Monday, December 23, 2013

Evaluating Controversial Claims

Someone makes a scientific claim, typically as an argument for some policy. Examples would be current claims with regard to global warming, claims fifty years ago about the consequences of population growth, claims early in the Obama administration about the need for large deficits to bring down unemployment. There are at least four different ways in which an interested observer can decide whether or not to believe the claim.

1. Partisanship. If you support the policy, believe the claim. If you don't, don't. This is probably the most common approach.

2. Evaluate the arguments for yourself. This is  the most entertaining and educational approach but no more reliable than the first—and likely to give the same answer. There is always controversy about the claim among people better equipped to evaluate it than the random observer, although one side or both may try to deny it. In the case of global warming, the relevant claim is not merely that temperatures are going up, or that the reason is human activity, or that they can be expected to go up by enough to cause serious net costs, but all of those plus the additional claim that there are ways of reducing the increase that are worth their cost. To evaluate all of that you need a reasonably expert knowledge of climatology, statistics, ecology, economics, and probably two or three other fields I have not thought of. Since you don't have all that, you end up believing whichever arguments you want to believe.

3. The argument from authority. You try to figure out what the consensus of the people who are experts is or what some authoritative source of information says. An outsider trying to figure out what professionals in a field believe is at risk of overvaluing whatever position has the most support from public sources of information, such as the mass media, or has done the best job of getting its supporters onto the committees of scientific organizations that put out public statements. And even if he could figure it out for one field, that isn't sufficient. Again taking the global warming case, it is not enough to know what the consensus of the climatologists is, even if you can separate the facts from the puffery on that subject. Climatologists are not economists, so  could be correct about the expected temperature increase and wrong about the magnitude or even the sign of its consequences. Economists are not ecologists, so might show the costs they are looking at to be insignificant while missing the effects of climate change on other species. I discussed problems with this approach at greater length in an earlier post.

4. Prediction. Once such a controversy has been going for a while, partisans have a track record. If they have made confident predictions that turned out to be wrong, that is good evidence that they are either dishonest or arguing from an incorrect theory. Figuring out whether the arguments for a theory are right or wrong is much harder than finding out what that theory predicted. Sometimes all the latter takes is  a book or article by its supporters written a few years back.

The clearest case is the population hysteria of the 1960's. Paul Ehrlich's Population Bomb, published in 1968, confidently predicted mass famine in the third world over the next decade, with hundreds of millions of people starving to death. Not only did it not happen, the real world moved in the opposite direction, with calorie consumption per capita in the third world going up, not down. That is very strong evidence that Ehrlich can not be trusted. It is somewhat weaker evidence that the movement of which he was part, whose members generally took him and his arguments seriously, can not be trusted.

Weaker examples apply to my other two cases. Early in Obama's first term, the Administration offered predictions of what the unemployment rate would be without a stimulus and how much lower it would be with the stimulus that the Administration wanted and got. Actual unemployment rates for the next several years were higher with the stimulus than predicted without it. That does not tell us whether the stimulus was a good policy. It is possible, as its supporters argued after the fact, that things were simply worse than they thought. But it is good evidence that predictions made by Administration economists can not be trusted, that either they were deliberately fudging the results or were using models much less reliable than they claimed.

For the case of global warming, we have the IPCC's repeated overpredictions of global temperatures, hurricane rates that are strikingly lower, not strikingly higher, this year than the average, and a number of other predictions to which the real world has failed to conform. Again, that does not show that the underlying argument is wrong. It does show that the people and models that have been generating the mistaken predictions cannot be trusted.

Which is about the most that the interested outside observer can hope to learn.

---

P.S. Not surprisingly, a lot of the comments on this post focus on the particular case of global warming rather than the general argument. One commenter provides a link to an article by Chris Landsea on the effect of global warming on the frequency and strength of hurricanes. One conclusion is that global warming by the end of the century might result in a slight increase in the strength of hurricanes and might also result in a substantial decrease in their frequency. 

Another is that the historical record provides no support for the claim that hurricanes have been becoming more frequent or stronger over the past century or so. The reasons that hurricane damage has trended up is that the total value of property in coastal counties has increased. The reason that the number of recorded hurricanes has trended up is probably the large improvement in our ability to detect hurricanes, in particular ones that fail to make land. For details see the article.

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39 Comments:

At 10:47 PM, December 23, 2013, Blogger Tim Lambert said...

For the case of Global warming, the IPCC reports are publicly available, so we can check what they actually say and find that what David says about them is not true. This doesn't mean that the IPCC is right, it does mean that David can't be trusted on topics he knows little about.

 
At 11:09 PM, December 23, 2013, Anonymous Anonymous said...

Tim: For the case of the debate about the debate about global warming, neither side has provided any links. This doesn't mean that either side is right, but it does mean that someone should post some links.

 
At 11:14 PM, December 23, 2013, Anonymous Anonymous said...

I came here to say that this is a great post on evaluating expertise. Additionally, as Socrates noted, how do we even evaluate who is an expert?

I noticed Tim's comment before posting. And while Tim's point is valid that Mr. Friedman's post doesn't cite evidence that climate change predictions are too warm, Tim, you also don't cite any counterevidence.

My limited understanding is that Mr. Friedman is correct on both points. The latest IPCC AR5 draft (admittedly not published yet) shows the models clearly too warm (and these are current models, I think Mr. Ridley has an analyis of previous models which are even worse) - search for "The real IPCC AR5 draft bombshell." And as far as Mr. Friedman's point about the experts overestimating extreme events, Dr. Pielke Jr also reviews the IPCC AR5 draft and shows how they are now backing down on their estimations of extreme events, in line with peer reviewed evidence.

However, I think it is a valid point that neither of you cited much.

 
At 2:58 AM, December 24, 2013, OpenID undertallen said...

5 - Follow the money...
The Climate industry spends $1 billion per day.
http://joannenova.com.au/2013/10/nearly-1-billion-a-day-to-change-the-climate-the-invisible-vested-elephant-in-the-room/

In 2009, Big Government had spent 3000 times as much as Big Oil on the climate industry:
http://joannenova.com.au/2009/11/skeptics-handbook-ii-global-bullies-want-your-money/

Joanne Nova was a science reporter. Her husband grumbled and said "there is nothing in the claims of AGW". Can't be true, she thought. But then she had the same reaction as I did. The arguments that are most prominent are false.

One of the things that made me look into it is the attempt to make the Medieval warm period disappear. Having tried to bury anti-tank mines during my military service in frozen ground, I can assure you that the Vikings on Greenland did not bury their loved ones in permafrost.
You find her short "Skeptics Handbook" I & II here:
http://joannenova.com.au/global-warming/

One other thing is that anyone using a "consensus" as an argument is not worth listening to. They might have science degrees, but they don't follow the scientific method.

Also this from Jo Nova where she compares the "consensus" on cholesterol with that on global warming:

http://joannenova.com.au/2013/10/catalyst-says-consensus-wrong-on-cholesterol-but-unquestionable-on-climate/

 
At 5:57 AM, December 24, 2013, Blogger Bear Nichols said...

„Wenn die Theorie nicht mit der Wirklichkeit übereinstimmt, umso schlimmer für die Wirklichkeit“. If the theory doesn't fit with reality, all the worse for reality.

 
At 7:08 AM, December 24, 2013, Blogger David Friedman said...

Bear: I'm fond of that quote from Hegel, as elegant in its arrogance.

Tim: If the point of my post was to defend my views on global warming, the criticism that I didn't provide links to the evidence would be valid. But that was offered as one example in a post about how to deal with claims, and the post was already a long one.

I also did not offer links to evidence about calorie consumption in the third world or actual and predicted unemployment rates, my other examples. In each case I think I provided enough information so that a curious reader could look up the data for himself.

I'm curious, however, about what part of my claim you think is false. Is it not true that the projections of global temperature in the first four IPCC reports, conditional on the increase in CO2 (which we now know), showed current global temperatures higher than they actually are? That current temperatures are not only below the mean of those projections but at or below the bottom of the 95% confidence range?

I did not, by the way, attribute claims about hurricanes to the IPCC. As best I can tell the current report does not make such claims, or at least not with any confidence. I think earlier ones did, and I am quite sure that other people in the more general movement did. As you probably remember, I had a fairly lengthy discussion of the question on this blog some years ago, in the context of Chris Landsea's resignation from the IPCC.

 
At 7:42 AM, December 24, 2013, Anonymous Max said...

In 45 years, all the hubbub over global warming/climate change will seem as ridiculous as the fear of catastrophic overpopulation does to us now. Then, as now, the memory of the masses will be so short that none will suffer reputational consequences for having misled the public for years and wasting trillions of taxpayer dollars. There will be a new crisis, and new "deniers," and a new industry whose primary purpose is to transfer resources from productive right-wingers to destructive leftists. Nothing ever changes.

The Cathedral is a cancer whose continued existence can result in nothing other than western civilization lying in ruins. If we don't end it, it will end us.

 
At 8:20 AM, December 24, 2013, Blogger jimbino said...

Just trust your Bible. If you can accept talking snakes and donkeys, ghosts, giants and unicorns, wine and wafer changing into body parts, you can accept anything on higher authority. No need to read and analyze articles. More than half your fellow Amerikans agree with you and you can all vote!

 
At 8:25 AM, December 24, 2013, Anonymous Max said...

Just trust the Cathedral. If you can accept AGW, KFM, and HNU, you can accept anything on higher authority. No need to read and analyze articles. More than half your fellow Amerikans agree with you and you can all vote!

 
At 9:10 AM, December 24, 2013, Anonymous Anonymous said...

The first thing you should do is separate your questions. The question of whether anthropogenic global warming is occuring and will continue to occur is a scientific one and has been answered in the affirmative beyond reasonable doubt. The policy questions about what to do about it are a whole other thing and about which I am quite willing to say "I don't know."

 
At 9:19 AM, December 24, 2013, Blogger David Friedman said...

Anonymous:

I agree that global warming is real and probably anthropogenic, although "beyond reasonable doubt" strikes me as a little strong. But that still leaves open the magnitude of the effect. As best I can tell, the size of the feedback used in the IPCC models is not well established and may well be too high, which might mean a temperature increase of one or two degrees C by the end of the century rather than three or four.

But my major criticism, made in past posts, is of the economics, not the climate science. I am not convinced that there are good reasons to believe net effects are negative, let alone negative and large enough to justify costly actions to slow warming.

 
At 10:30 AM, December 24, 2013, Anonymous RKN said...

But it is good evidence that predictions made by Administration economists can not be trusted, that either they were deliberately fudging the results or were using models much less reliable than they claimed.

It's worse than that -- it's hypocritical on its face to compare the result of an experiment ($800 billion stimulus) to the supposed result of an experiment that was never performed (no or much less stimulus), and to simultaneously claim your administration is on the right side of science.

 
At 1:05 PM, December 24, 2013, Blogger jimbino said...

Right David, but there's more:

Is global warming occurring? (climatology)

Is it anthropogenic? (science)

Does it have negative effects? (religion and politics)

If it has negative effects, should I be concerned? (religion)

Most importantly, who the hell determined that I should sacrifice oil consumption now in order to make the world safe for the breeders' kids, especially when the flora and fauna might rather see the kids disappear?

 
At 3:54 PM, December 24, 2013, Anonymous RKN said...

Speaking of controversial claims...

It's amusing, isn't it, that human beings were supposedly "as-if" designed for reproductive success, yet the fulfillment of this supposed innate drive may eventually lead to the species' undoing.

That's one reason I doubt the reproductive success story. I have an alternative story! Stay with me here.

See, I think the heterotrophs (>= 95% of all life) were "as-if" designed to metabolize and exhale carbon dioxide in service of the autotrophs, which of course respire carbon dioxide, and, under my hypothesis, predated the heterotrophs. I realize this is at odds with the consensus view (speculation really) that the autotrophs evolved after (as a food source for) the heterotrophs. I claim that's backwards! Autotrophs produce their own food! Heterotrophs can't. And since autotrophs require carbon dioxide for photosynthesis, then when carbon dioxide became scarce in the atmosphere the autotrophs "got together" and "as-if" designed a new branch of organisms that would produce a steady supply of carbon dioxide! Sexy, right?

 
At 7:21 PM, December 24, 2013, Blogger David Friedman said...

RKN:

There's nothing odd about behavior that leads to reproductive success for the individual leading to failure for the species--it's the biological equivalent of situations where individual rationality fails to produce group rationality, as with the underproduction of public goods.

It sounds as though you are confusing the evolutionary claim, which has to do with the individual, with the common misinterpretation, which has to do with the species.

 
At 9:08 PM, December 24, 2013, Anonymous Nat Filosof said...

Prediction is not always available, and understanding is possible if you have scientific competence, but it requires weeks of effort. Scientific claims are supposed to have proofs that are coherent to scientists. When you read a literature like global warming, it is easy to see that the scientific claims of skeptics are not addressed, and therefor that the arguments have holes you could drive a truck through, and therefor are not actual scientific arguments. On this basis, for example, I correctly predicted since the 90's the global warming situation, but moreover predicted the unemployment rate very precisely. When Rohmer and Bernstein published their white paper predicting the unemployment with and without stimulus, I realized they had a sign error on the Keynesian multiplier, which would really be -1.5 not the 1.5 they assumed with no justification, so to generate my prediction of the unemployment rate using their labor model, I reflected the "without stimulus" line across the with stimulus line.

 
At 9:14 PM, December 24, 2013, Anonymous Nat Filosof said...

I meant: reflected their with stimulus line through their without stimulus line to get my prediction of the unemployment with stimulus, which in fact turned out to be spot on.

Its plain from a lot of historical data, including Rohmer's own work, that the Keynesian multiplier (defined as change in GDP/change in gov't spending) is negative.

 
At 2:09 AM, December 25, 2013, Anonymous Anonymous said...

Tim Lambert (google) back again? He never returned after he had his ass kicked from here to Sunday over his dishonesty last time he showed up.

I wonder if his employer appreciates the fact that he he's going around the web accusing people of lying and dishonesty over the past decade?

Focus on your job and this time try and keep it, you clown Tim.

 
At 2:19 AM, December 25, 2013, Anonymous Anonymous said...

And where's Lambert's evidence of his counter claim? He offers nothing other than smarmy accusations.

Just remember, you're working in the private sector Lambert and that sort of attitude doesn't go very far. There's no parachute to Macquarie university if you get booted like last time.

It's clear the internet is not a place you ought to be frequenting for your mental health.

 
At 9:50 AM, December 25, 2013, Anonymous RKN said...

@David,

I didn't describe a situation where one individual wins and the group loses, but one where all or most individuals win (fulfill their "as-if" imperative) and the group, eventually, loses (overpopulation: pick your favorite doomsday consequence), then mocked that "as-if" metaphor by offering my own for evaluation.

Btw, with respect to evolution, I would submit that there is more than one claim depending on which level and kind of order one seeks to explain.

 
At 10:24 AM, December 25, 2013, Anonymous Anonymous said...

My version of 'The Scientific Smell Test.’

This test has several parts:

- Is there sufficient detail given so that the conclusions become obvious?

- Are the assertions plausible?

- Are key parts of the story missing?

- Do those parts of the presentation where I do have expertise match my understanding?

- Are the arguments so much arm waving?

- Are the arguments logically consistent?

- Is superposition and/or other properties of linear systems claimed for what is a significantly non-linear system?

- Is the claim made that: “Everybody knows or Everybody agrees?”

- Are their clear overreaches in the presentation?

- Willingness or lack thereof in sharing raw data and details of methodology.

- Willingness to address questions / ideas / explanations posed by others who do not hold your view.

- Are “Straw man” games being played? (Claiming that those you see as opponents have said things they haven’t and then demolishing those arguments.)

- Does what is being presented appear to be “Good science.” Good science does not have an agenda, political or otherwise. It lets the chips fall where they may.

- Really good science includes discussions of what you don’t know as well as what you do. It also gives facts which weaken its case.

This list is far from complete but I’m sure you are getting the idea.

This is not part of the scientific smell test but a smell test of its own: Follow the money.

As I continued to research this material I was somewhat surprised by the extent that the pro AGW material was not passing my smell tests and also to the extent the skeptics material was passing it.

One area that really smells to me is the claims made about the results of climate models. We have a name for instantaneous climate: its called weather. Weather prediction programs do not have a good track record at predicting more than a few days ahead. There are significant non-linearities and phase change phenomena (Two are extremely important and neither are well understood or well modeled: cloud formation and precipitation.) involved such that any claim that it would be possible to get the details wrong and the trends right is just not plausible. Yet climate models are routinely trotted out as proof of impending doom.

Mac

 
At 1:53 PM, December 25, 2013, Blogger David Friedman said...

"- Do those parts of the presentation where I do have expertise match my understanding?"

That's a good point, and a method I sometimes use in trying to evaluate a source of information.

 
At 6:00 PM, December 26, 2013, Anonymous Anonymous said...

Lol... I see Tim Lambert is here again. Last time he was around these here parts was when he was accusing David of the very things Lambert had done himself. As I recall, Lambert was beaten harder than a rattle snake in a suburban back yard.

 
At 6:31 PM, December 26, 2013, Blogger Tim Lambert said...

David, with regards to hurricanes, the IPCC and Landsea agree on the prediction that hurricanes will get more intense. You seem to think that they predicted that they would get more numerous. Even if they had made such a prediction, a single year with a low number of hurricanes would not falsify it.

In your post you referred to "the IPCC's repeated overpredictions of global temperatures". If they had been consistently wrong, then it would be a reason not to trust them. But they haven't been.

In your comment you seem to have changed your tune. Now you are making the much weaker statement that current temperatures are below what that predicted. While that is true, at other times temperatures have been above what they predicted. They never claimed they could predict every up and down, but rather the overall trend which they seem to have got right, and they have certainly done better than their critics who predicted that there would be no global warming.

You did miss one thing that they seem to have gotten consistently wrong -- the rate of Arctic sea ice melting. They predicted summer ice would disappear by the end of the century and it's melting much faster than that.

This suggests that they are too conservative and things are likely to be worse than what they predict.

 
At 9:22 PM, December 26, 2013, Anonymous Anonymous said...

Landsea resigned from the IPCC, Lambert you dishonest turd. He resigned because that New Zealand whacko was attempting to portray Nth. Atlantic Hurricane activity as more active than it really was.He resigned in protest. Now split hairs as much as you want (as is you normal modis) but that is what occurred.

How's life in the private sector going? :-) The fast lane. You think you can handle it?

 
At 9:28 PM, December 26, 2013, Anonymous Anonymous said...

David:

Some advice. Lambert Facebooks his employer, which is supposedly Google. If he calls you a liar again, as he did on an earlier occasion, which was the time he made an total hypocritical dickhead if himself, lodge a complaint and see what Google HR thinks of his trolling and teach the offensive git a lesson.

 
At 9:48 PM, December 26, 2013, Anonymous Anonymous said...

Chris Landsea's resignation letter from the IPCC.




Excerpt from the letter showing Lambert is lying again.

"Shortly after Dr. Trenberth requested that I draft the Atlantic hurricane section for the AR4's Observations chapter, Dr. Trenberth participated in a press conference organized by scientists at Harvard on the topic "Experts to warn global warming likely to continue spurring more outbreaks of intense hurricane activity" along with other media interviews on the topic. The result of this media interaction was widespread coverage that directly connected the very busy 2004 Atlantic hurricane season as being caused by anthropogenic greenhouse gas warming occurring today. Listening to and reading transcripts of this press conference and media interviews, it is apparent that Dr. Trenberth was being accurately quoted and summarized in such statements and was not being misrepresented in the media. These media sessions have potential to result in a widespread perception that global warming has made recent hurricane activity much more severe.

I found it a bit perplexing that the participants in the Harvard press conference had come to the conclusion that global warming was impacting hurricane activity today. To my knowledge, none of the participants in that press conference had performed any research on hurricane variability, nor were they reporting on any new work in the field. All previous and current research in the area of hurricane variability has shown no reliable, long-term trend up in the frequency or intensity of tropical cyclones, either in the Atlantic or any other basin. The IPCC assessments in 1995 and 2001 also concluded that there was no global warming signal found in the hurricane record.

Moreover, the evidence is quite strong and supported by the most recent credible studies that any impact in the future from global warming upon hurricane will likely be quite small. The latest results from the Geophysical Fluid Dynamics Laboratory (Knutson and Tuleya, Journal of Climate, 2004) suggest that by around 2080, hurricanes may have winds and rainfall about 5% more intense than today. It has been proposed that even this tiny change may be an exaggeration as to what may happen by the end of the 21st Century (Michaels, Knappenberger, and Landsea, Journal of Climate, 2005, submitted).

It is beyond me why my colleagues would utilize the media to push an unsupported agenda that recent hurricane activity has been due to global warming. Given Dr. Trenberth’s role as the IPCC’s Lead Author responsible for preparing the text on hurricanes, his public statements so far outside of current scientific understanding led me to concern that it would be very difficult for the IPCC process to proceed objectively with regards to the assessment on hurricane activity."

It's quite clear from his letter of resignation Landsea doesn't believe any such thing as Lambert dishonestly attributes to Landsea about intensity.



http://cstpr.colorado.edu/prometheus/archives/science_policy_general/000318chris_landsea_leaves.html

 
At 11:54 AM, December 27, 2013, Anonymous Alaska3636 said...

I don't know who Tim Lambert is, but Antartic sea ice has had a bull year.

http://joannenova.com.au/2013/10/antarctic-sea-ice-still-at-record-high-where-is-springtime-melt/

 
At 7:53 PM, December 27, 2013, Anonymous Anonymous said...

More of Chris Landsea's views.
eciamss not
All up, when forced to give an opinion on hurricane intensity, Landsea guesses that wind speed will increase by a whopping 1 to 2 miles and hour in 100 years or so.

Landsea also believes the jury is
still out on sensitivity.


"Landsea concludes the changes we can expect with significant warming are not major (the largest being a ~25% decrease in numbers of storms, offset by a ~3% increase in intensity – damagewise, I suspect that might be a wash)."


So this shows Lambert's attempt to deceive, something the turd has tried to do since he started blogging.

See more of Landsea's updated views here

http://wattsupwiththat.com/2011/12/02/hurricanes-and-global-warming-opinion-by-chris-landsea/

 
At 7:58 PM, December 27, 2013, Anonymous Anonymous said...

"I don't know who Tim Lambert is, but Antartic sea ice has had a bull year."


He's no startling intellect. Take a look his academic work record and draw you own conclusions.

 
At 11:03 AM, December 29, 2013, Anonymous Daublin said...

I agree that prediction is the gold standard. This is true among insiders as well as outsiders. For example, Einstein only really got credible after he started making predictions about astronomical phenomena.

I would add, as you have pointed out in previous posts, that it is also worth doing spot checks for honesty. If you find out someone has been grossly misleading you on one particular point, then you should distrust them on all the other points you don't spot check them on.

I am not sure it is hopeless to learn the source material, although for sure there is a problem with confirmation bias. At the very least, it is worth learning enough to be able to break down the larger claims into a collection of smaller ones, and to see how they all fit together.

 
At 11:04 AM, December 29, 2013, Anonymous Daublin said...

I agree that prediction is the gold standard. This is true among insiders as well as outsiders. For example, Einstein only really got credible after he started making predictions about astronomical phenomena.

I would add, as you have pointed out in previous posts, that it is also worth doing spot checks for honesty. If you find out someone has been grossly misleading you on one particular point, then you should distrust them on all the other points you don't spot check them on.

I am not sure it is hopeless to learn the source material, although for sure there is a problem with confirmation bias. At the very least, it is worth learning enough to be able to break down the larger claims into a collection of smaller ones, and to see how they all fit together.

 
At 1:19 PM, December 30, 2013, Anonymous Anonymous said...

"In your comment you seem to have changed your tune. Now you are making the much weaker statement that current temperatures are below what that predicted. While that is true, at other times temperatures have been above what they predicted. They never claimed they could predict every up and down, but rather the overall trend which they seem to have got right, and they have certainly done better than their critics who predicted that there would be no global warming."

What an incredibly ignorant comment.

So Tim Lambert is saying ; the models were wrong some times and right the next and that's okay.

The idiot is also saying that critics have been wrong too.

So this dunce is expecting the world to spend treasure changing the energy mix with the strength of these arguments.

 
At 8:00 PM, December 30, 2013, Anonymous Jim Henshaw said...

re this: "In the case of global warming, the relevant claim is not merely that temperatures are going up, or that the reason is human activity, or that they can be expected to go up by enough to cause serious net costs, but all of those plus the additional claim that there are ways of reducing the increase that are worth their cost. To evaluate all of that you need a reasonably expert knowledge of climatology, statistics, ecology, economics, and probably two or three other fields I have not thought of. Since you don't have all that, you end up believing whichever arguments you want to believe."

Not quite. Since the claim about global warming is based on ALL of the above claims being simultaneously correct, then you only have to have expert knowledge of one of those fields to rationally dismiss the theory if even one claim seems false.

To rationally support it, you would need to be an expert in a plethora of fields and not find any of those fields disproving the hypothesis. So virtually no one has the knowledge to rationally support it on this basis.

 
At 6:19 AM, December 31, 2013, Blogger David Friedman said...

Jim: You make a legitimate point, but I think somewhat overstate it, because the different parts of the question are not independent. I am skeptical of the claim that warming by 3 degrees C over a century would have serious negative effects. Convert that to 30 degrees over a decade, on the other hand, and my skepticism vanishes. So I have to know enough about both fields to bound the likely increase and estimate the effects of an increase of that size.

And, as I think I pointed out in a past post, the claim that the cause of warming is human activity isn't central to the argument, although it's relevant to how one might deal with the rise. If the rise is occurring for some other reason but is a very bad thing, it would be worth figuring out if there are things humans can do to stop or slow it.

 
At 8:43 AM, January 02, 2014, Blogger Abe Heward said...

There's this: http://www.skepticalscience.com/contary-to-contrarians-ipcc-temp-projections-accurate.html

 
At 1:04 PM, January 02, 2014, Anonymous Mac said...

Possibility Matrices for Global Warming

A number of people have suggested a simple 2 x 2 matrix.
X axis:
- a) Global warming is real and disastrous
- b) Global warming is not real.
Y axis:
- a) We do nothing
- b) We reduce CO2 emissions.
– At first Kyoto was deemed to solve problem. Later Cap and Trade. (Implication seems to be at only slight cost)

I will suggest that this matrix is very flawed. First it does not correctly cover the possibilities.

Second the idea that we can significantly reduce CO2 emissions by regulation at reasonable cost is a pipe dream.

A better matrix might be:

X axis:
- a) Global Warming is real and catastrophic
- b) Global Warming is real and annoying but not catastrophic.
- c) Global Warming is real but benign (no significant effects either way).
- d) Global Warming is real and beneficial.
- e) Global Warming is not real.
- f) Global Warming is not real but additional CO2 is beneficial.

Y Axis:
- a) Expand use of fossil fuels.
- b) Do nothing
- c) Do essentially nothing (Kyoto or Kyoto like programs).
- d) Massive Nuclear plant construction (including thorium long term).
-- Accept reprocessing waste.
- e) Attempt to reduce CO2 with wind and solar.
-- Economically expensive alternatives (lowers GDP)
-- Energy storage problem not solved.
-- Will take many decades to implement - if ever.
-- Accept bird kills, pollution problems, erratic power, etc.
- f) Impose limits on CO2 generation (high tax, caps, etc.)
-- Accept smaller GDP (higher unemployment, more poverty, etc.)
- g) Impose drastic limits on CO2 generation.
-- Accept economic collapse (mass starvation, riots, revolution).
- h) Utopia: a workable fusion power plant is developed and widely deployed.
-- Don’t hold your breath.


My take on the second matrix

X axis

Comment: We have no reason to believe that the climate of the early 20th. Century is optimum. Yes, it was a livable climate, but that is all we can say about it.

I suspect that the most likely outcome is f. AGW is not real but the additional CO2 has a significant fertilizing effect on food plants. Additional CO2 also causes plants to need less water.

We have the historical experience of the medieval warm period which was a very prosperous time in both Europe and China. Therefore, it would seem that if AGW is real that d. would be the most likely outcome.

Nonetheless being an engineer I am disciplined to look at the worst case and doing a worst case analysis we do need to consider a and b, however implausible they may seem. After all we are betting the planet.


Y axis:

Obviously if AGW is not real then from purely a climate viewpoint a or b is optimal.

There are obviously geo-political reasons to wish to reduce oil imports as well as pollution reasons to reduce fossil fuel consumption.


If AGW is real and is annoying then we need to make a trade off between economic damage caused by AGW and damage caused by our programs to ameliorate it. These trade offs will not be easy to make. The political process is ill equipt to make them. We will likely end up with the worst of both worlds (Significant GDP damage with lots of CO2).

We currently get about 80% of our energy from burning fossil fuels. Nuclear provides just under 10%. Solar and wind are way down there, 0.08% and 0.34% respectively (2007 numbers).

If we were to attempt to reduce our energy use by enough to make a significant dent in CO2 generation we would probably end up losing millions of people to starvation and/or freezing to death. So this will not happen, at least not intentionally.

The only option which will have any hope of success is d. massive nuclear power. It is, however, very likely that the political environment will close off this option. We do not seem to be pursuing option h.

We need to remember that China makes more CO2 than we do and they are adding a new coal fired power plant every week.

 
At 1:47 PM, January 02, 2014, Anonymous Mac said...

For those who remember grade school science: Green plants convert CO2 and water into glucose in a process called photosynthesis. The clucose is converted to everything else in the plant. It terns out that higher levels of CO2 cause plants to grow faster and be more robust (more able to resist disease and insect attack). There is a second benefit according to Freeman Dyson: The photosynthesis occurs within the pores of the leaves. Normally about 100 water molecules leave for every CO2 molecule entering. At higher CO2 concentrations the entrance closes down somewhat so that plant still gets more CO2 but loses less water.

It is likely that the extra plant growth caused by the extra CO2 prevented the mass starvation predicted for decades past.

 
At 8:08 AM, January 06, 2014, Blogger Andres Valencia said...

Excellent piece Dr. Friedman. Thanks for your clarity.

 

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