31

A recent spate of newspaper headlines reported that 97% of scientists agreed with the theory of anthropogenic global warming (AGW). The UK's Daily telegraph reported:

A review of 12,000 scientific papers has found the consensus among scientists that humans are to blame for climate change is “overwhelming” and the dissenting view was held by less than two per cent of scientists.

Discovery reported:

97.2 percent of the papers that took a position on the subject being rated by their own authors as supporting the notion of human-caused global warming.

NASA used the headline:

Consensus: 97% of climate scientists agree

I was struck, though, by this statement in the original paper:

We find that 66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming.

Which suggests that the 97% headline is not a strictly accurate summary of the findings as about 2 in 3 papers didn't seem to take a clear position.

So are the headlines a fair summary? Was the study itself a useful way to judge either consensus or truth?

Sklivvz
  • 78,578
  • 29
  • 321
  • 428
matt_black
  • 56,186
  • 16
  • 175
  • 373
  • I would like to make this an answer, but I don't know how to support it with references: "It is not known if 97% of climate scientists agree with the theory of anthropogenic global warming (AGW)." –  May 18 '13 at 22:58
  • 3
    Your Discovery quote appear to be accurate: "97.2 percent of the papers *that took a position* on the subject ..."; the others are apparently mis-quoting or poorly summarizing. – KutuluMike May 19 '13 at 13:12
  • @MichaelEdenfield Thats a pretty good concise summary of what I thought, though even discovery quote omits the context of the proportion having an opinion. – matt_black May 22 '13 at 20:24
  • 8
    There was a time when 99+% of experts agreed that the Sun revolves around the Earth. Much much later, 99% of experts agreed that true gentlemen doctors should not be asked to wash their hands before delivering babies in the hospital. 99% of published biologists in USSR agreed that Mendelian genetics is a bourgeois fakery. Frankly, the mere fact that AGW pushers feel the overwhelming need to use this "statistic" to shut up opponents is what caused me to be skeptical of AGW before I knew of any of the details. – user5341 May 24 '13 at 15:58
  • No answers yet have asked whether the statistical methods of the authors were sound. Some have certainly queried them in the blogosphere, and not just the anti-AGW crowd. Others have questioned whether the rating system or the sampling used were reliable. – matt_black May 27 '13 at 21:16
  • Say we want to know the ratio of posters on a sports blog that think that England will win the next Ashes series. We sample comments containing the keyword "cricket" and find that 66.4% of comments expressed no position on the Ashes series (perhaps because they were discussing West Indian cricket etc.), 32.6% thought that England would win, 0.7% thought that Australia would win and 0.3% were uncertain. To determine the level of support for an England series victory, the thing to do is to analyse those comments that expressed an opinion on the series outcome, which would give the answer 97%. –  Sep 12 '13 at 15:41
  • 1
    Similarly, not every paper on climate change is concerned with the cause of climate change, whether natural or not. For instance they are concerned with the consequences of climate change, or some methodological issue in analysis of observations. Scientists generally refrain from making statements that are not directly supported by the findings presented in the paper, so we should not expect even the majority of papers on climate change to express an opinion on the cause of the climate change, even if the authors are known to be strong supporters of AGW. –  Sep 12 '13 at 15:44
  • Papers that do not state a position on AGW provide no information on the question, and hence should be excluded. Including them and concluding that the support for AGW is only 36.2% is making the error of treating a lack of an explicit statement of support as an implicit statement of a lack of support. –  Sep 12 '13 at 15:48
  • 1
    define "expert". – Brad Nov 23 '13 at 13:28

7 Answers7

34

The paper does not claim that that 97% of scientists endorse AGW. The study was conducted to evaluate the consensus within the published literature, and it found that an overwhelming percentage of published papers expressing a view on the question do endorse the premise that human activity is causing global warming.

Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming. In a second phase of this study, we invited authors to rate their own papers. Compared to abstract ratings, a smaller percentage of self-rated papers expressed no position on AGW (35.5%). Among self-rated papers expressing a position on AGW, 97.2% endorsed the consensus.

When scientific findings are summarized in the popular press, things often get a bit distorted. The key finding of the referenced paper is given as the last sentence of the abstract:

Our analysis indicates that the number of papers rejecting the consensus on AGW is a vanishingly small proportion of the published research.

As to the papers that did not endorse or deny the existence of AGW, the paper offers this explanation:

Of note is the large proportion of abstracts that state no position on AGW. This result is expected in consensus situations where scientists '...generally focus their discussions on questions that are still disputed or unanswered rather than on matters about which everyone agrees' (Oreskes 2007, p 72). This explanation is also consistent with a description of consensus as a 'spiral trajectory' in which 'initially intense contestation generates rapid settlement and induces a spiral of new questions' (Shwed and Bearman 2010); the fundamental science of AGW is no longer controversial among the publishing science community and the remaining debate in the field has moved to other topics. This is supported by the fact that more than half of the self-rated endorsement papers did not express a position on AGW in their abstracts.

Some of these papers may have stated a position within the body of the paper, but the study only looked at the abstract. Many others may not have stated a position at all, as the purpose of the paper was to report on some particular new finding in the climate science field, rather than to point out that the climate is changing due to human activities. New papers published in the thermal sciences field don't include an explicit endorsement of the laws of thermodynamics.

Mark
  • 7,777
  • 3
  • 46
  • 44
  • Is the 97.2% figure mentioned at all? – Oddthinking May 18 '13 at 19:01
  • Yes it is. I've added it to the answer. – Mark May 18 '13 at 20:24
  • "**human activity is causing global warming**" gives the impression that climate scientists believe that human causes are the *primary* cause of global warming. Only a slight majority [54% (+/-4%) of climate scientists](http://stats.org/stories/2008/global_warming_survey_apr23_08.html) think that recent temperatures are outside natural fluctuations. So, you might want to say, "human activity is one of the causes of GW", (but, there is considerable debate how much of an effect humans have on the climate) – user1873 May 22 '13 at 03:36
  • 2
    From the article to which you linked: "Eighty-four percent say they personally believe human-induced warming is occurring." – Publius May 22 '13 at 13:44
  • 2
    @Avi: but *is occurring* is not the same thing as *is the primary cause*. Actually it is not even the same thing as *is an important cause*. – nico May 22 '13 at 15:41
  • 1
    It specified that they were asking about human-induced warming. If it's human-induced, how does that not make human activity the primary cause. Surely if the primary cause were something else, it would be called whatever-that-thing-is-induced warming. – Publius May 23 '13 at 00:07
  • @Avi, Yep. Those same scientists would also say that they personally believe that Avi-induced warming is occurring, or cat-induced warming is occurring, etc. – user1873 May 23 '13 at 03:04
  • 1
    [citation needed]. If the question is as meaningless as you say, then 100% of scientists should have answered yes. – Publius May 23 '13 at 04:01
  • @Avi there's still enough ambiguity for some to answer no. For instance, the word "is" has an unspecified timeframe; since the trend [just for the last decade](http://www.woodfortrees.org/plot/hadcrut4gl/last:120/plot/hadcrut4gl/last:120/trend) is one of (slight) global cooling, somebody might focus on a measure like that to say that even *some* warming isn't happening, for suitable definitions of "isn't". While others who look at longer trends would disagree. – glenra Jun 07 '13 at 01:32
24

If you do the arithmetic, the statement that struck you:

We find that 66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming.

gives the 97%. You throw out the 66.4% that did not take a position since they provide no data on the question. 32.6 / (32.6 + 0.3 + 0.7) = 0.97. Of the papers that took a position, 97% endorsed AGW.

Note that the 66.4% did not say they were unsure about AGW. They said nothing about AGW (in the abstract). 0.3% actually said that they were unsure.

As to whether this is a good experiment to determine whether "97% of climate scientists agree", it was not intended to answer that question. They sampled those climate scientists that made a statement about AGW, which might bias the result in one direction or another since the sampling was not random. The 66.4% might not have the same distribution as the 33.6%. A small random sample of the positions of the authors of those 8,000 papers would let you know if there's anything surprising there.

The authors didn't do exactly that, but they did something like it, which was to ask the authors of some of those 8,000 papers if they thought their paper expressed a position, and if so, what that position was. About half said that there was a position, and with that new data, the bottom line number changed from 97.1% to 97.2%. So the result seems to be robust.

I would conclude from this that the consensus on AGW among scientists who publish on the subject is well north of 90%.

Mark Adler
  • 349
  • 1
  • 6
  • 5
    Then, the claim "97% of climate scientists agree..." is unsupported. What is supported is "97% of papers that took a position on AGW accept it". –  May 18 '13 at 22:35
  • 7
    The paper correctly concludes: "Our analysis indicates that the number of papers rejecting the consensus on AGW is a vanishingly small proportion of the published research." – Mark Adler May 18 '13 at 22:46
  • Yeah, the paper concludes that. I'm just saying that the claims in the headlines are false. –  May 18 '13 at 22:55
  • 3
    Good answer but despite what @Sancho said in an earlier comment, the newspaper headlines *are* an accurate representation of this number. Such numbers are *never* derived by querying the whole population, they *always* rely on a sample. Why single out this one number? The sample is going to be more or less representative and unless somebody has a reasonable doubt about a particular bias here, what makes this number less reliable than any other survey? – Konrad Rudolph May 19 '13 at 12:09
  • 1
    @KonradRudolph the paper explicitly didn't try to figure out the position of the scientists themselves, but the position on AGW in the published scientific literature. While the headlines are not strictly speaking correct, I personally don't mind it that much as I find the angle in the paper even more convincing than a pure poll of scientists would be. While the paper does not explicitly support it, I think it is safe to assume that the opinion of scientists is likely close to the consensus displayed in the published literature examined in the paper. – Mad Scientist May 19 '13 at 12:31
  • @Fabian Granted, it’s a proxy. But then other surveys also use proxies so once again I think this is a fair representation. – Konrad Rudolph May 19 '13 at 12:34
  • You realize that they contacted some of the scientists later and found that 35% "Expresses position that human's role on recent global warming is uncertain/undefined" Not only that, but of those respondents whose papers were previously rated as "No Position", only 54% endorsed AGW (meaning 46% either rejected it or were uncertain). If you apply those results to the other ~8000 abstracts, you get a 66%/33% split for endorse AGW versus undefined. – user1873 May 22 '13 at 13:39
  • Yes indeed the 97% is a real number based on some of the data, but is it fair to quote it without the relevant context? – matt_black May 22 '13 at 20:27
  • 2
    @user1873 - "only 54%endorsed AGW". I think you're misunderstanding the paper. The authors were not asked whether they endorse AGW. They were asked whether their papers endorsed AGW. As I've noted elsewhere, approximately zero percent of astronomical papers endorse the heliocentric theory of the universe, but I'm quite confident that approximately 100% of authors endorse it. – Mark May 23 '13 at 01:32
  • 1
    @Mark, I didn't. Was referring to the authors position on whether their papers endorsed 62.7% ("green-house gasses cause global warming", even those from humans), rejected AGW 1.8% ("natural mechanisms are the main cause of global warmin"), or undefined/no position ("humans role in recent warming is uncertain") 35.5%. As I have noted, an abstract was classified as **implicitly endorsing AGW** from the mere fact that the humans produce CO2 and CO2 is a greenhouse gas. Using this criteria, these papers would implicitly endorse Martian AGW, and earth felinegenic GW, and earth caninegenic GW. – user1873 May 23 '13 at 02:55
  • @Mark the number of papers rejecting the consensus was 78, or 0.6%. If that's "vanishingly small", it's at least MORE than the number of papers (65) that claimed humans are primarily responsible for recent warming. – glenra Jun 02 '13 at 15:06
  • @user5582 - no, it's not false. If a paper explores issues or questions that are grounded on the pre-condition of accepting AGW as fact, then not mentioning whether AGW is actual or not in the abstract does not denote any kind of uncertainty on the issue. – PoloHoleSet Jun 02 '17 at 17:24
14

No, 97% of peer reviewed studies do not endorse that global warming is human caused

The study found that 97% of abstracts about 'global climate' or 'global climate change', at least "Implied humans are causing global warming. E.g., research assumes greenhouse gas emissions cause warming without explicitly stating humans are the cause." versus abstracts that rejected humans as the main cause of global warming. This eliminated 2/3rds of the abstracts that either stated that the extent of human contributions are undefined/uncertain, or expressed no opinion.

What is vitally important to this study, is that they excluded self-rated papers that rated themselves as a (4). They pretended that this wasn't a position on AGW, which allowed them to increase their endorsement from 62.7% to 96.4%. (see Table 4)

Endorse AGW[a]      62.7% (1342)    97.2    62.7% (746)     96.4

No AGW position[b]  35.5% (761)     —       34.9% (415)     —

[b]Undecided self-rated papers have an average rating equal to 4

From (Table 2), we know what a 4 rating represents.

(4b) Uncertain - Expresses position that human's role on recent global warming is uncertain/undefined - 'While the extent of human-induced global warming is inconclusive...'

What is even more telling, is that the papers were only reporting as either endorsing, expressing on opinion, or rejecting AGW. They did not choose to report the level of endorsement which the peer-reviewed studies were classified. So, from this study it is impossible to know what percentage of study abstracts/respondent authors endorse the position the humans are the primary cause of recent global warming. There have been other studies that put that figure around 54% (+/-4%). Which interestingly enough, matches the public's perception on the matter.

Explicit endorsements were divided into non-quantified (e.g., humans are contributing to global warming without quantifying the contribution) and quantified (e.g., humans are contributing more than 50% of global warming, consistent with the 2007 IPCC statement that most of the global warming since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations).

user1873
  • 8,931
  • 42
  • 81
  • 2
    Good find. Of course this answer is farcical since it pretends that AGW proponents posit the strawman that “AGW denialists believe that humans do not contribute *any* CO2” which is clearly ridiculous and not a position actually expressed anywhere. But that fact doesn’t detract from the criticism of the paper. It would, however, be beneficial to remove the second sentence from the actual answer since it’s actually completely irrelevant and tries to subtly discredit the study’s methodology (“more accurate”, “volunteers from …”). This pretends that text mining isn’t a common scientific tool. – Konrad Rudolph May 22 '13 at 13:33
  • 3
    @Konrad:Text mining might be a useful scientific tool but it is only valid in the right contexts. It is completely invalid for politically charged issues (like this one), in particular when taking one position or the other could be perceived as being "politically incorrect" and thereby could potentially damage a researchers career if they were to not accept the "politically correct" position. – Dunk May 22 '13 at 22:00
  • @konrad and Dunk - I'm a little confused about the references to text mining as a useful or common scientific tool. I see text mining as taking a quote out of context in order to support a view that the author doesn't agree with. This is not a scientific tool in any sense, but is an important part of the anti-scientist's toolbox, cropping up frequently in arguments against evolution and AGW. How do you see this as a useful or common scientific tool? – Mark May 23 '13 at 01:59
  • 2
    You're omitting a few details from the paper here, they also include "implicit rejection" in their categorization, not only for the endorsment of AGW. And the paper survey (not the self-rating) also separates "no position" from "uncertain", and "uncertain" were around 1%. So the eliminated papers are nearly all of the "no position" type. But I'd also would have liked to see a more detailed table of the results according to their categorization. – Mad Scientist May 23 '13 at 11:53
  • @Mark You’re thinking of *quote mining*. [Text mining](http://en.wikipedia.org/wiki/Text_mining) is a sub-disciplin of data mining and represents an important research tool in many different contexts. Roughly speaking, it’s an automated literature search but there’s a huge body of theory behind it. – Konrad Rudolph May 23 '13 at 12:40
  • @Fabian, the study differed considerably from what an implicit rejection was versus an implicit endorsement. "3 research assumes greenhouse gases cause warming. 5 Implicit Rejection: implies humans have had a minimal impact on global warming, proposing a natural mechanism is the main cause. A rejection required quantification, an endorsement did not. As for the 1% being "uncertain", that was not a [possible selection](http://iopscience.iop.org/1748-9326/8/2/024024/media/erl460291suppdata.pdf) (S2. top page 4) for self-rating even though the study said the same rating criteria was used. – user1873 May 26 '13 at 01:31
  • @user1873: In this study the "percentage of study abstracts that endorse the position the humans are the primary cause of recent global warming" was either half of a percent or 1.5% depending on if we exclude the "No position" articles. See my answer for more on this. – glenra Jun 03 '13 at 04:44
10

No, it is not accurate to say (based on that study) that 97% of experts agree that global warming is anthropogenic.

One problem is that there are two different definitions of "consensus" being used. The original consensus claim used by the IPCC was that it was very likely that most of the recent warming (>50%) was caused by humans. When we say that "global warming is anthropogenic" that is the common-sense definition people have in mind. Not simply that CO2 is a greenhouse gas that causes some unquantified amount of warming, but also that the amount of this warming is highly significant - that the biggest cause of warming is human activity in the form of releasing CO2.

The Cook study did not find 97% support for that proposition.

The study counted an article as "supporting the consensus" if it merely implicitly accepted that CO2 is a greenhouse gas. Since most skeptics accept that CO2 is a greenhouse gas, that doesn't tell us much we didn't already know - it uses too weak a definition of "consensus" to be useful.

Fortunately, the Cook et al database of rated abstracts is available to be searched on line. So we can check how many abstracts were in each sub-category, even though that info wasn't reported in the paper proper. (I've added links to queries that should return the actual abstract lists, so long as the database sticks around)

The Cook study gave papers a numeric rating. Rating #1 was "explicitly endorses and quantifies AGW as >50%". Out of 12,464 papers considered, only 65 papers were in this category (note: this was just based on study participants reading the abstracts, not the full paper).

Based on that statistic alone, one could defend the claim that one half of one percent of papers on AGW clearly claim humans are the chief cause of it. That headline finding would be "less than one percent of expert papers explicitly agree that global warming is anthropogenic."

But maybe it's not fair to include the "no position" papers. Let's exclude those. In that case, the headline finding is "1.5% (65/4215) of expert papers that took some position on global warming explicitly agree that global warming is anthropogenic."

The full list of endorsement categories were as follows:

  1. Explicitly endorses and quantifies AGW as >50% (65 articles)
  2. Explicitly endorses but does not quantify or minimize (934 articles)
  3. Implicitly endorses AGW without minimizing it (2934 articles)
  4. No position (8269 articles)
  5. Implicitly minimizes or rejects AGW (53 articles)
  6. Explicitly minimizes or rejects AGW but does not quantify (15 articles)
  7. Explicitly minimizes or rejects AGW as less than 50% (10 articles)

If we sum the rejection categories 5-7 together, there were 78 articles rejecting AGW, versus only 65 explicitly supporting the consensus. So another defensible headline finding is: "More articles implicitly or explicitly reject AGW than claim more than half of AGW is anthropogenic."

Or we could look at JUST the papers that give an explicit numeric percentage estimate. Comparing category 1 with category 7, we get this defensible headline: "87% of scientific articles that give a percentage estimate claim more than half of warming is anthropogenic". (though it would be important to note the actual number of articles in that case isn't much of a sample: 65 for versus 10 against).

Or if we want to rescue the original Cook number, that can be accomplished by adding a few caveats. Like so: "97% of articles on global warming that take a position on the matter either implicitly or explicitly endorse that human activity is causing some global warming"

Since the vast majority (98.5%) of these papers don't quantify how much warming, that's about as far as we can go.

glenra
  • 216
  • 1
  • 6
5

There certainly seems to be a strong scientific consensus on climate change. Here are some figures showing scientific concurrence with Anthropogenic Global Warming, or that unprecedented warming is occurring in the earliest studies:

  1. 67% from a 1992 Gallup poll of 400 members of AGU and AMS

    • Gallup Poll, No direct online link but discussed here and elsewhere, 1992.

  2. 80% from Bray & von Storch 1999 survey of 1000 German, US & Canadian climate scientists

    • Dennis Bray and Hans von Storch, Climate Science: An Empirical Example of Postnormal Science, 1999.

  3. 100% from Oreskes 2004 from articles by 928 scientists (75% agree with IPCC, 25% took no position, 0% opposed)

    • Naomi Oreskes, Beyond the Ivory Tower: The Scientific Consensus on Climate Change, 2004.

  4. 97% from Harris Interactive 2007 surveyed 489 randomly selected members of AGU

    • Harris Interactive Poll, Survey Tracks Scientists' Growing Climate Concern, 2007.

  5. 100% from IPCC 2007, by definition this is the consensus of the 2000 scientists that contributed to this work – “anthropogenic (human-sourced) greenhouse gases are responsible for most of the observed temperature increase since the middle of the twentieth century”

    • Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Understanding and Attributing Climate Change, 2007.

  6. 83.5% from Bray and von Storch, 2008 from just 373 climate scientists worldwide (AGW: 34.6% very much agree, 48.9% agreeing to a large extent, 15.1% to a small extent, and 1.35% not agreeing at all)

    • Dennis Bray and Hans von Storch, CliSci2008: A Survey of the Perspectives of Climate Scientists Concerning Climate Science and Climate Change, 2008.

  7. 97% from Doran and Zimmerman 2009 from a data set of 79 top climatologists (GW: 90% agreed and AGW: 82% agreed of 3,146 general scientists surveyed)

    • Peter T . Doran and Maggie Kendall Zimmerman, Examining the Scientific Consensus on Climate Change, 2009.

  8. 97.5% from Anderegg et al 2010 surveyed publications by 1,372 climate researchers

    • William R. L. Anderegg et al, Expert credibility in climate change, 2010.

  9. 84% from Farnsworth and Lichter 2011 from 489 members of AGU and AMS (AGW: just 5% disagreed)

    • Stephen J. Farnsworth & S. Robert Lichter, The Structure of Scientific Opinion on Climate Change, 2011.

  10. 98.5% from Cook et al 2013 from published literature of 10306 scientists and direct contact with a subset to ensure correct interpretation

    • Cook et al, Quantifying the consensus on anthropogenic global warming in the scientific literature, 2013.

  11. Every national or respected scientific organization in the world endorses the IPCC conclusions about the human causes of the present climate change (about 45 agencies at my last count). This is notable because it takes a lot of convincing to get even one group of scientists to agree on a major topic. When every single group agrees, I’d call that a consensus.

    • A list of 45 links can be provided if I receive enough requests (I beg you not to).

cloudpoint
  • 83
  • 4
  • Could you please provide links to the citations you are putting into the answer? – Larian LeQuella May 27 '13 at 01:45
  • Expressions like "Cook et al" are only useful if there is a bibiography where we can look up all of the authors. I've added one reference to show roughly what we are expecting. A reference to a book is also acceptable. – Oddthinking May 27 '13 at 03:32
  • 1
    2.) Isn't a good example to prove your case. On a scale of 1-7 the mean response was 3.3 when asked if GW has been detected and is underway. (3) isn't a link to the Okeskes study (which makes it difficult to assess if the scientists are agreeing with the IPCC's statement, "most of the warming is human caused," or some other less strong statement that gets misreported. (4) I linked to this in my answer it is interesting how we came to such different conclusions about what the data shows. – user1873 May 27 '13 at 17:44
  • @user1832, the 3.3 figure refers to the detection of AGW. Back in 1998 AGW hadn’t yet been clearly observed or detected. That took another few years to reach the threshold that they could see it happening with confidence. It was reported as a key conclusion in TAR (2001). – cloudpoint May 28 '13 at 02:57
  • Many questions were asked in # 2, the subjects were all climate scientists. One question climate scientists were asked was if they felt “There is enough uncertainty about the phenomenon of global warming that there is no need for immediate policy decisions” (1 = strongly agree, 7 = strongly disagree; one claim of ambiguity). The authors said, here there is undisputed support for immediate policy to be implemented with the overall mean response of 5.6 and no statistically significant differences among groups. I believe this tells us what climate scientist really thought even back in 1998. – cloudpoint May 28 '13 at 02:58
  • (5)Why do you think you can say 100% of ghe scientists, just because the IPCC report makes that claim? If the head of a company makes a claim can we say 100% of the people who work there agree (this is similar to the reporting that the AMA endorses the IPCC report, and yet a large percentage of meterologists don't. (6) Which chart are you referring to? (7) The Doran study has many issues with it. It was a small sample 76 climate scientists, and the questions were ambiguous. – user1873 May 28 '13 at 02:58
  • I think you can spin each study a certain way or find minor flaws with each one but, like all science, it is the repeatability of the results leading to the same conclusions using very different methodologies by independent sources that points us to the greater truth. You are nitpicking. – cloudpoint May 28 '13 at 02:59
  • The climate change consensus is no mere consensus but is a much more powerful concept; it is a "consilience". The science of human-caused climate change has overwhelming consilience, not just consensus, the convergence to highly similar conclusions from independent sources using varying experimental and theoretical methods in wide-ranging fields. This is why so many scientists accept AGW as settled science for the most part. – cloudpoint May 28 '13 at 03:00
  • " the 3.3 figure refers to the detection of AGW. Back in 1998 AGW hadn’t yet been clearly observed or detected." Actually it was just about GW. "One final aspect of this part of the discussion, concerning the scientific interpretation of scientific "facts," concerns the detection of climate change. Scientists were asked first, to what degree he or she felt for certain that **global warming** was a process already underway, and second, to what decree he or she felt certain that, without change in human behavior, **global warming** will definitely occur sometime in the future." – user1873 May 28 '13 at 03:38
  • @cloudpoint, "I think you can spin each study a certain way or find minor flaws" No you have to examine deeply the study methodology to determine what conclusions can actually be drawn from the study. For example your (10) is the study in the OP that I thoroughly examined in my answer. Several problems exist. For one, the choices were different between the raters and the self-rating (4b) Uncertain ... Was missing. 2ndly, the implied rejection of the AGW required quantification (hard to do thst when you cannot detect it) where implied agreement only required that the paper treated CO2 as a ghg – user1873 May 28 '13 at 03:46
  • Thirdly, none of the studies when doing a comparison between Oreskes during the same time period actually agreed with the IPCC's conclusion that more than 50% of GW is human caused. If you are going to link to a study as evidence, please actually quote the relevant part. – user1873 May 28 '13 at 03:48
  • “Actually it was just about GW”. You are correct. I’m not sure it matters. The A in AGW is less disputed than the GW – we know where the CO2 is coming from. The question is whether GW is of a magnitude that we should worry. We just had to see if it emerged from the noise after 2000 as climate models predicted it would. It did. – cloudpoint May 28 '13 at 04:41
  • # 3 just means they agreed with the IPCC’s latest conclusions at that time, i.e. TAR (2001). Attribution studies such as Tett et al. (2000) and Meehl et al. (2004) were already out by the time of the # 3. I know of at least 10 more studies since then showing well over 50%, over 100% sometimes, so this point is not really doubted now. [It's time to abandon this thread, it's getting too long.] – cloudpoint May 28 '13 at 04:43
  • "user1832, the 3.3 figure refers to the detection of AGW." So you are saying you were mistaken. You are not sure it matters? If climate scientists are unsure that they can detect GW, how can they measure thst humans are responsible for most of the recent warming? My point was that you keep linking to these studies that don't support your position that there is a strong scientific consensus with regard to AGW. Please provide a relavant quote from the study so that we can see exactly what climate scientists are agreeing with. For example, – user1873 May 28 '13 at 06:14
  • You said," [97% from Harris Interactive 2007](http://stats.org/stories/2008/global_warming_survey_apr23_08.html) surveyed 489 randomly selected members of AGU" but you didn't say what that 97% said. When you learn that 97% say that we have warmed since some time after the little ice age, that isn't surprising. "Ninety-seven percent of the climate scientists surveyed believe “global average temperatures have increased” during the past century." This doesn't have any bearing on do humans cause GW, nor what percentage of GW is human caused.(althouh you using it as an example implies that) – user1873 May 28 '13 at 06:18
  • I didn’t say I was mistaken. I didn’t even speak to the 3.3 number in my answer. I just said that I agreed with your comment about the 3.3 number because detection wasn’t observed by climate scientists back in 1998 when the survey was done. The scientists were answering the survey honestly. GW has since been detected, and I already gave you a relevant quote from that study (see “The authors said …”). – cloudpoint May 29 '13 at 03:02
  • Harris Interactive 2007: The survey found 97% agreed that global temperatures have increased during the past 100 years; 84% say they personally believe human-induced warming is occurring, and 74% agree that “currently available scientific evidence” substantiates its occurrence. What more do you want? Why do you leave out the full evidence in your blinkered criticisms? The LIA ended well over 100 years ago, and it was mostly a local effect around the North Atlantic, not global. Get serious with your questions. – cloudpoint May 29 '13 at 03:04
  • (5) is inaccurate on several counts. (1) the stated position on the consensus was that it was "very likely" which corresponds to a subjective probability assessment of only 90%. (2) the fact that a view is chosen to reflect the consensus summary does NOT mean every scientist involved in the IPCC process supported that view. Many dissenting views were ignored by the lead authors and many experts only looked at specific areas. (3) hundreds of "scientists" did help write the thing but not *2000*; the larger publicized reviewer and author counts included many non-scientist environmental advocates. – glenra Jun 07 '13 at 01:20
  • @glenra, ‘Very likely’ or 90% is the confidence level (this will jump to 95% in the coming AR5). This is not the level of agreement, which is higher. Lead authors seek a compromise between the opinions of experts on all sides. As such, IPCC statements tend to be on the conservative side and represent a view that nearly all the experts can sign off on and defend using the body of evidence available. A consensus doesn't mean that everyone agrees, just a very substantial number of the group agree (they can’t please everybody). – cloudpoint Sep 14 '13 at 23:20
  • Environmental advocates aren't generally allowed to contribute to the IPCC report unless they possess very specialized knowledge (polar bear counts maybe) or they have peer-reviewed support for what they claim. There were 619 contributing authors (all bona fide scientists) to IPCC AR4 WG1 section alone, not to mention their many more colleagues that published all the literature from which they determined the consensus opinion. – cloudpoint Sep 14 '13 at 23:21
3

No. I'll try to answer in order of strength of argument (this is re Cook 2013).

First off, many of the authors of the papers counted as "endorsing" AGW have publicly debunked the claim that their papers supported AGW. That fact alone invalidates the study. You can easily verify this at WUWT where scientists' refutations are posted.

http://wattsupwiththat.com/2013/05/21/cooks-97-consensus-study-falsely-classifies-scientists-papers-according-to-the-scientists-that-published-them/

http://www.populartechnology.net/2013/05/97-study-falsely-classifies-scientists.html#Update2

https://twitter.com/RichardTol/statuses/337126632080957441

Second, the definition of "endorsement" was extremely vague. If a study assumed AGW, that's counted as an endorsement.

Third, the definition of "AGW" is extremely vague. Nearly all prominent skeptics agree some amount of warming is anthropogenic -- this study would count them as supporters.

Fourth, the methodology is beyond awful. The study was done by AGW proponents from a website promoting AGW, no pretense of objectivity was attempted (e.g. by inviting skeptics to participate). The referees were not independent as was claimed (they openly discussed the refereeing on the site). They ignored hundreds of papers from highly respected journals that explicitly questioned AGW, on the basis the authors were not "climatology experts" even though that definition is practically synonymous with "AGW supporter" because skeptics are prevented from publishing in climate journals by the pal review process. Again, easily verifiable on WUWT. http://www.bishop-hill.net/blog/2013/5/27/landmark-consensus-study-is-incomplete.html http://wattsupwiththat.com/2013/05/15/skeptical-science-kidz-channel-inigo-montoya-in-new-consensus-paper/

The Anderegg and Lewandosky studies have similar problems. http://wattsupwiththat.com/2013/05/05/lewandowsky-et-al-2013-surveying-peter-to-report-on-paul/ http://wattsupwiththat.com/2012/07/18/what-else-did-the-97-of-scientists-say/

In short, 97% is a hard number to support, even if you mean things that AGW skeptics generally agree with too.

Statistical problems http://wattsupwiththat.com/2013/06/01/tol-statistically-deconstructs-the-97-consensus/

Approval process issues http://wattsupwiththat.com/2013/06/04/self-admitted-cyber-thief-peter-gleick-is-still-on-the-iop-board-that-approved-the-cook-97-consensus-paper/

I couold cite many more, but I assume I'll get the usual "can't cite WUWT" complaint, the last refuge of those who can't deal with facts, even though relatively little of what WUWT posts is even original research. Sigh.

And not strictly on topic, but this is a good list of problems with AGW theories generally.

http://wattsupwiththat.com/2013/06/05/global-warming-theory-has-failed-all-tests-so-alarmists-return-to-the-97-consensus-hoax/

TallDave
  • 77
  • 2
  • 2
    I actually think your criticism have some validity, but logic alone doesn't meet the rigorous standards of skeptics.SE. We need reliable references and (possibly) some block quotes to demonstrate people said what you claim. Quoting WUWT alone won't meet this standard as it is as partizan in this debate as the site used by Cook et. al.. But you might be able to demonstrate the credibility of the WUWT discussion by tracing the comments themselves to their makers who have reputations independent of WUWT. I'd upvote if you made that case. – matt_black Jun 13 '13 at 21:12
  • The 97.2% figure is from scientists' self-ratings of their papers, thus your first (strongest) point is irrelevant. – Mark Jun 13 '13 at 23:05
  • 1
    [Welcome to Skeptics](http://meta.skeptics.stackexchange.com/q/1505)! Please [provide some references](http://meta.skeptics.stackexchange.com/q/5) to support your claims. – Larian LeQuella Jun 14 '13 at 02:07
  • matt_black -- So? Cook is partisan too. Indeed, nearly all the authors cited above are strong partisans, as are most of the publications cited. WUWT is far more credible. mark -- Where did you get the idea every paper reviewed was self-rated? – TallDave Jun 14 '13 at 15:28
  • I never said they were, where did you get the idea that I have that idea? As quoted above "Among self-rated papers expressing a position on AGW, 97.2% endorsed the consensus." – Mark Jun 14 '13 at 22:14
-3

Christopher Monckton wrote an essay called The Collapsing ‘Consensus’ concerning the Cook, et al. unscientific survey:

  • It did not discuss, still less refute, the principle that the scientific method is not in any way informed by argument from consensus, which thinkers from Aristotle via Alhazen to Huxley and Popper have rejected as logically fallacious.
  • Its definition of the “consensus” it claimed to have found was imprecise: that “human activity is very likely causing most of the current anthropogenic global warming”.
  • It did not put a quantitative value on the term “very likely”, and it did not define what it meant by “current” warming. There has been none for at least 18 years.
  • It cited as authoritative the unscientifically-sampled surveys of “consensus” by Doran & Zimmerman (2009) and Anderegg et al. (2010).
  • It inaccurately represented the views of scientists whose abstracts it analysed. It disregarded two-thirds of the 12,000 abstracts it examined, on the unscientific ground that those abstracts had expressed no opinion on Man’s climatic influence. It declared that the one-third of all papers alleged to have endorsed the “consensus” really amounted to 97% of the sample, not 33%.
  • It suggested that the “consensus” that most recent warming is manmade is equivalent to the distinct and far less widely-supported notion that urgent action to prevent future warming is essential to avert catastrophe. Obama fell for this, twittering that 97% found global warming not only real and manmade but also dangerous.
Oddthinking
  • 140,378
  • 46
  • 548
  • 638
Dr. Delos
  • 37
  • 2
  • 4
    The first point misses the point. No-one claims truth is determined by consensus. Climate denialists claim (when presenting to the public) that the science is controversial and there is serious scientific debate in progress. This paper addresses that by demonstrating the converse. Monckton's claim that there has been no warming for 18 years has been repeatedly debunked. His claim that it is "unscientific" to ignore irrelevant papers isn't explained. – Oddthinking May 22 '13 at 14:43
  • Extended References From Delos: Anderegg, W.R.L., J.W. Prall J. Harold, and S.H. Schneider, 2010, Expert credibility in climate change, Proc. Nat. Acad. Sci. USA 107: 12107-9. Cook, J., D. Nuccitelli, S.A. Green, M. Richardson, B. Winkler, R. Painting, R. Way, P. Jacobs, and A. Skuce, 2013, Quantifying the consensus on anthropogenic global warming in the scientific literature, Environ. Res. Lett. 8: 024024 (7 pp), doi:0.1088/1748-9326/8/2/024024. Doran, P., and M. Zimmerman, 2009, Examining the scientific consensus on climate change, EOS Trans. Am. Geophys. Union 99: 22-23. e – Dr. Delos May 22 '13 at 14:44
  • 4
    The fifth point is ludicrous. How many papers on evolution include an explicit endorsement of evolution? How many papers on thermal sciences explicitly endorse the laws of thermodynamics? How many papers on astronomy endorse the heliocentric model of the solar system? By Monckton's methods we would conclude that that only a tiny fraction of scientists accept any of these concepts. – Mark May 22 '13 at 16:43
  • 1
    Is that last point seriously contesting the dangerousness of a drastic change in climate? I can understand arguing causes, but the effect is absolutely known and catastrophic. – Doug Kavendek May 23 '13 at 14:13
  • @DougKavendek The argument that climate change is likely to be *catastrophic* is much more contentious than the claim that it is happening as are most suggested measures to avoid it. Many believe the world is warming, but not catastrophically and many believe in warming but not the prediction of models. so the claim the "effect is absolutely known and catastrophic." is quite hard to defend. – matt_black Jun 13 '13 at 21:17