Some people believe the famous 97% global warming consensus paper, published by the people at Skeptical Science, should be described as finding:

There’s a 97% consensus supporting the AGW theory, and 1.6% put the human contribution at >50%.

One member of the project, Tom Curtis, says “[t]hat position, however, is also incoherent.” Another member of the project, Rob Honeycutt, says (in an inline response) of that statement:

[RH] It is a misinterpretation of the results.

In fact, it seems the only person who believes that statement is reasonable may be Dana Nuccitelli, second author of the paper and creator of the scale used in the paper. When he created the scale, Nuccitelli explained:

The way I see the final paper is that we’ll conclude ‘There’s an x% consensus supporting the AGW theory, and y% explicitly put the human contribution at >50%’.

Which is word-for-word the statement the Skeptical Science team labels an “incoherent” “misinterpretation,” just with the numbers from their paper plugged in.

In fact, Nuccitelli seems to agree with the critics of this paper. When he first introduced the scale the paper would wind up using, Nuccitelli said:

As another option, we could have two different consensuses (consensi?). The first being ‘humans are causing most of the observed warming’, the second just being ‘humans are causing global warming’.

The first is a stronger point, but relatively few papers will qualify as endorsements (but it should still be a clear consensus). The second is a weaker point, but you’ll have a much larger consensus.

I think every critic of the paper agrees with Nuccitelli. Almost all of them agree there are two different issues. Most of them say the issue, “Is global warming real?” is already resolved. Almost everyone agrees humans have some impact on the planet’s temperatures. They just disagree about how large an impact it is.

Nuccitelli said we should clearly distinguish between “humans are causing global warming” and “humans are causing most of the observed warming.” Skeptics around the world cheer at that idea. They like the idea of saying there is only a 1.6% consensus humans are the dominant cause of global warming.

Nuccitelli was prescient about this, explaining how to avoid letting the skeptics get away with that:

Maybe it turns out that very few papers explicitly endorse AGW > 50%. That’s fine, then don’t use that as the consensus definition. But if it turns out that a lot papers do explicitly endorse AGW>50%, that’s critical information. I’m just saying don’t limit yourself before you’ve even started the project. If you leave your options open and collect as much info as possible, who knows what you’ll find.

If lots of papers say humans are the dominant cause, Nuccitelli thinks they should use that as the “consensus” definition. If not many papers say humans are the dominant cause, Nuccitelli thinks they should use a different definition of “consensus.”

In fact, Nuccitelli explained how to measure the two different definitions of the “consensus” his scale could measure:

  1. Explicitly endorses and quantifies AGW as 50+% cause of the observed warming (or consistent with the IPCC, or something similar)
  2. Explicitly endorses but does not quantify AGW
  3. Implicitly endorses AGW (by definition does not quantify)
  4. Neutral
  5. Implicitly minimizes AGW (i.e. says the sun is playing a big role)
  6. Explicitly minimizes AGW (less than 50%, less than IPCC, less than consensus, etc.)
  7. Explicitly says there’s no anthropogenic effect on climate/temperature

For ‘humans are causing most of the warming’, #1 qualifies as an endorsement, while #5 through 7 are rejections.

For ‘humans are causing warming’, #1 through 3 are endorsements, while only #7 is a rejection.

With those categories, we can just go ahead and rate the papers and see how the percentages turn out for each possible consensus position. It gives us more flexibility than if we choose one or the other definition of AGW beforehand.

A naive person might think Nuccitelli’s ideas about defining the “consensus” are unremarkable. A naive person might see categories specifically labelled as “does not quantify” and think the categories should not be used to measure the idea “humans are causing most of the observed warming.”

But the Skeptical Science team thinks otherwise. Tom Curtis explained why we should believe a paper which merely says methane is a greenhouse gas endorses the idea “humans are causing most of the observed warming” by saying:

It is my opinion that interest in the reduction of greenhouse gases, the only criteria under which the treatment was tested, is only relevant if greenhouse gases are the major contributor to global warming, and only a recommendation of greenhouse gases are the major contributor to global warming. Hence implicitly the abstract assumes that greenhouse gases are the major contributor to global warming (which is also implicitly assumed to be a bad thing).

Or maybe the team doesn’t think that way. Nuccitelli did warn against the exact sort of argument Curtis makes:

In short, in case I’m not being clear, my problem is that if you define AGW as “>50% observed warming over the past ~century is anthropogenic”, then either:

you’re forced to make major assumptions in claiming that a large percentage of papers are endorsing that definition (for which you’ll be criticized, and rightly so), or

you can break out those which explicitly endorse that definition and those which simply endorse “AGW”, in which case you’re not making any such assumptions (which IMO also makes it less subjective, though perhaps you can replace much of my ‘subjectivity’ concerns with ‘assumption’ concerns).

If you go back up to John’s update on the first post above, he asked:

“…all these papers endorse the consensus because we say they do?”

That’s my concern too. Replace “we say they do” with “we assume they do” – same thing.

So who is right in all this? Are Tom Curtis and Rob Honeycutt right to call Dana Nuccitelli’s envisioned description of the results an “incoherent” “misinterpretation”? Was Nuccitelli, the guy who created the scale used in the paper, a complete buffoon when he explained why he made the scale the way he did?

It’s hard to say. I agree with Nuccitelli. I know a lot of the paper’s critics agree with him too. We all think, like he said, it is right to describe the results by saying:

There’s a 97% consensus supporting the AGW theory, and 1.6% put the human contribution at >50%.

But we need to find out who is really right. If multiple people working on the same project can’t agree, the obvious solution is to ask the project leader. The project leader for this paper was John Cook. Fortunately, he’s already answered our question:

So what is annoying about Dana is when we have a long, convoluted discussion and at the end, I end up just agreeing with what Dana was saying at the very start of the conversation.

So since Dana Nuccitelli said we should describe the results as:

There’s a 97% consensus supporting the AGW theory, and 1.6% put the human contribution at >50%.

John Cook apparently agrees we should describe the results as:

There’s a 97% consensus supporting the AGW theory, and 1.6% put the human contribution at >50%.

Yet somehow the group keeps saying things like:

C13 classified abstracts of climate science papers based on the level of endorsement that most of the recent global warming is man-made (AGW, Categories 1–3)

Even though Nuccitelli clearly explained the 95.4% of the papers which endorse the “consensus” in Categories 2 and 3 are:

not endorsing “the consensus position” – we have to demonstrate what the consensus is. They’re endorsing the AGW theory in general without being specific about the human contribution to AGW.

This is the assumption problem I was talking about earlier. We can’t assume that just because a paper says “anthropogenic global warming” that they agree the human contribution is >50%, but they have explcitly endorsed that humans are contributing. Thus they go in category #2.

How does this work? I agree with Dana Nuccitelli. Every critic of the paper I’ve talked to would agree with him too. What he said when designing the scale for this project is the same thing we’ve been saying all along. The critics of the paper agree with the person who designed the scale of the paper.

And John Cook agreed with him. That means the critics of the paper agree with the lead authors of the paper! It’s surreal. Apparently the people responsible for this paper agreed with the critics of the paper… until they saw their results. Then they changed their tune. Maybe finding a 1.6% consensus did that to them.




    For this categorization to be consistent it must satisfy two criteria:

    1) No paper must fall under more than one classification;


    2) If different levels of concensus represent different minimum percentages of anthropogenic contribution, they must change monotonically with classification level.

    Now clearly if “endorse AGW” means “endorse that “at least some of recent warming has been anthropogenic”, then the categorization fails criteria (1). That is because any paper endorsing >0% but <50% anthropogenic warming must be categorized either 2 or 3, but also 7. Further, it also fails condition (2) for category 1 clearly applies only to papers which endorse 50% or more anthropogenic contribution to recent warming, while category 7 applies only to papers that endorse less than 50% anthropogenic contribution. The only monotonic ordering of endorsement levels possible, therefore, is on in which for all categories endorsement of AGW means endorsing 50% or more of recent warming as anthropogenic, and disendorsing means endorsing less than 50%.

    If there are two ways to interpret a paper, one of which is consistent, and one of which is inconsistent, then clearly we must give preference to the consistent interpretation. Doing otherwise merely raises a strawman. Therefore, there is no rational way to interpret endorsement in Cook et al as anything other than "endorsement that 50% or more of recent warming was anthropogenic".

  2. MikeN, that that explanation is wrong is obvious given Nuccitelli specifically said:

    For ‘humans are causing most of the warming’, #1 qualifies as an endorsement, while #5 through 7 are rejections.

    For ‘humans are causing warming’, #1 through 3 are endorsements, while only #7 is a rejection.

    The reality is there is no way to compare Categories 1-3 with Categories 5-7. They never intended to compare them that way. They only did so when they realized comparing them the way they originally planned would lead to embarrassing results.

    The reason there has been so much controversy over the definition of their “consensus” is they intentionally moved away from the clear definitions they originally used and created a new “consensus” position which doesn’t actually have a definition.

    Of course, they’re free to disagree with this. In that case, they have to explain why the approach they had in mind while doing the project is wrong.

  3. If Tom Curtis and Rob Honeycutt are correct, then EVERY abstract rated as a 2 or 3, must endorse humans as causing MOST warming.

    So, showing them even one single counter-example of such a paper would prove them wrong.

    And the two attempts I’ve made to do exactly that have both been redacted by the moderator, Rob Honeycutt, as a violation of their comments policy.

  4. Russ R., you do have to account for the fact errors happen. If you could only show one or two counter-examples, there’d be little reason to care given there are 3000+ papers in those two categories. Or at least, that’d be true if they responded, “Well, those were mistakes.” I don’t think they’d ever do that.

    MikeN, it seems a time honored tactic in the global warming debate. Check out these three examples of climate scientists responsible for temperature reconstructions openly admitting to it:

    By the way, the thing which baffles isn’t that they chose their methodology after the fact. What baffles me isn’t even that they specifically laid out how they’d present their results in advance then changed it because they didn’t like what they found. What baffles me is they adamantly insist it is wrong to present their results the way they said their results should be presented.

    Does anyone remember the responses to this post of mine:

    Cook et al members and their defenders condemned me for comparing Category 1 to Categories 5-7, saying such a comparison was wrong and even dishonest. They insisted the only appropriate comparisons were symmetrical ones. Dana Nuccitelli responded to my post by saying:

    The beauty of our system is that it’s symmetric. If you only want to consider quantifications, you can compare Categories 1 and 7. If you only want explicit endorsements, you can do 1+2 vs. 6+7, and so forth, as Bart has done. But to compare 1 to 5+6+7; that’s skewing the data in order to give you the answer you want.

    Yet when designing the rating system, Dana Nuccitelli specifically said:

    For ‘humans are causing most of the warming’, #1 qualifies as an endorsement, while #5 through 7 are rejections.

    How is that possible? How can someone specifically create a scale to allow certain comparisons be made then call people dishonest for making those comparisons?!

  5. Brandon,

    You’re quite correct… one counter example could be an outlier, easily explained by error. But dozens or hundreds would indicate a systemic issue.

    I’d be happy to bring a Category 2 or 3 example to their attention every single day and force them to either explain exactly how the abstract endorses “humans cause MOST warming” vs. “humans cause warming”, or else explain it away as a random error in the rating process.

  6. Good luck with that. They delete comments for all sorts of reasons, including ones that aren’t real, aren’t fairly applied or aren’t even coherent. I like how they always refer people to their comments policy in exchanges where they delete things like “stolen” material. I’m not sure what part of their comments policy they expect people to read which tells them that’s not okay (especially when they still promote the stolen Heartland documents).

  7. And don’t even bother asking what part of the comments policy you violated. Doing so is deemed to be a “moderation complaint” and is itself an unwritten violation of the comments policy, which will be immediately deleted.

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