Posts Tagged ‘IPCC’

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.

IPCC troubles in context: Some good Dutch media coverage

September 3, 2010

One of Holland’s quality newspapers, the Volkskrant, had some excellent coverage of the IAC’s review of the IPCC process. Below is my translation of (part of) an editorial column (discussed in Dutch in an earlier post):

In a way it was inevitable that the UN climate panel IPCC got cornered earlier this year when some mistakes were discovered in its reports. The IPCC, as a volunteer organization with a small staff, could no longer cope with the societal polarization which was the consequence of the unwelcome message of global warming and climate change. Thus, professionalization is required.


The mistakes and glitches which were discovered in the IPCC’s 2007 report were the result of clumsiness and sloppiness. They did not undermine the knowledge that the climate is changing.

I would add that most IPCC mistakes were minor or even imaginary, and most were in working group 2 about (regional) effects of climate change; they did not concern the physics of climate and why it is changing. (See  e.g. my commentary on the 2035 – 2350 glacier mistake, which is the only serious mistake, even if it is in a relatively insignificant and hardly read portion of the whole report. The Dutch area-under-sea-level slip was mostly clumsy.)

In spite of this it caused a wave of distrust, which suggests that climate science and IPCC as its flag bearer had a problem with their public image.

With not a little help from large quarters of the media. And of course human psychology to rather not believe things that you don’t want to be true.

On the one hand climate scientists are expected to keep themselves to the facts only. At the same time their results and understanding are also arguments in the societal discussions about climate change. But as soon as they participate in this discussion accusations of bias come up.

A more professional IPCC should not only work on the internal weaknesses and make and present itself as scientifically solid as possible. It will also have to make clear that its work has political implications, but that that doesn’t mean that it’s engaged in doing politics.

The last portion (my bold) should be self-evident, but since in reality many people and media chose to paint it as the opposite, it is unfortunately necessary to point out the obvious.

IPCC review by InterAcademy Council IAC

September 1, 2010

The IAC has released their report evaluating the IPCC procedures. They did not investigate the actual contents of the IPCC reports.

From the executive summary:

The Committee found that the IPCC assessment process has been successful overall. However, the world has changed considerably since the creation of the IPCC (…)

The IPCC must continue to adapt to these changing conditions in order to continue serving society well in the future.

Their key recommendations appear sensible and constructive:


The Committee’s main recommendations relate to governance and management, the review process, characterizing and communicating uncertainty, communications, and transparency in the assessment process.

Recommendation: The IPCC should establish an Executive Committee to act on its behalf between Plenary sessions. The membership of the Committee should include the IPCC Chair, the Working Group Co-chairs, the senior member of the Secretariat, and 3 independent members, including some from outside of the climate community. Members would be elected by the Plenary and serve until their successors are in place.

Recommendation: The IPCC should elect an Executive Director to lead the Secretariat and handle day-to-day operations of the organization. The term of this senior scientist should be limited to the timeframe of one assessment.

Recommendation: The IPCC should encourage Review Editors to fully exercise their authority to ensure that reviewers’ comments are adequately considered by the authors and that genuine controversies are adequately reflected in the report.

Recommendation: The IPCC should adopt a more targeted and effective process for responding to reviewer comments. In such a process, Review Editors would prepare a written summary of the most significant issues raised by reviewers shortly after review comments have been received. Authors would be required to provide detailed written responses to the most significant review issues identified by the Review Editors, abbreviated responses to all non-editorial comments, and no written responses to editorial comments.

Recommendation: All Working Groups should use the qualitative level-of-understanding scale in their Summary for Policy Makers and Technical Summary, as suggested in IPCC’s uncertainty guidance for the Fourth Assessment Report. This scale may be supplemented by a quantitative probability scale, if appropriate.

Recommendation: Quantitative probabilities (as in the likelihood scale) should be used to describe the probability of well-defined outcomes only when there is sufficient evidence. Authors should indicate the basis for assigning a probability to an outcome or event (e.g., based on measurement, expert judgment, and/or model runs).

(See e.g Gavin’s comment regarding this point in an in-line response at RC here. It is certainly important to be very clear in explaining what the basis is for assigning a certain level of confidence or probability, a point also made by Judith Curry.)

Recommendation: The IPCC should complete and implement a communications strategy that emphasizes transparency, rapid and thoughtful responses, and relevance to stakeholders, and which includes guidelines about who can speak on behalf of IPCC and how to represent the organization appropriately.

The Committee recommends that the IPCC establish criteria for selecting participants for the scoping meeting, where preliminary decisions about the scope and outline of the assessment reports are made; for selecting the IPCC Chair, the Working Group co-chairs, and other members of the Bureau; and for selecting the authors of the assessment reports. The Committee also recommends that Lead Authors document that they have considered the full range of thoughtful views, even if these views do not appear in the assessment report.

Climate Central offers the following translation “from report-ese into English”:

  • The IPCC should create an Executive Committee to run the organization in between major conferences.
  • Rather than have the IPCC director serve for two six-year terms, a new director should be appointed for each major assessment report (there have been four so far). Since the IPCC is well into the fifth assessment, it isn’t clear whether Dr. Pachauri will step down (he’s evidently said that any decision will have to wait for the next IPCC meeting, in Korea in October).
  • The reviewers who decide what makes it into the final report and what doesn’t should work harder to address comments from authors, and to let dissenting views be reflected more fully in the finished product.
  • Statements about certainties and uncertainties about climate science need to be more explicit, need to be based on a more uniform set of criteria, and need to be clearer about how they were calculated.
  • The IPCC in general needs to be more open and transparent about how it goes about its business.
  • The IPCC needs to improve the way it deals with so-called “grey literature” — that is, non-peer-reviewed reports that contain valuable information, but which haven’t already been subjected to strict scientific scrutiny.

Much of the media still uses this as a coat rack to rehash (often exaggerated) stories about alleged errors or misconduct.

IPCC procedures doorgelicht door IAC – Uitstekend commentaar door de Volkskrant

September 1, 2010

Het InterAcademy Council (IAC) heeft haar rapport naar buiten gebracht waarin het IPCC werd doorgelicht (wat betreft proces en procedures; niet inhoud).

De Volkskrant publiceerde vandaag een uitstekend redactioneel commentaar over de perikelen rondom het IPCC:

Dat het VN-klimaatpanel IPCC dit voorjaar in het nauw raakte door de ontdekking van enkele fouten in zijn rapporten, was in zekere zin onvermijdelijk. IPCC is als vrijwilligersorganisatie met een kleine staf niet meer opgewassen tegen de maatschappelijke polarisatie die de onwelkome boodschap van opwarming en klimaatverandering nu eenmaal opwekt. Dus is professionalisering gewenst.

Het IAC rapport (persbericht) geeft hiertoe een aantal constructieve suggesties.


De foutjes die dit voorjaar in de IPCC-rapportage van 2007 bleken te zitten, waren het gevolg van onhandigheden en gemakzucht. Ze ondergroeven echter niet het inzicht dat [en waarom (mijn toevoeging)] het klimaat verandert. Dat ze niettemin een golf van wantrouwen losmaakten, geeft aan dat de klimaatwetenschap en het IPCC als aangever daarvan vooral een imagoprobleem hadden gekregen.

Aan de ene kant worden klimaatwetenschappers geacht zich strikt bij de feiten te houden. Tegelijk zijn hun gegevens en inzichten ook argumenten in de maatschappelijke discussies over het klimaat. Maar zodra ze zelf aan die discussies meedoen, ontstaat weer de suggestie van partijdigheid en vooringenomenheid.

Een professioneler IPCC moet niet alleen de interne zwakheden wegwerken, en zich wetenschappelijk zo solide mogelijk maken en presenteren. Ook moet het duidelijk maken dat zijn werk weliswaar politieke implicaties heeft maar dat het daarmee niet zelf ook politiek bedrijft.

Martijn van Calmthout schreef gisteren in de Volkskrant:


Die fouten bleken bij nader onderzoek doorgaans ondergeschikte details die de realiteit van een ongewoon snelle klimaatverandering niet wegnemen. Preciezer onderzoek van de gestolen klimaatmails liet niets heel van de suggestie van vals spel.

Maar het publiek vertrouwen in klimaatwetenschap was weg. En de analyse van de geleerden van de IAC, gebaseerd op gesprekken met talloze betrokkenen, laat zien dat een dergelijke crisis rond IPCC haast onvermijdelijk was geworden. Het rapport dat maandag in New York werd aangeboden, ademt de sfeer van een academische organisatie die gaandeweg in steeds heikeler vaarwater verzeild raakte, zonder zich daarvan echt rekening te geven.

Twintig jaar geleden was het een uitstekend idee om geregeld de beste klimaatwetenschap samen te bundelen en toegankelijk te maken voor beleidsmakers. Kennis moest leiden tot verstandige maatregelen, was het idee. En het netwerk van experts dat daartoe werd opgebouwd, mag inderdaad nog steeds indrukwekkend heten.

Maar met de toenemende realiteit van een door de mens veroorzaakte klimaatverandering werd het onderwerp steeds meer beladen. Het debat tussen voor- en tegenstanders van ingrijpend klimaatbeleid werd steeds scherper. En de druk op de leveranciers van de wetenschap onder dat beleid nam gaandeweg ongekende vormen aan.

Uit de analyse van Dijkgraafs onderzoekscommissie komt vooral naar voren dat het IPCC onvoldoende met zijn tijd is meegegaan. De wetenschappelijke vrijwilligersorganisatie die twee decennia geleden nog prima voldeed, blijkt inmiddels veel te kwetsbaar.

Het pleidooi van de IAC voor professionalisering kan maken dat een vernieuwd IPCC zich minder gemakkelijk zal laten overrompelen. Maar het terugwinnen van het verspeelde krediet zal er nauwelijks minder lastig om zijn.

Goede journalistiek bestaat nog.

Zie ook het stukje van Paul Luttikhuis op het NRC klimaatblog met een aantal citaten uit verschillende (Nederlandse en Engelse) media, waaronder ook een aantal voorbeelden van journalistiek zoals we dat ook gewend zijn: Dingen uit je duim zuigen om de lezer te behagen.

PBL checkt het vierde IPCC rapport (AR4 wg2): Commentaar van de media verschilt nogal

July 6, 2010

Het Planbureau voor de Leefomgeving (PBL) heeft het vierde IPCC rapport (AR4 wg2) gecheckt op fouten en onvolkomenheden. Alleen het onderdeel over de regionale effecten van klimaatverandering (een onderdeel van werkgroep 2) is onder de loupe genomen. Dat behelst dus niet de globale effecten en ook niet de vraag hoe en waarom het klimaat veranderd.


Hoofdconclusies VN-klimaatpanel over regionale gevolgen klimaatverandering overeind

Samenvatting van het rapport:

Het Planbureau voor de Leefomgeving (PBL) heeft, op verzoek van de minister van Milieu, de wetenschappelijke basis onderzocht van de belangrijkste conclusies die het IPCC in het Vierde Klimaatrapport van 2007 trekt ten aanzien van de mogelijke regionale gevolgenvan klimaatverandering. Deze conclusies zijn over het algemeen goed onderbouwd en bevatten geen enkele significante fout. De bijdrage van Werkgroep II aan het Vierde Klimaatrapport bevat ruimschoots bewijs dat regionale gevolgen van klimaatveranderingal worden waargenomen; de inschatting is dat deze gevolgen in de meeste delen van de wereld tot aanzienlijke risico’s kunnen leiden als de temperatuur verder stijgt. In sommige gevallen had de onderbouwing van de conclusies echter transparanter behoren te zijn. Hoewel expertbeoordelingen essentieel zijn in wetenschappelijke assessments, beveelt hetPBL aan om de transparantie van deze beoordelingen in toekomstige IPCC-rapporten te verbeteren. Bovendien zijn de onderzochte conclusies in hoge mate een selectie vande belangrijkste negatieve gevolgen van klimaatverandering. Hoewel deze selectie voor het Vierde Klimaatrapport was goedgekeurd door de lidstaten van het IPCC, adviseert het PBL om in het Vijfde Klimaatrapport het volledige spectrum van regionale gevolgen met de bijbehorende onzekerheden in de samenvattingen te vermelden. Om fouten en tekortkomingen zo veel mogelijk te voorkomen moet het IPCC meer gaan investeren in de kwaliteitscontrole.

De volgende aanbevelingen worden gedaan (uit de presentatie):

– Maak onderbouwing conclusies transparanter
– Geef volledig spectrum van regionale gevolgen weer
– Investeer meer in de kwaliteitscontrole
– Investeer meer in kennisopbouw

Het tweede punt raakt aan de kritiek dat werkgroep 2 de negatieve effecten meer in de schijnwerpers zet dan eventuele positieve effecten. Daar zegt het PBL rapport het volgende over:

Vierde AssessmentIPCC had focus op waarschijnlijke negatieve gevolgen

Deze ‘risicogerichte benadering’ is op zich goed te verdedigen:

– Politiek wil attent worden gemaakt op mogelijke bedreigingen en ontregelingen

– Samenleving prima in staat op positieve veranderingen te reageren, maar beleidsreactie is vaak vereist bij negatieve gevolgen

– Positieve en negatieve gevolgen kan je niet optellen

Maar kan nu beter op twee manieren worden aangevuld:

1. Geef ook rol van andere factoren dan klimaat aan, alsmede eventuele positieve effecten

2. Geef ook ‘worst case’ risico’s aan – kleine of onbekende kansen, grote gevolgen

Dit leidt tot een gebalanceerder overzicht van de regionale gevolgen voor water, voedsel, gezondheid, kustgebieden en ecosystemen

In combinatie met de eerste aanbeveling is het inderdaad belangrijk om transparant en expliciet te zijn over de gemaakte keuzes (bijv. een ‘risicogerichte benadering’) en de redenen daarvoor.

Enkele reacties van de media, waaruit aardig blijkt hoe verschillend de reactie op eenzelfde document kan zijn:


PBL kritiseert conclusies klimaatpanel

Financieel Dagblad:

Conclusies VN over klimaat overeind

En daar tussen in de Volkskrant:

Klimaatrapport kon wel wat beter;
Belangrijkste conclusies van klimaatpanel VN blijven overeind

Wel jammer dat veel media (inclusief het NOS journaal van 5 juli) niet heel duidelijk maken dat het alleen om de regionale hoofdstukken uit werkgroep 2 (klimaateffecten) gaat.

Update: Deze quote uit de volkskrant is (waarschijnlijk onbedoeld) cynisch:

De conclusie van het Planbureau is een optimistische. (…) Snelle opwarming door het broeikaseffect leidt wereldwijd tot problemen, vaak voor miljoenen mensen.

Huh? Wat een rare definitie van optimistisch… Tussen die twee zinnen, gemarkeerd door (…), staat de uitleg:

De centrale inzichten van het IPCC blijven overeind.

Oh, dus dat wordt er tegenwoordig onder optimistisch verstaan!

Assessing an IPCC assessment. An analysis of statements on projected regional impacts in the 2007 report

July 5, 2010

PBL Netherlands Environmental Assessment Agency has found no errors that would undermine the main conclusions in the 2007 report of the Intergovernmental Panel on Climate Change (IPCC) on possible future regional impacts of climate change. However, in some instances the foundations for the summary statements should have been made more transparent. The PBL believes that the IPCC should invest more in quality control in order to prevent mistakes and shortcomings, to the extent possible.

And from the presentation slides, regarding the focus of this assessment:

Media reported on errors in regional chapters of the Working Group II Report (impacts. adaptation, and vulnerability to climate change)
Investigation focused on 8 regional chapters in Working Group II Report, and on carry-over in summary of the IPCC Synthesis Report
Reports Working Groups I and III not investigated

Media reported on errors in regional chapters of the Working Group II Report (impacts. adaptation, and vulnerability to climate change)􀂃Investigation focused on 8 regional chapters in Working Group II Report, and on carry-over in summary of the IPCC Synthesis Report􀂃Reports Working Groups I and III not investigated

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.

RealClimate on the IPCC errors and their significance

February 15, 2010

RealClimate has a good post on the recent string of (alleged) errors in the IPCC report. It explains the IPCC proces, the nature and significance of the errors, and highlights the spin put on them by several media outlets.

Excerpt about the reported amount of land in the Netherlands that is below sea level:

Sea level in the Netherlands: The WG2 report states that “The Netherlands is an example of a country highly susceptible to both sea-level rise and river flooding because 55% of its territory is below sea level”. This sentence was provided by a Dutch government agency – the Netherlands Environmental Assessment Agency, which has now published a correction stating that the sentence should have read “55 per cent of the Netherlands is at risk of flooding; 26 per cent of the country is below sea level, and 29 per cent is susceptible to river flooding”. It surely will go down as one of the more ironic episodes in its history when the Dutch parliament last Monday derided the IPCC, in a heated debate, for printing information provided by … the Dutch government. In addition, the IPCC notes that there are several definitions of the area below sea level. The Dutch Ministry of Transport uses the figure 60% (below high water level during storms), while others use 30% (below mean sea level). Needless to say, the actual number mentioned in the report has no bearing on any IPCC conclusions and has nothing to do with climate science, and it is questionable whether it should even be counted as an IPCC error.

 And wrapping up the context of this whole manufacured controversy:

Do the above issues suggest “politicized science”, deliberate deceptions or a tendency towards alarmism on the part of IPCC? We do not think there is any factual basis for such allegations. To the contrary, large groups of (inherently cautious) scientists attempting to reach a consensus in a societally important collaborative document is a prescription for reaching generally “conservative” conclusions. And indeed, before the recent media flash broke out, the real discussion amongst experts was about the AR4 having underestimated, not exaggerated, certain aspects of climate change. These include such important topics as sea level rise and sea ice decline (see the sea ice and sea level chapters of the Copenhagen Diagnosis), where the data show that things are changing faster than the IPCC expected.

Open letter of Dutch climate scientists regarding the IPCC and the attacks on science

February 11, 2010

55 of the top Dutch climate scientists have published an open letter about the IPCC and the mistakes in the latest climate report. They put the mistakes in the context of what we know, and show that the mainframe of our knowledge of the climate system is not adversely affected by these errors.

I’m glad for this highly needed voice of reason in the popular debate, which has recently been overshadowed by far reaching claims of fraud and conspiracies.

An English version of the open letter is available here. It’s well worth reading.

Dutch version here.

Update: It’s now possible to support this open letter by signing it (PhD holders only). Go to

Open brief van vooraanstaande Nederlandse klimaatwetenschappers

February 11, 2010

55 vooraanstaande Nederlandse wetenschappers hebben een open brief geschreven om de huidige commotie omtrent klimaatonderzoek in de juiste context te plaatsen (pdf hier). Absoluut lezenswaardig, en ik blij dat meer wetenschappers van zich laten horen in het publieke debat. Het is te lang overschaduwd geweest door tendentieuze berichtgeving en verdachtmakingen.

Update: Het is nu mogelijk je steun te betuigen aan de open brief middels een ondertekening (alleen voor Dr.’s en Prof.’s). Zie

Hieronder volgen de belangrijkste passages uit de brief (uhm, dat is meer dan de helft):

Fouten in het IPCC klimaatrapport worden thans door sommigen aangegrepen om de hele klimaatwetenschap in diskrediet te brengen. In de Tweede Kamer zijn klimaatwetenschappers onlangs zelfs neergezet als ‘bedriegers’ en ‘klimaatmaffia’. Zulke kwalificaties missen grond in de feiten en zijn daarom misplaatst. Dat het IPCC niet onfeilbaar is, maakt haar hoofdconclusies nog niet onwaar of gekleurd. Wel zou het IPCC grootmoediger moeten worden in het snel en openlijk erkennen en corrigeren van fouten.

Met deze open brief vanuit de wetenschap beogen wij het ontstane beeld bij te stellen. Wij vragen om de discussie dichter bij de feiten te houden. We gaan achtereenvolgens in op de hoofdboodschap uit de klimaatwetenschap, op de werkwijze van het IPCC en op de kwaliteitsborging van het IPCC. We sluiten af met handreikingen voor verbetering van ons werk en herstel van het gedeukte vertrouwen in de klimaatwetenschap.

Het klimaatprobleem

Sinds 1990 is de kennis over en de ernst van klimaatverandering als gevolg van menselijk handelen snel toegenomen. Belangrijke componenten van het klimaatsysteem zijn daarbij binnen de natuurwetenschap goed begrepen. Het staat vast dat de hoeveelheid broeikasgassen in de atmosfeer sterk is toegenomen sinds de industriële revolutie. Dat deze broeikasgassen in de atmosfeer een hoofdrol spelen bij de temperatuur aan het aardoppervlak is elementaire fysica. Door de toename van broeikasgassen verandert de balans van de warmtestraling van de aarde, waardoor deze zeer waarschijnlijk opwarmt. Een wereldwijde opwarming van ruim een halve graad in de afgelopen eeuw is al waargenomen. Door een na-ijleffect op de al gerealiseerde toename van broeikasgassen in de atmosfeer stijgt de wereldgemiddelde temperatuur naar verwachting in de komende decennia verder met tenminste 1°C. [Dit heeft m.i. betrekking op de verwachte temperatuursstijging als gevolg van de huidige concentratie, oftewel, exclusief het effect van toekomstige emissies. BV]

De toename van broeikasgassen komt hoofdzakelijk door de wijze waarop kolen, olie en aardgas worden gebruikt en door ontbossing. De onzekerheden over de toekomstige uitstoot van broeikasgas en de effecten daarvan zijn groot. Studies van gerenommeerde onderzoeksgroepen laten zien dat bij onbelemmerde voortzetting van de uitstoot van broeikasgassen de wereldwijde opwarming ook doorzet, met 1,1 tot 6,4°C in 2100 (ten opzicht van de periode 1980-1999). Mede doordat er in het klimaatsysteem tal van kantelpunten zitten, kan dit al in de komende honderd jaar deels onvoorspelbare en mogelijk verstrekkende en onomkeerbare gevolgen hebben voor mens en natuur.

In het akkoord van Kopenhagen is afgesproken dat gevaarlijke verstoring van het klimaatsysteem voorkomen moet worden en dat daarom de wereldgemiddelde opwarming moet worden beperkt tot maximaal 2°C (ten opzichte van pre-industrieel). Onderzoek laat zien dat dit economisch en technisch mogelijk is met emissiereducerende maatregelen en door veranderingen in het consumptiepatroon.

Het IPCC en Klimaatrapport 2007

IPCC is een open netwerkorganisatie die gebruik maakt van gerenommeerde deskundigen uit heel de wereld, vooral van universiteiten, waaronder de meeste Nederlandse universiteiten, en van onderzoekinstellingen zoals in ons land KNMI, ECN, en PBL. In IPCC werken thans 194 landen samen, waaronder Nederland.


De 2007-rapporten zijn geschreven door circa 44 schrijfteams, met in totaal 450 hoofdauteurs. Die auteurs zijn op grond van hun expertise geselecteerd, met inspraak van alle 194 deelnemende landen. Nog eens 800 wetenschappers hebben tekstbijdragen aangeleverd over specifieke aspecten.


Bij het laatste rapport gaven 2.500 referenten samen ca. 90.000 commentaarpunten op de 44 hoofdstukken. Voor elk afzonderlijk commentaarpunt is door de betreffende auteurs met argumenten aangegeven hoe dat commentaar is verwerkt. [verschoven naar voren. BV]

Fouten in het IPCC rapport

Het onjuiste jaartal voor het verdwijnen van de Himalaya gletsjers en het onjuiste percentage ‘land volledig beneden zeeniveau’ zijn voorbeelden van fouten die ruiterlijk moeten worden erkend en rechtgezet. Zij doen echter niets af aan de hoofdconclusie dat de mens het klimaat zeer waarschijnlijk verandert, met op termijn ingrijpende gevolgen.

In verhitte discussies die rond deze fouten zijn ontstaan, zijn vragen gerezen over de kwaliteit en integriteit van het IPCC. De kwaliteitsborging van het IPCC blijkt niet waterdicht. Maar het beeld dat er opzettelijk is geknoeid met wetenschappelijke kennis vindt geen grond in de feiten.

Ook het beeld dat de hoofdconclusies van het rapport afhangen van dubieuze bronnen wijzen wij met kracht van de hand. De referentielijst van het circa drieduizend bladzijden tellende klimaatrapport verwijst naar ruwweg 18.000 bronnen waarvan het overgrote deel gepeerreviewde wetenschappelijke studies betreft. Voor het verantwoord omgaan met zogeheten grijze bronnen geeft IPCC een heldere richtlijn. Bij de Himalayafout is die richtlijn niet goed nageleefd. Die naleving behoeft bij nieuwe rapportages extra aandacht.


Wij concluderen dat de IPCC procedures transparant en grondig zijn, ook al zijn zij niet feilloos. Het schrijven van IPCC rapporten en de kwaliteitsbewaking daarvan blijft immers mensenwerk. Een garantie op een foutvrij rapport is een onhaalbaar ideaal, hoezeer dat ook gewenst is. Wel is het essentieel de procedure steeds weer te evalueren en waar nodig aan te scherpen, door lessen te trekken uit de gebleken fouten.



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