An Honest Appraisal of the Global Temperature Trend — Part 2

Readers were kind enough to point to the newest revision of global temperature data from the Hadley Centre/Climate Research Unit in the U.K., the HadCRUT5 data (a revision of the HadCRUT4) data.

The HadCRUT4 data were in disagreement with the other surface temperature data sets, namely those from NASA, Berkeley Earth, and NOAA. But the new HadCRUT5 data set agrees with them excellently:

All except HadCRUT4 show evidence that global temperature increased faster since the year 2000 than it did during the interval 1980-2000, but that the evidence doesn’t reach “statistical significance.”

At least, not with the data as is. However, much of the fluctuation is due to known causes, so we can estimate it and remove it for the HadCRUT5 data, just as we did for the others. Then we can compare the warming rate 1980-2000 to that since 2000, like this:

The evidence does reach statistical significance for NASA, Berkeley, NOAA, and HadCRUT5 as well. It does not do so for HadCRUT4, RSS, and UAH.

A note: someone asked about the error bars in the graph like this one, for the RSS and UAH data (satellite data of lower-troposphere temperature). I had indeed plotted the wrong analysis for those two data sets; I’ve corrected it in the above graph.

Other note: before adjustment, the error bars for satellite data are much bigger than for surface data. This is because they respond so much more dramatically to those known fluctuation factors, el Nino and volcanic eruptions. When those are removed, the uncertainty in trend from satellite data is comparable to that from surface data.

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25 responses to “An Honest Appraisal of the Global Temperature Trend — Part 2

  1. At what altitude(s) are the satellite lower tropospheric temperature readings taken (i.e. the altitude at which the air has that temperature, not the altitude of the satellites)? And do you know if the satellite readings are consistent with those obtained from weather balloons (when a satellite and a balloon temperature reading is obtained at the same altitude, in the same location, at the same time)?

  2. Thanks Tamino,

    As luck would have it my Arctic alter ego been discussing the HadCRUT5 data in the context of COP26 with some “skeptical” fellows on Twitter. Please feel free to criticise my “trend line”!

  3. Hi

    To clarify, what was wrong with the HADCRUT4 dataset? My understanding is that it has to do with how they treat Arctic data (or maybe they don’t have any above a certain latitude).

    I assume their revised HADCRUT5 dataset treats Arctic data roughly the same as all the others (the revised rate of change is very similar).

    Finally, does the fact that the rates of change decouple around 2000 suggest that the real world change in the rate of warming is largely driven by Arctic amplification


    • The HadCRUT5 description paper is below.

      Two main changes are that they have a version that allows statistical infilling to non-measured regions. Taking the Arctic as an example, they previously assumed it changed at the global average rate in grid boxes where there were no measurements. Now it’s assumed to be changing more like nearby Arctic measurements.

      Also the ocean data have been updated. A while back we found that Hadley sea surface ship data had a bit of a trend drift compared with independent satellite, buoy and Argo float data. They might have corrected for this.

      Click to access HadCRUT5_accepted.pdf

  4. brettschmidt:

    Satellites do not measure temperature. They measure radiation. A model is used to interpret the radiation data into temperature estimates. Different radiation measurements from the different sensors on the satellite allow the models to estimate temperature based on a weighted range of heights in the atmosphere -some more “surface” than others.

    The following link at explains the details and illustrates the altitude-weighting of different estimates in the satellite data. Comparison with weather balloons is a standard part of the process of evaluating the satellite models.

  5. Thank you for your reply and the link you provided. I’ve started reading it, though I haven’t finished yet. I had always figured that satellite measurements of atmospheric temperatures would have to be based on measurements of electromagnetic radiation (emr) emitteted by atmospheric atoms and molecules, since I don’t think that there is any other way to measure temperature from a distance, but I had always assumed that the determination of atmospheric temperature from emr readings was a simple, straightforward matter, much like the measurement of body temperature using infrared thermometers. Based on what I’ve read so far, it seems that I was wrong about that latter assumption.

  6. Damn it Tamino, I recently submitted a paper on this!

    Are your trend error bars using ARMA(1,1) degrees of freedom correction on the adjusted trendlines based on the full-fit residuals?

    I actually disagree with those being a good estimate of the confidence intervals for adjusted fits to global temperature, and my estimate is that we’d have to wait longer to detect acceleration. That said, I did my calculations slightly differently so will have to confirm that and get back to you.

  7. On a similar subject – have you had a look at the site which some deniers are using as evidence that we are cooling and that all scientists who say it is warming are corrupt and part of a conspiracy etc. etc.

    • Why would one look at propaganda site? I simply don’t understand why. I guess it’s something basic to humans, but it must have missed me.

    • Looks like the same nonsense that’s been pushed by some for decades. For example:
      “It uses unadjusted surface temperatures”
      Either the authors don’t know much about how to calculate global temperature, or they’ve intentionally selected a way to give you an inaccurate & biased answer.

      A quick google should bring up plenty of info on these issues – the results from the Surface Stations project, Berkeley Earth, HadCRUT4, ERSSTv4 etc.

  8. You admit that the results are not statistically significant and that’s all I need to know. ‘Scientists’ who promote the global warming religion cannot ever produce models which show that CO2 can produce warming to any degree of statistical certainty.

    It’s the job of scientists to show that CO2 can cause climate change to a degree of certainty beyond that of random chance. This, nor anything else shows that.

    The point I’ve always made is that there’s no hard evidence whatever regarding the size of the impact of CO2 on global warming or climate change. All that we have for this is computer modelling. That in itself would not be a problem if the models could be relied upon. However, they can’t, not only because the number of variables involved is very large but also because climate is hugely complex, non-deterministic and the data that models need simply cannot be measured at anything close to the granularity required.

    [Response: There was a time (not too long ago) when such comments might actually increase fear, uncertainty, and doubt (FUD) among casual readers who might happen upon it. I don’t think that’s true any more. Of course the flat-earth crowd will lap it up (there’s no reaching some people) but reasonable folks are better educated on the subject, and finally on to the fact that this nonsense is nonsense. All you really accomplish is to make yourself look ridiculous.

    Congratulations, you are irrelevant.]

    • If you had actually bothered to read the post, you would have seen that it is not about whether or not there has been statistically significant global warming which can not be explained by natural factors, but whether or not there has been a statistically significant increase in the rate of global warming since the year 2000. There is overwhelming evidence that there has been a statistically significant increase in mean global surface temperatures over the last several decades as a result of increasing concentrations of atmospheric GHGs (greenhouse gases) as a result of human combustion of fossil fuels. Again, that is not what this post is about. I suggest you follow the following advice:

      It is better to keep your mouth shut and be thought a fool than to open it and remove all doubt.

  9. Straight in with the ad hominems! Typical of the so called ‘scientists’ who can never show the evidence.

    I work with Monte Carlo simulations as part of my job and I know the limitations of models. The variables involved in climate is too complex to get an honest assessment of how it can change. There is NO evidence that CO2 can cause climate change with a confidence interval within an acceptable limit, that shows it’s occurring beyond random chance.

    Though the personal attacks are typical of what we see from ‘scientists.’

    • Mark–

      1. Climate is, as you say, “hugely complex”. And, some subset of climate variables may well be chaotic, but I truly know of no climate scientist actually who would assume, as you state without a trace of evidence, that climate is “non-deterministic”. Most, since Lorenz, assume deterministic chaos. Since you say you work with Monte Carlo simulations–which are quite useful in exploring deterministic chaos–I would have assumed you knew about this point.

      2. The blog entry in no way finds blanket non-significance as you state. The long term significance of the global record is astronomically clear. What it examines is a different point entirely.

      3. This article isn’t even exploring whether or not CO2 causes warming. It’s examining how various proxies differ. over periods of 20 years. Other studies have long shown that CO2 “can cause climate change” and have so shown since the latter 19th Century.

      4. An ad hominem argument is of the form:

      Given: Mark is a ridiculous person who states X
      Therefore: The proof that X is false is because Mark is ridiculous.

      The argument here is quite different…

      Given: Mark states. without evidence but rather totally by unsupported assertion, that all the evidence in favor of climate change is ridiculous/unproven.
      Therefore: Since Mark provides no evidence that climate change is ridiculous/unproven, Mark, given his lack of evidence, made an irrelevant–and ridiculous–argument.

      That is not an “ad hominem” argument. It is a conclusions based on evidence which you provided.

      • Well said. Notice too that Mark West insulted climatologists by putting the word “scientists” in quotes, and then had the nerve to complain about what he (wrongly, as you point out) called an ad hominem attack. Since I started commenting on AGW on the question and answer site in 2019 (after years of learning as much about the science as I can), I’ve been amazed and appalled at the rudeness, arrogance and hypocrisy of AGW pseudosceptics, covidiots, anti-vaxxers, racists, holocaust deniers and other [insert expletive here] who make rude, derogatory comments about climatologists, Dr Fauci and other epidemiology experts, and other honest people without a shred of evidence, and then cry “ad hominem” when someone calls them out on it. On one occasion, someone on Quora accused scientists who say that AGW is real are lying and that those of us who believe them are “brainless sheep”. I responded, “don’t judge everyone by yourself. Some people are actually honest and genuinely interested in finding out the truth.”. He then indignantly accused me of engaging in an ad hominem attack against him! Another buffoon said that AGW is bullshit, because “Greta Thunberg is ugly”. When I remarked that his comment is proof of the maxim “there is no statement so stupid that no-one would ever make it,” he retorted, “typical communist and nazi. You can’t refute my argument, so you attack me personally.”

      • It’s a mere tactic to allow them to play the “victim” card even if they aren’t victims in the least and don’t even know what an ad hom argument is in the first place. Ignorance clearly on display, but they think they are pwning you. They’re not.

      • Quite frankly we do not have a clue as to what controls the climate, so to make bold claims that we can deterministically proscribe climate change to a given variable like CO2 is just nonsense. I am sorry to say, but such comments just demonstrate how little you understand about statistics when validating climate change. How does the global warming cult deal with statistical certainty with so many variables? It is quite frankly impossible to demonstrate that current temperatures are correlated to CO2 rise as a result. For it to be statistically significant it needs to meet a statistical certainty which puts it beyond random chance, which it doesn’t. Therefore, it doesn’t disprove the null hypothesis that climate change is natural, so we must assume it is natural.

        What the hard evidence from science provides is that man-made emissions have and will continue to make a small contribution to global warming and climate change. However, it proves nothing more, which is surprising given the incredible increases in CO2 that we’ve seen over the past 20 to 30 years. If the models were correct we’d now be frying.

        It is important to discuss the causes of climate change because global warming cultists, like this blog (which acts as a kind of global warming Bible), demand we make changes to society which will have distinct harm on the poor. They demand we curb CO2 usage, which will mean people won’t be able to travel to work as cheaply, poor people will have to choose between food and heating. It’s already pushing people into poverty and causing the youth of today to become depressed. This needs stopping.

        Wealth creation through capitalism has been the greatest saviour to mankind, bringing so much out of poverty. The left want to stop this through false claims of CO2 driving climate change, which will stop the ability for wealth to be created and technological advancement.

        It’s unsurprising that ‘scientists’ have jumped on the bandwagon to virtue signal their supposed green credentials and display a similar disdain for such advancement, as it’s not exactly hidden that most are Marxists.

        [Response: You might want to ponder, why do you believe most scientists are Marxists?]

      • Quite frankly, you can always count on Mark West to double down on stupid when challenged for his refusal (or inability) to cite any evidence what so ever in support of his illogical blanket assertions, go off on tangents concern-trolling about the poor and the benefits of capitalism, and then resort to ad hominem use of terms like “global warming cult”, “global warming Bible”, and “Marxist” scientists, all while complaining about “ad hominem” attacks on himself.

        Mark is clearly off the crank meter, as he has demonstrated repeatedly in this and other comment forums. As Tamino succinctly pointed out, he is irrelevant, full stop.

    • Well, if you look at Tamino’s analysis, he systematically removes all the other factors (el nino, volcanoes etc), and what is left is a steady increase that can really only be CO2. Or fairies at the bottom of the garden. Never forget about them…

      • MW: It is quite frankly impossible to demonstrate that current temperatures are correlated to CO2 rise as a result.

        BPL: No, it’s quite easy, and the results are very significant. Please don’t just make stuff up.

        Not only is the correlation between CO2 and temperature anomalies very high, it is significant well beyond imagining, and accounts for most of the variance. 85% from 1850-2019. That means that every other cause of the variation, KNOWN AND UNKNOWN, can only account for 15%. You need to take an introductory statistics course, Mr. West. And concentrate hard on “analysis of variance.”

  10. michael Sweet

    This comment is on covid but that thread is closed.
    According to the New Your Times summary of the CDC data, Florida and Louisiana are currently in the second and third lowest position of covid cases of all the states. There are two more Republican states in the bottom ten. Six weeks ago all these states were in the top five positions for most disease. I live n FLorida. Few people wear masks in public and schools are open, most with out masks. (free)

    It seems to me that these states have reached herd immunity from the spread of disease and that is why covid is retreating there. States that have been more proactive, like Maine, currently have more disease. It is expected if they prevented disease two months ago that they have more people who can still get sick than those states who allowed everyone to get sick two months ago.

    This study
    estimated that 83% of blood donors in the USA in May 2021 were seropositive for Covid. Only about 50% were vaccinated. Approximately two undetected covid infections were estimated for each diagnosed infection. If the 83% applies to the general population, the number of infections in the third wave could bring the total up to near 95 or 100%.

    If the USA is near herd immunity than a mutation that avoids the vaccine and/or previous infection is the only way there could be a new wave of covid. Much of the rest of the world is probably near herd immunity since the delta covid is so infectious.

  11. MW: There is NO evidence that CO2 can cause climate change

    BPL: Yes, there is. Tons of it. The fact that you aren’t familiar with the evidence doesn’t mean there’s no evidence.

    Please pick up a book on atmosphere physics and read through it. I can recommend some good ones, if you want to learn.

    • But that’s just it, Barton, Mark has no desire to learn, he already “knows” that global warming is a hoax perpetrated by Marxists scientists to undermine capitalism and thereby hurt the poor. In other words, he’s batshit crazy.