Wednesday, September 29, 2010

Aerosols or natural variability ?

A second paper authored by Thompson, Wallace, Kennedy and Jones, focused on quirks of the global temperature record in the 20th century has appeared in Nature. As the first paper, it carries the rather humdrum title, An abrupt drop in Northern Hemisphere sea surface temperature around 1970, but after reading it it seems to me that it contains quite explosive material.

After filling in our questionnaire, our dear sceptic readers in this blog should devote a certain amount of time in reading a few papers that have appeared recently - authored by very much respected mainstream climatologist - and  that in substance question the ability of climate models to reproduce the evolution of the observed hemispheric and global mean temperatures. The most recent of these papers aims to characterize a sudden change in the difference between the Northern and Southern Hemisphere annual mean temperatures. Common wisdom so far is inclined to think that the temperature difference between both Hemispheres in the 20th century was been mainly due to the larger thermal inertia of the Southern Hemisphere and the effect of the aerosol radiative forcing due to industrial atmospheric pollution, which is supposed to have been stronger in the Northern Hemisphere. The magnitude of this forcing is quite uncertain, as are the mechanism by which industrial aerosols may affect the radiative balance directly or indirectly by modulating the characteristics and life time of clouds. All in all, aerosol forcing may have almost completely offset the potential warming due to anthropogenic greenhouse gases or, alternatively, be almost negligible. The most recent estimations I am aware of tend to indicate that the cooling effect of aerosols may have been smaller that previously thought, and therefore the warming effect of CO2 on the 20th century temperatures would have been also smaller. But what the paper by Thompson et al now tell us is that a large portion of the cooling or lack of warming observed in the 1970's has been due to oceanic natural variability. They reach this tentative conclusion by looking at the patterns of temperature difference between the Northern Hemisphere and the Southern Hemisphere, and so they do not really investigate what are  those mechanisms of natural variability may be moreprecisely. Further analysis will be undoubtedly follow.

The same authors had published previously another paper that tried to explain an abrupt change in temperature observed around 1945. This time the ultimate reason for this sudden change seems to lie on the observing systems, and not on the temperatures themselves. During those years a major switch occurred in the proportion of US and UK ships reporting temperature data occurred. As each Navy applied different measurements methods, the varying proportion of the reports originating from one or the other could explain this rather abrupt change.

The lesson for climate modellers is that it becomes increasingly difficult to defend that climate models can reproduce the observed temperature evolution in the 20th century, even after adjustments to the data, as in the first paper, or after concluding that natural variations have played a more important role. If models can reproduce the 20th century temperatures, irrespective of whether they have been caused by external forcing and natural variability, I would conclude that the discriminative and predictive power of the models would not be as solid.

A third paper published in Geophysical Research Letters this year by some of the same authors, Fyfe, Gillet Thompson, and that has been, as far as I know, totally overlooked, deals precisely with the comparison of model and observed recent temperature trends. The ongoing debate about the skill of the models to replicate the observed temperature trend of the last 20 years is , as one can assume, quite lively. Even  more surprising is that this paper has not received much attention. The authors apply a statistical method to subtract the influence of known natural variations (ENSO, volcanism,..) in the global temperature record. They argue that the signal of the external forcing should be more apparent in the resulting temperature residuals than in the full temperature data. And, indeed, the uncertainties in the estimation of the 20th century temperature trends seem to be reduced more or less by half. Good news, one would be tempted to think. However, they also conclude that

We have also shown that the observed and simulated uncertainty in 1950–2000 trends drops by about half when the natural signals are removed, making clearer where the anthropogenic response in some models deviates significantly from observed. The simulated and observed global mean temperature trends are statistically indistinguishable in 12 of 24 models for the raw data, but in 8 of 24 models for the residual data

Using the residual temperature, only one third of the IPCC models are found to be compatible with observations. Perhaps the dawn of paper democracy will usher in the end of model democracy


Anonymous said...

" very much respected mainstream climatologist "? Phil Jones??
Is this article supposed to be satirical?

The second article you refer to, on the "previously overlooked discontinuity" was taken from a climate audit post "The Team and Pearl Harbor" posted a year previously.
See also the CA post "Nature Discovers Another Climate Audit Finding"
and the discussion at Nature News,

Anonymous said...

Dear Mr. Zorita,

This is kinda funny. I've just tried to find out if I really had become less sceptic during the last two years. Well, lets say during the last few months (since Klimazw(ei)bel (in English);-). I first wanted to check "Don't know" or something similar. I don't remember the exact possible answers.

But after all, believing in you, Mr. Von Storch, Mr. Pielke Sr and many other "honest brokers", and having read this last survey, I decided to check "less sceptic" (or sth. similar).

But then again I thought that still some (in my opinion) very crucial questions haven't really been answered.

And now, "Ironie des Schicksals", are you blogging this very sceptic meal (Futter für die Skeptiker).

You must be joking, Mr Feynman ;-)))

I never found this blog particularly funny. Some other german "scientific" bloggers think they are very very funny. They confuse being sarcastic or being extremely insulting with being funny.

Well, I find this blogpost very funny

Thank you



There is one very important question I would like to ask the real AGW-believers. I mean those people who are as laymenlike as myself and who are 100% convinced that a worldwide threat from human global warming is real. Why do they believe this, an why do they really think everybody who doesn't is an illiterate idiot?

What is the essential proof? And/or is it solely the fact that 2859,05 (climate) scientists do so? Or/and may it only be an pure expression of political liberty?

eduardo said...

Dear anonymous #1, dear Yelph #2

" very much respected mainstream climatologist "? Phil Jones??

no, it is not satirical. What I meant is that these 3 papers, which actually question some aspects of the observational records or its interpretation, are not authored by well-known sceptics, quite the contrary.
I wanted to illustrate that, contrary to what many sceptics may believe, climate scientist do keep checking and re-checking their findings. One thing is what one can read in texts aimed at the public opinion, where the political slant may be very obvious, and other thing is what scientific papers say, or even the IPCC report for that matter. Sometimes one only needs to dive a bit in the original publications.

I may perhaps disappoint you, but I do not think that, within the community of climatologist, the qualifications of Jones have been in anyway questioned. The disagreements may have risen about the way of presenting the scientific to the public or about the way of interacting with other scientist.

Yes, in these cases you can read Jones questioning the role of aerosol forcing. In other case, you find Fyfe, Gillet and Thompson questioning the skill of a large proportion of IPCC models. I think this is just healthy scepticism.

'And now, "Ironie des Schicksals", are you blogging this very sceptic meal (Futter für die Skeptiker)'

I think the classification sceptics-warmist is not very .useful. I would rather say that the dividing line lies between people that think of themselves as being always right and people who always would consider the likelihood of being wrong. These papers are examples of,say, mean stream IPCC-climatologist expressing doubts about previous findings, and in these sense I found them very interesting.

Jonathan said...

It is indeed heartening to see "mainstream" climatologists finally accepting the blindingly obvious fact that the historic temperature record already rules out most of the IPCC ensemble of models, leaving only the bottom end still plausible. We lukewarmers have known this for years, not for political reasons but simply because bloggers like Lucia Liljegren have been convincingly demonstrating this fact for some considerable time.

Better late than never. But it's still rather odd that it took you so long.

itisi69 said...

Dr.Zorita; "...climate scientist do keep checking and re-checking their findings"

The "re-inventing peer review" quote and other emails of the very same Dr.Jones and his peers is quite in the contrary of your above statement.

Personally it's hard to believe that this kind of publications would be possible in pre-Climategate times without the authors being crucified, banned for life from the climatology society and living in exile at the outskirts of the scientific world.

FYI: From The Man Behind the Climate Models:

"Washington stresses that today's climate models are reliable. They have been subjected to so many tests and trials over such a long period of time that scientists have a high level of confidence in their ability to project how the climate is likely to change when it is subjected to a range of highly specific scenarios. One such test, says Washington, is the so-called twentieth-century reconstruction. Researchers start the computer model with data from 1850 and run it to the present. Only when the model is accurate enough to reproduce the actual climate features of the twentieth century will scientists use it to estimate possible future climate change."

ingno said...


From the man behind climate models: Today's models are reliable becaus of the twentieth-century reconstruction.

That man should know that a successful recontruction of the past gives NO reliability for the future. A failed reconstruction of the past gives even less ... ;-)

Anonymous said...

It is very strange that those who place so much confidence in models are so ignorant of basic principles of modelling.

Anybody who has undertaken financial modelling, say of a development project, understands that what happens if you undertake Monte Carlo simulation (using for example the excellent program @risk). If you select, say, 10 of the most important input variables, and apply uncertainty ranges to those, then run the model, what one often finds is the kurtosis of the output is very flat. That is, there is a more or less equal probability of any outcome. Put another way, the first standard deviation of the result is very wide if expressed as a percentage of the median value.

In the case of financial models, results depend critically on three major issues. The volatility of the revenue stream, volatility of costs, and the margins. For some projects where revenues are more or less constant, costs are stable, and margins good delivery highly reliable model outcomes. However, these are very much the exception.

Climate is so much more complex, with many more variables, and much greater uncertainty on the inputs. Applying @risk to a climate model would, I am sure, demonstrate that the models are worthless.

It amazes me therefore that supposedly well educated people place any faith in models at all.

eduardo said...

#7, Dear Anonymous,

this has been and is being done with some climate models as well. One important difference between a climate model and an economic model is - as far as I can judge- that to run a climate model is much more expensive. For instance, to run a single 100-year simulation can take about one week on one of the best supercomputers. To run an ensemble of simulations by randomly varying ten parameters and choosing say 50 values for each of those parameters would need a huge amount of computing time.

The way this is done today is by distributing a somewhat simplified model over many private home PCs that have volunteered to run the model in the background. Details can be found here, a somewhat deeper explanation here. Results have been published five years ago here (unfortunately, subscription required).

Short of varying the model parameters randomly, one can consider the ensemble of IPCC models, and take this ensemble as a random sample of the parameter uncertainty. There is much debate about how to interpret this model ensemble. It is however known to all of us that all models simulate warming for the 21th century, albeit the range is large even when the models are driven by the same emission scenario.

eduardo said...

dear itsi,

well, the oldest of these papers was published in 2008 and I may remind you that one of the authors was Phil Jones.

Although I do understand what you mean, I would ask you to try to adopt a different perspective for a moment. Climate science is not an homogeneous block of dummies or fanatics. These are a few examples of the fact that within climate science, models and the standard sets of observations (CRU,GISS, etc ) are not necessarily deemed perfect.

Anonymous said...


Why should those people all be dummies or fanatics? This is the other side of climate science I don't like. Some people really think Phil Jones is some kind of criminal.

But from a neutral point of view (Standpunkt), those very famous scienstists known from the CRU-mails have not really been honest. How would you feel as a lay man when you ask questions on those blogs and those people never really speak out the truth (relatad to those questions). First you think that there is some kind of misunderstanding. Then you feel like Jim Carrey in the Trueman show. But in the end you feel deceived and start to mistrust those people.

Now that we (lay men) know that todays science is not what Feynman or Popper wanted it to be. Now that we know that especially climate science seems to be "influenced by external politics in the last 10 years" and that it is not a "value-neutral science", we wonder what we shall think about all this.

For instance in the doping discussions these last years in cycling sports, we ask ourselves if there is one single athlet who is not part of this whole system of doping betrayal.

Phil Jones has done a good job and I think it is not fair what happened to him. But is he not part of a whole system? Is it really absurd to think this way if even the climate scientists ask the same questions?

Not every athlet is a fanatic or part of a worldwide conspiracy. But is everybody who has some doubts about sports and doping a dummie or a fanatic?

It was not me who won races in an unfair way or who presented climate "facts" in a special way. But just wanting to speak about my doubts has made me a very bad or dangerous person for some people. I have been banned from blogs etc...

I would never say Alberto Contador is a criminal or a dummie, because I don't think he is.

Everybody must decide for himself what he wants to be, but in the case that you have really doped or lied or something similar, you must not be surprised when the dummies out there call you a liar or a fanatic etc...

Being honest today seems to be a very hard burden?


Anonymous said...

And "one word" about this aerosol thing. This was one of the first questions an honest scientist had to ask himself. What caused the cooling at the beginning of the Co2-explosion?

These are questions that have never really been answered on "Forums" and blogs. We were told many kind of things, but none of them said that it could be a "natural cycle".

A similar question can be asked now. Why is the warming rate now so small?

Some years ago many "climate scientists" (I don't know if they really were) told me that there is no natural cooling in the climate cycle. ... because I asked if the actual warming (1998 etc..) could not have a natural component and that an equal cooling could eventually occur later ...

Today they tell us, and this time we know that they are really climate scientists", that the actual "cooling" is a natural cycle.

Things have NEVER been admitted until the moment they could no more be denied.

Like Mojib Latif said: ... We must answer the questions before the others try to do so ...

This seems not to be a very open an honest kind of science.

That's also why I found this blogpost "funny".

(Das ist nicht negativ gemeint gegen Sie Herr Zorita, sondern im Sinne ie hier erklärt. Ironisch, dass ich oben schreibe, dass ich jetzt eigentlich mehr Vertrauen in die Klimawissenschaft weil einige wenige "honest broker" wahrscheinlich die Wahrheit sagen ... ;-) Ich habe einen grossen Respekt vor allen Klimawissenschaftlern.)


rcs said...

The ability of various models to predict the change in 20th century temperature depends on the calibration of the model.

Given that there has been an increasing CO2 concentration throughout the 20th centurey and a variable temperature rise, a first order calibration is possible.

The problem is the assignment of physical processes to that calibration. We know that simple absorption of radiation by CO2 (Beer-Lambert) is insufficient to account for the rise, so a feedback multiplier is hypothesised to account for difference in temperature. That's fine, but the whole basis of the scientific method is prediction from that hypothesis. What apperas to be happening is that the predictions of various calibrated models do not have good predictive power and therefore they should be rethought or abandoned. This is pretty basic science.

Frankly, I'm not surprised that they don't predict temperature changes as many of the important climatological and oceanographic features that are now known to exist have not been incorporated in them. One has to conclude that the simplistic idea of feedback in the models does not seem to exist and that other mechanisms for the increase in temperature should be sought.

rcs said...

PS. The concept of Monte-Carlo methods to evaluate model sensitivity fills me with horror. Perturbation methods to establish parameter sensitivity would seem more practical

Anonymous said...

RCS. "The concept of Monte-Carlo methods to evaluate model sensitivity fills me with horror."

What are you saying?? Do you understand what Monte Carlo simulation is? Do you know the "@risk" methodology? What exactly about Monte Carlo simulation "fills you with horror"?

I can tell you that what fills me with horror is that climate scientists develop all of these models WITHOUT doing Monte Carlo simulation. By definition, they have no idea at all about just how reliable (more accurately how unreliable) their models really are.

ghost said...

nice post... other good reviews are in the Andy Revkin blog (with a lot of opinions of different researchers) and in the Guardian. Both are very nice posts, in particular Andy Revkins (

Nice to see that Prof Jones is back. Interesting that nobody have seen this drop before.

Is it inevitable that with possibly lower aerosol influence the CO2 influence is also lower? Could it mean, the sensivity to forcings is possibly lower or how is this reasoned?

eduardo said...

@ 10
Dear Yelph

'But is he not part of a whole system? '

I doubt that such 'system' really exist. The community is very large and varied and the 'lay' persons have been mostly exposed to only particular personalities within this community. Even the aspects of these personalties that have been made public do not reflect the whole story.

I havent seen any outright conspiracy. One proof are these papers, as I have tried to explain. One problem is of all the papers that are published, the blogosphere filters through just a tiny portion. I would again recommend to take time and read the IPCC report WG1. We would be sometime surprised about all caveats and nuances there

eduardo said...

@ 11

dear Yelph,

I think you should not think that climate scientist as a whole have a single view. Some aspects are shared by a majority and others are not shared by many. For example 'Some years ago many "climate scientists" (I don't know if they really
were) told me that there is no natural cooling in the climate
cycle. ... ' was probably an opinion of one or a few climate scientist. Others may have given you another opinion that happened not to be reflected in the blogosphere at that time. Now you can read more diversified opinion on some issues, although the bulk of the widespread agreement (or the 'consensus' if you prefer) has not changed much. What it did happen is that some years ago some assertions were presented as part of this consensus when they weren't.

eduardo said...

@ 15

Dear ghost,

if GHG had been the only factor governing the temperature increase in the past 50 years, it would be easier to estimate the climate sensitivity: something related to the observed temperature increase divided by the observed increase in forcing - not considering the thermal inertia for the moment. However if other forcing have been active as weel, for instance aerosols, the temperature rise has to be 'distributed' among all forcings. If one of these forcings is uncertain, as in the case of aerosols, the estimation of the sensitivity is trickier.

If the cooling effect of aerosols has been strong, they have abated the real effect of GHG, and the sensitivity to GHG would then be large: it has just been offset by the aerosols. On the contrary, if the effect of aerosols has been small, all of the temperature rise can be ascribed to GHG, and the sensitivity to GHG would then be smaller

PolyisTCOandbanned said...

McI has not published a science paper since 2005 (GRL). He has a history of writing little snippets on his blog (self publishing) that are not even really formed thoughts (thus not falsifiable) and that he defends as "lab not scratchings", but yet still wants to claim he has created some opus of real criticism that indicts climate science. And then you have Watts and such who are way worse. (And whom McI makes common cause with and refuses to call out, when in error.)

The followers of McI like to say he is not publishing because of peer review censorship, but when challenged to show unpublished white paper quality writings, there is NOTHING.

I've seen good work in science, engineering, corporate life, military, etc. The stuff from CA is shoddy. To his credit, interesting possible questions are raised. But that is IT. He refuses to make common sense estimates of impact or sensitivity and basically plays a game of hide and seek in terms of trying to say bad things about his oppononents without being called on it. I find this actually physically disgusting. It is just intellectually low order cowardice.

The "hoi polloi" hanging on his words and his 5 year tease, need to have their heads examined. They are as bad as the Wikipedia crew thinking that eventually a good product will emerge somehow, when all they are doing is really a social phenomenon and the game of playing that they are doing something when they are not.

Strange Weather (El Nino) pretty much accurately analyzed McI and the skeptic crew in terms of social phenomenon.

I trust you and Burger and Huybers and Curry and such to try to find truth, to publish stuff whichever "side" it helps. Oh...and that guy from Wisconsin who critizes the models. I don't trust McI to publish his insights honestly. He will be selective and will also play games to avoid clear accusations and falsification (while still trying for a PR impact).

I also liked that computer guy from London who found the Met service math mistake in uncertainty bounds. He's the kind of guy who finds out stuff whichever way it goes.

Not really impressed with Lucia or Moshpit either. They have been very late to the party and very chummy with Watts and the like and reluctant to really challenge their own assumptions. If you browbeat the hell out of them, you can eventually get them to see a flaw. But when you raise it at the time, they tend to refuse to consider it.

I'm so sick of the skeptic crew.
If they have anything, they can publish clear papers with clear analysis and labeled graphs and all that. It's not that hard! It's a normal form of discussion!