Archive for the ‘Media’ Category

A critical look at “The uncertainty has settled” documentary by Marijn Poels

July 17, 2017

(Zie de Nederlandse versie door Jos Hagelaars op ons Klimaatverandering blog)

The documentary “The uncertainty has settled” from Dutch filmmaker Marijn Poels follows him on his journey in rural Austria and Germany to witness how energy policies impact traditional agriculture. That is the stepping stone to also look into different ideas about how and why the climate is changing. Unfortunately Poels has no clue how to distinguish fact from fiction, and by his own admission he has no interest in making that distinction. As a result the documentary offers a mix of basic scientific insights, plain falsehoods, and misleading statements regarding climate science. As an unwitting viewer you are left utterly confused –cued by Poels’ facial expression at those times- how to reconcile these seemingly opposing viewpoints. Creating confusion was apparently his objective (as he acknowledges on his website), but it makes for a surreal experience if you know you’re being fooled. I think spreading falsehoods is doing a disservice to the public, as I’ve said to Marijn Poels during a radio-debate (in Dutch).

Let’s look more closely at some of the things being said about climate change in the documentary.

Marijn Poels meets another Dutchman in rural Germany, who laments how climate policies have led to the disappearance of local nature. He says it’s insane to think that a CO2 concentration as low as 0.035% (currently 0.04%) could have any impact on climate. That’s clearly fallacious reasoning (argument from incredulity): there are plenty of examples of compounds that have serious impacts at the same or lower concentrations (e.g. a CO detector will sound the alarm at such a concentration and you had better leave the premises). Without any CO2 in the air the globe would quickly become a frozen ball of ice, since the main air constituents (nitrogen 78%, oxygen 21%, argon 1%) don’t impede the infrared heat loss to space.

Later in the documentary he meets with climate scientist Hans von Storch, astrophysicist Piers Corbyn and physicist Freeman Dyson. Those in the loop will immediately recognize that this is not at all a fair representation of the scientific debate, but rather provides a very skewed vision thereof by emphasizing outlier views that are demonstrably false.

Hans von Storch accurately describes our current knowledge about climate change: We know that the earth has warmed and we can’t explain this warming without considering the human-induced increase in greenhouse gases in the atmosphere. He also distinguishes how scientific knowledge may be very uncertain in specific details, while the core tenets are robustly known: “The fact that CO2 has a significant influence on climate is indisputable.”

It’s astonishing how many falsehoods and conspiracy theories Piers Corbyn mentions over the course of few minutes.  Some of the things he said:

FALSE: The increasing CO2 concentration in the atmosphere is coming from the oceans

If Corbyn were right, the concentration in the ocean should have decreased in order to explain the increased atmospheric concentration (a simple consequence of conservation of mass). However, CO2 concentrations have been observed to increase both in the atmosphere and in the ocean. In reality, the excess CO2 in both atmosphere and ocean originates from fossil fuel burning, as is evident from the isotopic signature and the concomitant decrease in atmospheric O2 concentration.

FALSE: CO2 only follows temperature

During the ice age cycles CO2 acted as an amplifying feedback on the warming which was initiated by changes to the earth’s orbit. During those times of relatively slow warming the temperature indeed started to increase before the CO2 concentrations did, after which the CO2 caused even more warming. Hence it’s a bit of a chicken-egg issue with CO2 and temperature, but Corbyn’s statement is misleading. The current CO2 increase is unequivocally anthropogenic and ~100 times faster than it was in glacial to interglacial transitions. Moreover, we have known since the mid-nineteenth century that CO2 absorbs infrared radiation and thus acts as a greenhouse gas which impedes planetary heat loss and thus warms up the surface.

FALSE: Termites produce more CO2 than human activity does

Termites produce less CO2 than human activity does. Moreover, while anthropogenic emissions have led to the increased CO2 concentration, there’s no sign of tremendous changes in termite populations or emissions. In general, CO2 uptake and release by the biosphere (through assimilation and respiration/decomposition, respectively) approximately balance over multi-annual timescales. Termites also emit methane, another greenhouse gas, though around 40 times less than is released through human activity.  [Text about termite emissions has been updated 17-07]

FALSE: A new mini-ice age cometh

Corbyn has been predicting this for a while now (at least since 2010), but reality so far has been going in the opposite direction compared to his predictions. Scientists have investigated the potential consequences of a quieter sun in the near future, but generally find that increased greenhouse gas concentrations will dwarf any realistic decrease in solar activity, and hence the globe will continue to warm for the foreseeable future.

CONSPIRACY THEORY: The increased temperatures are a result of fraud with the observations

Globally averaged temperatures are computed independently by a number of different research group and they all agree within a close margin of each other. The raw data are available, so everyone who’s interested and who has the requisite skill can try to reproduce (or falsify) these calculations. A number of ‘skeptical’ people have indeed done so, and lo and behold, they found the same result: the globe really is warming.

Corbyn continues with his conspiracy theories and doesn’t even seem bothered that they’re mutually inconsistent with each other: on the one hand he claims that the ‘climate ideology’ has been made up by international big business interests, on the other hand he also claims that the ‘myth of climate change’ is a scheme to de-industrialize the West. How can you possibly take someone like this seriously?

Next up is renowned physicist Freeman Dyson, who is very skeptical of the ability of climate models to make accurate projections of future warming. In the documentary he paints a false dichotomy between observations on the one hand and models on the other hand, whereas in modern science they really go hand in hand and models form an integral part of science. Model simulations agree very well with observations, despite Dyson’s claims to the contrary. For good measure he also throws in a conspiracy theory by claiming that climate modelers only want to scare people, because they wouldn’t get money for their research otherwise. This goes to show that otherwise brilliant people can still make silly claims about a field of science that they don’t know much about.

So why did Marijn Poels chose to interview people who are demonstratively wrong (and who are not actually climate scientists)? His whole idea with the documentary was as a personal quest in which he listened to various viewpoints without judgment or evaluation. In a radio-debate I did with him on Dutch Radio NPO1 he proclaimed that he doesn’t feel any responsibility to figure out who’s talking sense and who’s talking nonsense. On twitter he has since confirmed that he doesn’t care what true and what’s not. I find that a very strange attitude for a documentary-maker, as I tried saying at the end of the radio-debate:

Scientists are seeking a better understanding of the world around us. What I hear Marijn Poels say is that it doesn’t matter to him what’s true and what’s not. That goes against everything I value as a scientist.

He also tweeted that “if there are multiple scientific perspectives, then it’s worthy of debate”. So the problem is not only that he doesn’t care about whether something is true or not; he doesn’t see that some of what he calls “scientific perspectives” are plain untruths. Claiming that the CO2 might just have come out of the ocean is no more a ‘scientific perspective’ than claiming that vaccines cause autism or that smoking is not linked to cancer. Science has conclusively shown these statements to be false.

In a public debate about smoking regulation there’s no point in discussing whether smoking is really bad for you: we know that by now, based on scientific evidence.

Likewise, in a public debate about climate policies  there’s no point in discussing whether CO2 really contributes substantially to climate change: we know that by now, based on scientific evidence.

FAQ for the article “Scientists’ Views about Attribution of Global Warming”

August 11, 2014

published in Environmental Science and Technology (open access), DOI: 10.1021/es501998e, Supporting Information here.

A formal version of the FAQ is also available at the website of the PBL Netherlands Environmental Assessment Agency. A blog post with a brief description of the main conclusions is here.



1. What are the objectives of this survey?

The PBL aimed to characterize the spectrum of scientific opinion about physical climate science issues. The research was focused on issues that are a frequent topic of public debate, and explored questions such as:

  • On which issues is there widespread agreement amongst scientists?
  • On which issues do scientists hold varied opinions?
  • How does the spectrum of scientific opinion compare to IPCC assessments?
  • How do scientists view skeptical arguments and viewpoints?

2. What is the relevance of an opinion survey or of measurement of consensus in trying to assess the science?

Science is based on the critical evaluation of available evidence in the context of existing knowledge. It is not “just an opinion.” With this survey, we tried to identify how scientists assess the different viewpoints that exist in public discussions of climate science. If the evidence for a certain viewpoint has become sufficiently strong and stable over time, the scientists’ aggregated opinion could be expected to reflect that.

3. Are the survey results publicly available?

The full survey results are not publicly available, because the PBL intends to use the data for further analyses.
Graphs with the ‘straight counts’ for every question (i.e. the number of responses for each answer option) are available in a background report. These results are not segregated in different sub-groups.



4. How does this study compare to the often-quoted 97% consensus?

Our results are consistent with similar studies, which all find high levels of consensus among scientists, especially among scientists who publish more often in the peer-reviewed climate literature.

Cook et al. (2013) found that 97% of papers that characterized the cause of recent warming indicated that it is due to human activities. (John Cook, the lead author of that analysis, is co-author on this current article.) Similarly, a randomized literature review found zero papers that called human-induced climate change into question (Oreskes, 2004).

Other studies surveyed scientists themselves. For instance, Doran and Kendall-Zimmermann (2009) found lower levels of consensus for a wider group of earth scientists (82% consensus) as compared to actively publishing climatologists (97% consensus) on the question of whether or not human activity is a “significant contributor” to climate change. Our results are also in line with those of e.g. Bray and von Storch (2008) and Lichter (2007).

In our study, among respondents with more than 10 peer-reviewed publications (half of total respondents), 90% agree that greenhouse gases are the largest – or tied for largest – contributor to recent warming. The level of agreement is ~85% for all respondents.

While these findings are consistent with other surveys, several factors could explain the slight differences we found:

  • Surveys like ours focus on opinions of individual scientists, whereas in a literature analyses the statements in individual abstracts are tallied. Literature analyses have generally found higher levels of consensus than opinion surveys, since the consensus is stronger amongst more heavily published scientists.
  • This study sets a more specific and arguably higher standard for what constitutes the consensus position than other studies. For instance, Doran and Kendall-Zimmermann (2009) asked about human activity being a “significant contributor” to global warming, and Anderegg et al. (2010) investigated signatories of public statements, while we asked specifically about the degree to which greenhouse gases are contributing to climate change in comparison with other potential factors.
  • Contrarian viewpoints are somewhat overrepresented in our survey and they may have overestimated their self-declared level of expertise (see question 9).

5. How is the consensus or agreement position defined?

The consensus position was defined in two ways:

  • Greenhouse gases contributed more than 50% to global warming since the mid-20th (Question 1). This is analogous to what was written in IPCC AR4.
  • Greenhouse gases have caused strong or moderate warming since pre-industrial times (Question 3). “Moderate” warming was only interpreted as the consensus position if no other factor was deemed to have caused “strong” warming. This response means that greenhouse gases were considered the strongest –or tied for strongest- contributor to global warming.

The former definition exactly mirrors the main attribution statement in IPCC AR4 and served as a ‘calibration’ for the latter.

6. What does “relative response” mean on the y-axis of many Figures?

This gives the percentage of the respondents (often within a certain sub-group) for the specific answer option. We opted to show the relative response rather than the absolute response to enable comparing the responses of different sub-groups (with differing group sizes as denoted by N=…) within one graph.

7. What are “undetermined” answers?

Those are the sum of responses “I don’t know”, “unknown” and “other”.

8. Why do IPCC AR4 authors show a higher consensus than the other respondents?

AR4 authors are generally domain experts, whereas the survey respondents at large comprise a very broad group of scholars, including for example scientists studying climate impacts or mitigation. Hence we consider this to be an extension of the observation -in this study and in e.g. Anderegg et al. (2010) and Doran and Kendall-Zimmermann (2009) – that the more expert scientists report stronger agreement with the IPCC position. Moreover, on the question of how likely the greenhouse contribution exceeded 50%, many respondents provided a stronger statement than was made in AR4. Using a smaller sample of scientists, Bray (2010) found no difference in level of consensus between IPCC authors and non-authors.

9. How reliable are the responses regarding the respondent’s area of expertise and number of peer-reviewed publications?

Respondents were tagged with expertise fields, though these were in many cases limited and not meant to be exhaustive. These tags were mainly used to ensure that the group of respondents was representative of the group that the survey was sent to. A subset of respondents was also tagged with a Google Scholar metric. Those who were tagged as “unconvinced” reported more expertise fields than the total group of respondents and also a higher number of publications compared to their Google Scholar metrics, if available (see Supplemental Information).

10. Since most scientists agree with the mainstream and therefore most media coverage is mainstream, what is the problem with “false balance”?

Scientists with dissenting opinions report receiving more media attention than those with mainstream opinions. This results in a skewed picture of the spectrum of scientific opinion. Whether that is problematic is in the eye of the beholder, but it may partly explain why public understanding lags behind scientific discourse (e.g. the “consensus gap”).


Survey Respondents

11. How many responses did you get to the survey?

Out of 6550 people contacted, 1868 filled out the survey (either in part or in full).

12. How did you compile the list of people to be surveyed?

Respondents were selected based on

  • keyword search in peer-reviewed publications (“global climate change” and “global warming”)
  • recent climate literature (various sources)
  • highly cited climate scientists (as listed by Jim Prall)
  • public criticisms of mainstream climate science (as listed by Jim Prall)

13. Are all of the survey invitees climate scientists?

The vast majority of invitees are scientists who published peer-reviewed articles about some aspect of climate change (this could be climate science, climate impacts, mitigation, etc.). Not all of them necessarily see themselves as climate scientists.

14. Why did you invite non-scientist skeptics to take part in the survey?

They were included in the survey to ensure that the main criticisms of climate science would be included. They constitute less then 5% of the survey respondents. Viewpoints that run counter to the prevailing consensus are therefore somewhat magnified in our results.

15. How representative are the survey responses of the “scientific opinion”?

It’s difficult to ascertain the extent to which our sample is representative, especially because the target group is heterogeneous and hard to define. We have chosen to survey the wider scientific field that works on climate change issues. Due to the criteria we used and the number of people invited we are confident that our results are indeed representative of this wider scientific field studying various aspects of global warming. We checked that those who responded to the survey were representative of the larger group of invitees by using various pieces of meta-information.

16. Did you take into account varying levels of expertise of respondents?

Respondent were asked to list their area(s) of expertise and their number of peer-reviewed publications. These and other attributes were used to interpret differences in responses.

17. How did you prevent respondents from manipulating the survey results, e.g. by answering multiple times?

An automatically generated, user specific token ensured that respondents could only respond once.

18. How did you ensure respondent anonymity?

Survey responses were analyzed by reference to a random identification number.


Survey Questions

19. Are the survey questions public?

Yes, survey questions and answer options are available on the PBL website and as Supporting Information (part 2) to the article.

20. How did you decide on the questions to ask?

The survey questions are related to physical science issues which are a frequent topic of public debate about climate change.

21. Was the survey reviewed before it was sent to respondents?

Yes, before executing the survey it has been extensively tested and commented on by various climate scientists, social scientists and science communicators with varying opinions, to ensure that questions were both clear and unbiased. Respondents were not steered to certain answers.


Reference: Bart Verheggen, Bart Strengers, John Cook, Rob van Dorland, Kees Vringer, Jeroen Peters, Hans Visser, and Leo Meyer, Scientists’ Views about Attribution of Global Warming, Environmental Science and Technology, 2014. DOI: 10.1021/es501998e. Supporting Information available here.

Please keep discussions on this thread limited to what is mentioned in this FAQ and to other questions you may have about the survey or the article. Discussion of the survey results should be directed at the more generic blog post.

Survey confirms scientific consensus on human-caused global warming

August 11, 2014
  • A survey among more than 1800 climate scientists confirms that there is widespread agreement that global warming is predominantly caused by human greenhouse gases.
  • This consensus strengthens with increased expertise, as defined by the number of self-reported articles in the peer-reviewed literature.
  • The main attribution statement in IPCC AR4 may lead to an underestimate of the greenhouse gas contribution to warming, because it implicitly includes the lesser known masking effect of cooling aerosols.
  • Self-reported media exposure is higher for those who are skeptical of a significant human influence on climate.

In 2012, while temporarily based at the Netherlands Environmental Assessment Agency (PBL), my colleagues and I conducted a detailed survey about climate science. More than 1800 international scientists studying various aspects of climate change, including e.g. climate physics, climate impacts and mitigation, responded to the questionnaire. The main results of the survey have now been published in Environmental Science and Technology (doi: 10.1021/es501998e).

Level of consensus regarding attribution

The answers to the survey showed a wide variety of opinions, but it was clear that a large majority of climate scientists agree that anthropogenic greenhouse gases are the dominant cause of global warming. Consistent with other research, we found that the consensus is strongest for scientists with more relevant expertise and for scientists with more peer-reviewed publications. 90% of respondents with more than 10 climate-related peer-reviewed publications (about half of all respondents), agreed that anthropogenic greenhouse gases (GHG) are the dominant driver of recent global warming. This is based on two different questions, of which one was phrased in similar terms as the quintessential attribution statement in IPCC AR4 (stating that more than half of the observed warming since the 1950s is very likely caused by GHG).

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

Figure 1. The more publications the respondents report to have written, the more important they consider the contribution of greenhouse gases to global warming. Responses are shown as a percentage of the number of respondents (N) in each subgroup, segregated according to self-reported number of peer-reviewed publications.

Literature analyses (e.g. Cook et al., 2013; Oreskes et al., 2004) generally find a stronger consensus than opinion surveys such as ours. This is related to the stronger consensus among highly published – and arguably the most expert – climate scientists. The strength of literature surveys lies in the fact that they sample the prime locus of scientific evidence and thus they provide the most direct measure of the consilience of evidence. On the other hand, opinion surveys such as ours can achieve much more specificity about what exactly is agreed upon and where the disagreement lies. As such, these two methods for quantifying scientific consensus are complementary. Our questions possibly set a higher bar for what’s considered the consensus position than some other studies. Furthermore, contrarian viewpoints were likely overrepresented in our study compared with others.

No matter how you slice it, scientists overwhelmingly agree that recent global warming is to a great extent human caused.


BBC interview: global warming pause, climate sceptics, long timescales

September 27, 2013

I was interviewed by Matt McGrath from the BBC last week, as were several other Dutch climate spokespeople (including PBL’s senior scientist Arthur Petersen and skeptical science writer/journalist Marcel Crok). Short parts of these interviews have appeared on the web  and on Radio 4 (“The World Tonight”, 26-09). Below I try to provide a bit of context to my quotes.

Both pieces are centred, as is fashionable these days, on the apparent smaller rate of surface warming in the past 15 years. The web piece is entitled “Climate sceptics claim warming pause backs their view”. Of course they claim it does. What sceptics did achieve –credit where credit is due- is to put this so-called “pause” on the agenda of mainstream media, until it got so fashionable that they all feel forced to use it as an anchor for any reporting on climate. But, as Gavin Schmidt is quoted as saying:

focus on a global warming pause over the past 15 years is a “misplaced” distraction that misses the big picture. He said, “The IPCC and the issue of climate change is not about the weather next year or the next five years; it’s about the long-term climate change that we are engendering.”

See also this useful figure from Stefan Rahmstorf, underscoring the silliness of drawing all too strong conclusions from 15-year trends.

giss2012c - Rahmstorf - Global temp with two silly trendlines

Figure showing NASA GISS global average temperatures with trendlines from 1992-2006 (light blue) and 1998-2012 (green) as well as the most recent 30-year trend in red. Naturally, starting in a very cold volcano-influenced or very warm El Nino influenced year will inflate or deflate the trend. (source: Stefan Rahmstorf)

I am quoted in the BBC piece as follows:

Bart Verheggen is an atmospheric scientist and blogger who supports the mainstream view of global warming. He said that sceptics have discouraged an open scientific debate.

“When scientists start to notice that their science is being distorted in public by these people who say they are the champions of the scientific method, that could make mainstream researchers more defensive.

“Scientists probably think twice now about writing things down. They probably think twice about how this could be twisted by contrarians.”

The discussion was about to what extent climate science isn’t open/transparent enough, as contrarians routinely claim. Matt also asked to what extent skeptics actually play a positive role in making science more open/transparent and more self-critical. I said ideally they would. People who are critical usually have a good influence that way. But many climate contrarians don’t just stop at raising partly valid criticism, but go on to distort the science. That has the opposite influence, as scientists noticing this behavior become more careful and more defensive, and(have to) think ahead how their words might get twisted by contrarians. So they may become less open and less frank, and more careful in how they chose their words.

That is the opposite of what contrarians claim they want to achieve, so it’s quite ironic (though entirely logical) that this is the more likely effect of their behavior. It shows quite a lack of self-awareness on their part that they don’t see how their actions and their behavior affect the dynamics of the public debate. For the worse, in most –though not all- cases.

There may also be some lack of self-awareness among the mainstream that they respond in a way that’s not conducive to a long-term open and frank dialogue with society. From an older comment of mine:

If the valid criticisms wouldn’t be packaged in such conspiratorial/accusative/exaggerated (c/a/e) ways, they would be welcomed much more than they currently are. The art that mainstream scientists and their defenders must learn is to take the valid parts of the criticisms and deal with/respond to them, and leave the c/a/e packaging for what it is. That is increasingly difficult because the critics and their supporters will try to keep the c/a/e in (presumably because this packaging is what is most effective at decreasing the scientists’ credibility and sowing doubt). That dynamic needs to be broken. It needs effort from both sides, as difficult and unfair as it sounds.

As I wrote in my earliest (and still rather positive) reflection on the Curry-turn:

There is a tendency of ‘circling the wagons’ within the scientific community, in response to the continuous attacks on the science. Attacks that are mostly based on smear and insinuation rather than solid arguments. (…) I think the ’us-versus-them’ feeling amongst many scientists and their supporters is understandable (as a reaction to the contrarian c/a/e attacks on the science), but counterproductive in the long run.

In the Radio 4 show (at ~33:50 min in; earlier in the downloadable mp3 version), I am saying a few things about the timescale of the problem and of the solution. I brought this up when the discussion was about whether we now have more time to respond to climate change. This is a vastly underappreciated point in the climate discussion:  The climate system will take much longer to cool down than it did to warm up. This is a consequence of how the carbon cycle works. In this context, I said the following:

We’re going somewhere, and if we don’t like where we’re going, we have to turn that wheel in time.  As when you’re on a giant supertanker on the ocean, you can’t say “oh, I’ll wait until I can feel the iceberg with my pinkie and then I’ll turn the wheel”. Then you’re a bit late, so you have to start doing that in time. That’s the other side of the coin. But if you keep banging the drum saying “it’s five to twelve! It’s five to twelve!” doesn’t work either. And that could be counter-effective to engage those who are a bit more skeptical.

Global warming is a problem in slow-motion, hence the “five to twelve” line is not the most useful one to get people on their feet, because if it remains five to twelve for too long, they will tune you out. That’s what happened in the aftermath of COP15 in Copenhagen for example (where the 5-to-12 line was used a lot, and not much has changed in the years since). The supertanker analogy is more appropriate I find, since that makes clear that even though the problematic situation that’s on your path isn’t in close proximity yet, it is necessary to change course, if you wish to avoid it.


The fallacy of the middle ground

August 5, 2013

There’s been quite some climate discussion in the Political Science section of the Guardian lately. Warren Pearce had an invited post in which he asked the rhetorical question “Are climate sceptics the real champions of the scientific method?

He makes some good observations about the dynamics of the public debate and the nature of skepticism (e.g. most contrarians don’t deny the basic physics underlying the greenhouse effect, but rather dispute the magnitude of warming that would result from an increased greenhouse effect). On the other hand, he misses the mark in other areas (e.g. he correctly describes how contrarians see themselves but doesn’t investigate how their argumentation really stacks up; often they are guilty of what they accuse mainstream science of).

My main beef with his piece though is his flawed argument of why a well-known contrarian blogger like Anthony Watts, according to Pearce, should be seen as someone who “seeks to uphold standards, through transparent and auditable scientific practice” and “a ‘mainstream’ sceptic who can challenge key areas of climate science without entering into pseudoscience”. Why this praise? Because Watts publicly disagreed with the fringe group Principia Scientific who deny the basic physics underlying the greenhouse effect (which was first established in the 19th century).

That is not a logical argument to make though: Regardless of what one may think of Watts, contrasting an extremist with someone who is even more extreme doesn’t make him mainstream. Regardless of what one thinks of Watts, contrasting someone who frequently flirts with pseudoscience with an all-out pseudo-science lover doesn’t free the former from any link with pseudo-science.

That is what I would call the fallacy of the middle ground.


Revkin on Steig, O’Donnell, peer review and solid scientific basics

February 12, 2011

Andy Revkin wrote a good overview of the recent kerfuffle between Eric Steig and Ryan O’Donnell. His piece is centred around contrasting the conflicting views at the edge of the scientific development with the well understood basics of scientific knowledge that makes up the big picture:

I also hope that tussles at the edges of understanding, where data are scant or uncertainty is high, don’t distract the public too much from the basics of climate science, which are boringly undisputed yet still speak of a rising risk that sorely needs addressing.

That’s a very important point to make, and I applaud Revkin for doing so. Media attention to new results (which are usually disputed to a certain extent) can sometimes lead to a skewed picture of the scientific knowledge in the field as a whole, which tend to be underreported. That’s why Revkin’s framing here is important, as it drives home the fact that a dispute at the edge of knowledge (spatial statistics as applied to Antarctic temperature trends) does not mean that the whole theory of climate change is suddenly disputed. Revkin:

Everything laid out above tends to draw attention away from the broad and deep body of work pointing to a growing and long-lasting human influence on the climate system.

Revkin does however exhibit a misunderstanding of peer review when he writes:

The exchanges between Steig and O’Donnell do raise questions about peer review, given that Steig has said he was an early anonymous reviewer (…)

This got quite a few people riled up. I wrote in to state that I think it still is a

Very good article, and good to see attention to detail not go at the cost of also providing the context of what is known.

One comment:
You say this all argument raises questions about peer review. But in fact, it is completely normal, or expected even, that authors whose paper is being critized are one of the reviewers. They are most familiar with the issues, plus it enables the editor to hear both sides.

Of course the editor needs to be aware of the position of this reviewer as the one being critiqued and weigh the review accordingly with other reviews from more disinterested parties. Revkin has since posted Louis Derry’s response, an editor of a geosciences journal:

1. Editors make final decisions. Reviewers make recommendations only.

2. It is common for a submission that critiques previous work to be sent to the author of the critiqued work for review. 2a. That emphatically does NOT mean the reviewer has veto power. It means that his/her opinion is worth having. Such a choice is usually balanced by reviewers that editors believe are reasonably independent, and the review of the critiqued is weighted accordingly. Suggestions that asking Steig to review O’Donnell was somehow unethical are utterly without support in normal scientific practice. Obviously, Steig did not have veto power over O’Donnell’s paper.

3. The fact that O”Donnell’s paper went through several rounds of review is absolutely unsurprising and unexceptional. Many papers on far less public topics do the same.

4. Some have questioned why Stieig 09 got “more” visibility than O’Donnell 10. The answer is simple. Steig had a “result,” O”Donnell had a technical criticism of methodology.

He also chimes in about the importance of the context as provided by Revkin:

Finally, Revkin’s point that the Steig vs O’Donnell debate is not unusual in the progress of science and does not have much of anything to say about the majority of the evidence is correct. Disagreement about how to model the flight of a Frisbee correctly doesn’t imply that basic aerodynamics are wrong. Disagreement about how many EOFs [empirical orthogonal functions] to use to model Antarctic [temperature] changes doesn’t imply that climate physics is wrong.

The Frisbee comment reminded me of one of my favorite sayings: Observing a bird in the sky doesn’t disprove gravity. The science may not be settled, but solid it is.

Some more things have been said about peer review by others. E.g. Andrew “Bishop Hill” Montford writes in the Hockeystick illusion, page 205 (h/t Tim Lambert):

As the CC [Climatic Change] paper was critical of his work, McIntyre was invited to be one of the peer reviewers.

 Guess we can all agree on that aspect of peer review now.

Update: John Nielsen-Gammon has some useful things to say about peer review here (on revealing the identity of reviewer), here (retelling the story and why it makes sense to have had Steig as a reviewer; quoting Steig; interesting dicussion), and here (explaining the dynamics of peer review and making the interesting suggestion of mentoring  relative outsiders navigate peer review).

The Food Gap predicts 2.4 degrees by 2020? I don’t think so.

January 20, 2011

The Food Gap study by an Argentinian NGO contains an embarrassing mistake: As its first key finding, it sais:

Following the current business-as-usual path, by 2020: The temperature of the planet would be, at least, 2.4ºC warmer.

This is of course patently wrong, and it only takes a quick look at the IPCC projections to figure that out. Which makes it doubly embarrassing, since as the first guiding principle they state: 

The analysis is based on the scientific evidence and conclusions from the IPCC Fourth Assessment Report (AR4).

The Guardian has the story; Realclimate has the scientific context.

Now of course this is being spun as if it’s alarmist propaganda gone wrong. Even the otherwise sensible Keith seems to frame it that way. No organization that wants to be taken seriously though would knowingly put in a glaring error like that, as it clearly blows away any credibility they may have had. The most likely explanation is that they honestly believed their own calculation. 

What can be learnt from this:

– Make sure you have the required expertise to write your story, and if you don’t, get people with such expertise to advise you. Base yourself on a proper reading of the relevant literature and/or on people who do.

– If people alert you to an error, check it (or let it be checked), and then fix it, even if that means postponing a deadline or changing something for the gazzilionth time.

Their refusal to correct their mistake after it was pointed out to them is flabbergasting. How stubborn, how stupid. I hope they learnt their lesson.

Moving the debate forward: Tom Fuller’s league of 2.5

October 21, 2010

Tom Fuller has an interesting proposition:

I nominate 2.5C as a working definition of sensitivity until we get better data and start making plans accordingly.

He also aired it over at WUWT in slightly different terms:

So, I call for all those involved in the climate debate to throw down their weapons, embrace this practical solution [presumably referring to climate sensitivity being 2.5] as being of use to the rest of the world, climb aboard the Peace Train and sing Kumbaya. Right.

Ok, all together now: Kumbaya!!

I interpret his ‘motion’ as suggesting: Let’s assume that climate sensitivity is 2.5 deg C per doubling of CO2 and move the discussion to how we’re going to deal with that in terms of mitigation and adaptation.

This movement of the debate to the policy sphere is close to what I suggested to Fuller over a year ago, when I wrote:

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 ‘next generation questions’ in my view relate to the last one: How are we going to deal with this?



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.”

Climate sensitivity.

Tom gets at the 2.5 number by using the Mauna Loa time series for CO2 and comparing its 19% increase with the 0.5 deg C temperature increase over the same time period. Obviously there are some major issues with this approach:

– The net climate forcing is only poorly known because of large uncertainties in aerosol forcing. (Aerosol forcing is close, but opposite in sign, to that of the other greenhouse gases, so accidentally the net forcing is close to the CO2 forcing, though with a very large uncertainty dominated by the aerosol effects.)

– The climate hasn’t fully responded to the current climate forcing yet, as it takes time to equilibrate (mainly due to ocean thermal inertia). This reflects the warming in the pipeline.

– Temperature depends logarithmically on CO2; not linearly.

Nevertheless, his approach more or less accidentally arrives at a very decent estimate, which is right in the ballpark of more accurate estimates of climate sensitivity (3 +/- 1 degree C per doubling of CO2).

The warming we can expect in the future depends not only on the climate sensitivity (which we have just tentatively agreed to put at 2.5 for sake of the argument), but also on future emissions: How much greenhouse gases and aerosols are we going to dump in the atmosphere together? That depends on the choices we make, obviously. But it helps to move the debate forward by assuming a reasonable estimate of the former so we concentrate the debate on the latter, which is where it really gets difficult, because this is where tough choices have to be made and where values clash.

An example of the latter can be seen in the comments to Fuller’s WUWT post. But his message gets lost on most of them: Instead of discussing their values and political wishes, they attack the premise of Fuller’s climate sensitivity or climate science as a whole and ignore the difficult questions. A missed chance.

Hoeveel energie -uitgedrukt als boterhammen pindakaas- gebruiken we nu eigenlijk?

September 11, 2010

Professor Van der Meer licht ons energieverbruik toe aan de hand van boterhammen pindakaas. Bedoeld voor kinderen, maar ik vind het een heel mooi voorbeeld van hoe je wetenschap dichterbij de mensen kunt brengen: Breng het in voor hen begrijpelijke taal. Verschenen in het Reformatorisch Dagblad (laat je daardoor niet afschrikken):

Als je energie op is, wat doe je dan? Dan neem je een boterham met pindakaas.  (…)

Hoe moet je dan rekenen als je elektrische energie gebruikt? Of aardgas? Of benzine? De hoogleraar introduceert daarvoor deze middag een nieuwe eenheid: alles is te berekenen in boterhammen pindakaas oftewel aantallen Calvé; een boterham met pindakaas is evenveel als 1 Calvé.

En dan is de rekensom eenvoudig. Ons lichaam gebruikt 10 Calvé per dag. Dat is evenveel als een droogbeurt met de wasdroger, 8 minuten douchen of 4 kilometer autorijden. (…)

Vervolgens neemt Van der Meer het dagelijkse energieverbruik van de gemiddelde Nederlander onder de loep. Aan gas is hij in totaal 192 Calvé kwijt, voor verwarmen, warm water en koken; aan elektrische energie 46 Calvé. Binnenshuis heeft hij bij elkaar opgeteld al 238 Calvé nodig, voor het overige komt daar nog 562 bij, zodat de gemiddelde Nederlander 800 Calvé aan energie verbruikt per dag.

Dit laat ook zien dat het huishoudelijk energieverbruik gedomineerd wordt door verwarmingskosten (in Nederland vnl. aardgas), terwijl veel mensen in eerste instantie alleen aan elektriciteit denken. Ik weet niet waar de energiekosten buitenshuis uit bestaan, maar ik neem aan dat transport voor een groot deel daarvan verantwoordelijk is. De energie die nodig was om producten te maken, voedsel te verbouwen en services te verlenen is natuurlijk ook een biggie (maar het is altijd de vraag of/hoe die verrekend worden). Ik heb de hiergenoemde getallen niet gecheckt overigens.

Wanneer de hoogleraar dat vergelijkt met het energiegebruik van 1200 Calvé van de gemiddelde Amerikaan lijkt dat mee te vallen. Het staat echter in schril contrast met de 40 Calvé die een doorsnee Afrikaan opmaakt.

Als hij het gewenste energieverbruik van 600 Calvé vergelijkt met de exponentieel groeiende wereldbevolking is zijn conclusie helder: Als zij dezelfde hoeveelheid energie willen gebruiken als wij, moet het aantal Calvéfabrieken harder groeien dan de wereldbevolking. En dat lukt vooralsnog niet.

Van der Meer illustreert het overmatige gebruik van fossiele brandstoffen in de westerse wereld door de dagelijkse consumptie van 80 miljoen vaten olie (van 159 liter) naast elkaar te zetten. Dan heb je een lint van 40.000 kilometer dat een keer rond de wereld past.

Om in 2050 de doelstelling van 50 procent minder CO2-uitstoot ten opzichte van 2005 te realiseren, moet minimaal 46 procent van de energiebronnen hernieuwbaar zijn, stelt de hoogleraar. Om dat voor elkaar te krijgen, zijn jaarlijks wereldwijd onder meer 17.750 windmolens, 80 zonnecentrales en 32 grote kerncentrales extra nodig. Hij besluit zijn relaas: We zijn er dus nog lang niet.

Een heel aardig boekje over energie is trouwens de Energie Survival Gids van Jo Hermans. Prettig geschreven, helder gepresenteerd en met interessante inzichten. Zo legt hij uit waarom het benzineverbruik zo sterk toeneemt bij hoge snelheden. Verrassend vond ik de vergelijking in energiegebruik van verschillende manieren van transport.

Ik ben vroeger wel vaker met de boot naar Engeland gegaan om expres niet met een energieverslindend vliegtuig te hoeven. Hermans toont echter aan dat –gemiddeld gesproken- een passagiersboot meer energie verbruikt per reizigerskilometer dan een vliegtuig (omdat een passagiersboot zo zwaar is en er dus relatief veel energie nodig is om maar relatief weinig mensengewicht (bv 0.3% van het totaal) te verplaatsen). Een vrachtboot daarentegen is wel weer relatief zuinig, omdat de nuttige lading voor vrachtboten vele malen groter is dan die voor passagiersschepen.

Fietsen slaat alles: Als de energie-inhoud van het extra benodigde voedsel wordt omgerekend in benzine fietsen we 1 op 500. Fietsen is daarmee ook efficiënter dan de meeste andere manieren van voortbewegen die we in de natuur zien (uitgedrukt in benodigde energie per kilometer en per kilogram lichaamsgewicht). Toch leuk om te weten als je weer op je fiets springt.

Open letter of US NAS members on climate change and the integrity of science

May 10, 2010

The open letter of US National Academy of Science members is worth reading. After initially being behind a paywall (rather at odds with the ‘openness’ of the letter…), it is now freely available at Science.

I agree with the gist, well exemplified by the opening paragraph:

We are deeply disturbed by the recent escalation of political assaults on scientists in general and on climate scientists in particular. All citizens should understand some basic scientific facts. There is always some uncertainty associated with scientific conclusions; science never absolutely proves anything. When someone says that society should wait until scientists are absolutely certain before taking any action, it is the same as saying society should never take action. For a problem as potentially catastrophic as climate change, taking no action poses a dangerous risk for our planet.

Scientific conclusions derive from an understanding of basic laws supported by laboratory experiments, observations of nature, and mathematical and computer modeling. Like all human beings, scientists make mistakes, but the scientific process is designed to find and correct them. This process is inherently adversarial—scientists build reputations and gain recognition not only for supporting conventional wisdom, but even more so for demonstrating that the scientific consensus is wrong and that there is a better explanation.

Indeed, the scientific process is meant to ascertain that, despite scientists being human with their individual characters and inherent flaws, the collective outcome is as good a representation of reality as possible at the time. And science (including climate science) has proven to be rather good at that.

But there is nothing remotely identified in the recent events that changes the fundamental conclusions about climate change:

(i) The planet is warming due to increased concentrations of heat-trapping gases in our atmosphere. A snowy winter in Washington does not alter this fact.

(ii) Most of the increase in the concentration of these gases over the last century is due to human activities, especially the burning of fossil fuels and deforestation.

(iii) Natural causes always play a role in changing Earth’s climate, but are now being overwhelmed by human-induced changes.

(iv) Warming the planet will cause many other climatic patterns to change at speeds unprecedented in modern times, including increasing rates of sea-level rise and alterations in the hydrologic cycle. Rising concentrations of carbon dioxide are making the oceans more acidic.

(v) The combination of these complex climate changes threatens coastal communities and cities, our food and water supplies, marine and freshwater ecosystems, forests, high mountain environments, and far more.

However, as Revkin notes:

The open letter letter has a defensive tone that hasn’t served scientists particularly well in the past, but is understandable given the pressures that have been mounting on this field of inquiry.”

I agree with both parts of that assessment.

Also noteworthy is the accompanying editorial by a deputy editor of the journal Science, which has a distinctly different tone to it (not dissimilar to Judith Curry’s statements):

We thus must move beyond polarizing arguments in ways that strengthen this joint commitment. The scientific community must recognize that the recent attacks stem in part from its culture and scientists’ behavior. In turn, it is time to focus on the main problem: The IPCC reports have underestimated the pace of climate change while overestimating societies’ abilities to curb greenhouse gas emissions.

I’d say that the main problem now is, that given our current understanding of climate change, how are we going to respond? There is no such thing as ‘no response’. Any action (including business as usual) is a response, and it better be decided on rationally and based on all the available evidence. That’s the way I look at it.

He also calls for more effort (and commensurate funding) towards data curation, handling and infrastructure. Perhaps that’s something we could all agree on, and perhaps those most critical of the current data handling practices could support such calls for more funding of these basic, though necessary efforts.

He ends with a good quote from Carl Sagan, which is especially apt today:

“We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology.” “This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.”

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