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« Diary date for Cambridge | Main | Hansen the hopeful - Josh 98 »

A response to Cox and Stockwell

Retired geophysicist Geoff Davies has responded to the Cox and Stockwell article (discussed here) about Hansen's new paper on climate model representation of ocean heat uptake and mixing. He accuses them of misrepresenting Hansen.

The article contains basic misrepresentations of Hansen and of the substance and implications of a draft paper by Hansen.

The Hansen paper does not weaken the case that humans are the main cause of global warming. On the contrary, it suggests we have unwittingly and temporarily shielded ourselves from the full effects of our activities.

I've only whizzed through both the Cox/Stockwell and the Davies articles, but I think the difference is over the credibility of Hansen's explanation. Hansen is saying that ocean heat uptake has been overestimated, and therefore the reason we haven't seen much warming is that we must have got aerosols wrong too, with the two errors effectively having balanced each other out. Cox and Stockwell are saying that maybe the effect of CO2 is not as strong as previously thought.

Is that right?

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Reader Comments (34)

Geoff says:

"It is a widespread misconception, evidently shared by Cox and Stockwell, that the case for human-caused global warming rests mainly on computer models and is therefore vulnerable to the aerosol uncertainty. This misconception is part of the disinformation put about by the professional deniers funded by the likes of ExxonMobil."

If this is the level of argument I am not sure this article is credible.

May 20, 2011 at 9:51 AM | Unregistered CommenterJosh


May 20, 2011 at 10:14 AM | Unregistered CommenterBBD

Sorry - BH: yes

May 20, 2011 at 10:14 AM | Unregistered CommenterBBD

It is almost, but not quite as bad, as they first thought

May 20, 2011 at 10:17 AM | Unregistered Commentergolf charley

Yes, and the aerosol bit is another untested theory being used to support another tested theory that is not being confirmed by observations.

May 20, 2011 at 10:22 AM | Unregistered CommenterBreath of Fresh Air

It's a funny old world is "climate science".

There is a lot of confusion - confusion in concepts, confusion between cause and effect, strange use of words.

For example we often read this kind of thing: "the 5 year drought was caused by climate change". This is a real mixup - the 5-year drought was climate change. It's like saying "the symptoms were caused by the symptoms".

Then the word "masking" has a bizarre meaning in climatology. We often read that "the warming was masked by some cooling effect". You could just as easily turn this round and claim that the cooling was masked by the warming.

Normally masking is an instrumental or observational error - eg "the true speed was masked by the speedo stopping at 75".

Then there is the concept of a global climate. Not sure how useful it is to average out the hot and dry deserts with the hot and humid jungles and the cold dry antarctic areas and the oceans and everything in between.

May 20, 2011 at 10:27 AM | Unregistered CommenterJack Hughes

Another example in the text:

"it suggests we have unwittingly and temporarily shielded ourselves from the full effects of our activities"

This is a weird way of writing that some activities counteract the effects of other activities making the net result smaller.

May 20, 2011 at 10:30 AM | Unregistered CommenterJack Hughes


Your characterization of Hansen's position is correct, but I would say that both Hansen and Davies fail to distinguish between the fact of the lack of fitness of models, and the speculation that the problem is the parametrization of the aerosols. We say that a skeptical position is that the shortfall may be remedied by changing the CO2 sensitivity, rather than modifying the aerosols. There are many empirical sources (Spencer, Douglass, Shaviv, Idso, Schwartz, Lindzen) backing the skeptical position. I don't know, but I trust the measurements more than I trust the models.

May 20, 2011 at 10:31 AM | Unregistered CommenterDavid Stockwell

Can anyone turn up some references to papers that deal with the supposed cooling effects of anthropogenic aerosols (or just any old species of aerosols really) between ~1940 - 1970?

This is the argument advanced by the orthodoxy. Tuning aerosol forcing is the methodology used to get GCMs to hindcast that cool phase 'correctly'.

I'm not having much luck. What I'm looking for is any observational evidence that this is in fact what really happened.

May 20, 2011 at 10:34 AM | Unregistered CommenterBBD

To be clear - I've looked at Wild's 2009 review paper, and want to know if there are more or better aerosol measurement data available for the mid-century cool period.

May 20, 2011 at 10:41 AM | Unregistered CommenterBBD


From his own website

'Geoff sees the world in a crisis of transition. Old ways of living and organising no longer work. New ways are being created, but have yet to reach critical mass. Much better worlds await us, and the challenge is to minimise the pain before we gain.

The crisis is not just of industrial economies, but of how we live on the planet and how we organise ourselves into large societies. We need not just new ideas but new values, not just a second industrial revolution but a new kind of civilisation.

Not only are there people already demonstrating the practicalities of how industry can function according to the imperatives of the organic world, there are people who are reinventing small community and there are people who understand well where our destructive passions come from and how to manage and heal them. In the words of Stan Dale, we are learning how to replace ignorance and fear with awareness and love.

Some years ago Geoff conceived of merging his rational, scientific self with his emotional, loving, even spiritual self. Rationality and passion each are valuable, but each on its own can be taken to destructive extreme. On the other hand rationality and passion ought to be both more powerful and more humane together than they are apart. His book Economia is a personal expression of that quest, because it uses rational analysis and scientific creativity in the service of a loving heart.

The current crisis seems to require us, singly and collectively, to seek this kind of wholeness, merging our unprecedented fund of scientific knowledge with compassion, old wisdom and new insights into who we are, where we have come from and how we can live healthy and fulfilling lives'

He may be a distinguished geophysicist, but clearly his agenda is wider than just the pursuit of scientific truth. The general tone of his article seems to be a desperate attempt to shore up a crumbling AGW edifice against some severe bombardment...

May 20, 2011 at 10:46 AM | Unregistered CommenterLatimer Alder

From here, the idea of improperly understood aerosol effects mitigating warming seems like a classic ad hoc immunizing hypothesis. Not so dissimilar in fact to the idea we were discussing yesterday - viz. that tree ring proxy records should not be used after 1960 because of their loss of "temperature sensitivity".

May 20, 2011 at 10:48 AM | Unregistered CommenterNicholas Hallam

"the credibility of Hansen's "


May 20, 2011 at 10:51 AM | Unregistered CommenterPete H

Nicholas, exactly right, as Popper said about irrefutability of an argument by using auxiliary hypotheses. I agree with Hansen that about the need for a satellite to measure aerosols and settle this.

May 20, 2011 at 10:56 AM | Unregistered CommenterDavid Stockwell

To protect the AGW hypothesis Hansen is argueing that the models are fundamentally correct but the observational data is lacking, uncertain or plain wrong.

When you have looking for over 30 years for data to match predictions as Hansen has done and in the process built a career and a reputation around a single hypothesis there is no way, no way, you are going to admit that you have been wrong. There is far too much at stake for this current generation of climate scientists to say, "What if AGW is wrong?"

The only way for these climate scientists can protect this beautiful theory is to cast doubt on reality.

Why should aerosols, real or imagined, be blamed for the failings of the AGW hypothesis and its models.

May 20, 2011 at 11:01 AM | Unregistered CommenterMac

"Aerosols" is simply the deus ex machina that is invoked, ex post facto, to explain away any period in time that does not warm in accordance with CO2 models. It would be more impressive if they would have actually FORECAST the current flat spot, rather than just mix in a bit of aerosol magic after the event to make the numbers fit.

The obvious point that occurs to unbiased persons - maybe the CO2 model is wrong - is simply not up for discussion. After all, if you've staked your entire career on a particular thesis, the last thing you're going to do is say: "You know what, maybe that thesis is just wrong". So to those persons, it makes perfect sense to make your model work by assigning arbitrary adjustments and calling it "aerosols" AFTER THE EVENT. To anyone else, if you need to arbitrarily add or subtract numbers to make you model fit, you've got a bad model.

Imagine, for instance, Dr. Hansen was selling a Beat the Bookie horse racing system, or a red/black roulette wheel predictor. Every time you lose money, you're told that you needed to allow plus or minus this or that for length of the grass, or the temperature in the room, or whatever, and you would have got the correct result. Well, pretty soon, people would be calling a spade a spade and this person would be out of business or worse. But for some bizarre reason, climate science still seems to get a free pass. Too many people are still too eager to positively look for reasons why the model is still good. Like a bunch of wide-eyed gambling addicts.

May 20, 2011 at 11:01 AM | Unregistered CommenterAngusPangus

@ Nicholas Hallam,

I agree with you; chopping off tree ring data is the same "trick" a with aerosols. It makes perfect sense to anyone in thrall to the CO2 or temperature-proxy model. To anyone else, it looks like obvious cheating. Note that I don't accuse Hansen or Mann or anyone else of cheating. I've come to the view that they honestly and in good faith hold the views that they do. Simply, they are blinded by their faith in their CO2 model such that what looks to outsiders like obvious manipulation and "cheating" is, to them, genuine and bona fide efforts to refine and finesse their model.

May 20, 2011 at 11:11 AM | Unregistered CommenterAngusPangus

Well this piece of science concludes that the IPCC has overestimated direct cooling from aerosols.


The science:


IPCC 2007 estimate = -0.5 Wm-2, (-0.9 to -0.1 Wm-2.)

Myhre estimate = -0.3 Wm-2

I suspect that what Hansen is talking about is the indirect effect of aerosols, i.e. cloud formation.

It looks like Hansen has his head in the clouds.

May 20, 2011 at 11:22 AM | Unregistered CommenterMac

Any 'scientist' who dismisses serious comment by alluding to critics of his favoured fantasy being funded by Exxon-Mobil is obviously suffering from an aversion to reality and thus cancels any credibility he may have started out with. By his own statements, Davies is an extreme alarmist and is indulging in a deranged hissy-fit that Hansen, one of his idols, is being criticised.

May 20, 2011 at 11:27 AM | Unregistered CommenterAlexander K

Hmmm ... Davies says:

[Hansen] is trying to improve [...] the accuracy of climate models. All climate modellers know there are inaccuracies and poorly-constrained factors in the models.

Looks like the IPCC hasn't yet spread the word (as conveyed to Beddington at that March 2010 meeting we probably weren't supposed to know about):

[IPCC's Dr. Kristie Ebi, Executive Director, Working Group II Technical Support Unit] added that she was concerned by countries focussing on "improving" the models rather than the impacts of climate change.

"Improving" the models may well be passé ... so we (and Hansen, presumably) should just forget about all the "inaccuracies and poorly-constrained factors".

May 20, 2011 at 11:47 AM | Unregistered Commenterhro001

I'm sure many here have seen Bob Tisdale's analysis of the Hansen draft paper, but if you haven't - it's here.

Tisdale concentrates on OHC and the rate of energetic uptake. But note his remarks on the supposed 'Pinatubo rebound' at the end.

All in all Hansen fails to convince.

May 20, 2011 at 11:57 AM | Unregistered CommenterBBD

Well it would appear that you can discount aerosols having a larger indirect cooling effect than IPCC estimates. More problematic for Hansen is that it appears that this effect has been diminshing since the 1990s.

So we have evidence to support a lower direct effect and evidence to support a diminishing indirect effect of aerosol cooling.

I do think there is a black cloud forming over Hansen's head on this matter. He is running out of escuses.

May 20, 2011 at 12:06 PM | Unregistered CommenterMac

So apparently its (CAGW) all down to those pesky ice ages! Namely they cannot be fully explained by Milankovitch cycles!
- Little correlation between Ice volumes and the intensity of the Sun so we need to invoke a CO2 feeback mechanism to explain them. We can brush over issues such as "why did the positive feedback stop" or "does this not imply a very unstable climate - dominated by positive feedbacks" - which clearly it is not!
- We then spawn a multi-billion dollar "industry" to analysis the issue and to implement "preventive measure"

Guess they never read Gerard Roe's paper "In defense of Milankovitch" (GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L24703, doi:10.1029/2006GL027817, 2006)!

No point in spoling a good story with the facts ;-)

BTW - I appreciate the physics of C02 and the implications that our increased emmisions will cause the planet to warm. However, I have seen no evidence to suggest that this will be anything other than mild and that all the credible evidence suggests that a mild warming will be a net postive for humanity (considerably better than the opposite). However, since I do not believe in CAGW neither do I agree with the IPCC conclusion I must be a DENIER!

May 20, 2011 at 12:24 PM | Unregistered CommenterCurious from Cleethropes

Hansen claims reduced ocean heat transfer means that to balance high CO2-AGW based on imaginary 'back radiation', an artefact of Arthur Milne's mistake in 1922 [Miskolczi, 2006], you must double cooling by 'indirect aerosol forcing'.

But the latter is also a mistake: the incorrect 'two stream approximation' to the optical physics of aerosols assumes one optical process, biased diffuse scattering, so goes badly wrong by predicting pollution increases the albedo of thick as well as thin clouds.

You can easily prove this: as pilots and satellite jockeys know, clouds about to rain, larger droplets, have highest albedo and much is pseudo-reflection you can't explain by diffuse scattering.

Following the failure to prove ‘cloud albedo effect’ cooling experimentally, in 2004 NASA substituted a fake ‘surface reflection’ explanation for Twomey's correct physics he had he warned couldn’t explain the behaviour of thicker clouds:

In reality, the effect of aerosols reducing droplet size is to make clouds transmit more light by switching off direct backscattering you get from applying Mie analysis to the first few scattering events. That’s another AGW, GW when applied to palaeo-climate via bio-feedback.

Hansen appears to be twisting on the hook crafted when he and Lacis introduced Sagan’s incorrect optical physics to climate modelling in 1974 and made their careers by using imaginary 'cloud albedo effect' cooling it to offset equally imaginary 'high-feedback CO2-AGW'.

May 20, 2011 at 12:33 PM | Unregistered Commenteralistair

Hansen's excuse "its all the aerosols fault" can be discounted on the basis that;

1. The direct effect of aerosol cooling is lower than IPCC estimates.

2. The indirect effect of aerosol cooling has been diminishing since the 1990s.

3. Hansen's claimed "Pinatubo Delayed Effect" has been shown to have had little impact on oceanic heat content.

To me that is three and out.

May 20, 2011 at 12:41 PM | Unregistered CommenterMac

Rule one in climate science if the models and reality differ, the errors in reality.

May 20, 2011 at 1:04 PM | Unregistered CommenterKnR

Who needs aerosols when one can add a dephlogistication factor to the models?

May 20, 2011 at 2:30 PM | Unregistered CommenterJane Coles

David Stockwell @ 10:56 am

What I find ironic is that it is the real Flat Earthers who proceed in this way, protecting a favoured theory from refutation by adding unsubstantiated hypotheses ad hoc to immunize it - for example, they argued that a ship sailing over the horizon could be accounted for by changing our laws of optics rather than conceding the curvature of the earth. The truly scientific attitude, which is also the truly sceptical attitude, is the very antithesis of this.

May 20, 2011 at 5:33 PM | Unregistered CommenterNicholas Hallam

Mac @ 12:41pm

Excellent analysis. Thanks for the links.

Nicholas Hallam

The truly scientific attitude, which is also the truly sceptical attitude, is the very antithesis of this.


May 20, 2011 at 6:10 PM | Unregistered CommenterBBD

Basically Climate Science is Hogwah

May 20, 2011 at 6:56 PM | Unregistered CommenterCinBadTheSailor


Rule zero of climate science is "Everything is worse than we thought".

May 20, 2011 at 8:42 PM | Unregistered CommenterJack Hughes

Jack Hughes

This is a weird way of writing that some activities counteract the effects of other activities making the net result smaller.

Your text doesn't properly capture that "it's all about us."

Hansen's text shows quite clearly that he believes the "A" in AGW stands for anthropocentric and not anthropogenic.

May 21, 2011 at 12:41 AM | Unregistered CommenterJohn M

Hansen et al. (2011) also state that “the latent energy associated with increasing atmospheric water vapour [H2O] in a warmer atmosphere is an order of magnitude too small to provide an explanation for the high estimates of atmospheric heat gain” (like those in Dessler et al. 2008), and thereby confirms the findings of my own paper for ACE2011, that the direct anthropogenic contributions to [H2O] of currently over 300 GtH2O p.a. are much more significant than the claimed positive [H2O] feedback effects from the essentially trivial increase in global temperature since 1900 of about 0.007oC a year. That is why the Hansen and IPCC predictions of 3oC from doubling of [CO2] are failing.

May 21, 2011 at 2:07 AM | Unregistered CommenterTim Curtin

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Jun 18, 2011 at 11:19 AM | Unregistered Commenterheartbeats

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