Posts Tagged ‘IPCC’

Gavin Schmidt and Judith Curry on Science Advocacy

December 23, 2013

Gavin gave a fantastic talk at this year’s AGU conference about science advocacy (good report on it by Yale CMForum and Dot Earth). The video is available via the AGU youtube channel:

He argued that it’s best to be explicit about one’s values and clearly distinguish when one is talking values (“ought”) and when one is talking science (“is”). I entirely agree. I would add that it’s important to distinguish recommending a generic (e.g. mitigation) vs a specific (e.g. CCS) course of action, especially when the latter is not one’s area of expertise. I wrote about the public role of scientists before, which touches on many of these same issues.

Judith Curry also chimed in, complimenting Gavin but also giving some criticism, much of which is rather off-base imho.

Both Gavin and Judith refer to this statement by Thomas Stocker at the end of the (well worth watching) IPCC AR5 video:

Continued greenhouse gas emissions cause further climate change and constitute a multicentury commitment in the future.  Therefore we conclude that limiting climate change requires substantial and sustained reductions in greenhouse gas emissions.

Is this a normative statement (“ought”) or a factual statement (“is”)? Gavin claimed it’s the latter, Judith claimed it’s the former. It would be advocacy if the goal was left out, as in “we should reduce GHG emissions”. But that’s not what Stocker said. Instead, what he said comes down to “if this is the goal, then that is what needs to be done to achieve it”. Curry claims that adaptation, carbon sequestration or geoengineering would also be options to limit climate change. That’s only partly true. Adaptation doesn’t actually limit climate change, as the word says it means adapting to climate change. As such it helps in the short term (and is definitely important), but in the long term adaptation without mitigation is like mopping the floor while leaving the tap running (see also the Rabett). Carbon sequestration is a viable option to reduce atmospheric concentrations, but with current technologies it can only make a minor contribution. So it could limit climate change to a very limited extent one might say. Geoengineering is a more complicated story. Basically, it exchanges one type of climate change (temperature changes) with another type (hydrological changes), so it changes climate change.

Perhaps Stocker’s statement could have been made more specific by including e.g. something like “limiting climate change to what societies are adapted or can adapt to requires substantial and sustained reductions in GHG emissions” which I think is what he meant anyway.

Curry goes on to state ” And there is a missing element in this argument that warming is ‘bad’, which is a value judgment and has nothing to do with science.”

This is a strawman argument, as it’s not a (hidden) element in Stocker’s argument as given above. Again, it would be true if the goal was omitted or left implicit (but it wasn’t). If one feels that limiting climate change is not needed (because it’s not bad) than the needed cure (reducing emissions) is not needed, obviously. That is entirely consistent with what Stocker said.

Curry further offers the following list of “examples of potential hidden values that are rather inconvenient (because) these are why the public distrusts scientists as advocates”. I offer my comment with each (in italics). It’s not at all clear that these would all go in the direction of a bias in favor of the mainstream (as Curry seems to implicitly assume); to the contrary.

  • personal career advancement: Unclear in which direction this would most likely go.
  • research funding: idem, though this could cause a tendency to increase the apparent magnitude of uncertainties.
  • the value in terms of professional recognition (e.g. awards from professional societies) that supporting the scientific consensus can provide (recognizing the ostracism that con result from straying): No bigger reward for a scientist than to prove the scientific consensus wrong.
  • media attention: This goes in the direction of providing relatively more media attention to contrarian voices, Judith Curry herself being a good example (assuming that she wasn’t as prevalent in the media before her U-turn away from mainstream science). This got confirmed in the large survey amongst climate scientists that I conducted last year (not yet published).
  • influence within the scientific community: This hinges on using solid arguments, so usually provides the correct incentive.
  • influence at the power tables in terms public policy: Like with media attention, extreme voices seem to have disproportionate influence. Look at the regular line-up for US senate hearings for example. If you crave media attention and political influence, being loudly contrarian is a sure way to achieve that. In the Netherlands the same tendency is apparent.
  • broader political objectives that support any/all of the above: This goes more likely in the direction of downplaying rather than overplaying AGW I would argue.

The Dutch view on the future of the IPCC – what it does and what it does not say

July 15, 2013

Guest post by Hans Custers. Dutch version is here.

The IPCC invited the governments of all participating countries to give their view on the future of the climate panel. The IPCC is a complex organization, dealing with a very complex subject, so perfection will be impossible to achieve. Or, from an optimistic point of view: there’s always room for improvement. And of course, a transparent process of self-reflection is a very good start for improvements. But well, this is the IPCC, so there is a catch. Whatever happens in this process, it will be spun by the anti IPCC and anti climate science campaign as ‘evidence’ for their claims. Every bit of criticism on the IPCC’s procedures and methods will be spun as substantial criticism on the scientific content of the assessment reports. And if governments would be reluctant to criticize, because they know it will be taken out of context, it would be seen as ‘evidence’ for the huge climate conspiracy.

The Netherlands has finished their submission and it was published (pdf) on KNMI’s website early last month. In my opinion they did what they should have done: they presented a straightforward view, not worrying about the inevitable spin by the skeptic campaign. And, oh yeah, inevitable it was. The next quote appeared in internet discussions again and again, after skeptics found the submission:

The IPCC needs to adjust its principles. We believe that limiting the scope of the IPCC to human-induced climate change is undesirable, especially because natural climate change is a crucial part of the total understanding of the climate system, including human-induced climate change. The Netherlands is also of the opinion that the word ‘comprehensive’ may have to be deleted, because producing comprehensive assessments becomes virtually impossible with the ever expanding body of knowledge and IPCC may be more relevant by producing more special reports on topics that are new and controversial.

Skeptics don’t seem to understand, or don’t want to understand, that this is about the IPCC organization only, and not about the content of assessment reports, or even climate science in general. They suggest the Dutch government thinks that natural influences and controversial topics may have been underestimated in previous assessments. There are some things they overlook.

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Comment on EER interview with Fritz Vahrenholt

June 11, 2012

Also published in European Energy Review (EER).

Greenhouse gases are responsible for warming, not the sun

Scientists working on climate on a daily basis must have been rather astonished by the interview with Professor Fritz Vahrenholt (European Energy Review, May 2, free registration required). Vahrenholt, chief of RWE Innogy, self-proclaimed climate expert and author of the book Die Kalte Sonne (The Cold Sun), claims that “the contribution of CO2 to global warming is being exaggerated”. These claims, however, do not stand up to scientific scrutiny. We assess his ideas in the light of the scientific literature on the role of the sun versus other climate forcing factors. The dominant influence of greenhouse gases follows not only from their basic physical properties, but also from their “fingerprint” in the observed warming. The sun, in contrast, has not exhibited any warming trend over the past 50 years. The sun is thus not responsible for the warming seen during this period. Greenhouse gases in all likelihood are.

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IPCC SRREN: Conflict of interest or just a bad press release?

June 19, 2011

The blog discussion of the week seems to be about IPCC’s Special Report on Renewable Energy Sources and Climate Change Mitigation. Question is, has a study headed by a Greenpeace employee been overly hyped? I think the short answer is that it has in the press release but it hasn’t in the underlying report.

One would think that that would be the end of it. It’s become the norm that press releases highlight an eye catching finding rather than trying to paint a full picture of the underlying report. The former draws media attention; the latter does not. Media need a news hook after all, as we’re frequently told by journalists. That’s not necessarily a good thing for science journalism and science literacy, but it’s the case nevertheless.

Then why does the bulk of the criticism go to the whole of the IPCC process? That’s a bit of a rhetorical question of course, as the answer is fairly obvious: There are legions of people looking for excuses to throw the IPCC under the bus. And sometimes even people who have a decent understanding of the issues are enclined to support such efforts, if they become convinced of serious wrongdoing. Think Monbiot with regards to “climategate” and now Mark Lynas with the SRREN. Mind you, I think the questions that Lynas posed to the IPCC are fair and deserve to be answered:

Here, repeated, are the questions I have posed to the IPCC’s Edenhofer:

1: what was the process for writing the press release, and who decided whether it faithfully represented the main conclusions of the SPM/main report?
2: why was the SPM released more than a month before the full report?
3: was Sven Teske in any way involved in the decision to highlight Teske et al, 2010 as one of the four ‘illustrative scenarios’ explored in greater depth as per Section 10.3.1?
4: what is the IPCC conflict of interest policy with regard to lead authors reviewing their own work, and having affiliations to non-academic institutions, whether campaign groups or companies?

The Carbon Brief has a good rundown of issues. One paragraph though struck me:

the use of word “could” in the IPCC’s press release (“Close to 80 percent of the world’s energy supply could be met by renewables by mid-century”) is likely to refer to future uncertainties, but may well have been perceived by journalists and the public as a straightforward statement about the technical potential of renewable energy.

I think it’s the opposite: I think the word “could” refers to “technical potential” rather than to future uncertainties. As in, if we really wanted to and put the effort (and money) in, this is what we could achieve. Whereas most reading this understand it in the other way and then interpret is as hopelessly optimistic and biased.

I agree that it’s not wise to put a rather unrealistic scenario forward as an example in the spotlights. My point is not so much to argue how silly vs wise, or how realistic vs unrealistic is it, but rather to distinguish that which is technically possible from what is societally and politically realistic. David Keith (in a different context) made some pertinent comments to this:

However when people and the political community hear technical people say “can’t be done” they assume we mean that technically can’t be done and that is untrue and destructive.
It’s destructive because it hides the central moral choice: we could cut emissions if we want to, we could have started decades ago when the scientific warnings about climate change were first raised, but we decided not to. It was a choice, implicit or not. A choice that, in effect, we cared more about current consumption than we did about preserving our grandchildren’s chances to enjoy a climate like the one in which our civilization developed.

McIntyre, in a comment at DotEarth, seems to agree that the central issue is the press release:

Andy, I don’t think that you adequately highlighted that the Greenpeace scenario was the one that was featured in the IPCC press release and covered by the world media. Had the problem been limited to the Chapter 10 discussion, it would be less of an issue.

Which leads Michael Tobis to remark:

It does appear that whoever wrote the press release did a disservice. This seems so common in press reports of science that I am starting to think of it as typical. If Mr. McIntyre had limited himself to such a claim, as he does here, I would have no quarrel with his behavior in this case. But he proceeds, on his blog, to use this incident to call for “Everyone in IPCC WG3 [to] be terminated and, if the institution is to continue, it should be re-structured from scratch.”

Thus he continues to play to the “climate science as fraud” crowd that frequents his blog while adopting a more reasonable pose here.  

(…)

The persistent substitution of fake problems for real ones is a key to derailing serious conversations these days.

The important conversation that we should be having, connected with the issues in the SRREN, is about what kind of future we want.

“Those who want search for a way. Those who don’t want search for a reason.”

IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation (SRREN)

May 11, 2011

This month the IPCC will release its Special Report on Renewable Energy Sources and Climate Change Mitigation. For now, only the Summary for PolicyMakers (SPM) is available; the full report will follow May 31st.

From the Press Release:

Ramon Pichs, Co-Chair of the Working Group III: “The report shows that it is not the availability of the resource, but the public policies that will either expand or constrain renewable energy development over the coming decades. Developing countries have an important stake in this future—this is where most of the 1.4 billion people without access to electricity live yet also where some of the best conditions exist for renewable energy deployment.”

This is also where the impacts of climate change are expected to be most severe.

While the report concludes that the proportion of renewable energy will likely increase even without enabling policies, past experience has shown that the largest increases come with concerted policy efforts.

Though in some cases renewable energy technologies are already economically competitive, the production costs are currently often higher than market energy prices. However, if environmental impacts such as emissions of pollutants and greenhouse gases were monetized and included in energy prices, more renewable energy technologies may become economically attractive.

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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.

Judith Curry goes from building bridges to burning them

November 5, 2010

In her recent post, Judith Curry takes issue with the politicization of science. But rather than making a well reasoned argument backed up by evidence, her post comes across as a strong but largely unfounded allegation of widespread bias and dogmatism.

What to think of a passage like this:

Once the UNFCCC treaty was a done deal, the IPCC and its scientific conclusions were set on a track to become a self fulfilling prophecy. The entire framing of the IPCC was designed around identifying sufficient evidence so that the human-induced greenhouse warming could be declared unequivocal, and so providing the rationale for developing the political will to implement and enforce carbon stabilization targets.

This sounds like an accusation that the IPCC conclusions were predetermined before it even started assessing the science. That is a far reaching and very bold claim. All that Curry presents in favour of this claim is her narrative of a trio between UNFCCC, enviro advocay groups and scientists. The actual history and mandate of the IPCC however look quite different to me. Btw, that doesn’t mean that no valid criticism could be leveled against the IPCC, see e.g. Eric Steig’s comment at Judith’s or James Annan‘s frequent critiques.

And then:

When I refer to the IPCC dogma, it is the religious importance that the IPCC holds for this cadre of scientists; they will tolerate no dissent, and seek to trample and discredit anyone who challenges the IPCC.  Who are these priests of the IPCC?

Excuse me? Is this a respected scientist talking? Someone who is trying to build bridges between scientists and their critics? By calling respected scientists “high priests of the IPCC”?

This kind of accusatory framing, based on mere innuendo and speculation, is the main reason that she gets a lot of flack from other scientists. It increases, rather than decreases, the polarization, and it starts to overshadow those issues where she does (or at least did) make valid points.

I was actually quite sympathetic to Curry’s attempts at building bridges, and see a lot of truth in her criticism of circling the wagons. Keith Kloor, in an interesting post contrasting Judith’s post with Gavin’s at RC, aluded to an over-defensive reaction to criticism which is occurring both amongst those who portray themselves as heretics (such as Judith Curry) but also amongst mainstream scientists (quite understandably so, but probably counterproductive).

Her unfounded allegations are insulting for the whole profession. It increases the polarisation and doesn’t add to the building of bridges (perhaps a one-way bridge). And I’m saying this as someone who, on the “pro-AGW” bloggers side, was probably one of the most receptive to her ideas. I am sincere and anti-dogmatic and I take great issue with her painting a whole scientific field, at the edge of which I work myself, as quasi religious dogma.

Update:

Eduardo Zorita – not a big fan of the IPCC – agrees that “Curry’s reflections are too broad-brushed” and add to the polarization.

Some more stunning things from Curry, e.g. when she wrote

The media also bought into this [blind support of the IPCC against its critics], by eliminating balance in favor of the IPCC dogma.

This couldn’t be further from the truth. The media has actually suffered from the opposite, creating an image of false balance by giving minority viewpoints equal footing with the mainstream evidence based outlook.

She also aludes to there being no sign of a climate change problem in 1992 when she wrote about that time period:

Wait a minute, what climate change problem?

whereas she is quite aware of e.g. the National Academy of Science writing in 1979

A plethora of studies from diverse sources indicates a consensus that climate changes will result from man’s combustion of fossil fuels and changes in land use.

Update 2:

Coby Beck has a detailed critique of Curry’s “positive feedback loop” post.

Judith Curry has had quite a few follow up posts in the meantime, trying to explain where she’s coming from. The posts on “dogma” were not very helpful, but her recent post on “ideology” makes more sense. My reply to that post is here (I may try to make it into a post some day).

 

IPCC history and mandate

October 1, 2010

The purpose of the IPCC was to assess the state of knowledge on the various aspects of climate change including science, environmental and socio-economic impacts and response strategies.

I.e. it was meant to report on and asses the scientific knowledge. This includes the question of how much evidence and (as a result) how much agreement amongst experts (consensus) there is for human induced climate change.

Some science historians point to other important aspects of IPCC’s history. The National Academy of Sciences wrote in 1979:

A plethora of studies from diverse sources indicates a consensus that climate changes will result from man’s combustion of fossil fuels and changes in land use.

Oreskes shows that the IPCC was set up in response to the emerging consensus in the 70’s/80’s that global warming due to GHG emissions would likely become a problem.

Spencer Weart writes:

The concern [about impending climate change] gave rise to the IPCC.

And also points to the Reagan administration being in favor of the clumsy IPCC approach, hoping that it would downplay the scientists’ fears.

When pointing to scientists who disagree with the IPCC consensus, it is important to note that people can agree in basically two directions. The survey by Brown, Pielke Sr and Annan for example shows this to be an approximate bell curve: Most (45-50%) of the respondents (scientists) more or less agree with the main thrust, and sizeable minorities (15-20%) think that IPCC overstated or understated its case. I discussed this survey and the broader question of why the consensus matters before. And I probably will pick this up again soon.

Scientifically, the more uncertain areas are the most interesting. However, if I look at the political decision making in terms of emission reductions and knowledge of the big picture (and the length of time that we’ve known about this big picture, albeit in gradually more certain terms), I can’t but conclude that the politics is hopelessly lagging behind the scientific knowledge in taking this problem seriously. (see e.g. my Dutch post “tijd voor de politiek om wetenschap serieuzer te nemen”.) Of course I’m aware that there’s more that informs politics than just the science, but still, there seems to be an uncomfortably big disconnect there. Stark warnings from science are ignored at our peril.

At this point in time, the uncertainties are pretty much irrelevant for policymaking, because any realistic change in the uncertain details is not going to affect the main trust of what we know, and thus the policy response that people may favour. For the long term, of course we need to finetune our knowledge, so research is still needed. (Hey, I’m a scientist, so I kind of have to say that, right?)

As Herman Daly said:

“Focusing on them [the big picture of what we know] creates a world of relative certainty, at least as to the thrust and direction of policy.” On the other hand, focusing on the more uncertain rates and valuations creates “a world of such enormous uncertainty and complexity as to paralyze policy”.

Perhaps that’s indeed what’s happening now, also cf. Judith’s uncertainty monster and complexity monster.

“To make the point more simply, if you jump out of an airplane you need a crude parachute more than an accurate altimeter.”

Funny how Daly and Curry both address the huge issues of uncertainty and complexity and arrive at diametrically opposed strategies of dealing with them. In terms of public communication, I’m with Daly.

From the principles governing IPCC work:

The role of the IPCC is to assess on a comprehensive, objective, open and transparent basis the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation.

IPCC reports should be neutral with respect to policy, although they may need to deal objectively with scientific, technical and socio-economic factors relevant to the application of particular policies.

Funnily enough, a commenter at Judith’s, Paul in Sweden, took this as proof of a “blatantly biased agenda”. Which is a little strange in light of the history of climate science and of the IPCC as mentioned above. Its mandate is a consequence of the scientific evidence for human induced climate change having become increasingly strong and societally relevant. It doesn’t state what the conclusion ought to be –it has to follow the science-, but of course it states what it’s supposed to assess.

Judith Curry also seems to suggest that the IPCC reports are working towards a predetermined conclusion, when she claims that they are akin to a legal brief (meant to persuade). If true, that should be reflected by large differences between the scientific evidence and the IPCC reports, and between scientists’ opinions and the IPCC reports.  I have not seen evidence of either.

Tom Curtis made some very thoughtful comments on the consensus thread at Judith’s, e.g.

In other words, the IPCC was tasked with reporting the consensus view of the science, were such a consensus existed; and to explain and report the differing opinions where no such consensus existed. Whether they have done that is not best judged by whether they have explained and included the opinions of every crackpot fringe group with an axe to grind on global warming; nor even those of every climatologist, no matter how small a number might support their views. Rather, they are to be judged by the agreement between the IPCC reports and the known consensus and divergences of scientific opinion.

Fortunately, we have available several anonymous surveys of the scientists opinions, which show conclusively that the IPCC reports fairly represent the consensus of relevant scientists on those topics on which it reports. (…)

The purpose of IPCC is to provided as succinctly as possible the best possible scientific advice for policy deciders to operate on. If they were required to consider all and every idea on climate change that circulates on the blogosphere; then the resulting document would be to large, and to ill organised to be usefull as a guide to policy.

Nevermind that the politicans still wouldn’t have a clue as to what is more likely true. The science has to be assessed and weighted; that is what makes the IPCC process useful. There already is another outlet for every crackpot idea out there (NIPCC report); it doesn’t need to be done by the IPCC as well.

To quote the Dutch newspaper “Volkskrant” again:

its work has political implications, but that that doesn’t mean that it’s engaged in doing politics.

And since I discussed history as well, see also my first blog post where I described the IPCC process. I don’t think anyone has read it yet, so I’d be much obliged. And while doing self-promotion, I kind a like this oldie featuring Fred Singer.

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.


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