Posts Tagged ‘Tom Fuller’

PBL survey shows strong scientific consensus that global warming is largely driven by greenhouse gases

August 4, 2015

Updates:

(5 Sep 2015): US Presidential candidate Rick Santorum used an erroneous interpretation of our survey results on the Bill Maher show. My  detailed response to Santorum’s claim is in a newer blogpost. Politifact and Factcheck also chimed in and found Santorum’s claims to be false. The blogpost below goes into detail about how different interpretations could lead to different conclusions and how some interpretations are better supported than others.

As Michael Tobis rightly points out, the level of scientific consensus that you find “depends crucially on who you include as a scientist, what question you are asking, and how you go about asking it”. And on how you interpret the data. We argued that our survey results show a strong scientific consensus that global warming is predominantly caused by anthropogenic greenhouse gases. Others beg to differ. Recent differences of opinion are rooted in different interpretations of the data. Our interpretation is based on how we went about asking certain questions and what the responses indicate.

To quantify the level of agreement with a certain position, it makes most sense to look at the number of people as a fraction of those who answered the question. We asked respondents two questions about attribution of global warming (Q1 asking for a quantitative estimate and Q3 asking for a qualitative estimate; the complete set of survey questions is available here). However, as we wrote in the ES&T paper:

Undetermined responses (unknown, I do not know, other) were much more prevalent for Q1 (22%) than for Q3 (4%); presumably because the quantitative question (Q1) was considered more difficult to answer. This explanation was confirmed by the open comments under Q1 given by those with an undetermined answer: 100 out of 129 comments (78%) mentioned that this was a difficult question.

There are two ways of expressing the level of consensus, based on these data: as a fraction of the total number of respondents (including undetermined responses), or as a fraction of the number of respondents who gave a quantitative or qualitative judgment (excluding undetermined answers). The former estimate cannot exceed 78% based on Q1, since 22% of respondents gave an undetermined answer. A ratio expressed this way gives the appearance of a lower level of agreement. However, this is a consequence of the question being difficult to answer, due to the level of precision in the answer options, rather than it being a sign of less agreement.

Moreover, the results in terms of level of agreement based on Q1 and Q3 are mutually consistent with each other if the undetermined responses are omitted in calculating the ratio; they differ markedly when undetermined responses are included. In the supporting information we provided a table (reproduced below) with results for the level of agreement calculated either as a fraction of the total (i.e., including the undetermined answers) or as a fraction of those who expressed an opinion (i.e., excluding the undetermined answers), specified for different subgroups.

Verheggen et al - EST 2014 - Table S3

For the reasons outlined above we consider the results excluding the undetermined responses the most meaningful estimate of the actual level of agreement among our respondents. Indeed, in our abstract we wrote:

90% of respondents with more than 10 climate-related peer-reviewed publications (about half of all respondents), explicitly agreed with anthropogenic greenhouse gases (GHGs) being the dominant driver of recent global warming.

This is the average of the two subgroups with the highest number of self-reported publications for both Q1 and Q3. In our paper we discussed both ways of quantifying the level of consensus, including the 66% number as advocated by Tom Fuller (despite his claims that we didn’t).

Fabius Maximus goes further down still, claiming that the level of agreement with IPCC AR5 based on our survey results is only 43-47%. This result is based on the number of respondents who answered Q1b, asking for the confidence level associated with warming being predominantly greenhouse gas-driven, as a fraction of the total number of respondents who filled out Q1a (whether with a quantitative or an undetermined answer). As Tom Curtis notes, Fab Max erroneously compared our statement to the “extremely likely” statement in AR5, whereas in terms of greenhouse gases AR5 in Chapter 10 considered it “very likely” that they are responsible for more than half the warming. Moreover, our survey was undertaken in 2012, long before AR5 was available, so if respondents had IPCC in mind as a reference, it would have been AR4. If anything, the survey respondents were by and large more confident than IPCC that warming had been predominantly greenhouse gas driven, with over half assigning a higher likelihood than IPCC did in both AR4 and AR5.

PBL background report - Q1b

Let me expand on the point of including or excluding the undetermined answers with a thought experiment. Imagine that we had asked whether respondents agreed with the AR4 statement on attribution, yes or no. I am confident that the resulting fraction of yes-responses would (far) exceed 66%. We chose instead to ask a more detailed question, and add other answer options for those who felt unwilling or unable to provide a quantitative answer. On the other hand, imagine if we had respondents choose whether the greenhouse gas contribution was -200, -199, …-2, -1, 0, 1, 2, … 99, 100, 101, …200% of the observed warming. The question would have been very difficult to answer to that level of precision. Perhaps only a handful would have ventured a guess and the vast majority would have picked one of the undetermined answer options (“I don’t know”, “unknown”, “other”). Should we in that case have concluded that the level of consensus is only a meagre few percentage points? I think not, since the result would be a direct consequence of the answer options being perceived as too difficult to meaningfully choose from.

Calculating the level of agreement in the way we suggest, i.e. excluding undetermined responses, provides a more robust measure as it’s relatively independent of the perceived difficulty of having to choose between specific answer options. And, as is omitted by the various critics, it is consistent with the responses to the qualitative attribution question, which also provides a clear indication of a strong consensus. If you were to insist on including undetermined responses in calculating the level of agreement, then it’s best to only use results from Q3. Tom Fuller’s 66% becomes 83% in that case (the level of consensus for all respondents), showing the lack of robustness in this approach when applied to Q1.

Verheggen et al - Figure 1 - GHG contribution to global warming

Some other issues that came up in recent discussions:

See also the basic summary of our survey findings and the accompanying FAQ.

 

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Tom Fuller’s advice for “warmists”

December 27, 2009

Tom Fuller had a post on how science minded folk (“warmists” he calls them) should talk with “sceptics”. Well meant, but coming from the perspective of the “skeptics” having a lot of useful things to say about the science, which is only rarely the case if you ask me. Below are his main points with my replies:

1. Tom: Without ‘reaching across the aisle’ you will not have adequate support to implement your policy preferences.

Me: Coming from a scientist point of view, my prime concern is to advance the public understanding of the issues, and to fight efforts at increasing misunderstanding. From a policy advocacy position, you’re surely right. Though it’s an illusion that you could possibly get 100% of people to agree with your position. Some people are just dug in too deep.

2. Tom: What most skeptics want more than anything else is a seat at the table–to be listened to and taken seriously.

Me: Play by the scientific rules, and you have a seat. Publish, come to meetings, use real arguments.

Tom’s comeback: Climategate seems to show that the rules can be bent, and that some of those saying skeptics should get published in peer-reviewed journals are conspiring to prevent that from happening.

Me: “Climategate” shows that scientists are human too. I’ll concede that some unfortunate statements were made in a minuscule fraction of these emails. However, concerning peer review, the major problem discussed in the emails was how peer review broke down at Environmental Climate Research, by letting a methodologically flawed paper sail through review. See e.g. a recount of the story by then editor-in-chief Hans von Storch, who is as close to a non-alarmist climate scientist as you can get. See also an opinion piece on the stolen emails by him and Myles Allan in Nature. Specifically, they write: ”Even we —the two authors of this piece — find it impossible to agree whether or not some people went too far to ensure dominance for particular points of view. We do agree, however, that it is absurd to suggest there is some kind of global conspiracy involving all climate scientists.” And “What the e-mails do not prove — or even suggest — is that the main product of the CRU, namely the record of global surface air temperature based on thermometer readings, has been compromised.”  This commentary is also very insightful. The widespread attack on science and on scientists is entirely uncalled for.

3. Tom: It has been convenient for ‘warmists’ to class all opposition as ‘denialists,’ usually adding such terms of endearment as ‘flat-earthers,’ etc. This has had the unfortunate effect (for ‘warmists’) of uniting the opposition.

Me: Although I try to refrain from using that term for pragmatic reasons, it seems befitting for more than a few. ‘Denialism’ relates to using certain tactics, and it exists in other areas as well (e.g. health issues). See also here.

Tom’s Comeback: I think ‘denialist’ is a political term used for political reasons, to class anyone who doesn’t agree with the activist point of view alongside those who denied the Holocaust. I don’t like it.

Me: The phrase “being in denial” is common English AFAIK, and is not only attributable to holocaust deniers. There are more things being denied by people than the holocaust. It is unfortunate that the term “denier” brings up associations with these characters, but it does not mean that the term doesn’t also apply to others.  See e.g here, where they argue that denialism is based on conspiracy, selectivity (cherry-picking), fake experts, impossible expectations (also known as moving goalposts), and general fallacies of logic. What other name could be given to those engaging in these types of tactics? It’s clear that it has nothing to do with sincere scepticism. For lack of a better word, and to avoid angering people who are not aware of the ins and outs of the internet debate, I usually refer to them as “sceptics” in quotation marks. Where I agree with you is that it is not smart nor correct to class everybody who disagrees as a denier or denialist. Disagreement comes in many flavours, and not all amount to denialism (though some do, unfortunately).

4. Tom: Acknowledge error. Start with Steve McIntyre.

Bart: Genuine errors should, and are usually acknowledged. It’s a tricky thing to do so with people who are overtly hostile and having smeared you through the mud though. Scientists are human too: Accuse them too often of fraud, and they’ll stop listening to you.

Tom’s Comeback: Bart, is there any way you could justify hiding the divergence of proxy temperatures from real data in a presentation for non-scientists? For politicians debating on whether or not to spend $1 trillion a year of our money in response to what the graphic showed them?

Me: Admittedly I haven’t followed the details of the divergence discussions, but AKAIK, it was discussed in the IPCC report back then. In speaking to the public, the message necessarily has to be adapted, and it often means simplified. If I go to a scientific talk even remotely outside of my field, it’s incredibly hard to follow. Let alone if I were to go to a talk of a totally different discipline. There’s a catch 22 for scientists talking to the public.

More importantly, the decision to spend a trillion dollars doesn’t hinge on one graph. The importance of the hockeystick graph has been overstated to the extreme. Initially also by the IPCC itself, but since then mostly by the “sceptical” camp.

5. Tom: Free the data. Free the code. Open up the debate. From what I’ve seen of the people you think are your bitter enemies, they will respond with help, kindness and forgiveness of your boorish behaviour in the past.

Bart: There are more data and code available than you think. And your second argument that the response will be helpful, kind and forgiving is utterly naïve. It won’t change a single thing in the witch-hunt and anti-scientific attitudes.

Tom’s Comeback: Try us. Specifically, try Steve McIntyre. Ask him for help in his area of competence.

Bart: If McIntyre were sincerely interested in contributing to the science, he would do so. I looked in some detail into his role in the Yamal-debate. I was not impressed. For a more recent example, see eg here. He has made a niche for himself, and it is to provide fodder to “sceptics” and harass scientists. Whatever you say can and will be used against you, seems to be his motto. I completely understand why scientists are loath to try and accommodate him, even if at instances it may be counterproductive, and even if at instances he has a point. Basically, you’re damned it you do and damned if you don’t accommodate.

Constructive criticism is one thing; harassment is quite another. Do too much of the latter, and your efforts at the former will be stonewalled. Misguided? Perhaps. Human? Certainly.

6. Tom: Say a fond but firm farewell to those who have served you poorly in the struggle to gain public support. Al Gore. Joe Romm. (Not Jim Hansen or Gavin Schmidt.) Michael Mann. Phil Jones.

Bart: Scapegoating is not the answer.

Tom’s Comeback: I’m not saying get rid of them because I don’t like them, or even because I think they have acted wrongly. I’m saying get rid of them because they are a hindrance, not a help to your cause.

Bart: There is no board of scientist-directors anywhere who have the power to “get rid of” anyone as they seem fit. Apart from that, I disagree about the people you mention all having been a hindrance to advance public understanding; in some cases quite to the contrary (even if not without faults). There could be some (rather unethical) pragmatism to get rid of people who are receiving the most blame, in an effort to clean our plate, at least in the mindset of the “sceptical” public. But I disagree with such scapegoating.

7. Tom: Abandon the tactic of artificial deadlines and panic attacks. We have more than 10 minutes to save the Galaxy.

Me: There is no strict deadline. OTOH, the longer we wait with taking measures, the more drastically we have to reduce emissions later, which in the end will probably be more difficult and more expensive. Not to mention it increases the chance of crossing dangerous tipping points. So time is of the essence.

Tom’s Comeback: It will be more expensive, but we should be richer, right? As for tipping points, I think this is the core of our disagreement on the future of our climate in the near term. I just don’t see it happening.

Me: “Tipping points” is perhaps too loaded of a term. The world doesn’t end after it is crossed, nor is everything fine when it’s not crossed. Consider for example the increasing melt of both the Greenland and the Antarctic ice sheets. The dynamics of these melt processes are very uncertain (and potentially worrisome), but it’s very likely that once big changes are set in motion, it’s very difficult to reverse them. Even more so because the CO2 concentration responds only very slowly to emission reduction efforts. So by the time society realizes “whoops, we’re in serious trouble now”, it may be too late to reverse it by ordinary means. Warning signals from the science are ignored at our peril.

The costs of reducing emissions doesn’t rise linearly with the amount of emissions to be reduced. It rises more or less exponentially. That makes your argument that we’ll be richer in the future moot, at least beyond a certain level. There are arguments made that 4% emission reduction per year is more or less the maximum achievable; beyond that the regular way of innovation and change (learning curves etc) doesn’t apply anymore. It would necessitate much stronger and much more costly and invasive measures to go beyond that. Typically the kind of measures that the “sceptics” oppose most strongly.

Those who oppose strong control by the government, should really favor emission reductions to start sooner rather than later, to reduce the pain that the measures would otherwise cause. That point is easily overseen.

The last point, and in addition the fact that more uncertainty should make one more, not less careful, are the key concepts that “sceptics” are missing the mark on, I think.

8. Tom: Accentuate the positive. Almost all of the measures you advocate to help bring about a greener world are justified without a trace of global warming. Emphasize the common-sense approach

Me: True, but it risks painting a rosier picture than it really is. If solar energy is expensive, people won’t do it just because it’s cool or because it creates jobs. They may because it gives an innovation advantage down the road (but that already implies the reality of AGW).

Tom’s Comeback: I have no comeback. I will actually have to think about this for a while…

9. Tom: Don’t ever again be trapped into untruths by a desire to shorten the story line.

Bart: I don’t’ understand the “again” in this context. Which untruths? If anything, scientists are way too long winded and fond of weasel words as it is. (Guilty as charged…)

Tom’s Comeback: True, but they stayed out of trouble (and the limelight) most of the time before.

10. Tom: Be the first to bring this debate out of the morass of partisan politics. This isn’t a left vs right debate.

Me: Entirely correct. CO2 absorption isn’t influenced by political leanings. This is mostly a message though for those who let their political views blur their judgment of the science.

A mirror story, advice for “skeptics” is here.

Global warming survey

November 1, 2009

Tom Fuller is doing a survey on global warming. He’s writing for the Examiner, with regular commentary about environmental (usually climate change) issues. He’s framing the survey as a search to see where common ground could be found in terms of policy reponses to global warming, which is an interesting and useful goal to pursue. It is explicitly not meant to be a survey of how many people ‘believe’ in AGW. Based on the bulk of comments on his site, it will be skewed to the “skeptical” point of view anyway. But that’s not the point…

Tom Fuller is a self desecribed ‘lukewarmer’. He has grown quite suspicious of climate scientists and their motives, based to a large extent on blogs where scientists are routinely bashed criticized. He’s an honest guy though, and exemplifies the kind of person with whom it’s both useful and possible to search for common ground, despite (sometimes large) differences in viewpoints.

Update: Survey is now closed. Outcome (>3000 respondents, 85% from WUWT) is heavily influenced by “skeptics”, which offers an interesting glimpse in their kitchen. Half is over 55, a quarter is emeritus. What was that about teaching old dogs new tricks? That they’re mostly republican and libertarian is less of a surprise. But some mitigation measures are more supported (or less opposed) than others. Neither cap and trade and carbon tax are supported, which doesn’t make a lot of sense to me; you’re not necessarily paying more for those measures than for straight taxes on some other measures that you could chose from. I don’t see the rationale behind it, but perhaps I’m looking for something that’s not there.

My ‘next generation questions’ on climate change

August 19, 2009

Following an interesting conversation I’ve been engaged in with Thomas Fuller (see also the previous post), here is my take on what the next generation questions on climate change are.

Let’s distinguish the following main issues:
– To what extent is climate change occurring, and to what extent is it man-made?
– To what extent is that (going to be) a problem?
– What can or should we do about it?

The first questions are strictly scientific; the middle has a judgment value to it, and the latter is primarily a political/moral judgement (and has more to do with technology than with climate science).

 We have made much more progress in addressing the first question than in addressing the last one. The limiting factor in addressing the issues relating to climate change is not a lack of knowledge about the exact nature of the changes; rather, it is the unwillingness of society to deal with (the consequences of) this knowledge. Even if climate change is less bad than currently expected, we need to dramatically step up our policy response.

I don’t say this to downplay the uncertainties in climate science; there are many, and many of them are large (scientifically speaking). However, within realistic boundaries of the uncertainty, we still don’t do enough to deal with the issue: Any realistic change in our scientific understanding is not going to change the needed policy response, at least not in the short to medium term (~decades). As Herman Daly noted: “If you jump out of an airplane you need a crude parachute more than an accurate altimeter.” And Tom Yulsman: “With a bit of luck, maybe we can agree that regardless of [the details regarding] climate change, we need an Apollo-scale effort to develop transformational energy technologies.” How to shape that effort is the next generation question.

So the ‘next generation questions’ in my view relate to the last one: How are we going to deal with this? There are a lot of tough questions to be answered in that arena, e.g. relating to different technologies (nuclear, biomass, CCS, electric vs hydrogen transport, geoengineering, to name just a few highly contested topics), and relating to more institutional-political matters (e.g. carbon tax vs cap and trade, landuse, changes in consumption patterns, equity issues). Michael Tobis has some excellent writing on the latter topics.

Regarding the ‘next generation of questions’ strictly relating to climate science, some examples of important areas with high uncertainty are the following:
– Regional climate effects
– Climate sensitivity
– The role of aerosol and clouds
– Sea level rise (update: added after Heiko’s suggestion)

However, we need to keep in mind that uncertainty goes both ways, and that science usually progresses with small increments: Three steps forward, two steps back. It is wise to be very skeptical of any claim that the science is radically wrong. Any new piece of evidence just adds to the puzzle; it doesn’t replace existing evidence. Context and perspective are key, and they are often missing in loud proclamations against the consensus.

Let me give an example from an area of research that I’ve been working in for a number of years: Aerosol formation. For at least a decade, sulfuric acid has been regarded a key compound in the formation aerosol particles. The potential contribution of other compounds (ammonia, iodine, ions, organics) has been (and still is) hotly debated, but if someone tries to tell me that sulfuric acid has no noticeable effect on aerosol nucleation, I would not tend to take them very seriously, unless they have extraordinary evidence to back up that (scientifically radical) position. Nothing is impossible, but it’s not very likely.

I think we know a great deal more about the role of CO2 in the climate system than we do about the role of sulfuric acid in aerosol nucleation. I don’t expect a landslide change in scientific thinking on the subject. If someone does, they better bring very strong evidence to the table; a photograph or two won’t do.

(update: the next post elaborates on the major climate science uncertainties)

Next generation questions on climate change

July 12, 2009

Over at the Examiner, Thomas Fuller had a post outlining a ‘new generation of skeptical arguments against the theory of anthropogenic global warming’ (AGW), which he felt had a lot of merit. I got to his post via a comment thread at RealClimate, where he asked for input. He did get quite a lot of feedback, but unfortunately, a lot of it was packaged in a rather negative tone. (I’ll come back to communication strategies in another post.) Since he appeared to be sincerely interested, I felt compelled to react. I responded to (his framing of) his questions as follows:

You frame your questions/topics as “skeptical arguments advanced against the theory of anthropogenic global warming”. You also acknowledge that scientists are getting frustrated “answering the same ‘primitive’ objections repeatedly, only to see them resurface shortly thereafter, something that I am sure is frustrating.” I think a logical consequence is that your framing of the topic arouses a defensive reaction from climate scientists and their supporters. Based on you being aware of the scientists’ frustration in this matter, your choice of framing is rather odd, and so is your surprise about the reactions you received at RealClimate (mostly from commenters by the way; not from the RC editors). In between the snark, you did get some feedback there as to the contents of your questions/topics. It’s your choice whether to focus attention on the former (the snark) or the latter (the feedback to the content).

Most points on your list are neither new nor a threat to the theory of anthropogenic global warming. That said, some of your points have some validity in that the related uncertainties are large. Reframing your questions as “which areas in climate science have the greatest uncertainties?”, opens the door to a more constructive discussion. 

A quick glance at the points your raise:

Data gathering and analysis. Points 1-4 are pretty meaningless for reasons explained at length elsewhere. The revised ocean heat content data (nr 5) don’t show a decrease of ocean heat content AFAIK, and moreover, trends have to be decided upon at appropriately long timescales. I’m not familiar enough with Tropical troposphere trends to comment on, though Santer et al (2008) found no discrepancy between modeled and measured tropical tropospheric temperatures.

Climate sensitivity and feedbacks. There is considerable uncertainty in the precise value of climate sensitivity, so in my newly proposed frame, this would be a valid point. However, taking all constraints on climate sensitivity into account, it seems very unlikely that it is far outside the boundaries you quote: 1.5 to 4.5 degrees for a doubling of CO2. The chance for all previous work to be shown totally wrong by one new piece of work is perhaps not nil, but it definitely is very small.

Plateau in current temperatures. Trends have to be decided upon at appropriately long timescales. The apparent plateau is close to meaningless for deciding on climatic trends. This truly is an old classic that gets scientifically minded persons’ defenses up.

Tipping points. The exact nature and especially timing of tipping points is extremely uncertain, so yes, this is an area where the existing knowledge is very limited. However, the limited knowledge we do have (mainly based on paleoclimate) points to the existence of tipping points, eg related to the amount of ice cover. The policy relevance may be limited to “If it’s bad, it’s really bad. If it’s good, it’s still pretty bad”.

Other climate forcings. No news there. Those other forcings are taken into account and indeed, they are additive to the changes from GHG emissions. They do not negate the radiative properties of those greenhouse gases however. Also keep in mind that many of the stronger feedbacks respond to temperature, so the amplification (or dampening) of the temperature response does not differ greatly between different forcings. That means that there is not a huge amount of wiggle room to decrease (or increase) the importance of the role of greenhouse gases (at least not without violating basic physics).

I would add one more point: Aerosols. The uncertainty surrounding them and their impact on climate change is very large. But again, don’t expect a landslide change in current wisdom just because of that. That would be wishful thinking.

It is good to keep in mind that uncertainty is not the same as knowing nothing, and that uncertainty can go both ways: for the better or for the worse. We’ll have to make decisions in the face of uncertainty, whether we like it or not. Climate policy should be about rational risk assessment, based on solid science.


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