A quick ‘n dirty guide to falsifying AGW


(Nederlandse versie hier)

Have you ever heard of Newton’s theory of gravity? Well, it’s all made-up nonsense. You’ve been fooled.

The reasoning goes as follows:

  1. According to the theory of gravity, objects should fall to the Earth’ surface.
  2. That bird in the sky remains there, without falling.
  3. Theory of gravity is wrong.

This reasoning bears a lot of resemblance to the following, equally strong reasoning that falsifies the theory of anthropogenic global warming (AGW):

  1. According to AGW, CO2 controls the climate.
  2. For the past 10 years, global temperature remained more or less steady whereas CO2 levels went up.
  3. AGW theory is wrong.

Voila, problem solved. If only it were that simple…

What’s wrong with these arguments? They sound so logical at first sight.

  1. The theory to be falsified has been oversimplified. (There are more forces than only gravity; there are more factors influencing climate than only CO2).
  2. The observation has been oversimplified. (The bird has wings which can be used to exert an upward force; the expected trend in temperature does not necessarily rise above the expected level of yearly variability over the course of a decade).
  3. Therefore the conclusion does not hold. 

It appears that a lot of “skeptics” start with their desired conclusion and work back to which part-observations and simplifications are needed to get there. I prefer not to fall either, but the fact is, observing a bird in the sky doesn’t disprove gravity. Whether we want to or not, we’ll have to learn through falling and getting up.

Update: Gravity has apparently been shown to be a hoax based on Newton’s private correspondence being released.


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26 Responses to “A quick ‘n dirty guide to falsifying AGW”

  1. robbie Says:

    Dear Bart

    What you say here is obviously correct — except I can’t imagine that even Lord Monckton (whose political views I do not agree with) would use such simplistic arguments against AGW. I presume he’s a ‘ “skeptic” ‘.
    If global mean temperature remained more or less steady for the next 100 years, say, then even that would not actually falsify AGW, as it might well rise after that for the next 1000 years. But can anything truly falsify such a theory?

    Robbie Verdon, Canberra, Australia.

  2. Bart Says:


    The kind of reasoning that I laid out here is being used a lot. Hans Labohm is a prime example, and I believe Mockton does too. The whole “global warming stopped in 1998” line is based on this reasoning. It’s a staple of the “sceptics”.

    If the known net forcing remains strongly positive, yet the global average temperature and other metrics of global warming remain flat for hundred years, that would definitely warrant reconsidering our understanding, of course.

  3. Inadequate proof that AGW is bunk » Mind of Dan Says:

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  4. bagzzz Says:

    It was not skeptics that started looking at trends over 10 years. Remember the hockey stick? Skeptics have always said that we do not have enough data, but the response was that we should take drastic measures just in case. Now that the trend is down, the alarmists have stopped using 10 year trends and started using 10 year averages for their “trends.” That will give them another 10 years to panic everyone. There is a reason Gore didn’t use 10 year averages for his debunked movie.

    Skeptics still say that there is not enough data, but the point is that there never was enough. Really the good data only just started to be collected through satellite imaging, so it is all conjecture anyway. When the alarmists admit that, there will be no need to point to the only good data we have…. the cooling trend of the last 10 years.

  5. Bart Says:

    What cooling trend?

    There will never be enough data to satisfy some.

  6. bagzzz Says:

    It is simple math. Do a least squared progression on the last 10 years. The number is small but it is negative. You can call it more or less steady if you want. The arguments don’t change.

    Is there enough data to satisfy you? All the data we have so far does not give us any proof of AGW. That is why IPCC relies on models… models that are pathetic at predicting anything.

  7. Bart Says:

    Congrats bagzzz, you’ve just falsified the theories of gravity and of AGW.

  8. Robert Grumbine Says:

    Bart: You can combine climate and gravity —

    Clouds disprove gravity. Just look at them floating along, failing to fall to earth. Immanuel Velikovsky thought that clouds had their own anti-gravity system, or at least proved that gravity didn’t work as Newton or Einstein said.

    bagazz: It wasn’t scientists who called 10 years climate. You need 20-30 years of data to determine a trend. See also what cooling trend for some actual computations of the trends. Hint: Last 10 years don’t have a cooling trend. No 10 year period in more than the last 20 have.

  9. Bart Says:

    Hi Robert,

    That’s an interesting anecdote. On his wikipedia page it sais about Velikovsky that he gained “enthusiastic support in lay circles, often fuelled by claims of unfair treatment for Velikovsky by orthodox academia”.

    Hmm, that rings a bell, doesn’t it…?

  10. The relevance of rooting for a unit root « My view on climate change Says:

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  11. nickname Says:

    What is the theory of AGW and what are the real grounds for falsification?

  12. jj Says:

    I agree with bagzzz…

    At the end, what matters is who is right. After all, if AGW is false, we will be happy for not having wasted our time and effort in reducing pollution, reducing our waste, our exploitation of our seas and resources, etc…

  13. Jason Hoerner Says:

    Robert Grumbine: “Hint: Last 10 years don’t have a cooling trend. No 10 year period in more than the last 20 have.”

    Only if you consider surface temperature records. Most skeptics believe the surface temperature record is flawed due to urban heat island effects, poorly sited stations, and flawed statistical methods used to compute temperatures. Skeptics prefer to follow lower troposphere satellite records since 1979, which are clearly unbiased, and not subject to urban heat island effects. If you look at those, the trend has been down starting in early 1998.

    You are free to disagree about whether the surface temperature record is flawed, but your blanket statement is false. It should correctly read “no 10 year period shows a cooling trend, assuming we ignore satellites, the most reliable source of temperature data”.

  14. Marco Says:

    Jason, UAH MSU LTL currently gives a positive trend for 1998-2010, as well as for every year after 1998.

    And whether satellites are such reliable sources of data…we all know that Spencer and Christy have had to alter their methodology on multiple occasions, and that each of the major updates (expect the recent attempt at correcting for seasonal drift) has significantly increased the warming rate.

  15. Robert Grumbine Says:


    As I mention from time to time at my blog, it’s easy to make assertions. You should really have done your homework. Using the UAH satellite shows again no 10 year period with a cooling trend for a long time. And certainly not including the present.

    How reliable the UAH record is, is a different question. As Marco mentions, there have been many changes to the processing — hence it now being version 5.3 — and every one of them has had the result of increasing the degree of warming. I’d be a little cautious about using a series that’s been changed so many times in such a short period, and has always shown the same bias. Much less to call it ‘most reliable’.

    Of course you also should consider the question ‘most reliable at what. Even if it worked perfectly, the satellite is reporting an average temperature over the lower several thousand feet of the atmosphere. Since I live near the surface, rather than a few thousand feet above it, it seems to me that the most relevant temperature is the surface temperature.

    You illustrate, though, why it is you’re not a skeptic. A real skeptic would have run the numbers himself before declaring that there is a downward trend in the satellite since 1998. It’s more work to do that, but being a real skeptic is work.

  16. Jason Hoerner Says:

    1998-2009 was a very slight negative trend in satellite temperatures (RSS Version 3.2 Channel TLT, Land+Ocean). That’s the data set I’m looking at. 2010 has been very warm so far, although not quite as high as 1998, but enough to turn that into a slight positive trend. I’m just saying that there is a 12 year period with a negative trend in the last 20 years, not that the trend to present day is negative.

  17. Bart Says:

    Is that what they call “backpedaling”?

  18. Jason Hoerner Says:

    Robert: I have run the numbers myself. I have an Excel spreadsheet with the RSS Version 3.2 Channel TLT data in it, which I update every once in awhile with the latest numbers, when I’m interested. I’ve been maintaining the spreadsheet for over two years now. I have it compute trend lines starting at each date to present. Last time I updated it was December 2009, and as of that date, the trend was still negative. I updated it again, and it’s creeped back to positive, which is why I admitted that fact. I read every article on WUWT, and occasional articles on Climate Audit and Real Climate (to see the opposition viewpoint).

    We are entering a La Nina event, which should be accompanied by cooling. So I expect the trend to go back negative within a year and a half. While satellite temperatures show a substantial upward trend, it’s also true that the satellite record starts at the end of a cooling period from 1940 through 1970. So the satellite record is starting from a local minimum of the temperature series, and its short term trend cannot be extrapolated to infinity. We need more data.

    In my opinion, CAGW becomes falsified once the actual temperature deviates sufficiently from the estimated trend of the climate models. The problem is it takes a long time to find that out. The only climate model old enough to compare to reality is Hansen’s early work, and it has already been shown to be wrong. Although alarmists claim that it’s not wrong by enough to be outside the range of natural variation, or that computer models have improved since then, and are more accurate. So we need to wait a bit longer to see the next set of models proven wrong.

    The other thing to try is to compare the models’ behavior at predicting current real world phenomena at a global scale. I.e., does any current model predict cyclical phenomena like El Nino and La Nina? Does any model accurately predict cloud cover patterns? Does any model accurately predict the distribution of temperature increases between the poles and equator? The answer is “no”. But alarmists will argue that such details don’t need to be predicted correctly for the models to still be accurate in terms of overall long term trend.

    Since I live in a house, rather than outside, the most relevant temperature is what my thermostat is set to. Seriously, if you have a problem with the climate where you are living, just move — a change of address will dwarf any warming signal. The point I’m making is that the surface temperature records are mostly in urban areas or near airports, and suffer from UHI. And yes I know alarmists say UHI has minimal effect on the trend.

    That’s the problem with arguing about climate science — you eventually end up disagreeing about a point of fact, like how much the surface temperature record is affected by UHI or other factors. I can point to studies that say one thing, you’ll point to studies that say the opposite, and nobody’s mind will be changed either way. I could ask you to try to refute the study on my side, or vice versa, but neither of us can afford to do the original research necessary to refute the other side’s study, since this is just a hobby.

    But I do ask you to try to counterpoint some of Anthony’s work on surface stations — for example his most recent article which found a +5 degree trend adjustment in Nepal. Can you explain that? [crickets chirping]

  19. Marco Says:

    “Seriously, if you have a problem with the climate where you are living, just move”

    Good, you accept a few Pakistanis in your neighbourhood? You’ll have to help them get there, though, they don’t have the money…

    And considering Anthony Watts’ work on the surface stations: we’ve had JohnV who in the early days already showed Watts’ storyline of “poorly placed stations introduce a warming trend” did not show up in the data. We’ve had Menne et al show the same with a larger set. We’ve had Zeke Hausfather and the people at clearclimatecode showing Watts (and D’Aleo) falsely claimed that removing high latitude and high altitude data introduces a higher warming trend. And then we’ve even had Jeff Id who claims that GISSTEMP and HADCRUT *underestimate* the warming trend!

    And it isn’t Watts who did ‘the work’ on Nepal. That would be Willis Eschenbach:
    His excuse is the same as it was then: *I* (=Eschenbach) don’t know why they did the corrections, and as long as they do not explain it to me, it’s data manipulation/fraud. In short, the argument from ignorance…

  20. Jason Hoerner Says:

    Sorry about attributing Willis’s article to Anthony. The link to the article about Willis “lying” illustrates my point about the difficulty of rational argument between skeptics and warmists. Basically, that warmist article is saying “Willis is lying because he’s looking at raw data, rather than adjusted data”. Duh, the whole point of the skeptic argument is that the adjustments made to the data are bogus! Not necessarily deliberately fraudulent, but unjustified and incorrect.

    Looking at the article, there was a station type change, and that resulted in a step change to the temperature record. And you see a corresponding step change in the adjustment graph of around 1.1 degrees. Makes perfect sense. However, beyond that step change, there is a linear trend adjustment applied that gets warmer and warmer over the next several decades, by around 0.8 degrees, plus some adjustments before the step change.

    It is exactly these gradual warming adjustments that make no sense to skeptics. The point of homogenization is to pick up discontinuities, so why does it seem that every adjusted temperature series has these linear trends applied, and only in the last few decades? Why do far more adjustments result in temperature increases than decreases, versus balancing each other out? Saying a sophisticated computer algorithm produced these results is not proof that the results are valid.

    That seems to be the excuse of the warmists: it doesn’t matter if computer algorithms generate obviously nonsensical data. If the authors of the algorithm spent “a great deal of effort on it”, it must be correct. In short, the argument of appeal to authority…

    The article didn’t prove that Willis “lied”, only that Willis “exaggerated”. There was a legitimate looking adjustment, but also bogus looking adjustments. If you included only the station type step change in the adjusted series, you would have a nearly flat temperature trend, with insignificant warming.

    In the article you linked, they quote the creators of the adjustment technique: “using an approach based on a reference series created from surrounding stations means that the adjusted station’s data is more indicative of regional climate change and less representative of local microclimatic change”. In other words, they’re saying looking at a specific station’s adjusted data in isolation doesn’t necessarily mean anything. The whole point of bringing up Nepal is that the IPCC specifically points out Nepal in its report, indicating it has a large temperature increase. But that large increase only shows up in adjusted data. In other words, the IPCC is quoting climate information derived from a statistical approach that the authors of that approach specifically state should not be used that way!

    Who’s lying now? It looks a lot worse when a government sponsored international body lies than a skeptical hobbyist. And I would argue Willis simply made a mistake — what’s the IPCC’s explanation? Surely they can’t claim not to know the limits of the adjustment methods.

    For the record, I’m a lukewarmer. I believe that AGW is real, but that climate sensitivity to CO2 is far less than alarmists claim. I also believe that positive and negative effects of increased CO2 will balance each other out. And if there are negative effects, the cost of adaptation is orders of magnitude less than the cost of preventing the emissions.

    I don’t think many alarmists have really thought through the consequences of reducing worldwide CO2 emissions by 80% or more, in terms of economic and political cost. The problems would dwarf a few Pakistanis on our doorstep.

    The chief issue is China. Without China being on board, any hope of worldwide reduction is moot. Perhaps we will invent a magic new technology like CCS. But even if it could be developed (which isn’t guaranteed), there’s no way to police things in a country like China. There’s no accurate way to prove companies aren’t cheating and claiming the carbon is sequestered. There is no way to prove that it will stay sequestered and not leach back out of the ground. And it’s likely that retrofitting CCS will not be possible in most cases, so you have to convince them to rebuild their whole infrastructure. And that’s assuming they even agree to do anything in the first place!

    The only way you are going to slow down China’s emissions is with military threat, in my opinion. World War III sounds a lot worse than a few Pakistanis on my doorstop. Seriously, I’d like anyone to take a shot at explaining how to stop China from emitting, assuming their government continues to believe that emissions are not a problem.

    Luckily I think action will be stalled long enough to prove the warmists wrong, and 20 years from now, we’ll look back on these couple decades and laugh. Maybe the warmists will go back to worrying about an ice age, and will say we need to increase CO2 emissions even more to try to avert it?

  21. Marco Says:

    Jason, the articles show that Willis, because he does not know why a correction has been made, makes large claims. Those articles show WHY changes have HAD to be made, several points which Willis easily could have found himself. Willis Eschenbach simply invited this snark, when he cried “FRAUD!” in the article on Darwin. Oh, you missed that one? Perhaps read it again, will you?

    And there are many articles in the literature that describe why there are so many adjustments. They are not all done in the same way. GISTEMP has another correction method than the BAM. Sometimes this results in differences, sometimes not. In this case (Darwin) there is hardly a difference.

    Willis uses the same narrative he tried for Darwin to jump up and down. Only difference, this time he did not cry “fraud”.
    But you then do make it worse in not understanding the difference between microclimate (as in “Kathmandu measurement station”) versus regional (as in “Nepal”).

    Finally, China DOES consider emissions a problem, and is actively working to limit them to a MUCH greater extent than e.g. the US. Unfortunately, China is rapidly growing, economically, which essentially offsets the mitigation efforts. But imagine if they had not done anything? Or if the West had not done anything? We may have well bought us a few years to find solutions, which will require active carbon capture. Of course, I also note your naivity in thinking that “a few Pakistani’s” is better than “war”. What do you think will happen when large populations start to move elsewhere? Greeted with open arms? That’ll be the first time ever in history, invariably it has led to war or regional conflicts in the past.

    Sadly, I think your prediction is very much wrong, and in 20 years people will angrily scream at scientists for “not properly predicting the problems that lay ahead”. Upon which the scientists can only shake their heads, point to the IPCC reports, and shake their heads again.

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  23. Will M. Says:

    How could AGW be falsified? One way is as follows – construct a computer model of a planet’s temperature that can correctly model the past temperature record and predicts an unimportant sensitivity to CO2 level increase as you assert. We have the best climate modelers in the world competing for their livelihoods against each other. They have all produced physical models of climate that correctly produce climate trends of the past. All of them predict devastating impacts to our economy and ecology given the current trajectory. Denialists have attempted and failed at this effort multiple times with massive funding. They don’t have one, just as they don’t have an alternative to gravity or evolution, which are also falsifiable theories that have been tested rigorously and produced important insights that improved the human condition.

    I speak for everyone when I say that I hope your are correct. I hope that the greatest scientists in the field of climate modeling from around the world have all made a mistake, but there is no evidence that that is the case, and all of the best scientific bodies in the world agree with AGW. Until there is real evidence, the only prudent course is to change the course of this ship and prevent levels of CO2 that doom our planet to devastating ecological changes. Read Nordhaus “Climate Casino” for the clear economic case that doing nothing is a horrendous economic risk that no business would ever make.

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  25. mark4asp Says:

    The AGW hypothesis is wrong because it proposes testable scenarios: such as upper tropospheric warming in equatorial zones. Warming which is not found. Even the climate modellers admit that. So the models are wrong. AGW only has its models as evidence, so AGW is wrong.


  26. bartverheggen Says:


    The so called “hotspot” that you are referring to is not specific to an enhanced greenhouse effect, but is expected to occur from any surface warming, irrespective of the cause of said warming. Thus its presence or absence is no proof or disproof of anthropogenic global warming.

    See also https://ourchangingclimate.wordpress.com/2013/08/19/tropospheric-hot-spot/ for more background and https://www.carbonbrief.org/major-correction-to-satellite-data-shows-140-faster-warming-since-1998 for recent developments in satellite observations.

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