger

    “it should be obvious that the S hemisphere has been homogenised to match a nearby set of stations – the N hemisphere.” – I said that to Roger rather tongue in cheek via email, was a bit surprised that he stuck it in his post. Though we both have a sense of humour. I personally know next to nothing about homogenisation and am simply the messenger on this occassion. Evidently homogenisation works by comparing adjacent records and applies adjustments to make them more similar. And so when I see a set of records for the S hemisphere that show identical warming to the N hemisphere and am made aware that all these records are adjusted to smooth out differences it raises suspicion in my mind. Especially when the default position should be that the hemispheres should differ – should they not?

    In an earlier post Roger outlined a detailed example for Alice Springs where a raw record that had absolutely flat temperature was adjusted so that it then produced a warming trend. This makes me immediately suspicious. And it is multiple examples such as this that Paul Homewood and Christopher Booker are highlighting. Is there a remote possibility, for example, that the guys on the ground in Alice had already adjusted the records to correct for station moves etc and that applying homogenisation is correcting an already corrected record? I’m a geochemist by training (so is Roger in a sense) and we are both used to analysing large complex data sets. If we had bad data we would simply not use it. Hence Roger’s approach of selecting what he thought were good records and excluding the bad ones. I’m kind of surprised / shocked to learn that wholesale and automated corrections are applied to raw data.

    If I read the Cowtan chart you link to correctly, then it seems to show that temperature adjustments to raw data are overwhelmingly positive and result cumulatively in +0.3˚C warming since 1900. Why is it that the adjustments are so heavily skewed positive? That’s a genuine question, but if you are unable to answer in a civil and professional way, then please don’t bother answering at all.

    And you may think you have answered my main query, but you haven’t. Note that Roger points out that this discrepancy has no major impact on the over global temperature picture. But it is an interesting anomaly which I believe merits and explanation.

    1) Why do GISS N and S hemispheres show identical warming? (do they indeed show identical warming or has Roger made a mistake?)

    [Response: They don’t. GISTEMP LOTI: , Met stations index zonal mean changes can be seen here. – gavin]

    2) Why does Roger’s N hemisphere analysis match GISS almost exactly and the S hemisphere not?

    [Response: He can put out his code and data as is available for GISTEMP and people might be able to help him out. But without that, no-one has a clue. – gavin]

    Enquiring minds would want to know the answers to put sceptical minds at rest.

    Gavin links to this graph

    Which is not that helpful since it shows Land-Ocean temperatures and Roger’s query is specific to the land thermometer data. Curiously, on the GISS home page I spotted the graph shown below used as the icon to link to other graphs. It seems to show what Roger claims – i.e. that land measurements N and S are the same, but curiously this chart is not in the library of charts that the link leads to.

    I think at very least Roger needs to produce a list of stations used in compiling his index.

  12. Kevin O'Neill says:

    Euan, you purport to write about past climate changes, but you never really consider them. The Cenozoic saw alligators in the arctic and sea levels that were *75 meters* higher than today. This was a natural change, does that mean it’s OK we if we, as humans, induce such a change? The fact that something has occurred before due to natural causes does not mean it’s good or acceptable.

    Moreover, scientists have long known how to calculate the forcings from long-term changes in solar luminosity, Milankovitch oscillations, and other orbital changes. When they examine these natural changes they CANNOT come up with a total forcing that would move the planet from one observed temperature extreme to another. UNLESS they also take into account changes in atmospheric CO2.

    When we examine paleo data we find that global mean temperatures in the Eemian and Holsteinian were less than 1°C warmer than peak Holocene global temperature. Therefore, these interglacial periods were also less than 1°C warmer than global temperature in year 2000. Similarly, global temperature in the early Pliocene, when sea level was about 25 m higher than today was only about 1°C warmer than peak Holocene temperature.

    You state: “…Earth’s climate is still seeking equilibrium from the last glaciation and from the Little Ice Age that ended a mere 150 years ago…” Is it? To claim this you must know, first, the causes and, second, show that these agents of change are not in balance and that the earth system is designed for these agents to be in balance through some network of forcings and feedbacks. Interglacials are caused by changes in orbital parameters. The idea that the earth is seeking equilibrium in this context is just wrong. There’s no equilibrium to seek.

    I really think you should educate yourself on these subjects before you think you know enough to talk about them intelligently. You might start by simply Googling, “What does paleo data tell us about earth climate sensitivity”

  13. Euan Mearns says:

    Kevin, the whole point of the post is to point out that when sceptics talk about past climate change it is in the context of attribution to observed temperature changes in the last 160 to 1000 years. I don’t need to be an expert on all past and much more significant climate change to point that out. Understanding what causes the rises and pauses in the HadCRUT4 record is of course important, I’d have hoped that Climate Science would have come up with the answer by now – I believe the structure matches some of the multi-decadal ocean – atmosphere cycles such as PDO and NAO, but I can’t immediately recall the details. Part of the story is CO2 and part is natural variability.

    As for you comment about equilibrium, I no more need to show that equilibrium is being sought than you need to show that it was achieved and disturbed by us. But this is a fundamental point. It seems that Climate Science likes to assume equilibrium was reached and can then attribute all change to Mankind. Sceptics take the view that equilibrium is probably never reached in the turbulent ice age that we live in.

    CO2 required to force glacial climates. If you look at Vostok carefully – well its not even carefully, its obvious, that temperature goes down thousands of years before CO2 follows.


    Petite et al make the observation, but then forget to mention it again.

    As for sea levels. Of course I don’t want Man to be the cause of sea levels rising 75 meters. I’ve not checked, but I’m guessing that Antarctica was not over the pole back then. At current rate of sea level rise of 1.6 mm/y it will take 4688 years to get to +75m. I fully expect we run out of oil and gas to burn within 100 years. Coal is more tricky to estimate. But I am in principle not keen on in-situ combustion recovery processes since this could greatly increase the CO2 budget. Now I will get beaten to death by some of my “burn everything” commenters.

    IMO, the real crisis humanity faces this century is accessing sufficient energy to care for 9 billion souls. Best to allow the developing world to develop like we and most others did burning coal – much better than burning their forests, and to then work out a plan for what next – Th reactors?

  14. A C Osborn says:

    Yet another poster critising Euan who is full of their own Hubris.
    Take this for example
    ” Interglacials are caused by changes in orbital parameters.”
    not a single link to the proof of your statement.
    You also say “This was a natural change, does that mean it’s OK we if we, as humans, induce such a change”
    Without the slightest bit of evidence of how “we humans” can induce this change, not links no data.

    As to this statement
    “Moreover, scientists have long known how to calculate the forcings from long-term changes in solar luminosity, Milankovitch oscillations, and other orbital changes. When they examine these natural changes they CANNOT come up with a total forcing that would move the planet from one observed temperature extreme to another. UNLESS they also take into account changes in atmospheric CO2.”

    You are really pushing out the boat, from everything I have seen on the research CLIMATE Scientists have no clue about “total forcing that would move the planet from one observed temperature extreme to another.”
    They can’t even understand the sun and ACCURATELY predict what it is going to do from one cycle to the next.
    They don’t know the relationship between UV, Ozone and it’s affect on the climate.
    They don’t take in to enough consideration Cloud cover and it’s cooling versus warming.
    They don’t understand the total affects of Cosmic Radiation, Solar Wind and Solar Magnetic/Electric currents etc.
    They can’t even accurately predict the next ENSO event.

    So as someone who purports to really know all about CO2 does it’s work perhaps instead of your totally condescending “I really think you should educate yourself on these subjects before you think you know enough to talk about them intelligently. You might start by simply Googling, “What does paleo data tell us about earth climate sensitivity”
    you might like to actually give us some pointers, around 10 or 20 will do for a start.
    Perhaps a good starting point is why the all powerful CO2 which has always LAGGED the temperature increase has the ability to travel back in time to control the temperature increases.
    Or maybe why the Ice Ages still managed to occur when the all powerful CO2 was at over 4000ppm.
    Of course you could also explain the opposite, of how the temperature was maintained at 22 degrees C while CO2 varied from 7000PPM down to around 200ppm
    I await your responses with bated breath.

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