Comment on EER interview with Fritz Vahrenholt

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.

open thread april 2012

For all climate related discussions that don’t fit under a recent (yeah, that one) thread. Please be civil.

Dilemmas in science communication

Slightly different version has been posted and discussed at Planet3

A few weeks ago I attended a meeting on science communication and the increasing public distrust of science. Climate was not the major theme, though it did come up as an example (not least because I was an invited speaker, as a blogging scientist / scientific blogger).

Cees van Woerkum: Modern vs traditional communication

The first speaker was professor in communication science, Cees van Woerkum. I attended his lectures 19 years ago. He explained how the old model, of a sender and a receiver of communication, was no longer valid (if it ever was). Modern communication is characterized by a much more active role of the audience in selecting what information to take in. Also, the message is not inert, but rather gets meaning in an active and social process.

Drawing on examples from biotechnology, carbon capture and storage, and vaccination he argued that scientists should take the concerns of citizens seriously. Laughing at somebody for calling biotechnology “unnatural” is not going to take their worries away or change their mind. Calling fears of side effects from vaccinations “dangerous nonsense” doesn’t quite work either, especially not if those concerns have already been anchored to a certain extent through social construction. If a scientist calls the chance of CO2 leakage from a storage facility vanishingly small, the response is “so it’s not impossible?!” A potential way out according to van Woerkum is to ask what’s behind their concerns: What do you mean by unnatural?” Then you can at least start to have a conversation.

Jona Lendering: A different field of scientific inquiry facing large scale disinformation

This was followed by a presentation by author and historian Jona Lendering. Although the topic of his talk was something entirely different (about ancientPersia) the similarities with the climate debate were striking. He explained how this field of academic enquiry (about the origin of Western civilization) was being “attacked by anti-scientific tendencies” (aiming to glorify one culture’s role). The scientific establishment hardly participated in the public debate on the internet. As a consequence, the anti-scientific views got more traction and mainstream science failed in (what should be) one its core missions: Informing the public. He repeatedly stated the mechanism: “Bad information drives out good information”. He also mentioned the “intense hate” with which the “attack-machines” approach science. It was as if I was listening to Kevin Trenberth; the dynamic between a skeptical-cynical part of the audience and mainstream science was just too similar.

Me: Dilemmas in science communication

I talked about the dynamics of blog discussions and about the dilemmas that one encounters in trying to communicate scientific insights to a broad audience, mainly in the sphere of understandability vs completeness:

I mentioned that imho mainstream media suffers from too much emphasis on news (as opposed to robust knowledge) and on mere facts (to the detriment of explaining the scientific process of getting to understand those facts). In the blogosphere I see too much emphasis on details (to the detriment of the big picture) and on uncertainties (to the detriment of robust knowledge).

The last one on the list I actually added based on the dilemma that van Woerkum alerted the audience to: As a scientist (or science journalist), you can no longer easily claim “listen to me, I’ll tell you how it is”. You have to take the concerns of citizens seriously.

But what to do if those concerns are not openly expressed, but rather disguised in scientific sounding (but incorrect or sometimes even plain silly) arguments? “Climate change is due to the sun” or “Iranis the origin of Western civilization” or “vaccination causes autism”? The underlying reason for skepticism often remains hidden. As a scientist, you’re sucked into a quasi-scientific argument. How else can you react, than by saying: “no, that’s not the way it is. It’s this and this way, for such and such reasons”? But such a reaction is being characterized by skeptics ((mis-)using van Woerkum’s words) as “unjustified superiority of science”. Is explaining how science sees it a hopeless strategy?

In line with van Woerkum I think it’s important to focus on the underlying reasons for distrusting science. We should really discuss why we disagree so strongly about climate change (e.g. due to differences in worldviews and in risk perception). Keith Kloor cites Scott Denning (who spent a lot of time talking with contrarians, e.g. at two consecutive Heartland meetings):

Almost everyone that dismisses climate change as a problem does it for ideological or political reasons, not for scientific reasons.

Of course, there are also other potential reasons, but this one is surely a biggie.

Discussions about hockeysticks and feedbacks are all very interesting, but they are not the crux of why there is a such a heated and politicized debate about climate change. We don’t have a similar public debate about the mating behavior of fruitflies after all.

 

Climate survey discussion

On the previous post a discussion about climate surveys erupted. Please continue here. I’ll chime in when I habe more time.

I’m curious to hear what you find good or not so good about a particular survey and why. If you have contributed to the discussion on the previous thread, perhaps you want to condense your main arguments in one comment so that we can start a more structured discussion. If succesful, I’ll follow up with a post including the various contributions. Call it crowdsourced blogging if you wish.

A noteworthy survey that has not been discussed much is the one by Brown, Pielke Sr and Annan that I wrote about before:

A recent survey of scientists having authored a recent journal article on climate change found that the majority concurred with the IPCC position. A sizeable minority was of the opinion that the IPCC reports overstate the importance of and/or certainty regarding CO2 compared to other forcings (both natural and anthropogenic!). Only very few respondents were of the “skeptical” opinion that warming is predominantly natural. Nobody denied that the globe is warming. A large minority found the IPCC too cautious, understating the human influence on climate and/or the seriousness of the problem. Note that the authors do not claim that their survey is representative; less then 10% of the 1800 scientists contacted replied. Moreover, the positions that respondents had to choose between were sometimes a little ambiguous.

Others that have been discussed a lot include those by Bray and von Storch and the recent one by Doran and Kendal-Zimmerman.

2011 in review

Best wishes for 2012 everyone, and thank you for reading and commenting on my blog. It is gratifying to be able to provide food for thought and a forum for discussion.

Another year of blogging gone by. According to wordpress this blog was viewed 140,000 times in 2011, which is a bit less than in 2010.  I’ve averaged a bit less than one post a week (I read much more than I write, and I’m probably too perfectionist in my writing to be a prolific blogger).

A rather peculiar stat is about the search terms that people used to find my blog: Number one by far is Harry Potter (I wrote a sarcastic post once about the Harry Potter Theory of Climate, making the point that climate doesn’t change very much without being forced to (conservation of energy and all that). Other popular search terms such as dinosaurus and Sinterklaas don’t have much to do with climate either. Guess I should ramp up on my SEO, or alternatively capitulate to the thought that most people search the internet for entertainment rather than for information.

“NIPCC” remains the most popular climate related search term (unless you count “bart climate” as well), which is good, because it means that people searching for it will find my rebuttal to the rather misleading 2009 report (which has not been discussed much by other mainstreamers afaik).

These are the posts that got the most views in 2011 (though most of my posts are viewable from the root, so these posts were not necessarily the most read) :

• 1 Revkin on Steig, O’Donnell, peer review and solid scientific basics 541 comments February 2011
• 2 Harry Potter theory of Boating 36 comments April 2011
• 3 How science does and does not work (and how skeptics mostly fall in the latter category) 451 comments June 2011
• 4 Biodiversity, extinction and climate change 437 comments February 2011
• 5 Spencer and Braswell fundamentally flawed, journal editor resigns 226 comments September 2011

What else happened in 2011 with this blog? I received the Woody Guthrie award for a thinking blogger and I split my blog in two: This one for English posts and discussions, and Klimaatverandering for the Dutch speakers.

Looking back, I wrote relatively fewer original articles and did more copy and pasting from others. That sounds rather negative, but in some cases I’m actually rather pleased with the result, e.g. when I retell a discussion between some heavyweights in the climate scene that took place deep in comment threads elsewhere. To myself at least this serves the purpose of putting such a discussion in a context and preserving it in a more readable (i.e. without the off-topic ranting from the fanclubs) and more searchable format. I hope that for others it’s informative as well. Examples include the back and forth between Gavin Schmidt and Roger Pielke Sr about ocean heat content, between Richard Tol and Judith Curry about publicizing nonsense, and between Jeff Id and Chris Colose about the merits of bringing up Venus as a greenhouse example.

The last two examples have the added benefit of highlighting an interesting discussion that took place on blogs that most readers of my blog would not otherwise have read. In that same vein I reproduced a very interesting post and discussion from Bishop Hill about areas we agree on, from climate scientist Eric Wolff.

Sometimes I draft a post based on a discussion that ensued at my own blog (e.g. on walking the talk and on biodiversity and climate change), usually spontaneously and in an off-topic fashion. Since it’s dreadful to find an off-topic discussion back after a while, and since most discussions derail, I find it useful to condense the interesting parts in a separate post. In fact, I wish I had time to do that more often, because there are still many interesting discussions buried in off-topic comment threads (e.g. on Arrhenius or on consensus). Another possibility would of course be if people stayed on topic and requested a thread on a topic of their liking. Perhaps an idea for a newyears’ resolution…

Some other posts I like:

“Different approaches to the climate problem“, with some archetypical ways to view climate change and proposed solutions, that in many cases reveal a lot about underlying motives and agenda’s.

A policy relevant post is about conditions needed to get political action: strong evidence, realistic solutions, political pull, and sense of urgency. This post and the previous example are both influenced by a colleague of mine with decades of environmental policy experience.

Science communication: Who is responsible for its failing? (also an attempt the synthesize discussions on this ongoing theme from various blogs)

Using aerosol forcing as a wildcard to claim low sensitivity: Some (NIPCC) claim high aerosol forcing and thus low sensitivity, others (Lindzen, Crok) claim low aerosol forcing and thus low sensitivity. They can’t both be right and probably neither are.  Both arguments use the existing uncertainty to argue for an implausible end of the probability spectrum. This post got reproduced at SkS.

And these twin posts on sea level rise:

Sea level versus temperature

Past, current and future sea level rise

Both with some adapted graphs, context and many links.

Click here to see the wordpress end of year report.

For 2012 I expect lighter blogging, both for personal and for professional reasons.

What are the pros and cons of reducing CO2 vs other warming agents?

That is the question I’ve been pondering earlier this year and which’ pontifications you can now read on Planet3.

The difference is mainly in the timescale: CO2 lasts a lot longer in the atmosphere than most of the other warming agents (e.g. black carbon, ozone, methane). This means that the temperature will decrease faster when the emission of shortlived compounds is decreased, as compared to that of a longlived compound such as CO2.

The other side of the coin is that for long term warming, the cumulative emissions of CO2 are dominant, even if in the short term changes in its emission are relatively ineffectual. Other important aspects in this discussion are health effects from air pollution (e.g. soot and ozone) and political practicability (gridlock in global climate negotiations).

So the question is: Are you more concerned about the short term or the long term effects of climate change? Which is a similar question that is often implicitly present in climate debates: Weighing the right of this generation to economic wellbeing (through cheap fossil energy) with the right of future generations to a pleasant planet to live on (through us not using too much cheap fossil energy). Strangely enough, that central and deeply ethical question is usually embodied in the discount rate (as used in economics when comparing investments with the expected rate of return).

My conclusion:

It’s clear that for long term climate stabilization, cumulative CO2 reductions are paramount, and that for the short term, reducing other forcings can offer faster results and offer other benefits as well. So the answer to the question “what should we focus on” is “all of the above”. I would applaud more attention to the non-CO2 forcings in the International policy arena. However, let’s not forget that there’s a hefty price and/or climate tag to pay in the end for delaying CO2 emission reductions.

You can read the whole thing over at P3.

 

Planet3 is a community new(s) blog, aptly described by main driving force Michael Tobis (in an interview with Andy Revkin) as

opinionated yet skeptical, informed yet passionate

 

Conflict of interest statement: I live on the planet in question.

(via Elmar Veerman)

Open thread – Nov 2011

Another open thread for discussing climate related issues of the day. It’s a strange world where that includes private emails of scientists, but that’s the world we live in.

Try to be somewhat courteous to people you disagree with. No namecalling.

To publish BS or not, that’s the question

Richard Tol levied a strong accusation at Judith Curry for highlighting two seriously flawed papers (via twitter):

Its wrong, but with @JudithCurry lending her authority it becomes disinformation

Judith defended herself in a post where she tries to shift the blame to the mainstream scientists:

 Here is a quiz for you.  How many of these disinformation tactics [a list containing a mix of logical fallacies and avoidance tactics] are used by:

• JC (moi)
• Public spokespersons for the IPCC
• Joe Romm
• Marc Morano

If that’s not a dog-whistle I don’t know what is. 

Keith has a nice rundown of the discussion, and the ensuing thread over there contains many good comments. He’s got a knack for hosting interesting discussions.

Richard has since laid out his argument as to what’s wrong with the papers in a guest post over at CE.  Basically they’re methodologically flawed:

Using “detrended” fluctuation analysis to study “trends” was a dead giveaway that something is not quite right with these papers.

Tol goes on to write: 

7. There is a substantial body of climate research that is credible — even if it reaches opposite conclusions — but there are also papers (left, right, and center) that are just flawed.
8. If flawed papers reach a certain prominence, they should be debunked. Prominent but flawed research does damage as it misinforms people about climate change. Publicly criticizing such research hardens the existing polarization.
9. If flawed papers linger in obscurity, they should be ignored. The papers are wrong but do no damage. Lifting a flawed paper out of obscurity only to debunk it, is no good to anybody.

Curry takes especially issue with the last statement:

Yours isn’t a statement about science, but about playing politics with science, and reinforces the gatekeeping mentality in climate science that was embarassingly revealed by the CRU emails. (…)

Of course scientists don’t want the public to be misinformed about the science! So If I’m concerned about public understanding of science, I’m automatically “playing politics with science”? Then I sure hope every scientist is.

Judith rightly says that “Of course there are flawed papers that get published.” But why shining the spotlight on them? What’s gained by doing so?

It’s true that these discussions don’t occur about science without policy relevance. Research on the mating behavior of fruit flies won’t result in argument whether a flawed paper should be promoted in the public sphere or not.

The differences are that 1) such research is not present in the public sphere, because the public isn’t interested, and 2) even though flawed papers exist in any field, the more its conclusions clash with ideologies, the more attempts will be made to reach opposite conclusions and thus the more deeply flawed/biased papers will be published. It’s not a coincidence that there’s no fruitflies-version of EIKE or Heartland. 

Curry:

Most people don’t come to climate etc. to reinforce their prejudices (there are far too many echo chambers where this is much more satisfyingly accomplished). They come here to learn something by considering the various arguments.

The general tone of comments at CE makes me strongly doubt this last statement.

Tol:

@Anteros
I would agree with you [no harm done by highlighting flawed studies] if climate blogs were exclusively read by well-intentioned, well-informed, and intelligent people.

Richard further shows his mastery in the tweet-universe with one-liners such as

I argue for self-censorship. It is what separates adults from children.

Over at CaS, Roger Pielke Jr makes the point that wrong or bad articles can be a useful teaching tool. And indeed they can. But as Stoat rightly says,

within a managed class structure with someone guiding the discussion, it is fine to discuss flawed texts, for the reason given: it encourages critical thinking. That wasn’t what Curry was doing.

Tol:

Curry took two papers that almost nobody had read, and put them in the limelight.
The papers say 2+2=5.
There are a lot of people who would like to believe that. It is not true.
So now there is yet another dogfight about whether the answer is 3, 4, or 5. We can do without that.
There are plenty of real issues to argue over.

Jonathan Gilligan, consistently thoughtful, writes:

Pielke has said that he views blogs as more like the kind of discussions people conduct over beers at the neighborhood bar, and from that perspective Richard’s criticism makes no more sense than telling the crowd at the pub to leave sports commentary to the experts. 

Tol makes some valid points here, but Pielke is more persuasive. People will read these blogs or not as they choose, and when a blog repeatedly calls attention to crap, its credibility and its audience will adjust to reflect this. Climate Etc. is not The Wall Street Journal, so the greater danger in Curry’s gushing over crap is to Curry’s reputation, not to the public understanding of science.

I have also compared blogs to bar-discussions (quoting Bob Grumbine), but that comparison is about the presence (or lack) of quality control. As Tol rightly says, 

With academics blogging and tweeting, and journalists, and prime ministers, and institutes, departments, agencies and companies, I don’t think there is a one-rule-fits-all.

At CE, thousands of people are listening. Judith’s opinion and her writings make their way to the general public and politicians via mainstream media and Senate hearings as well. By the scale of those who are engaged in the conversation, that is orders of magnitude different from a discussion in a bar. That also means that the risk is twofold: Both to Curry’s reputation (her problem) and to the public understanding of science (everyone’s problem, even though Curry tries to belittle that).

Whereas Tol argued based on methodological flaws, Fred Moolten explains why the papers’ conclusions are unsupportable on physical grounds and I made a similar argument:

Conservation of energy precludes the climate to wonder off too far in any direction without being “forced” to by changing boundary conditions. Unless of course the energy is merely being redistributed within the system. Which it isn’t, since all other compartments of the climate system are gaining energy.

The paper’s conclusion that the observed warming is “predominantly a natural 100-year fluctuation” is at odds with conservation of energy.

All very reminiscent of the random walk saga and the Harry Potter theory of climate.

Ocean Heat Content: Can we monitor the transfer of heat through the top 700 metres?

At RC, Gavin Schmidt and Roger Pielke Sr are discussing how Ocean Heat Content (OHC) has changed in the recent past. The disagreement seems to be on how the apparent slowdown in heat uptake of the top 700 metres can be reconciled with apparent warming of the deeper ocean. It’s very informative to witness two experts debate this in public (even though the discussion is hampered by frequent misunderstandings and other derailing issues). I’ve found this a puzzling issue for a while and am still not sure if I fully grasp it, but here goes: 

On his blog, RPSr writes:

If heat is being sequested in the deeper ocean, it must transfer through the upper ocean. In the real world, this has not been seen that I am aware of. In the models, this heat clearly must be transferred (upwards and downwards) through this layer. The Argo network is spatially dense enough that this should have been seen.

Gavin responds to this statement at RC:

Obviously heat going below 700 m must have passed through the upper ocean. However, the notion that Argo could see this is odd. Argo measures temperature, not flux. The net flux into a layer is calculated by looking at the change in temperature. It cannot tell you how much came in at the top and left at the bottom, only how much remained.

Both arguments make intuitive sense. Whether indeed temperature measurements should have seen a transfer of heat depends on the precision and on the (spatial and temporal) density of the Argo network. Besides that, it also depends on the mode of heat transfer (episodic or continuous). Or perhaps better put: the extent to which the influx and outflux of heat balance each other.

Gavin does not agree with Roger’s last statement (that it should have been see), but argues instead that the signal would not likely be observable amidst the variability (response to 140): 

I have no confidence that the observations will be sufficient to distinguish the anomalous heat flux from the climatological mean with sufficient precision to be helpful.

Roger concedes that the observation network’s precision is an important precondition for heat transfer to have been observed, when he writes in response to my little summary over there: (Roger)

(…) we should still see a slight elevation in the temperature anomalies IF the Argo data precision is good enough. I do not know the precision of the temperature data measurements, and hope someone else can answer that.

And in 193 Roger writes:

First, I stated that the Argo data density was fine enough to see the movement of the heat downward, but am now unclear on this, and look forward to an Argo specialist to give us an overview of capability in this regards.

There is however a second if-statement to make, about the mode of transfer. In response to 2, Gavin wrote:

Most heat transport into the deep ocean will occur in the down-welling branches of the overturning circulation, centered in theNorth Atlanticand the Southern Oceans. Diffusive fluxes in the rest of the ocean will be much smaller.

Roger (140) says more or less the same, but arrives at a conclusion that is not shared by Gavin:

if this transfer occurs in globs associated with mesoscale and larger ocean circulation features (as suggested in the ECMWF data), we should clearly see this movement of heat.

About the mode of heat transfer Gavin writes in response to 155:

Heat transfer will be mainly continuous, not episodic.

I.e. the heat transfer is strongest in specific locations (agreed on by both), but continuous in time (which prompted a question from Roger “how do you know?”).

In a continuous case, for a while the same amount of heat may enter the top 700 m from above, as leaves it from below. As a result, no warming signal in this layer will be observed, whereas heat is being transferred through it. In an episodic case, it would in principle be observable (though still dependent on the precision and signal to noise ratio of the measurements).

In contrast to what I wrote in my little summary at RC (175), the disagreement is not so much on whether the heat transfer is concentrated in space (both seem to agree that it is), but rather on whether the heat transfer is continuous or episodic in time (Gavin thinks it’s the former; Roger doesn’t say) and on whether the data precision is sufficient (Gavin thinks it isn’t; Roger doesn’t say).

Figure 9b from Hansen et al., ACPD 2011, “Earth’s Energy Balance and Implications”. Note that this Fig gives the heat uptake, which is the slope of a figure of heat content (in Joules): A positive heat uptake means that the heat content is increasing.

Figure caption: Six year trends of ocean heat uptake estimated by Levitus et al. (2009) and Lyman et al. (2010) for upper 700 m of the ocean, and estimates based on Argo float data for the upper 2000 m for 2003–2008 and 2005–2010.

I’ll probably update this post as the discussion progresses. Over at SkS, there have also been informative discussions between Roger and the regulars over there.

Confusing the net cloud effect with a cloud feedback: Very different beasts

I stumbled upon a new post at WUWT today:

New peer reviewed paper: clouds have large negative-feedback cooling effect on Earth’s radiation budget

Note that Anthony has since changed the title to leave out the word “feedback”, which was the source of his confusion. It starts out as follows:

Oh dear, now we have three peer reviewed papers (Lindzen and Choi, Spencer and Braswell, and now Richard P. Allan) based on observations that show a net negative feedback for clouds, and a strong one at that. (…) The key paragraph from the new paper:

…the cloud radiative cooling effect through reflection of short wave radiation is found to dominate over the long wave heating effect, resulting in a net cooling of the climate system of −21 Wm−2.

The attentive reader will immediately spot the problem here. Watts is confusing two issues:

- the net radiative effect of clouds on climate (i.e. in comparison with having no clouds at all)

- the net feedback of clouds in response to a change in climate

The paper addresses the first, whereas Anthony interpreted it as if it addresses the second.

These are two distinctly different issues. The latter (clouds as feedback) is about how cloud cover and properties might change in response to a warming or cooling of the climate: Will the net cloud radiative effect (i.e. the former) become more or less negative.

The net radiative effect of clouds on Earth’ climate has long been known to be negative (i.e. cooling). See e.g this quote from the paper:

The overall global net cloud radiative effect is one of cooling as documented previously (Ramanathan et al., 1989).

That can be verified in any textbook on the subject and most introductions of papers on this topic. Or in my introductory post on aerosols, clouds and climate.

I pointed this error out in the thread, as did more than a few others after me (including Roy Spencer). Only after the author of the paper, Richard Allan, came in to say that this post mis-interpreted the paper, did Anthony change the title and added an update. The mistaken interpretations are still in the body of the text though.

Richard Allan wrote to me in email (reproduced with permission):

I was surprised that this paper was linked to cloud feedback since, as you mention, it attempts to quantify the well known influence of cloud on Earth’s radiation budget (at the top of the atmosphere, at the surface and within the atmosphere and also during day and night) and does not attempt to diagnose cloud feedback.

Watts goes on to say (bold in original):

The cooling effect is found to be -21 Watts per meter squared, more than 17 times the posited warming effect from a doubling of CO2 concentrations which is calculated to be ~ 1.2 Watts per meter squared.

He’s comparing apples and oranges. The 21 W/m2 is the top of the atmosphere (TOA) cloud forcing in reference to having no clouds at all (see table 1 in the paper); the 1.2 W/m2 is the surface forcing due to a doubling in CO2 concentrations. The TOA forcing of a doubling in CO2 is closer to 4 W/m2. But that’s not the “zero” point. The total greenhouse effect (due to water vapor, clouds, CO2 and other GHG) is about 150 W/m2.                                                                                                                   

In other words, this paper falls squarely within the mainstream; it further quantifies a (previously known) net cooling effect of clouds on the Earth’ climate; it does not quantify how clouds may change in response to warmer climate (cloud feedback), though it does provide a carrot stick in saying that these types of analyses are important “in assessing cloud climate feedbacks which contribute substantially to uncertainty in climate prediction.”. That may very well be, but it hasn’t been done in this paper (as confirmed by its author). 

Judging by the comments, many at WUWT took this, in combination with the whopping -21 W/m2, to mean that they discovered a gigantic negative feedback. Nope.

Tallbloke (from Lisbon fame) still insists that

if [cloud forcing] becomes slightly less negative, it’s still very negative, and overwhelms the effect of changes in co2.

… being very confused. Comments vary over a very wide range though. Many are confused (e.g. stating that as specific humidity goes up in a warmer world, so should cloud cover, whereas cloud formation depends on relative humidity rather than on specific humidity), there’s lots of laughing-at-the-scientists going on, but there are also sensible comments that either offer insight or good questions.

Mosher makes the following observation:

it is also fascinating because of what we dont see. usually you will see a whole crew of commeters pounce on the word “model”. This time they didnt.

They didnt because they thought the paper supported spencer. But it was on an entirely different topic. That misunderstanding kinda silenced the usual “models are bad” crew.