The latest critique of consensus studies is an attempt to re-analyse the data from Verheggen et al. (2014) to suggest that the consensus amongst climate scientists is only 47%, not 97%. I only have two things to say about this. Firstly, As Michael Tobis points out, you do need to consider who you include as a scientist, what question you are asking, and how you go about asking it. Secondly, these consensus studies are not to inform those who work in – or understand – this scientific area; it’s for those who do not and for those who dispute the existence of a strong consensus. If you analyse survey data that aims to address this issue and conclude that the level of consensus with respect to AGW is less than 50%, then you’re wrong. It’s clear (whether you look in the scientific literature or speak to relevant experts) that the level of consensus about anthropogenically-driven warming is very strong.

There’s a very simple reason for this. It’s because it is extremely difficult to construct a physically plausible scenario in which anthropogenic influences contributed less than 50% of the warming since 1950. Ed Hawkins has a nice back-of-the-envelope attribution calculation and I thought I might do something similar here, except the other way around. I want to see if it is possible to construct a scenario in which less than 50% of the warming since 1950 could – plausibly – be anthropogenic.

So, what do we know? We’ve warmed by about 0.6oC since 1950, and the change in anthropogenic forcing since 1950 is about 1.7Wm-2 ± 1Wm-2. In the absence of feedbacks, the equilibrium climate sensitivity (ECS) would be 1.2oC per doubling of CO2 (3.7Wm-2). If we assume that the TCR-to-ECS ratio is 0.7, then the transient climate response (TCR) would be about 0.85oC. Let’s start by assuming that the actual change in anthropogenic forcing is the smallest plausible (0.7Wm-2) and that the TCR is indeed 0.85oC. This would imply anthropogenic warming, since 1950, of about 0.15oC, which is indeed less than 50% of that observed (0.6oC).

Here’s the first problem, though. The Planck response to 0.6oC is 1.9Wm-2. We currently have a planetary energy imbalance of about 0.5Wm-2, which means that the change in radiative forcing/feedback since 1950 is about 2.4Wm-2. However, we’ve assumed here that the change in anthropogenic forcing since 1950 is only 0.7Wm-2, and we’ve assumed that there are no feedbacks to anthropogenically-driven warming. Therefore, something else must have produced a change of 1.7Wm-2. It can’t be the Sun, or volcanoes, so it can only be the response to the internally-driven warming (0.45oC).

However, the physical processes (clouds, water vapour, …) that would produce such a response are the same as those that would produce feedbacks to anthropogenically-driven warming. How can there be such a strong response to internally-driven warming and (as assumed) no feedback response to anthropogenically-driven warming? It doesn’t seem possible. Additionally, if the response to the internally-driven warming (0.45oC) is 1.7Wm-2, then that implies a feedback response of 3.8Wm-2K-1, which is large enough that internally-driven warming could produce a runaway, which is again virtually impossible.

Let’s do one more step. Let’s assume that the change in anthropogenic forcing is still only 0.7Wm-2, but that the anthropogenic warming is 50% (0.3oC). This implies a TCR of 1.6oC and an ECS (assuming a TCR-to-ECS ratio of 0.7) of 2.3oC. This would then imply a feedback fraction of 0.5, and – consequently – a feedback response of 1.6Wm-2K-1. So, 0.3oC of anthropogenically-driven warming is associated with a change in anthropogenic forcing of 0.7Wm-2 (assumed) and a feedback response of $0.3 \times 1.6 = 0.5$ Wm-2 – a net radiative response of 1.2Wm-2.

The remaining 1.2Wm-2 (2.4 – 1.2) is therefore associated with internally-driven warming and is still substantially greater than the feedback response to anthropogenically-driven warming. This, again, seems rather unlikely. Also, this would produce an internally-driven feedback response of 1.2/0.3 = 4Wm-2K-1 which would again imply that internally-driven warming could produce a runaway, which is – again – highly implausible.

I’ve made some fairly extreme assumptions here, and it has still turned out very difficult to construct a physically-plausible scenario in which less than 50% of the warming since 1950 was anthropogenic. As far as I can tell, if I change any of the numbers so as to make them a bit more realistic (make the change in anthropogenic forcing larger, and assume more reasonable TCR and ECS values, for example) it gets even more difficult to construct such a scenario. This is why it is extremely likely that most of the warming since 1950 has been anthropogenic; it’s very difficult to construct a scenario in which this is not the case. It really doesn’t matter what various surveys may or may not say; the strong consensus exists because those who work in this field realise that it is extremely likely that most of the warming since 1950 has been anthropogenic. Massaging numbers in surveys is not going to change this.

Of course, I’ve done this rather quickly and have rounded various numbers, so this isn’t intended to be precise. It’s also possible that I’ve missed something, in which case feel free to point it out. In fact, I’d be quite keen to see a physically-motivated argument as to how more than 50% of the warming since 1950 could have been non-anthropogenic, as I’ve never seen one and I don’t think it is actually possible to do so. Feel free to prove me wrong.

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48 Responses to 95%, attribution, and all that!

1. “Secondly, these consensus studies are not to inform those who work in – or understand – this scientific area”

Nicely said. That’s an important point, too often ignored. The science of climate change and the public policy debate interact, but operate by different rules. Conflating the two leads to confusion in both. That’s why we can learn much from other sciences with large public policy implications, especially in health care. While of course imperfect, I believe they handle these two tracks much better.

“it’s for those who do not and for those who dispute the existence of a strong consensus.”

That’s not what the authors of these surveys often give as their purpose. Rightly so, as ann indicator of the quality of the IPCC’s work is that they give confidence limits for the major findings. These are vital inputs for public policy decision-makers. As are surveys testing agreement with the IPCC’s findings.

2. “it’s for those who do not and for those who dispute the existence of a strong consensus.”

That’s not what the authors of these surveys often give as their purpose.

Why would it possibly be for any other reason? You don’t do consensus studies for those who work in a scientific field; they already know the answer. Typically, you don’t do it at all, as all you would need to do to discover the level of consensus would be to talk to some relevant scientists. The only possible reason for doing it in climate science is because a strong consensus is disputed by some and so these studies exist to illustrate the level of consensus to those outside the field, not for those inside the field.

3. Fabius,
Oh, by the way, I did a quick calc using the Question 1b figure in your post. For each category (virtually certain, extremely likely, ….) for both those who suggest it is more than 50% and those who suggest less than 50%, calculate (by weighting according to the number who responded in each category) the probability of less than 50% warming. For example, extremely likely is 95%-100%, so at most a 5% chance of less than 50% warming. The probability is then the number of people who selected this option multiplied by 0.05. Repeat this for each category for both >50% and <50%. The overall result is a 16% chance of less than 50% warming according for the response for Question 1b.

4. (1) “these studies exist to illustrate the level of consensus to those outside the field, not for those inside the field”

Yes, I agree with this formulation. I believe that’s what I said. The dimensions of climate scientists’ consensus is a vital input to the public policy process. These surveys provide a valuable check on the IPCC.

Seeing this, as your initial statement implied, in terms of two teams misrepresents how public police debates operate.

(2) “I did a quick calc using the Question 1b figure in your post.”

I don’t see much value in examining these things under a microscope. The headline result (combining 1a and 1b) is what it is, providing a direct comparison to the keynote finding of WG1 of AR4 and AR5 — and for comparison with the many other similar surveys (which this improves upon).

The numbers of the subgroups are quite small, and it becomes a game of assembling the pieces to get the picture you find pretty. It’s just an exercise in confirmation bias.

5. Seeing this, as your initial statement implied, in terms of two teams misrepresents how public police debates operate.

My comment had nothing to do with public policy debates. It simply referred to the distinction between those who work in a scientific field, and would understand the level of consensus, and those who don’t. You should possibly try to not see division in everything other people write.

I don’t see much value in examining these things under a microscope.

Agreed. Bottom line : if you’re implying in your post that the actual level of consensus is about 47%, then you’re very obviously wrong. I was simply pointing out that there is a way to reconstruct the percentages in the responses to Question 1a, by doing a more complete analysis of the responses to Question 1b.

6. “My comment had nothing to do with the public policy debates.”

I based that on your statement that “You don’t do consensus studies for those who work in a scientific field”. I didn’t know there was a third field of debate.

“then you’re very obviously wrong”

Wave those hands! Thanks for the discussion.

7. Fabius,

I based that on your statement that “You don’t do consensus studies for those who work in a scientific field”. I didn’t know there was a third field of debate.

I know what you based it on. I’m simply pointing out that I was simply referring to the distinction between those who work in a scientific field and those who do not. Whether the others are policy makers, the general public is neither here nor there. The main reason these studies exist are because there continues to be people (yourself, for example) who suggest that there isn’t a strong consensus, when there very obviously is. That doesn’t make it right, but that it exists is clear.

“then you’re very obviously wrong”

Wave those hands! Thanks for the discussion.

Do a literature search; talk to some scientists. If you’re suggesting that the scientific consensus with respect to AGW is around 50% it should be easy to find papers that are not consistent with the consensus position. It should be easy to find scientists who would disagree with the consensus position. I’ve tried. It’s not. Maybe you will have more luck.

8. BBD says:

Astonishing that those who would wish to be taken seriously are still peddling the ‘no scientific consensus’ nonsense.

9. Kevin O'Neill says:

I forget my Roman history; is Fabius Maximus the Roman emperor who freed the Tol 300?

10. guthrie says:

So, basically there’s still no physical stuff being proposed for why most of the warming since 1950 is due to us.

11. I think Fabius Maximus was known as Cunctator which, apparently, means “delayer”.

12. BBD says:

🙂

13. Joshua says:

Personally, I ALWAYS go with what Richard Tol has to say.

“Published papers that seek to test what caused the climate change over the last century and half, almost unanimously find that humans played a dominant role.”

.

I love how for some “skeptics,” referring to the prevalence of agreement among climate scientists is an appeal to authority and antithetical to “true science,” …er…until it isn’t.

14. jai mitchell says:

[We currently have a planetary energy imbalance of about 0.5Wm-2,]

This is patently false as the NODC Ocean heat content values show. We are trending at Top of Atmosphere energy imbalance of 1.0 Wm-2 over the past 2 years and >1.3 Wm-2 over the past 6 months.

15. jai,
Well, yes, I was trying to be conservative. Most corrections to what I’ve done would probably make it even harder to generate a physically plausible scenario in which less than 50% of the warming since 1950 was anthropogenic.

16. jai mitchell says:

correction:

NODC World Ocean Heat Content Accumulation
http://data.nodc.noaa.gov/woa/DATA_ANALYSIS/3M_HEAT_CONTENT/DATA/basin/3month/h22-w0-2000m4-6.dat

2012.375 15.461 X 10^22 Joules
2013.375 17.426 X 10^22 Joules
2014.375 19.915 X 10^22 Joules

2 year delta = 4.45 X 10^22 Joules

Divide by 2 years, divide by 31,557,600 seconds per year, divide by 5X10^14 square meters at top of atmosphere boundary =1.38 Watts per meter Squared of ocean heat accumulation

Divide by 0.93 to acquire additional heat absorbed in atmosphere land ice

AVERAGE top of atmosphere energy imbalance from 2012 to 2014 is 1.49 Watts per meter Squared

The Last 6 months of global ocean heat content gains http://data.nodc.noaa.gov/woa/DATA_ANALYSIS/3M_HEAT_CONTENT/DATA/basin/3month/ohc2000m_levitus_climdash_seasonal.csv

Yields an astonishing 5.17 watts per meter squared!!!

17. Seems that the latest critique has been “peer-reviewed”:

An eminent climate scientists reviewed a draft of my article and said pretty much the same thing.

http://judithcurry.com/2015/08/01/week-in-review-science-edition-15/#comment-721985

The “same thing” was about the chances this 47% critique was covered by the MSMs.

***

It would be interesting to know what this eminent climate scientist agrees with the IPCC’s main attribution statement.

18. Tom Curtis says:

I have already commented on Fabius Maximus’s mathematical prestidigitation at Skeptical Science. The comment is quite long, but can be summarized in four points (not occurring in this order in the post):

1) If two papers are published on a topic where both obtain numerical results whose uncertainties overlap, they are considered to confirm each other, not to contradict each other. Ergo the raw percentage of respondents to the Verheegen survey agreeing with the IPCC is 65.9%. There is zero justification for attempting to constrain that number so that “agreement” is considered to require agreement not only on the central value but also on the error bars.

2) Even if we allow Maximus’s dubious method, he uses the wrong value for the IPCC likelihood. The IPCC gives different values for GHG and for all anthropogenic influences. Maximus uses as a cut of for agreement the “extremely likely” that was used for “human influences”, not the “very likely” for GHG, despite the survey question being about GHG.

3) The survey by design included respondents who are not climate scientists by any definition, being included because of their ‘skeptical viewpoint’. It also included climate scientists because of their ‘skeptical viewpoint’ solely because of their political expression of that viewpoint, where they would not have been included in the survey had they been selected by the standard criteria. Both of these groups should be excluded if you wish to use the survey to comment on the opinion of “climate scientists”.

4) Survey responses included a large number of expressions of personal ignorance (“I don’t know”) and incoherent responses (“other”). As it was not a survey of attribution experts, as knowledge of one aspect of climate science by no means entails knowledge of other aspects of climate science, and as the survey itself showed restricted specialized knowledge among climate scientists; it is inappropriate to include those non-responses in the overall statistics.

I summarized as follows:

“To summarize, if we did a valid comparison with the IPCC AR5, and did not pad out the survey numbers with known “skeptics” and by including explicity statements of ignorance and incoherent results to pad out the denominator, the proportion we would obtain would be, not 43%, but 66% agreeing on attribution and certainty, and 74% agreeing on attribution. That is, Maximus has deflated the agreement to fit his narrative by 35% at minimum. (Given that the survey is of climate scientists in general, not of researchers into attribution in particular, I would say he has deflated it by 58%.

Having said that, I would still not call 74%, let alone 66% a consensus. It is a supermajority. This should bring some caution in the over interpretation of studies like Cook et al (2013), which showed a 97% concensus in published literature – not among climate scientists. That however, has been evident for a while. What is known, however, is that the more expert climate scientists are on the topic, the more likely it is that climate scientists will agree with the IPCC consensus. The same is shown with Verheggen et al, with 84.5% of respondents having published 30 papers or more (and exlcuding those who express personal ignorance or have an incoherent response) agree with the IPCC on attribution. Only 8.5% think GHG concentrations are reponsible for less than 50% of warming, or think there has been no warming; and only 7% think the answer unknown. (Percentages calculated by pixel count, and are only accurate withing approx 0.5%). No doubt the percentage would be even greater among climate scientists with experience in attribution studies. “

19. Tom Curtis says:

Editor of the Fabius Maximus website:

“Yes, I agree with this formulation. I believe that’s what I said. The dimensions of climate scientists’ consensus is a vital input to the public policy process. These surveys provide a valuable check on the IPCC.
….
I don’t see much value in examining these things under a microscope. The headline result (combining 1a and 1b) is what it is, providing a direct comparison to the keynote finding of WG1 of AR4 and AR5 — and for comparison with the many other similar surveys (which this improves upon).”

Complete nonsense.

The IPCC result is the work of specialists in attribution studies surveying the relevant literature over a 12 month period, and distilling the results of that literature into a report. It is not, and is not intended to be a survey of the consensus opinion of all ‘climate scientists’, where the later is so loosely defined that a geologist being a coauthor of a single paper discussing paleoclimate counts as a “climate scientist”, ie, the effective definition for the Verheegen survey (once the “unconvinced”, ie, those invited to respond solely because of their expression of a political opinion on the web, and without regard to actual study of, or publication in regard to climate science).

If you wanted a double check on the IPCC on attribution, the proper method is an independent literature survey on attribution. As an approximate alternative, you could survey the opinion of climate scientists who specialize in attribution studies asking them as to:

1) Central estimate of the percentage contribution of anthropogenic (and/or GHG) to recent warming;
2) Their upper and lower bounds at 90 and 95% confidence on the attribution;
3) Their estimate as to the proportion of attribution experts whose central estimate lies within the IPCC value; and
4) Their estimate of robustness of the evidence in favour of their opinion (ie, how likely they think it is that their view of the central estimate will have changed significantly with 10 more years of information).

A general survey of climate scientists and deniers without regard their expertise in attribution is not a check on the IPCC.

What the Verheggen survey is a check on is not the literature surveys such as Cook et al, but on the misinterpretation of the literature surveys which treats them as surveys of scientists rather than of papers. It is also an update and check on Doran et al 2009, which found that:

“Results show that overall, 90% of participants answered “risen” to question1 and 82% answered yes to question 2.In general, as the level of active research and specialization in climate science increases, so does agreement with the two primary questions (Figure1). In our survey, the most specialized and knowledge-able respondents (with regard to climate change) are those who listed climate science as their area of expertise and who also have published more than 50% of their recent peer- reviewed papers on the subject of climate change (79individuals in total). Of these specialists, 96.2% (76 of 79) answered “risen” to question1 and 97.4% (75 of 77) answered yes to question2.”

Note that the finding of Doran et al that agreement with the consensus rise with both specialist knowledge of climate science and with increased publication (as a proxy of greater expertise). The appropriately corrected percentage of agreement (74% among climate scientists; 84.5% among those having published 30 or more papers) are less than the nearest corresponding result from Doran et al. That may be because of the more precise nature of the questions, or may be due to a decline in certainty. The first is almost certainly the case, but the second cannot be excluded from the data available.

20. Magma says:

Researchers working in a field generally have an excellent idea of what is settled, what’s new and interesting and what’s controversial. As ATTP notes, consensus studies aren’t done for their benefit but as an attempt to correct a false picture of unsettled science.

This seems so obvious as to hardly be worth mentioning, but like the consensus studies and the consensus itself, apparently it does need to be.

21. “I think Fabius Maximus was known as Cunctator which, apparently, means ‘delayer’.”
Surprising level of honesty in this one.

22. John Mashey says:

Really, classical education is valuable, as in study of the Punic Wars, to learn why the original Fabius Maximus was famous.

23. Tom,

The IPCC result is the work of specialists in attribution studies surveying the relevant literature over a 12 month period, and distilling the results of that literature into a report. It is not, and is not intended to be a survey of the consensus opinion of all ‘climate scientists’

Yes, I agree. Some of Fabius’s more recent comments on his site make me think he doesn’t understand the difference between attribution studies and consensus studies, or how the IPCC generates its reports. For example, I wouldn’t see consensus as a means of verifying what is presented in IPCC reports.

24. Lars Karlsson says:

ATTP,
The link you provide goes to the 2014 article, whereas Fabius Maximuas discusses the updated report from 2015. The latter provides a lot of intersting details.

25. Lars Karlsson says:

For instance, the median answer to the “certainty” question (Fig 1b in the updated report) is “>90%” even when including those that attribute less than 50% of the warming to GHGs. While there is no breakdown in this question into categories of expertise (i.e. number of relevant publications), judging from the break-down of answers to the “attribution” question in Figure 1a.2 it seems reasonable to assume that people with more expertise would provide higher degrees of certainty. So for the categories with most expertise, it seems likely that the median answer would be “>95%” which I think is well in line with the IPCC statement.

26. Harry Twinotter says:

The Fabius Maximus post is a con-job, nothing but shabby propaganda. The only point of it I can tell is to come up with that 43/57 graphic which in itself does not make any sense.

Why even attempt to apply a 2012 survey built around the IPCC AR4 report to a statement from the IPCC AR5 report done years later? The statement from AR4 is:

“Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.”

“very likely” in this context means > 90% confidence. I can only assume the Fabius Maximum figure of 95% (“extremly likely”) was taken from the IPCC AR5 report statement.

27. Lars Karlsson says:

In the GHG attribution question (1a) there is an option “More than 100%” selected by 17.1% of respondents. That option must really confuse Judith Curry,

28. Lars,
To be fair, it’s not only Judith who appears confused by that.

29. BBD says:

Hellish complex stuff, this physical climatology. Imagine having to account for a negative aerosol forcing…

30. Michael Hauber says:

I think it is quite possible for natural variations to exhibit runaway feedback. What is required is a feedback response that relies on a limited resource, so that the process is terminated before the oceans can boil away. As far as I can tell that the feedbacks in a developing el nino is a runaway response that is limited by the availability of warm water in the western warm pool, which is used up to drive this feedback. Once a threshold is reached el ninos tend to reliably amplify, until the western warm pool is used up (but there also seems to be a seasonal effect where the amplification is reliable in NH summer/autumn, but breaks down in winter). However I would expect that if there was such a process operating on multi-decadal scales that it would have left some evidence that someone would have noticed. AMO and PDO seem to be intermittent and I haven’t seen anything that looks like a self-amplifying processes in any part of their ‘cycle’.

Also I don’t follow why the feedback response to natural variation needs to be so high in your examples. Naively I would expect the feedback response to be similar to that for Co2, and a low Co2 warming would then require a large forcing from a natural variation and a small feedback. As an example we could pretend that a change in PDO phase causes a major alteration of global circulation which somehow results in a change in cloud cover that produces a relatively large albedo forcing, but with relatively weak feedbacks so as to give the required answer.

31. Michael,

I think it is quite possible for natural variations to exhibit runaway feedback. What is required is a feedback response that relies on a limited resource, so that the process is terminated before the oceans can boil away.

Yes, but if we’re talking about fast feedbacks, then that’s mostly water vapour/clouds which would only stop once the oceans boiled away.

Also I don’t follow why the feedback response to natural variation needs to be so high in your examples.

Because if we want to assign less than half of the warming to anthropogenic influences, that then requires that the radiative response to the internally-driven warming has to be much higher than the radiative response to the anthropogenically-driven warming. One way to solve this might be to assume an extremely small TCR-to-ECS ratio, but that would again be unlikely.

Naively I would expect the feedback response to be similar to that for Co2, and a low Co2 warming would then require a large forcing from a natural variation and a small feedback.

Well, yes, that is what you would expect. However, if the natural warming is internally-driven (not the Sun) then there isn’t an associated forcing, all that you have are physical processes that are equivalent to the feedback responses to the anthropogenically-driven warming. So, you can’t have low CO2 warming and a large forcing from natural variation with a small feedback.

32. appaling says:

The full name for Fabius Maximus is “Quintus Fabius Maximus Verrucosus Cunctator” (see Wikipedia), where “Verrucosus Cunctator” translates to “warty delayer”. I do not think the humour is intentional…

33. Willard says:

The full name of the Editor is “Editor of the Fabius Maximus website.” Here’s a latest example of a comment where he signs using this full name:

Joshua,

Re: Richard Tol’s statement [Published papers that seek to test what caused the climate change over the last century and half, almost unanimously find that humans played a dominant role.]

I agree, see links to most of those surveys here.

But this is science, not religion. Religion rests on binary statements of faith. Being science the IPCC gives confidence limits for its findings. The PBL survey is useful as the first to test for agreement of climate scientists with those confidence limits.

http://judithcurry.com/2015/08/01/week-in-review-science-edition-15/#comment-722206

Expressing scientific opinions and religion. Same same for the Editor.

The Editor’s website is pure ClimateBall. Not science.

34. BBD says:

The Editors apparently think It’s The Sun, so are in no position to come over all sciencey on anyone.

35. Joshua says:

I tried to have a discussion with Fabius over at his site. Apparently either he considers himself above a discussion with me, or he isn’t interested in actually discussing different perspectives on his opinions.

Samosameo?

36. BBD says:

They’re all ex-military, Joshua. Where they came from, you aren’t allowed to have ‘perspectives’ on the opinions of those ranked above you in the hierarchy. And as a goddamn civilian, you don’t even make the bottom tier 😉

37. It does say ex-military, but whoever is communicating as the Editor keeps pointing out that they have 35 years experience in finance, which seems more consistent with their behaviour than being ex-military.

38. nnoxks says:

I don’t post here often, but I have a particular interest in this debate. I had some raging climate arguments with FM a year or so ago, and I have been curious to see the result if FM ever engaged with the science-based climate blog community. I find many of the analyses on their site valuable, and FM has some interesting things to say about American folly in national government and foreign affairs. I don’t think there is any deceptive intent there, but they have some bizarre blinders on with regards to climate change. My main contention was that much of FM’s analysis appears to rely on the views of Pielke, Curry, Spencer, Christy, etc., and that resulted in a skewed perspective. FM took great offense, insisting that the IPCC is their guiding light for climate analysis; I don’t think their articles bear that out. I was disappointed when FM blocked me despite the fact that I broke no commenting rule. Since then I have read some of their political and social analyses, but I stay away from the climate stuff. Unfortunately, in my view, the credibility of the entire site is impacted by their stance on climate science.

39. anoilman says:

If there were that much lack of consensus, then I’d expect to see a lot more credible work into other theories. I haven’t seen any. Has anyone else? Anyone? Anyone? Fabius? Fabius?

Not to mention a lot of science fields should also be utterly floundering. You know… like the the fact that ocean data is was gathered by navies to sink subs, so I think they know that its right by now. Atmospheric spectral absorption is equally well understood (that’s air force data), and critically important to a lot of industries. Ocean acidification… well understood. (Dang navy data again!)

All too often we see someone simply say something is wrong while also offer no alternative explanation. That’s simply not credible, but its most certainly the most common denier methodology we see over and over. (and over and over and over and over…)

I wonder what Fabius thinks is happening? Pop up hidden volcanoes? Martian mercury gravity reducers? Oh tell us so we can stop hanging out here!

40. nnoxks,
Yes, your interpretation is somewhat similar to mine. Fabius seems to be not alone in being someone with a finance background who will regularly appeal to their own authority (“I’ve got 35 years experience in finance”) while dismissing any expertise of those who disagree with what they say. I’ve been pondering why this behaviour seems (small sample, though) common in people with such expertise. Is it because that’s how you progress in that environment? Is it because they think that all you need are expertise with numbers? He does seem to try to be reasonable, but then quickly resorts to condescension and appeals to authority.

AoM,
Indeed. I have pointed out that if you think the level of consensus is around 47% you should able to find many dissenting papers and scientisits.

41. BBD says:

I don’t think there is any deceptive intent there, but they have some bizarre blinders on with regards to climate change.

It’s just the usual: right-wing politics trumps reason, physics, truth etc.

42. nnoxks says:

Annoyingly, I must defend FM against charges of “right-wing politics.” See, for example: http://fabiusmaximus.com/2015/07/28/history-republican-opposition-arms-control-treaties-87687/; http://fabiusmaximus.com/2015/07/06/we-are-greece-86985/. In my view, FM’s refusal to acknowledge the seriousness of climate change comes from their general belief that the powerful on both the right and left use fearmongering as a primary means of controlling the populace. And I agree that manipulation through fear is a common political tool. Unfortunately, that does not mean that some things, like climate change, are not legitimately frightening on their own terms, without regard for politics.

43. Michael Hauber says:

ATTP: ‘Yes, but if we’re talking about fast feedbacks, then that’s mostly water vapour/clouds which would only stop once the oceans boiled away.’

The water vapor feedback is obviously limited by the ocean boiling away. Cloud feedbacks are not. For instance if the amount of cloud cover was driving a feedback then this would be limited when cloud cover reaches either 0 or 100%.

ATTP: ‘ However, if the natural warming is internally-driven (not the Sun) then there isn’t an associated forcing, all that you have are physical processes that are equivalent to the feedback responses to the anthropogenically-driven warming.’

So the natural variation is a feedback to what exactly? Or if it is not a forcing or a feedback then what exactly is it? There has to be some forcing somewhere before you can have a feedback, and I see no obvious reason why in theory this forcing could not be large. For instance a change from cool PDO to warm PDO might change the percent of cloud cover. This changes albedo and changes the radiative balance. This is not a feedback to anything, but an internally generated forcing.

Of course if such a large internally generated forcing had happened, the question would be why it wasn’t noticed. I would be very surprised if something like that was suddenly discovered and decades of climate research has to be redone.

Is co2 an external forcing? Or internally generated variation. Co2 is a substance found within the existing earth system that is being rearranged by entities that like to think they are special, but are ultimately still a part of that earth system.

44. Michael,

The water vapor feedback is obviously limited by the ocean boiling away. Cloud feedbacks are not. For instance if the amount of cloud cover was driving a feedback then this would be limited when cloud cover reaches either 0 or 100%.

True, but I don’t that changes that such a large radiative response to internally-driven warming is unlikely.

So the natural variation is a feedback to what exactly? Or if it is not a forcing or a feedback then what exactly is it? There has to be some forcing somewhere before you can have a feedback, and I see no obvious reason why in theory this forcing could not be large. For instance a change from cool PDO to warm PDO might change the percent of cloud cover. This changes albedo and changes the radiative balance. This is not a feedback to anything, but an internally generated forcing.

Okay, it’s a terminological issue. The change to a warm PDO is a form of internally driven warming, which could – as you say – produce a change in cloud cover and, consequently, a radiative response. I’ve called this a feedback to internally-driven warming. Call it internal forcing, if you wish. It doesn’t change my point that if you want to explain less than half our warming since 1950 anthropogenically, then the radiative response to internally-driven warming is still much larger than the feedback response to externally-forced warming.

Is co2 an external forcing?

By definition, yes.

45. Reblogged this on …and Then There's Physics and commented:

I noticed a discussion on Twitter about whether or not, from basic physics, we know that most of the warming since the 1800s has been anthropogenic. Of course, it’s probably not basic physics, because it is quite complicated. However, I do think – given our current understanding – that we can use some basic physics to show just how difficult it is to construct a plausible scenario under which most of our warming was not anthropogenic. I had thought of writing a post, but realised I had already largely done so, so am reblogging this one. Admittedly, I wrote this one with respect to 1950, but a similar argument could be made based on warming since the 1800s.

Essentially, given how much we’ve warmed (~ 1K), given the estimates for the external changes (solar, volcanoes, anthropogenic, …), and given that we still have a planetary energy imbalance (we’re still accuring energy) it is very difficult to construct a physically plausible scenario under which most of the warming is not anthropogenic. Of course, this isn’t some kind of claim of formal attribution, just a back-of-the-envelope approach to illustrate the point. It may also be possible to construct an alternative that is both physicall plausible (and not inconsistent). If so, feel free to point out how in the comments.