Thursday, July 07, 2011

Global warming in logical form

I just found this draft paper. I hadn’t heard of Professor Bill Johns before, but his credentials seem respectable, and the paper is fascinating. It summarises the evidence and science behind each of the arguments that carbon dioxide is the main cause of the current global warming. In each case, it finds that the evidence is weaker than appears at first sight. The main arguments are as follows.

1. The Vostok argument. This is named from the Vostok ice core drilled by the Russians through Antarctic ice, and a subsequent study finding a strong correlation between the concentration of carbon dioxide and temperature over a period of 450,000 years. The data is available here. Johns notes that the correlation is striking but does not prove that increasing carbon dioxide causes increasing temperatures (medieval logicians called this the ‘fallacy of false cause’ - fallacia secundum non-causam ut causam). It is possible that the correlation simply results from the fact that when the global temperatures are low, carbon dioxide dissolves in the oceans and its concentration in the atmosphere is correspondingly reduced.

2. The exceptional rise argument. The argument is that the current rate of temperature rise is higher than any rise experienced on Earth for at least 10,000 years. This suggests that industrialisation is responsible for climate change. He concludes, using statistical analysis of earlier changes in temperature over long periods, that there may be something unusual in the current rate of global warming. “However, the statistics give only weak support to the hypothesis that there is something climatically unusual”.

3. The current correlation argument. The argument is that the current correlation between atmospheric carbon dioxide concentration and global warming is significant. Johns concludes that, from statistics alone, there is no reason to believe that the correlation between global warming and increased carbon dioxide concentrations is other than coincidence. “It follows that this coincidence cannot form part of the science supporting the Carbon Hypothesis”.

4. The simple science argument. Much of the support for the Carbon Hypothesis (as our commenter Belette noted) is that mathematical models of climate change predict temperatures rises with catastrophic results (i.e. 3 degrees C or more). Johns argues that mathematical models were originally designed for chemical or physical processes that are well understood, but the physics and chemistry of climate processes is not so well understood. “Modellers do not have a set of similar planets to test their models on, or to evolve their modelling tools”. His comments about the interaction between water vapour (which is the most significant greenhouse gas), and carbon dioxide, are interesting. In the presence of excess water vapour the absorptivity of carbon dioxide is strongly suppressed, and at sea level the contribution of carbon dioxide to infra-red absorption is negligible compared to the natural variability of water vapour concentration in the atmosphere. Thus the science is not so simple.

5. The consensus argument. The IPCC has a number of reliable climate models from which it concludes that there is a 90% probability that carbon dioxide is causing global warming. How can all of those scientists be wrong? Johns notes that few of these climate scientists are “main-stream scientists”, and that most come from a weather-forecasting (meteorology) background. They are not used to formulating and testing models like other scientists because they cannot go back to the laboratory to test the various elements of the model; they have to wait for the climatic conditions to arise that test the models. We should therefore read ‘scientific consensus on global warming’ as ‘meteorologists consensus on global warming’.

Please note that I am simply summarising his arguments. Note also that this is a logic blog. Arguments like ‘X doesn’t understand climate science’ or ‘Y is a global warming denier’ are logical fallacies. From a logical point of view, there are essentially only two replies to an argument of the form “p and p implies q, therefore q”. The first is that p does not imply q. The second is that p is not true.

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36 Comments:

Blogger Belette said...

You're wasting your time quoting septic nonsense (an no, it isn't a draft paper). Effectively you're trolling, so I'm off.

10:47 pm  
Blogger Edward Ockham said...

>>You're wasting your time quoting septic nonsense (an no, it isn't a draft paper). Effectively you're trolling, so I'm off.

A very logical argument.

7:21 am  
Blogger DocRichard said...

The essence of the climate "sceptic" position is that climate sensitivity (CS) is low - probably in the order of 0.5*C.

This is a testable hypothesis. The major body of evidence from several different approaches, converges around a value of 3*C +/- 1.5*C.

The task for your Professor, no matter how respectable his credentials, is to provide robust evidence for a 0.5*C value, and to successfully deconstruct all the other work.

Until the low value is substantiated, sceptics will remain ideological critics without a scientific platform to stand on.

11:40 am  
Blogger Edward Ockham said...

>>Until the low value is substantiated, sceptics will remain ideological critics without a scientific platform to stand on.

The question is where the burden of proof lies. I began with the complaint that incandescent bulbs were no longer being sold. Is it up to me to prove that catastrophic global warming won't happen, or is it up to the person who wants to prevent me using them, to justify this to me?

I did go to considerable trouble to work through the Wikipedia articles, but, as explained, they have logical gaps. I said where these gaps are in previous posts.

I will have a look at the other site you mentioned, Richard. I also read through a very lengthy work published by the IPCC. Again, it didn't explain the things I wanted to know.

1:09 pm  
Blogger DocRichard said...

We are having a dialogue on a matter of science. The matter revolves about climate sensitivity (CS). The body of science points to a figure of 3, which has a substantial body of evidence to back it up.

Implicit in the sceptics' position is a low value, ~0.5*C. It is refuted by the majority evidence, and propped up by a handful of rather slight papers.

I am pretty sure your great progenitor, William of Ockham, would have gone for the simplicity of the climate science position:

1 CO2 is a GHG (fact)
2 CO2 has increased to historic highs (fact)
3 We cannot explain recent high temps without including the GHG component.

The sceptics' position depends on 1001 special pleadings, generalisations, and a deep coyness to defend their low CS position.

Scientists are bogged down in a matter of supreme importance to humanity. It is for the philosophers to go to humanity's assistance, and help them to resolve the matter. If the sceptics position has no scientific standing (i.e. their low CS figure cannot be stood up) then the debate is over, and humanity must change its energy policies.

1:34 pm  
Blogger Edward Ockham said...

>>3 We cannot explain recent high temps without including the GHG component.

As Johns argues, if you read his argument carefully, it is fairly easy to explain the high temperatures in other ways. I am not necessarily agreeing with him, just saying that a sceptic would challenge this.

The variability could simply be explained by chance. Much temperature change is clearly a random walk, all random walks reach extremes at some point.

6:51 pm  
Blogger DocRichard said...

"Chance"?? No, sorry, absoluement pas. We are talking physics here, macro physics. At quantum level you can bring in chance, but at global physical level everything has a cause. So that door is closed.

Johns finds "something unusual" in the current rate of warming, and then questions its significance. Which is normal for any statistical approach.

To set the opinion of one engineer (and it is noteworthy how many climate sceptics are engineers), an amateur in the field, against the work of many scientists who have trawled and retrawled over the data in massive surveys...is like preferring a Sun editorial's opinion over the Tractatus Logico-Philosophicus.

However, that is of course an appeal to authority - relevant but not critical. The heart of the matter lies in whether Johns and the sceptics can present a robust case for low climate sensitivity.

So far I have not even found an attempt systematically to put forward that case. I hope that together, from either side of the watershed, we can persuade them to make the attempt.

10:22 am  
Blogger Edward Ockham said...

>>"Chance"?? No, sorry, absoluement pas. We are talking physics here, macro physics. At quantum level you can bring in chance, but at global physical level everything has a cause. So that door is closed.

I think you misunderstand my meaning of 'chance'. I mean, unascertained cause, which has the appearance of randomness.

1:29 pm  
Blogger Edward Ockham said...

>>However, that is of course an appeal to authority - relevant but not critical. The heart of the matter lies in whether Johns and the sceptics can present a robust case for low climate sensitivity.

Johns is not arguing for low climate sensitivity. If you read him carefully, he is saying that the case is far from proven. There is a difference between 'it has been proved that p' and 'it has not been proved that p'. Elementary logic.

1:31 pm  
Blogger DocRichard said...

"unascertained cause"

The aim of the scientist is to ascertain causes. Climate science has identified the many causative factors in our climate: solar variation, greenhouse effect, aerosols from volcnoes and industry, ocean curents, albedo, lapse rate, water vapour, internal heat from Earth's core... maybe even cosmic rays. And there are more to be discovered, maybe. These factors interact to produce a resultant average global temperature, which is a proxy for the total result on our climatic system. Basically, changes in the average temperature will produce changes in our weather patterns.

Unfortunately, the weather extremes we are seeing at present are consistent with observed global warming.

More later.

The

7:53 pm  
Blogger PeteB said...

If you want to come up with some objections to the consensus position then you need to understand what the consensus position is and then come up with specific objections.

This seems a reasonable simplified version of the consensus position.

http://www.realclimate.org/index.php/archives/2007/08/the-co2-problem-in-6-easy-steps/

Step 1: There is a natural greenhouse effect.
Step 2: Trace gases contribute to the natural greenhouse effect.
Step 3: The trace greenhouse gases have increased markedly due to human emissions
Step 4: Radiative forcing is a useful diagnostic and can easily be calculated
Step 5: Climate sensitivity is around 3ºC for a doubling of CO2 (Note you don't need Global Circulation Models you can do it form observations - for more details see
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-6.html - 'Observational Constraints on Climate Sensitivity'
)
Step 6: Radiative forcing x climate sensitivity is a significant number

8:52 am  
Blogger Edward Ockham said...

>>Step 1: There is a natural greenhouse effect.

As agreed in earlier posts.If there weren't, the Earth would be too cold to support life.

>>Step 2: Trace gases contribute to the natural greenhouse effect.

Agreed, but the question is how much.

>>Step 3: The trace greenhouse gases have increased markedly due to human emissions

Agreed, the question is whether this has contributed to any marked increase in climate. I.e. whether there has been a marked increase, and whether these are the cause.

>>Step 4: Radiative forcing is a useful diagnostic and can easily be calculated

Do not agree. The IPCC give a range of values for CS, this suggests there is an uncertainty about the exact value.

>>Step 5: Climate sensitivity is around 3ºC for a doubling of CO2

That is the mean value of proposed values, but there is a high standard deviation around that mean.

>>Step 6: Radiative forcing x climate sensitivity is a significant number

It depends on the climate sensitivity - see above.

10:48 am  
Blogger Edward Ockham said...

>>If you want to come up with some objections to the consensus position

The purpose of this series of posts is not to come up with objections to the 'consensus position' - if there is one. It is to understand

1. What the consensus positition is.

2. What is the evidence in support of the consensus position

3. What are the replies to the objections to the consensus position.

There have been a few warmists commenting on these posts. They have offered some definitions of the consensus position which are reasonably consistent. But they have not cited any of the evidence for the consensus position (except for 'scientists say that') and they haven't given any replies to some of the objections cited here.

This is a logic blog, as I keep saying. We try to avoid fallacies like 'scientists say that' which is a logical fallacy - a version of 'argument from authority'.

10:54 am  
Blogger PeteB said...

Edward,

OK I will try and avoid 'scientists say' !

"Radiative forcing is a useful diagnostic and can easily be calculated"

Radiative forcing is an externally imposed perturbation in the radiative energy budget of Earth’s climate system. This can be accurately calculated for greenhouse gases.

There are other forcings e.g.albedo (changes in the reflective power of the earth's surface), aerosols, solar variation, etc.

There is certainly a fair degree of uncertainty on CS, (due mostly to uncertainty due to positive and negative feedbacks)

These feedbacks apply to all forcings (not just greenhouse gases), the change in temperature is amplified for example by water vapour, as the air gets warmer, more water vapour can be absorbed and water vapour is itself a powerful greenhouse gas.

There are basically two approaches to calculating CS, one is a 'bottom up' approach, where you try to calculate each element of the feedbacks and how it impacts the climate (this is the approach used in GCMs ) e.g.

http://pielkeclimatesci.wordpress.com/2010/01/06/guest-post-by-andrew-dessler-on-the-water-vapor-feedback/

The other is a 'top down' observational based approach where you are not really interested in each feedback element but just are interested in the total change in temperature for a given forcing.

e.g. http://julesandjames.blogspot.com/2006/03/climate-sensitivity-is-3c.html

or the last ipcc report had a whole section on it

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-6.html

both methods come up with around 2 - 4.5 Deg C range for CS, with models giving a most likely value of 3 Deg C and observations a most likely range of between 2 and 3 Deg C

8:15 pm  
Blogger DocRichard said...

"There is a difference between 'it has been proved that p' and 'it has not been proved that p'. Elementary logic."

Indeed! And you as a philosopher know that science does not do proof. The best an hypothesis can do is "not-yet-disproven". (Popper)

8:46 pm  
Blogger DocRichard said...

Step 2: Trace gases contribute to the natural greenhouse effect.

EO: Agreed, but the question is how much.

Exactissimo! "How much" translates into Climate Sensitivity. That is why CS lkies the core of the debate.

8:48 pm  
Blogger DocRichard said...

Sorry! "lies at the core of the debate"

And please, no wordplay on lies. This is serious.

8:49 pm  
Blogger DocRichard said...

Step 4: Radiative forcing is a useful diagnostic and can easily be calculated

EO: Do not agree. The IPCC give a range of values for CS, this suggests there is an uncertainty about the exact value.

RL: You are confusing RF and CS. RF is the amount of extra heat retained by a given amount of greenhouse gas (or other input) GHG, and can be calculated precisely, as Paul says.

CS is the extent (in terms of av global temperature) to which cliamte will vary for doubling of CO2. It has been evaluated in a variety of ways, and there is a pretty remarkable convergence around 3*C, and very little sound work to support less than 1.5*C.

I have blogged on this: here

Lindzen and others have a few papers going for an insignificant value. They are a tiny eddy in the stream of evidence pointing to 3*C.

Please look at skeptical science, for instance here: http://www.skepticalscience.com/empirical-evidence-for-global-warming.htm

It is a bloody excellent site, a good place. Please do not expect us to set out in detail every q you may have here, when it is already up in Skeptical Science.

9:06 pm  
Blogger DocRichard said...

" I began with the complaint that incandescent bulbs were no longer being sold. Is it up to me to prove that catastrophic global warming won't happen, or is it up to the person who wants to prevent me using them, to justify this to me?"

RL: Morally, it is now very much up to the AGW sceptics either to establish beyond reasonable doubt their case for low CS, or to admit that their fundamental objection is not scientific, but ideological.

Because if they are wrong, they have delayed vital action that should be taken urgently. If even the 100th part of what is predicted comes about, that will lie heavy on the moral conscience of the sceptics. So be very very sure of the skeptic case ("CS is below 1.5*C) before you commit to it.

9:13 pm  
Blogger DocRichard said...

I think William of Ockham would have been attracted to the approach I am advocating: testing of the sceptics position.

The sceptics have thrown hundreds of questions at us. (In fact, they boil down to about 60), but they have a Hydra-like quality to them. This has been going on for 3 decades.

We have just one question to put to the sceptics: How do you justify your minority view of CS<1.5*C?

9:18 pm  
Blogger DocRichard said...

PS I listened to a lot of Mahalia Jackson when I were a lad.

9:24 pm  
Blogger Edward Ockham said...

>> Radiative forcing is an externally imposed perturbation in the radiative energy budget of Earth’s climate system. This can be accurately calculated for greenhouse gases.

Even if these calculations are accurate, they are only so on the assumption that the inputs are accurate. The two most important inputs, as I understand, are albedo and effective emissivity. Both these quantities change with temperature, and the amount they change is uncertain.

On whether they are accurate, in fact they involve certain simplifying assumptions whose basis is not clear. I will post some more about these later. See section 6.3.5 of the IPCC third report.

>> There is certainly a fair degree of uncertainty on CS, (due mostly to uncertainty due to positive and negative feedbacks)

Yes, see first point above.

>> Please look at skeptical science, for instance here:

I will look at this.

8:10 am  
Blogger Edward Ockham said...

>>RL: You are confusing RF and CS.

No, I meant CS. There are a range of estimates about the exact value of CS. The lower ones suggest we don’t have to worry too much about the effects increasing amount of CO2 in the atmosphere. The higher ones suggest we do.

8:27 am  
Blogger DocRichard said...

The estimates vary from 1.5 to 4.5. It is the higher end estimates that are really worrisome, and these are difficult to pin down. Even at the lower end, we need to take avoiding action.

It is the fringe estimates ~0.5*C that would not require radical avoiding action - although even if CS were 0*C, we still need to decarbonise, in order to blunt the economic impact of Peak Oil.

Again, your eminent predecessor would have liked the "solve 3 problems for the price of 1" aspect of decarbonisation - the third problem being unemployment.

9:15 am  
Blogger DocRichard said...

"The two most important inputs, as I understand, are albedo and effective emissivity. Both these quantities change with temperature, and the amount they change is uncertain".

Yes, there are many variables and much uncertainty in the system, which makes it all the more impressive and remarkable that so many studies, approaching the problem from several different angles, still centre on the 3*C figure.

I can assure you that in medicine, if we had a situation where all the work pointed to 3, and a handful of idiosyncratic papers, often using very simple models and/or unconventional terminology, pointed to 0.5, the profession would act on the 3 value, and consign the 0.5-ers to the "fringe" category.

9:22 am  
Blogger Edward Ockham said...

Please note there are two arguments that I concede completely.

The first is the “Cautionary Principle” – if there is a risk of something very bad happening, act appropriately. The thing about incandescent bulbs was a bit of a joke – I use a car very infrequently, and am very careful how I heat my home. The second is that scarce resources should be used with care, for the benefit of future generations (your ‘peak oil’ argument).

9:39 am  
Blogger Edward Ockham said...

>>in medicine, if we had a situation where all the work pointed to 3, and a handful of idiosyncratic papers, often using very simple models and/or unconventional terminology, pointed to 0.5, the profession would act on the 3 value, and consign the 0.5-ers to the "fringe" category.

Yes, but this is not medicine.

9:40 am  
Blogger DocRichard said...

It is in a way. Disease is a perturbation of the normally harmonious functions of a biological system. Climate science has found perturbations of the normal planetary energy transfer system.

The analogy goes further. In some conditions - classically, eating disorders and alcoholism - the patient is unwilling to accept the diagnosis because it demands a big change in life style. In these situations, physicians experience exactly the same wall of argumentation that the climate scientists are experiencing.

The difference is that in medicine, only the person and their family is involved in the patient's decisions. In climate science, the whole of humanity is involved. Hence the pressure for sceptics to produce some pretty damn good evidence to (a) support their low CS value, and (b) to refute the large body of evidence converging on the 3 figure.

9:58 am  
Blogger PeteB said...

Edward,

Rather than the 3rd IPCC report, I recommend the 4th IPCC report for the latest position

I thought this was a rather good explanation on uncertainity from Richard Betts - one of the lead authors of the next (fifth) IPCC report

http://www.bishop-hill.net/blog/2011/7/4/testing-two-degrees.html?currentPage=2#comments


... uncertainty works both ways - it may well not be as bad as is presented by some people, but equally it may be "worse than we thought" to coin a popular phrase on this blog. The hard bit is then what do the decision-makers do with this? If you can't rule out a low-probability, high-impact scenario, what do you do? Do you hedge your bets? How "unlikely" does a very severe scenario need to be for you to avoid it? Even if there's only a 10% chance of something life threatening happening, do you take the chance? Of course this has to be weighed up against the consequences of taking action to avoid it - and that's why I'm a scientist not a politician....!

So my answer to Martin Brumby is that all I can do is communicate my science to the decision makers in as open and honest way as possible, with all the uncertainties laid bare, and then hope they can weigh this up effectively against all the other uncertainties they need to consider. Personally I guess I subscribe to the precautionary principle to some extent, but that's my personal view and others may disagree, and I don't feel strongly enough either way to overstate the case in order to influence a biased decision by those who have to decide what to do.

3:12 pm  
Blogger Edward Ockham said...

>>Hence the pressure for sceptics to produce some pretty damn good evidence to (a) support their low CS value, and (b) to refute the large body of evidence converging on the 3 figure.

Medicine does not have Jeremy Clarkson to contend with. My 15 year old son, and all his generation, worship Clarkson.

The warmist lobby needs better PR.

6:26 pm  
Blogger DocRichard said...

Pete, again, the key point on decarbonisation is that it addresses not only global warming, but also Peak Oil. Among all the uncertainties, it is certain that oil will run out one day, and while it is in process of running out, we need to make a transition from capital (finite, fossil) energy to income (renewable) energy. Put that way, we can see that our generation has been using up capital as though it were income - an error EF Schumacher pointed out decades ago. Which just shows how irrational we humans can be.

Edward
Yes. We need better PR. We need better journalists too. If they did their job, informing people about their world in an easy to read way, instead of hacking inconsequential tittle tattle out of phone messages, it would be a better world.

7:11 pm  
Blogger DocRichard said...

The thing is, Edward, that science uses inductive reasoning primarily.

We make an observation, and induce an hypothesis to account for the observations. This is a pattern recognition process, and therefore uncertain. So then we use deductive logic - "the hypothesis predicts this, so let's run this experiment to see if the prediction is fulfilled. If it is not, the hypothesis is wrong, and needs replacing or modifying."

The sensitivity of 3*C hypothesis is very well attested. What is impressive is the convergence around the 3* figure from so many disparate approaches. If it were a medical problem, we would be definitely acting on this weight of evidence.

8:01 am  
Blogger PeteB said...

DocRichard,

I think it is important to separate the 'science' based questions from the policy based questions.

We should be able to come to consensus on the 'science' based questions, but I think it quite valid for different people to have different views on what we should do about it, depending on there attitude to risk, economics, politics.

For instance Tim Worstall, who is a member of the Adam Smith Institute, who accepts the 'consensus' view on the science of Global Warming, suggests that Pigovian taxation is the way forward e.g. here

http://timworstall.com/2010/08/27/so-what-does-james-hansen-suggest-we-do/

9:13 am  
Blogger DocRichard said...

Pete, I agree. There is absolutely no point in debating measures to counteract global warming with anyone who believes that CS is low.

Thanks for the link. I will take a look at it. Personally I just want action - all of it, carbon taxes, carbon trading, personal allowances, carbon sequestration through enhancing natural processes, the lot.

3:38 pm  
Blogger PeteB said...

I think it is a little more nuanced than that (although I agree we are probably doing too little / the wrong things)

We need to balance the damage we are causing / going to cause from global warming with the economic damage caused by reducing fossil fuel use (a cheap and plentiful supply of energy), which comes down to economics.

There are few economists that have attempted this (this is basically what the Stern report was, also there is William Nordhaus and Richard Tol)

5:56 am  
Blogger DocRichard said...

Hi Pete
I had difficulty with the Worstall link, but now that I've seen it, it is excellent. I had Worstall down as an irredeemable free marketeer. Ver interesting.

11:20 am  

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