Posts Tagged ‘Judith Curry’

Judith Curry on anthropogenic versus natural causes of global warming

September 20, 2010

As most will know by now, Judith Curry has started her own blog, Climate Etc. In a recent post entitled “doubt” she said some things that highly surprised me. Basically, she claims equal evidence for anthropogenic forcing and natural variability being responsible for “most of the observed increase in global average temperatures since the mid-20th century”:

As an example, my personal weights for the Italian flag are:

1. white 40% [uncertainty and unknowns]

2. green 30%, [evidence for anthropogenic forcing]

3. red 30%. [evidence against anthropogenic forcing]

Before posting this, I had an email conversation with Judith Curry about these issues (so as to minimize any misunderstanding on my part). She wrote back (reprinted with permission):

I think you are misunderstanding what the IPCC actually says.  The statement says MOST (>50%) of the warming can be attributed to  anthropogenic, with an confidence of very likely (>90%).    My balance of 50-50 is a hair outside the IPCC range (which could include 51-49), and 1% difference is in the noise here.   Most can imply 51% or 90%.   I will be discussing the issue of attribution at length in a future point.  But my main point in the doubt post is the size of the white area, which is bigger than 5-10% IMO.

So she would translate the IPCC statement in the Italian flag style as anywhere between

white: 10 -1

green: 46 – 89

red: 44 – 10

Her own estimate is not that far off (in terms of the ratio between green and red) from the most conservative IPCC statement (where “most” means “just a bit more than half”), except having a much greater estimate of the uncertainty (which is her main point). So she seems to interpret red and green as portions attributable to anthropogenic and natural forcing, whereas initially I had interpreted them as evidence for the statement at hand versus evidence against. Both makes sense, but both are different. Also, one could claim that the IPCC statement encapsulates the uncertainty in the fairly wide “most of the warming”, i.e. it could still span a wide range, allowing for plenty of uncertainty. Similar as say, the weather in a week’s time is very uncertain, but I can still say that it’s very likely to be in between zero and thirty degrees C (being late september in Holland). These different interpretations make me doubt the usefulness of the Italian flag symbol to aid in clarifying (dis-)agreements.

Judith also claims equal evidence / equal portions of attribution for her “litmus test question”:

Will the climate of the 21st century will be dominated by anthropogenic warming (green) or natural variability (solar, volcanoes, natural internal oscillations)?

which is the question with the greatest policy relevance, IMO.  My scores on this one are

green 25%

white 50%,

red 25%.

This is astounding. I interpret this as claiming equal evidence pointing to natural variability being dominant over the next 90 years as compared to anthropogenic forcing. Or alternatively, an equal portion of 21st century climate change being attributable to human induced warming as to natural variability.

I’ve read quite a few “skeptical” papers that attempt to blame the warming on natural processes, and even if you’d take them as face value (even though in most cases they haven’t stood up to scrutiny), their collective body of evidence is a molehill compared to the mountain of evidence pointing to the dominance of anthropogenic forcing.

In a comment, Judith points to a blog post at Skeptical Science, with graphs of several natural forcings (solar) and cycles (PDO, ENSO) for the past 25-30 years. They exerted a slight cooling effect over this period. In contrast, CO2 exerted a strong warming effect, and indeed, the temperature has gone up. That hardly qualifies as equal amounts of evidence pointing to the warming being natural versus anthropogenic.

For future warming, her pronouncement is even stranger. In all plausible scenario’s, greenhouse gas concentrations will continue to rise for at least another few decades; in a business as usual scenario for many more to come. What natural forcing or variability could plausibly rival this relentlessly rising anthropogenic forcing in magnitude? Is there evidence at all for that being plausible? If so, is that evidence really as large as the evidence showing that greenhouse gas forcing will exceed the likely bounds of natural variability (if it hasn’t already)?

Take a look at how the global average temperature has varied over the past 130 years (yearly averages with 11 year running mean in bold):

An indication of unforced natural variability is given by the year to year variation, amounting to 0.1 to 0.2 deg C on a yearly basis. As the Skeptical Science article shows, natural forcings can not explain the most recent warming, because they don’t exhibit a trend of the needed direction or magnitude.

Now let’s stipulate that it’s all due to longer term natural variation (as opposed to a forcing) of an unspecified kind. What would that mean for the planetary energy balance? If internal variations would have been responsible for most of the planetary warming, the earth would be emitting more energy to outer space than it receives, resulting in a negative radiative imbalance at the top of the atmosphere (or the energy would have to come from other parts of the earth’s system).

Neither is the case. It’s actually opposite: There is a positive radiation imbalance and other reservoirs (e.g. oceanscryosphere) are also gaining more energy.

And then we haven’t even looked into the future yet. I recently posted this graph of two scenario’s that plausibly bracket a business as usual trajectory (red) and a stringent emission reduction trajectory (blue). The measured temperature increase up to now (which according to most scientists is strongly impacted by anthropogenic emissions) is given by the black line.

Judith’s estimates for the 21st century come down to a chance of warming of 0.25 + 0.75/2 = 0.625 versus a chance of cooling of 0.375, assuming natural factors having a 50% chance of either warming or cooling. So she deems the chance of warming to be roughly twice that of cooling, presumably even in a BAU scenario. Too bad that’s too long of a timeframe to place a climate bet on.

Look at how much the red -and even the blue- projections will likely deviate from the recent temperatures. I sure hope that there will be some magical counteracting cooling effect, but I haven’t seen any plausible evidence for such.

Postscript: From our email conversation, I understand her point of view better than before. But unlike the statement about the 20th century warming, which is not as far off from the IPCC as I had initially thought (except for the amount of uncertainty), her statement about the projected 21st century warming is hard for me to square with the mainstream scientific view, for which there is lots of evidence.

Citizen science as the new skepticism?

June 23, 2010

Over at Keith’s, I got engaged in a discussion with Judith Curry and others about the well educated skeptics who self identify as ”auditors” of climate science. She claims that

this group is definitely interested in moving the science forward.

The existence and flourishing of technical climate blogs that take a critical stance towards the mainstream scientific view shows that the dualistic view of professional scientists on the one hand and the amateur public on the other hand is too simplistic (especially if the public is deemed ‘ignorant’ of the science). It is clear that there is a continuum of interest, knowledge, skepticism, sincerity, etc amongst the public.

I agree that it’s not constructive to dismiss the expertise and energy of the more scientifically minded critics (“citizen scientists”). But then I would suggest that those sincerely interested clearly distance themselves from the contempt and suspicions raising crowd, since that are the public face of the critics, and it’s severely hampering communication with mainstream scientists and their supporters. Problem is, McIntyre himself has had a major influence in instilling contempt and suspicions into his very wide following. It doesn’t just raise my ire; it’s entirely un-constructive to moving the internet discussion with critics forward (regardless of how it all started). I suggest that those critics who are sincerely interested in moving the science forward engage more with scientists (rather than raging against them).

Citizen science

Judith Curry compares the technically savvy critics with citizen scientists in other disciplines, e.g. biology and astronomy. I think that comparison is only superficially true. In none of those other fields are the citizen scientists contemptuous towards the professional scientists (and vice versa). The ‘normal’ way for citizens to contribute to science is by providing observations; not so much in the interpretation. In none of the other cases I know of are the citizen scientists strongly critical and suspicious of the mainstream science.

Even in cases where the ‘auditors’ have superior technical skills, scientific intuition and broad background knowledge of the field is very important in placing results in context and in making a coherent scientific argument. These (especially the context) are what’s missing in many (not all) of the citizen scientists efforts regarding climate change, and yet, the conclusions are often uncritically taken to be of paramount importance for the field as a whole (e.g. talk of paradgim shift, Galileo and stuff like that).

Oftentimes, the specific details that the citizen scientists focus on and criticize are presented as needing to be resolved before the rest of the science can be discussed, and long before we may discuss policy options. That’s exactly what concerned scientists and citizens fear: That it’s used as an option to delay action (whether intentionally or not).

A constructive discussion about the best public actions to address global warming does notdepend on these technical details at all. That’s the crux of the matter. They make people not see the forest for the trees, in a very effective way. If that’s not McIntyre’s purpose, he should really rethink what he’s doing.

Michael Tobis made the observation that he agrees with the “citizen scientists” on many of their main points, but not on the policy direction. If they would be primarily interested in what they proclaim their key points are, and not in (obstructing) mitigation politics, the rational response would be to welcome Michael as an ally. However, he is “cast as an opponent, even as an extremist”. This is a very important point, and indeed, it suggests that their “real priorities have nothing to do with scientific process”.

In response Judith said that Michael’s stance on mitigation and uncertainties is what the self proclaimed “auditors” respond negatively to. The first point (on mitigation) is exactly what leads to Michael’s conclusion: Their primary interest is politics (disagreeing on the need for mitigation). The second point is untrue and unfair to Michael. He is most definitely not “in denial of uncertainty” as Judith later claimed.

Rather, he often makes the following pertinent points that I wholeheartedly agree with:

  • Some things are known more accurately than others.
  • The big picture of where we’re heading is clear, and this is what’s relevant for policy making.
  • Uncertainty cuts both ways. Combined with the knowledge about the big picture direction and the inertia in the system, uncertainty makes the case for action stronger rather than weaker.

I see a lot of self proclaimed “skeptics” mix up uncertainty with knowing nothing, and use that as an excuse for delaying action on mitigation. That is probably the number 1 argument to delay action. It is a policy statement, masquerading as a concern for science.

Genuine and pseudo skeptics

Undoubtedly climate skepticism comes in many shades of grey (as does climate concern). How can we distinguish between genuine skeptics and pseudo-skeptics? Undoubtedly, all self styles skeptics see themselves as genuine. I don’t really have an answer to that question. But the comparison with other areas of citizen science begs the question of why those in the climate change arena are predominantly critical, contemptuous even, about the mainstream scientific view? If their primary interest was in data analysis or observation quality, such an attitude wouldn’t make a lot of sense. I’d expect a group of citizen scientists to also have a spectrum of opinions on the science, but to see that spectrum go off in a totally different direction than the spectrum of views of professional scientists, is odd. Even if I’d take their criticism on the details at face value (which I don’t; call me skeptical), it doesn’t logically follow that their opinions of the science as a whole, let alone on mitigation, would be dramatically different.

The fact that many “citizen scientists” seem to be have such different views of the big picture makes me think that a sizeable proportion of them did come into this debate with preconceived notions. Something must have picked their interest in the science. Perhaps it’s more likely that they came to this debate with a skeptical inclination, rather than purely based on a love of the science in question, as is the case with archetypical examples of citizen science. This skeptical inclination could have extra-scientific reasons (e.g. psychological, ideological, political, etc) or it could be that criticisms they read about (e.g. from McIntyre) made them question the validity of the science, which they then decided to explore themselves. It’s important to distinguish between the details and the big picture. To what extent do they question the validity of the big picture, while exploring the details? And conflating the two? Without knowing the big picture, the McIntyrian way of looking at things probably sounds very convincing, especially to those from specialized technical fields.

The existing polarization, and subsequent defensive attitude of some spokespeople of mainstream science, may also have contributed to technically savvy people being drawn to ‘the other side’. That’s something we shouldn’t discount as a potentially important factor, and we should try to learn from it. It is clear that mainstream scientists (and their supporters) have not come to grips with these new skeptics, citizen scientists, technically savvy critics, auditors, or whatever name you’d want to give them.

See also some recent posts by Michael Tobis here and here.

Let me end by naming some constructive examples of citizen science:

Clear Climate Code

The making of a sea level study

Temperature reconstructions (and my reply to Lucia at Comment#46143)

Recent examples of citizen journalism also make clear that the less judgment is (perceived to be) passed onto the subject of study, the better it will be received.

Judith Curry on climate science: Introspection or circling the wagons?

April 27, 2010

Climate scientist Judith Curry has regularly spoken up about the rumblings in climate science, especially in light of the CRU emails and the alleged IPCC errors. And when she speaks, people listen. She’s a respected academic, and subscribes to the consensus view that climate is changing in (large) part due to human activity (so supporters of the consensus take her seriously). But she’s also increasingly critical of mainstream science, especially the way in which the consensus has been achieved and the way certain individuals have acted (so those disagreeing with the consensus listen as well; even more so, they love her as someone from within the establishment who’s openly critical).

Journalist-blogger Keith Kloor has a good Q&A with Judith Curry which is well worth reading. As I also wrote over there, I appreciate Prof Curry’s constructive criticisms and calls for introspection. However, I find it disconcerting that she doesn’t call out the many baseless and exaggerated attacks on climate science for what they are.

In the comments, Judith Curry writes

“To see such a respected academic accused in this way (with the accusations so obviously baseless) is absolutely reprehensible.”

With “respected academic” she means Wegman (one of the main hockey players of the ‘skeptics’). I have no opinion about him, but I do note that many respected academics, pretty much a whole profession even, have been accused in often baseless, and if not entirely baseless, surely exaggerated ways. I’d say, reprehensible is the right word to describe it.

Actually, Curry has been the target of ‘skeptics’ herself. In a newer post, she recites from what she calls ‘the hurricane wars’ that were the result of a paper of hers that was (coincidentally) released a few weeks after Kathrina hit New Orleans:

“While global warming was mentioned only obliquely in the paper, the press focused on the global warming angle and a media furor followed. We were targeted as global warming alarmists, capitalizing on this tragedy to increase research funding and for personal publicity, a threat to capitalism and the American way of life, etc.”

These are similar charges as are now levelled against the whole field, together with baseless charges of misconduct, fraud and data manipulation (*). What puzzles me is the apparent disconnect between her own experiences (of being viciously attacked on her science, clearly for extra-scientific reasons such as an appeal to the ‘American way of life’ etc.) and how she judges (or doesn’t judge at all) the current wave of attacks on climate science.

Perhaps the explanation is in the following:

“I learned several important lessons from this experience: Just because the other guy commits the first “foul” doesn’t give you the moral high ground in protracted academic guerilla warfare. Nothing in this crazy environment is worth sacrificing your personal or professional integrity.  After all, no one remembers who fired the first shot, all they see is unprofessional behavior.”

That is very true. But it doesn’t quite explain why not to call out reprehensible behavior for what it is. Something she isn’t shy of doing, clearly (e.g. regarding Wegman in the comments following the Q&A, and in a more subtle manner regarding the CRU emails).

Apparently she doesn’t find the way climate science is being attacked in the blogosphere and the mainstream media problematic, or if she does, she choses to focus on ‘cleaning up our own house’, while not letting the fringe talk get to her (she’s ‘been there, done that’). A commendable position actually. But I do sense a lack of critically assessing the criticism. ‘Corruption of the IPCC process’ is way too string of a statement in my mind. It’s not a very constructive start at ‘cleaning up our own house’ either, as it feels more like yet another attack on our house. The consequence, of course, is that the shutters will be closed, again.

Because that’s something where I do agree with Curry: 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. It in no way resembles a scientific argument, and shouldn’t be treated as such. So while I have no straight answer to the obvious question of ‘what else than cicling the wagons could we possibly do?’, Curry’s own part- answer is a good start: Do not engage in the guerilla warfare that you feel being drawn into. But that again states what not to do. What do you do instead? is the difficult part. Engaging with skeptics is only useful insofar as they are interested in constructive knowledge building. No doubt some are. But no doubt many aren’t. E.g. a commenter at climateaudit writes:

“It only takes one honest (wo)man to bring the whole rotten edifice crashing down.”

I’d wager that people referring to climate science as a ‘rotten edifice’ are not interested in constructive dialogue or in serious scientific inquiry.

Curry is much more positive about McIntyre than most climate scientists. While indeed he’s done quite a lof of analysis of climate related data himself, he also often engage in ‘dog whistle’ politics; making subtle insinuations of data manipulation, bias and misconduct. Sometimes it’s less subtle (e.g. a headline under an image of Mike Mann saying “try not to puke”). That behavior doesn’t invalidate the occasional good point he may or may not have (I’m not opining on that), but it does cause a near-continuous stream of messages that lowershe credibility of climate science. McIntyre’s influence on the latter (lowering science’s credibility) is much larger than his constructive influence on knowledge building. Even if McIntyre may have a point on details, most of his audience and the mainstream press gets away with a totally exaggerated and erroneous impression that the science is abysmal.

It is slightly ironic that back in 2002, Phil Jones provided McIntyre with data no problem. It’s only after he found out what McIntyre is all about that he stopped being helpful. Which leads McIntyre to ask the rhetorical question: “What has changed since 2002?” At WUWT, Steve Mosher takes issue with this change in Jones’ attitude as well. Looks like the scientific community is not the only place that could do with some more introspection.

Curry finds preaching to the converted not very interesting. But preaching to people who won’t listen (except when you criticize what they dislike) is even less useful. The challenge is to distinguish those who have genuine concerns from those who are merely slinging mud and will never accept anything, no matter the strenght of the evidence. And I think a similar tendency (a defensive attitude or ‘circling the wagons’) is happening at the ‘skeptical’ side of the fence: Also those with genuine concerns regarding the science or data analysis sling around accusations of misconduct, corruption, manipulation, etc. That’s a sure way of not getting heard by the scientific community. Which adds to the defensive attitude, and the circle is round.

I think both ‘skeptics’ and scientists feel they deserve more respect than they’re getting, and as a result adopt a defensive us-versus-them attitude. If anything, I applaud Judith Curry for highlighting this in the scientific consensus ‘camp’ and calling for more introspection and a critical look at ourselves. Perhaps someone could also step up to the plate at the ‘skeptical’ camp?


(*) CRU’s data handling has not inflated the warming trend, see e.g. here and here. The HadCRU temperature reconstruction agrees with those of other institutes, with those currently undertaken by bloggers (some ’skeptical’; some ‘consensus’), and also with satellite reconstructions.

Alleged errors and wrongdoings have been greatly exaggerated (e.g. RC and MT and this blog on the glacier issue).

As a whole, climate science stands up very well to the various the scientific methods (Oreskes; slides here (from slide nr 30 onwards)).

Partly based on my comment at Kloor’s.

See also William Connolley’s rather critical comments. His main point is that Curry’s allegations (towards individual scientists and the IPCC) are vague and unsubstantiated.

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