Science of Climate Change [Archive]

Matt

21st July 2008, 03:44 PM

Personally I think that man heas very little to do with climate change on the whole, and that the whole issue has become more of a religion than anything else.

I feel that this planet, of not the entire solar system, is just going through another of it's phases, and we happen to be around to witness this one.

As to evidence, the IPCC, for example, was set up explicitly to look for evidence that climate change is man-made...and guess what. they found it! That in itself should make one approach their reports very carefully...

Well lets separate the facts from the speculation.

The spectrum of the Sun is known, we even measure it from outside the atmosphere to make sure.
The spectrum of the Earth warmed by the sun and re-emitting it's heat is known.
The thermal properties of CO2 are known.
Therefore we know that CO2 in today's climate acts as a greenhouse gas.

Clearly CO2 levels play a role in affecting our temperature, but how much?

Our models tell us that if it were not for this greenhouse effect our average global temperture would be roughly 20 degree celcius lower then it is today. It is only fair that these models recieve scrutiny. There are assumptions to be questioned, there may be unknowns which have not been factored in. Those who offer such scrutiny fall into two camps, constructive and destructive. There are those who would question the models in use with a view to making better models. There are those who simply wish to tear down current models.

One of the unknowns is the way to greenhosue gasses play a part in a shifting dynamic equilibrium.

Increased CO2 levels lead to higher temperatures - fact. However it's also true that increased temperatures lead to higher CO2 levels.

We do know that we've been releasing vast amounts of CO2 into the atmosphere over the past century and at the same time destroying natural carbon sinks through changing land use.

We do know that atmospheric CO2 levels have increased dramaticly over the past century reaching levels that haven't been seen since at elast the time of the first homosapiens.

We do know that there has been a warming trend in the average global temperatures over the last century.

Whislt it seems quite obvious that our impact is what has caused the raise in CO2 levels and the the raise in CO2 cannot fail to have a warming effect, it is suprisingly difficult to prove exactly how much this each effects are linked.

It may be argued that unknown effects step in to ensure that our release of CO2 into the atmosphere and destruction of natural carbon sinks have a minimal (or only temporary) effect on atmospheric levels of CO2

It may be argued that the earth is warming (1) due to increased solar output and (2) due to unknown mechanisms at play in our complex and chaotic cliamte system.

It may be argued that it is the warming of the earth that has lead to an equilibrium shift increasing CO2 levels rather than an increase in CO2 levels leading to an equilibrium shift wich leads to warming.

Of course this lead to two different models which can be used to predict climate. These models can be fed historical data and we can see how well they perform.

As it turns out, models which ignore the possibility of human contributions to CO2 levels don't do so well. Over that last 30 years they think there should have been less than half the warming that we've actually seen. Factor in the greenhosue effect and we see where the other half of the warming comes from.

Another indicator is the nature of the warming. If all the warming were due to the sun's increased output then we'd expect all layers of the atmosphere to be warmed. If the atmosphere is trapping heat at the surface then the upper layers should be cooling. We see the upper layers cooling.

The IPCC wasn't set up to look for evidence that climate change is man made. Clearly the claimatre has been changing for millions of years. Man may have an impact on that change. The question for the IPCC was twofold. How much of the current change is man made? What are the implications for the future?

In answer to the first question we have an answer qualified by a degree of certainty. The concensus view is that they're 90% certain that at least 50% of recent warming is man made.

The second question allows for much greater latitude in speculation. If you want to be be skeptical about climate change then it is that area you should focus on. By arguing up the role of the sun and unknowns you're simply denying the best efforts at analysing empirical evidence.

Cuddles

21st July 2008, 03:58 PM

There can be little doubt that climate change is occurring

You might be surprised about that. Many deniers don't just question the cause and possible consequences, they also claim that there is not actually anything happening at all, or that there are regular cycles.

but the debate surrounds the cause. Is it being caused by human activity, is it some "natural" process or a combination of the two?

It's both. There always has been and always will be natural variation in the climate. The main question now is how much we can affect the climate compared to the natural changes. What seems likely is that we don't actually have that much effect by ourselves, but that even a small change can drive positive feedbacks which then cause much bigger changes. For example, water is a very potent greenhouse gas. If we increase the average temperature by a small amount, more water will evaporate, which will cause a much bigger change, and so on. However, more water vapour also means more clouds, which tend to reflect more sunlight and lower temperatures, so it's rather complicated to know what will actually happen.

Assuming it is human activity, is there anything we can do or is it too late?

Well, this is one area where no-one is really sure, and it depends a lot on what you mean by "do". Can we actually stop climate change? Probably not. We've already burned a huge amount of fossil fuels, and there's essentially no chance of stopping their use until they're all used up, so assuming that really does contribute to global warming, we're not going to stop it. If global warming is all natural with human contribution at all, things are even worse, since that would mean even with all our industry we don't affect things at all, and therefore certainly wouldn't be able to stop changes.

However, what we can do is be ready. Climate change has happened in the past on a much bigger scale, and life happily goes on without even many extinctions. It depends very much on what actually changes, but we may need to do as little as building better flood defenses and preparing for worse weather. On the other hand, we may need to move lots of people and move agriculture to more appropriate places. Either way, it's nothing we aren't capable of doing, we just need to first work out what is actually likely to happen and then have the political will to actually deal with it.

Human activity or not, should we be doing more to cope with the inevitable?

Probably. The main problem is human nature. Most people just don't want things to change, and won't radically change their behaviour without something big to force them to. Then there are the people who refuse to accept things that conflict with their ideology, and others who don't care what happens in the future and just want to make money now.

What is the evidence for climate change being linked to human activity?

One of the biggest pieces of evidence is that it's essentially impossible for us not to. CO2 absorbs certain wavelengths and not others. The wavelengths emitted by a relatively cool body, like the Earth, are absorbed while those from a hot body, like the Sun, can pass, which means that more CO2 in the atmosphere will trap more heat. This is pretty basic physics that has been known for well over a century.

Other than that, in general what we have are a lot of correlations. Atmospheric CO2 has increased since the industrial revolution, and various measures related to global temperatures have increased in more or less the same pattern. However, since climate is a very messy system with plenty of other factors, the correlations can be hard to find, or will be obvious some of the time but masked at other times, which is where the deniers jump in and decide that that means nothing is happening at all.

This whole area, I am a little ashamed to say, I know little about in terms of the scientific evidence. I have a feeling however, I am going to get educated.

If you look up the IPCC reports on Wikipedia you can find pretty good analyses of them in more understandable terms, along with links to the actual reports themselves. The IPCC is generally the best source to use since they are interested solely in the science without any political agenda.

What I would like to see is completely unbiased analysis by scientists without agendas, if such a thing is possible.

Which is exactly what the IPCC, and various other scientific institutes, do. Deniers like to pretend it's all political, and there is certainly plenty of political bollocks from both sides, but the actual science is done by scientists without agendas, it's only after they've made the reports that the politics starts up.

wagdog

21st July 2008, 06:51 PM

I feel that this planet, of not the entire solar system, is just going through another of it's phases, and we happen to be around to witness this one. All science can be explained away as one big coincidence. Solid masses just move around in completely random and totally unpredictable ways, but by amazing coincidence we happen to be around to witness when they move according to Newtons Laws of Motion.

As to evidence, the IPCC, for example, was set up explicitly to look for evidence that climate change is man-made...and guess what. they found it!Since you acknowledge that they found evidence that climate change is man-made, why do you still think it is "more of a religion than anything else"?

That in itself should make one approach their reports very carefully...Not sure I understand this logic. Are you suggesting that one should be sceptical toward any scientific theory that was validated using evidence found via experiments set up specifically to look for such evidence? That would include almost all of science.

wagdog

21st July 2008, 07:14 PM

I remember back in the seventies being warned (on Tomorrow's World I think it was) that we were heading for another Ice Age.

This is a common misconception and that the deniers of man-made global warming like pointing out. When one checks the scientific journals of that decade, there were only a handful of papers speculating on a future iceage and very few, if any, claimed one was imminent. (I'd include URLs with the details, but I haven't made 15 posts yet. For now I'd recommend googling "myth ice age site:realclimate.org")

It just goes to show that the mainstream media did as poor a job covering scientific issues in the 1970s as they are doing today.

What I would like to see is completely unbiased analysis by scientists without agendas, if such a thing is possible.All scientists have agendas. The agenda of a good scientist is to publish research that reveals something truthful about the physical world that is backed up with solid evidence. As far as I can see, the IPCC has done exactly that.

wagdog

21st July 2008, 07:35 PM

Would you rather take the word of journalists, politicians and spokespeople for oil companies? These are the only groups I see who oppose the climate scientist's conclusions.

I may have a more reliable group classification for those in the anti-climate science camp.

Libertarians who believe in laissez-faire capitalism tend to believe global warming is a hoax. Proponents of this economic model (Austrian School and Chicago School of economics) believe that all costs can be internalised, but environmental causes tend not to fit within this framework -- the best they can do is to view regional pollution as a violation of private property rights. Climate change with all its indirect global effects wouldn't work at all, so they either deny it, or apply the Bjorn Lomborg strategy of claiming that high discount rates make any future climate-related damage seem very cheap in today's money.

Have a look at Naomi Oreskes's work ("You can argue with the facts") - she explains more about this connection between climate denialism and libertarian think tanks.

Graham Lappin

21st July 2008, 08:34 PM

My natural inclination on global warming is to see some quantitative data. As Matt says "Clearly CO2 levels play a role in affecting our temperature, but how much?" I have searched but been unable to find data (modelling or otherwise) that actually matches the increase in atmospheric greenhouse gas with the increase in global temperatures. Moreover, the planet has gone through cyclical temperature change over millions of years, long before man was on the planet.

Cuddels says "... in general what we have are a lot of correlations. Atmospheric CO2 has increased since the industrial revolution, and various measures related to global temperatures have increased in more or less the same pattern. However, since climate is a very messy system with plenty of other factors, the correlations can be hard to find, or will be obvious some of the time but masked at other times"

I have not been able to find data showing that correlation, even given the messy nature of the weather system. But this is part of the point - it is so complex it is very difficult to be certain. I am not a denier but at the same time I am not entirely convinced. I just don't know.

I do think however that if global warming is man-made, then it is unlikely we will really do anything about it. Action needs to be by populations but the individuals will act on what's best for them. Overall therefore, I am more pessimistic on the outcome that I am skeptical of the cause.

wagdog

22nd July 2008, 01:01 AM

I have searched but been unable to find data (modelling or otherwise) that actually matches the increase in atmospheric greenhouse gas with the increase in global temperatures.

It depends on your criteria for what constitutes a match. There are many variables that affect temperature so it is unlikely you can point to a graph plotting CO2 levels and global temperature to reveal a straight line. There are also delays in the climate system. The warming we're experiencing today is caused in part due to CO2 released decades ago. The oceans play are part in this delay since they warm up slower than does land.

Moreover, the planet has gone through cyclical temperature change over millions of years, long before man was on the planet.This is not a very good argument against anthropogenic climate change. I'm sure there were lots of murders of children in the centuries before Myra Hindley was born -- does this prove she is innocent?

Alternatively, what if there were absolutely no evidence of temperature swings in any century prior to the 20th. Does this make the climate scientists' job easier? Of course not, because they would have far less data with which to build theories on.

it is so complex it is very difficult to be certain.This is why climate scientists do not simply look for correlations and conclude immediately when they find them (or fail to). They build models based on known physics and past observations, make predictions using these models, and then test those predictions -- just like in all other scientific disciplines. NASA scientist James Hansen did exactly that way back in 1988, and the temperature record since then has served well to validate his model. He actually ran 3 scenarios since he could not be expected to accurately predict how much CO2 humans would actually emit over the following two decades -- that would require predicting the boom bust cycles of the economy, the fall of communism which crashed Soviet CO2 output, etc. But what was clear was the very significant effect on temperature that varying the CO2 output had in his model. This was not an effect he explicitly programmed in; it emerged from the basic physics in the simulation. For details see:

Hansen, J., I. Fung, A. Lacis, D. Rind, Lebedeff, R. Ruedy, G. Russell, and P. Stone, 1988: Global climate changes as forecast by Goddard Institute for Space Studies three-dimensional model. J. Geophys. Res., 93, 9341-9364, doi:10.1029/88JD00231.

One can validate his predictions against the instrumental record at GISS Surface Temperature Analysis, or Google for "Hansen’s 1988 projections"

The question now arises is why do denialists single out climate models, but give a pass to equally complex physical models that make safety predictions concerning structural engineering of buildings, commercial planes, cars, electronics, etc.

Graham Lappin

22nd July 2008, 06:47 AM

Thanks for the information and I think you make some good points. However I do think that your point about cyclical changes has some faulty logic:

This is not a very good argument against anthropogenic climate change. I'm sure there were lots of murders of children in the centuries before Myra Hindley was born -- does this prove she is innocent?

I am trying to play "spot the logic fallacy" but I am pushed for time and so I will have to back to you on that. The changes in temperature over the years shows that the planet has a propensity for getting hotter or cooler in the absence of man and therefore those data have to be taken into consideration. Looking for such trends and fitting these into a model is conducted in science all the time.

Thanks for the references, I will try to have a look.

Cuddles

22nd July 2008, 10:22 AM

I have not been able to find data showing that correlation, even given the messy nature of the weather system. But this is part of the point - it is so complex it is very difficult to be certain. I am not a denier but at the same time I am not entirely convinced. I just don't know.

Did you try looking here (http://en.wikipedia.org/wiki/IPCC_Fourth_Assessment_Report) and here (http://www.ipcc.ch/) like I recommended?

I do think however that if global warming is man-made, then it is unlikely we will really do anything about it. Action needs to be by populations but the individuals will act on what's best for them. Overall therefore, I am more pessimistic on the outcome that I am skeptical of the cause.

Sadly, this is pretty much how I see it as well.

Graham Lappin

22nd July 2008, 12:31 PM

Did you try looking here (http://en.wikipedia.org/wiki/IPCC_Fourth_Assessment_Report) and here (http://www.ipcc.ch/) like I recommended?

Sorry - obviously not yet but I will. Posting at work and replying first thing in the morning, it's difficult to keep up.

wagdog

22nd July 2008, 12:53 PM

The changes in temperature over the years shows that the planet has a propensity for getting hotter or cooler in the absence of man and therefore those data have to be taken into consideration.

The probability that a human will eventually die is 1. The reason defence lawyers do not make a point of it when defending a client accused of murder, is because it can be assumed the jury already knows this on day one. All that this means is that the burden of proof is on the prosecution to show a murder had taken place and that the accused is responsible. Imagine that in response to the prosecutors presenting a boat load of evidence that the accused was guilty of murder, the defence made a big deal about the millions who have died long before the accused was born. What would the jury think of this line of argument?

Even children know that there were ice ages (there are cute animated movies about it) and that they ended long before man came on the scene. Pointing out this known fact as a response to the evidence of the IPCC is a silly argument at best, and at worst an insult to the intelligence of the climate science community.

Graham Lappin

22nd July 2008, 01:27 PM

Even children know that there were ice ages (there are cute animated movies about it) and that they ended long before man came on the scene. Pointing out this known fact as a response to the evidence of the IPCC is a silly argument at best, and at worst an insult to the intelligence of the climate science community.

I am no expert in the this area and so perhaps I am just having trouble grasping it. I am however a scientist (biochemist) and so I am very used to critical assessment of data. Like so many that come to these boards, I want to learn more but I am having real problems following your logic.

You seem to be saying that the fact that there have been big swings in temperature in the past is irrelevant to the current changes in climate. If that is what you are saying, then I do not follow this, I am afraid. I am not saying for one moment that past changes in climate must explain the present situation - this would getting cause and effect very confused. However previous climate change does show that changes can occur naturally and so this has to be taken into consideration before you can conclude the current change is man made.

Perhaps I have misunderstood your arguments but comparing climate change with child murders is confusing me. let's stick to the science and then I might become better educated in this area.

wagdog

22nd July 2008, 02:18 PM

You seem to be saying that the fact that there have been big swings in temperature in the past is irrelevant to the current changes in climate.

No I am not. The climate scientists are already aware of this, just as a jury is already aware that people can die of natural causes. Why bother bringing it up in the defence?

However previous climate change does show that changes can occur naturally and so this has to be taken into consideration before you can conclude the current change is man made.And it already has been taken into consideration, and yet denialists tend to bring it up anyway (e.g. Martin Durkin's C4 polemic made a big deal about medieval vineyards).

Perhaps I have misunderstood your arguments but comparing climate change with child murders is confusing me. let's stick to the science and then I might become better educated in this area.I'm merely using the same analogy that climate modeller Gavin Schmidt used in his "Cold Case vs. CSI" posting on the RealClimate blog. It is one of several articles I'd recommend for those who want to dissect climate change denialism.

How about this biological analogy? Suppose someone who is in denial about AIDS being caused by the sexually transmitted HIV virus, were to point out that people have been dying from pneumonia (an AIDS-related opportunistic infection) centuries before the HIV virus was identified. Is this evidence that AIDS researchers might be pursuing the wrong track in their search for an HIV vaccine?

Graham Lappin

22nd July 2008, 03:32 PM

Perhaps we just got off on the wrong foot. I think perhaps we are not so far apart now I am beginning to grasp the argument. I hope it's clear that I am not denying anything, I am just being honest and saying I don't know. It is often OK not to know!

No I am not. The climate scientists are already aware of this, just as a jury is already aware that people can die of natural causes. Why bother bringing it up in the defence?

I was not asking the question in defense rather than trying to understand it.

And it already has been taken into consideration, and yet denialists tend to bring it up anyway (e.g. Martin Durkin's C4 polemic made a big deal about medieval vineyards).

I'm merely using the same analogy that climate modeller Gavin Schmidt used in his "Cold Case vs. CSI" posting on the RealClimate blog. It is one of several articles I'd recommend for those who want to dissect climate change denialism.

This may be true for those in the know but I am not in the know. I will track the blog down and have a look.

How about this biological analogy? Suppose someone who is in denial about AIDS being caused by the sexually transmitted HIV virus, were to point out that people have been dying from pneumonia (an AIDS-related opportunistic infection) centuries before the HIV virus was identified. Is this evidence that AIDS researchers might be pursuing the wrong track in their search for an HIV vaccine?

Sorry, still think the logic is convoluted. Perhaps I know too much about HIV and not not enough about climate change. Let's leave the analogies alone and it will work a lot better I think.

wagdog

23rd July 2008, 11:20 AM

Let's leave the analogies alone and it will work a lot better I think.

We can reduce this to basic logic. There is a puzzle that most people easily get wrong, which involves four cards. On one side of each card is either the letter H or N. On the other side is either the number 3 or the number 0(zero).

You are presented with four cards on a table, some with the letter side face up, and others with the number side face up:

H N 3 0

You are given the task to confirm or disprove this rule: "Every card with an H on one side must have a 3 on the other"
Which cards must you flip over and which can you leave alone?

The H is an obvious choice - if there's 3 on the other side, then you've proven the rule holds for this card.

Most people make the mistake of picking card 3. Does the letter on the other side actually matter? Revealing a letter N doesn't disprove the rule.

People should turn over the card showing the 0(zero) to check if there is an H on the other side, which would disprove the rule.

Now I specifically chose those symbols on purpose: (H)umans, (N)atural cycles, (3) degree increase, (0)zero degree increase

So when Durkin and other denialists spend so much time highlighting the fact that it's been warm in the past before humans discovered oil it is like flipping the card with the 3 on it. I am not saying that past warming events are irrelevant. Paleoclimatological research is invaluable for validation of climate models. However, simplistic interpretations of warming events before humans as evidence that the current warming event is a natural cycle is erroneous logic.

There is one point in the Durkin polemic that he does the equivalent of flipping over the zero card. He interprets the slight cooling between 1950-1970 as evidence that burning fossil fuels are not heating up the planet. However the climate scientists already have an answer for this - sulphate aerosols which reflect sunlight back into space (i.e. global dimming). These were output in huge quantities as the industrialised economies grew, but environmental regulations forced a clean up of this pollutant after 1970.

Pebble

25th July 2008, 08:16 PM

You are presented with four cards on a table, some with the letter side face up, and others with the number side face up:

H N 3 0

You are given the task to confirm or disprove this rule: "Every card with an H on one side must have a 3 on the other"
.

If I read this problem correctly, it is not stated that each H or N have a consistent number on the other side, thus the number 3 could be randomly associated with a H or an N, in which case, turning over the 0 adds no information.

Acleron

26th July 2008, 01:39 AM

I may have a more reliable group classification for those in the anti-climate science camp.

But reading your subsequent writings, I conclude you haven't

Libertarians who believe in laissez-faire capitalism tend to believe global warming is a hoax.

Do you have any evidence for this statement?

Proponents of this economic model (Austrian School and Chicago School of economics) believe that all costs can be internalised, but environmental causes tend not to fit within this framework -- the best they can do is to view regional pollution as a violation of private property rights.
Could you define some of the terms you have used here?
Internalised
private property rights

Climate change with all its indirect global effects wouldn't work at all, so they either deny it,
Sorry had to break that mid-sentence but what is indirect about global effects?

or apply the Bjorn Lomborg strategy of claiming that high discount rates make any future climate-related damage seem very cheap in today's money. Is this the normal and simplistic message that inflation makes every thing cheap or is it something more intellectual?

Have a look at Naomi Oreskes's work ("You can argue with the facts") - she explains more about this connection between climate denialism and libertarian think tanks.

I may do if you can make any sense of the above. ;)

wagdog

26th July 2008, 06:13 PM

Do you have any evidence for this statement?

It is based on Naomi Oreskes research ("A History of Denialism") and the stuff that I've noticed appearing on libertarian blogs regarding environmental issues.

Could you define some of the terms you have used here?
Internalised
private property rightsI'm referencing the terms used by republican presidential candidate Ron Paul who questions global warming (See Ron Paul's environmental platform on the Gristmill website). He is very libertarian in his politics. He believes environmental issues are best solved by ensuring that all the costs of any decision can be quantified and immediately reflected in the pricing of any choice at the time consumers are making their decision. Strengthening private property laws means that people have to pay if their pollution ends up in someone else's property. This extra cost is then passed onto whatever products they are producing that caused the pollution. Consumers then choose products according to a price that includes the cost of polluting the environment.

Sorry had to break that mid-sentence but what is indirect about global effects?Indirect effects are difficult to internalise using the private property framework above. Melting ice caps in polar regions may cause flood damage near coastlines all over the world. Warming oceans may intensify storms way out in the Atlantic and Pacific but end up damaging land-based properties. China and India's increasing CO2 output may indirectly lead to droughts on another continent. Or the reverse - increasing saturation of the atmosphere leads for more precipitation and more flooding. We don't even have to bring in climate change. Extra CO2 causes plant leaves stomata to close, lowering transpiration rates, and thus leads to more flooding. CO2 acidification may collapse the food chain in the oceans and rob fishermen of a livelihood.

That said, the city of Kivalina in Alaska is suing power companies on this very same indirect pollution mechanism. Power companies burn fossil fuels, CO2 causes warming, and this delays or prevents formation of sea ice, and thus Kivalina is more exposed to sea storms that lower property values through erosion.

Is this the normal and simplistic message that inflation makes every thing cheap or is it something more intellectual?The "Bjorn Lomborg Errors" website (See the "Copenhagen Consensus") explains this best. With a high enough discount rate, the value of losing the Neatherlands to the sea in 2100 can be more than compensated by investing a small amount of money in a growth industry today. The Stern Report uses lower discount rates which free market capitalists tend to criticise.

wagdog

26th July 2008, 06:17 PM

If I read this problem correctly, it is not stated that each H or N have a consistent number on the other side, thus the number 3 could be randomly associated with a H or an N, in which case, turning over the 0 adds no information.

But what if you found a card with H on one side and a 0 on the other? This would be a counter example to the rule: "Every card with an H on one side must have a 3 on the other."

VoodooJoe

26th July 2008, 10:01 PM

Personally i would give credence to the idea human CO2 emmissions are increasing the earths temperature.

Venus is somewhere near twice the distance away from the sun as what mercury is, yet venus is somewhere near twice as hot as mercury, this is because its atmoshpere is composed nearly entirely of CO2.

Pretty simple equation, pump more CO2 in the atmosphere the hotter things get.

Acleron

27th July 2008, 02:42 AM

It is based on Naomi Oreskes research ("A History of Denialism") and the stuff that I've noticed appearing on libertarian blogs regarding environmental issues.

So somebody else has said it, but you still have no evidence.

I'm referencing the terms used by republican presidential candidate Ron Paul who questions global warming (See Ron Paul's environmental platform on the Gristmill website). He is very libertarian in his politics. He believes environmental issues are best solved by ensuring that all the costs of any decision can be quantified and immediately reflected in the pricing of any choice at the time consumers are making their decision. Strengthening private property laws means that people have to pay if their pollution ends up in someone else's property. This extra cost is then passed onto whatever products they are producing that caused the pollution. Consumers then choose products according to a price that includes the cost of polluting the environment.
I'm in general agreement with the sentiments expressed here but cannot see a definition of 'internalise' or 'private property rights', this leads to further problems in the next section.

Indirect effects are difficult to internalise using the private property framework above. Melting ice caps in polar regions may cause flood damage near coastlines all over the world. Warming oceans may intensify storms way out in the Atlantic and Pacific but end up damaging land-based properties. China and India's increasing CO2 output may indirectly lead to droughts on another continent. Or the reverse - increasing saturation of the atmosphere leads for more precipitation and more flooding. We don't even have to bring in climate change. Extra CO2 causes plant leaves stomata to close, lowering transpiration rates, and thus leads to more flooding. CO2 acidification may collapse the food chain in the oceans and rob fishermen of a livelihood.

Why don't you just cut out the the silly parts like 'Indirect effects are difficult to internalise', they don't make sense and detract from your argument.

That said, the city of Kivalina in Alaska is suing power companies on this very same indirect pollution mechanism. Power companies burn fossil fuels, CO2 causes warming, and this delays or prevents formation of sea ice, and thus Kivalina is more exposed to sea storms that lower property values through erosion.

Now you are making sense and please don't say that all that internalisation and property rights nonsense was saying the same thing, it wasn't. There is nothing indirect about pollution unless you claim that anything at one remove from Quantum Electrodynamics is indirect.

The "Bjorn Lomborg Errors" website (See the "Copenhagen Consensus") explains this best. With a high enough discount rate, the value of losing the Neatherlands to the sea in 2100 can be more than compensated by investing a small amount of money in a growth industry today. The Stern Report uses lower discount rates which free market capitalists tend to criticise.

If this is the market-speak that marketeers employ:-
1) no wonder we are in such difficulties today.
2) getting rid of them would seem a great advantage.

Which benefit environment would best suit investment in the Netherlands today?

Pebble

27th July 2008, 09:41 PM

But what if you found a card with H on one side and a 0 on the other? This would be a counter example to the rule: "Every card with an H on one side must have a 3 on the other."

The point being that if there is no consistent relationship, then on the other side of zero might be H or N, if it is H the counter is true, but if N who knows, if one turned the 3 then finding an N proves the counter, but if a H who knows, in this respect one learns as little by looking at the 0 as the 3.

wagdog

28th July 2008, 10:29 AM

if one turned the 3 then finding an N proves the counter

No it doesn't. Showing that there is a card with N and 3 is not a counter example. If it did then you'd have to turn over the N card as well. This is assuming a false dichotomy - that if one can show that N implies 3, that must mean that H does not imply 3.

To see the flaw in this logic one need only apply this puzzle to a real life problem: Suppose a pub owner has to ensure that every customer who is drinking alcohol is aged 18 or over. He has the following four customers:

1. A person drinking an alcoholic beverage
2. A person drinking a non-alcoholic beverage
3. A 21 year old drinking an unknown beverage
4. A 16 year old drinking an unknown beverage

The pub owner can safely ignore 2 and 3. He needs to pay closer attention to 1 (find out the customer's age) and 4 (find out what the customer is drinking). Only then will the pub owner know whether or not he is in compliance.

Logically this is identical to the four card problem:
H = alcohol
N = non-alcohol
3 = 18 and over
0 = under 18

Cuddles

28th July 2008, 10:37 AM

The point being that if there is no consistent relationship, then on the other side of zero might be H or N, if it is H the counter is true, but if N who knows, if one turned the 3 then finding an N proves the counter, but if a H who knows, in this respect one learns as little by looking at the 0 as the 3.

You've added an extra rule there. The only rule you are trying to disprove is "Every card with an H on one side must have a 3 on the other.". You're also assuming the reverse, that every card with a 3 must have an H on the other side. Without that extra rule, turning a 3 over tells you nothing, since you know you can either find an N or an H on the other side.

There is only one way to disprove the rule - find an H with a 0 on the other side. This can be done either by turning the 0 and finding and H, or by turning the H and finding a 0. In the context of global warming, it's not possible for us to turn the H over, so that leaves only the one choice.

Tony Williams

2nd August 2008, 09:44 AM

Sorry to come into this one late, but I'm a newcomer.

I'm not a climate scientist but have been observing the debate with interest for years. There's a good, quick summary of the arguments on the New Scientist Environment website under the heading "Climate Change: A Guide for the Perplexed". This is the introduction:

Our planet's climate is anything but simple. All kinds of factors influence it, from massive events on the Sun to the growth of microscopic creatures in the oceans, and there are subtle interactions between many of these factors.
Yet despite all the complexities, a firm and ever-growing body of evidence points to a clear picture: the world is warming, this warming is due to human activity increasing levels of greenhouse gases in the atmosphere, and if emissions continue unabated the warming will too, with increasingly serious consequences.
Yes, there are still big uncertainties in some predictions, but these swing both ways. For example, the response of clouds could slow the warming or speed it up.
With so much at stake, it is right that climate science is subjected to the most intense scrutiny. What does not help is for the real issues to be muddied by discredited arguments or wild theories.
So for those who are not sure what to believe, here is our round-up of the 26 most common climate myths and misconceptions.
There is also a guide to assessing the evidence. In the articles we've included lots of links to primary research and major reports for those who want to follow through to the original sources.

Pebble

2nd August 2008, 09:01 PM

No it doesn't. Showing that there is a card with N and 3 is not a counter example. If it did then you'd have to turn over the N card as well. This is assuming a false dichotomy - that if one can show that N implies 3, that must mean that H does not imply 3.

You are right on that. However, I remain puzzled. If you turn over H, and find 3, all is well so far. If you turn over 0 and find H then you have disproven the rule. So here what one has done is to target the 16 year old and checked what they are drinking. If however you find an N this proves nothing. So here you have a 50% chance of disproving the rule, and no chance of proving it. The same goes for turning over the H (50% chance of finding 0). So the only cards not to turn over are the 3 and the N. Is that what you are trying to get at?

Still don't get what this has to do with climate change. Being a relative novice in environmental things, I would propose that man has deforested most of the globe, has released carbon stored for millions of years and released countless tons of pollution into the atmosphere. So it seems fairly clear that we are altering the balance of nature. It is reasonable to conclude that this activity is going to affect weather systems, even if we do not yet fully understand exactly how.
So given that the balance of evidence shoes that global warming is occurring presently faster than at any time in the past that we are capable of documenting, it seems reasonable to deduce that man is contributing substantially. As seen with pollution in the UK in the last century, reversing such effects takes a very long time, so applying the precautionary principle does not appear unreasonable.

wagdog

4th August 2008, 11:22 AM

Still don't get what this has to do with climate change.

The logical inference demonstrated in that puzzle is not about proving anthropogenic climate change. Instead, it serves to illustrate clearly the flawed logic of denialists such as Martin Durkin who mistakenly think his polemic disproves anthropogenic global warming -- the topic that began this thread. There are many other logical fallacies in the Durkin screed that are explained in this lecture at the University of Edinburgh (http://video.google.com/videoplay?docid=-1656640542976216573).

I simply want to point out there are good ways to be a skeptic (e.g. Michael Shermer (http://www.sciam.com/article.cfm?id=the-flipping-point), etc) and bad ways to be a skeptic (http://gristmill.grist.org/skeptics) (most anti-AGW blogs I've seen). There are already other websites (http://www.aip.org/history/climate/), forums and blogs (http://realclimate.org/) devoted to discussing AGW, evidence for it and so on, but delving into those details would probably go beyond the scope of the UK-Skeptics forum.

Tim the Mage

7th August 2008, 08:38 PM

Sorry if I'm new and naive but are we not supposed to be sceptical here? Reading through the comments is does seem that on this isue too many are willing to: 1) assume that the motivation of the scientist is above politics when we know that science and scientists have always played the very human game of politics (and been exploited by it); 2) that there is no negative motive behind the scientists who confirm or support my viewpoint but the one;s who support your viewpoint are in the pay of big business/leftie pressure groups/international capitalism/global terrorists (take your pick); 3) resort to political abuse rather than argument.

I am sceptical about the claims of those who propose an AWG thesis, if only because some of their evidence has been shown to be flawed - especially on the historical temperature record (that famously wrong 'hockey stick' graph). And I am angry that people wish to use this to break up efficient, scientifically-proven systems and replace them with untried and questionable interventions.

However, those who question the argument of the IPCC and other supporters of AWG also have questions to answer - especially on the modern temperature record where their arguments about start dates are statisically ignorant.

Finally, can we perhaps rise above reducing the scientific debate to a set of slightly abusive characterisations - "deniers", "warmists" and such are unhelpful away from the public bar.

Pebble

7th August 2008, 10:56 PM

Tony Williams

8th August 2008, 01:05 AM

An extract from the New Scientist web resource on 'Climate Change for the Perplexed', concerning that "hockey stick":

Ice cores from Antarctica show that at the end of recent ice ages, the concentration of carbon dioxide in the atmosphere usually started to rise only after temperatures had begun to climb. There is uncertainty about the timings, partly because the air trapped in the cores is younger than the ice, but it appears the lags might sometimes have been 800 years or more.

This proves that rising CO2 was not the trigger that caused the initial warming at the end of these ice ages – but no climate scientist has ever made this claim. It certainly does not challenge the idea that more CO2 heats the planet.
We know that CO2 is a greenhouse gas because it absorbs and emits certain frequencies of infrared radiation. Basic physics tells us that gases with this property trap heat radiating from the Earth, that the planet would be a lot colder if this effect was not real and that adding more CO2 to the atmosphere will trap even more heat.
What is more, CO2 is just one of several greenhouses gases, and greenhouse gases are just one of many factors affecting the climate. There is no reason to expect a perfect correlation between CO2 levels and temperature in the past: if there is a big change in another climate "forcing", the correlation will be obscured.

So why has Earth regularly switched between ice ages and warmer interglacial periods in the past million years? It has long been thought that this is due to variations in Earth's orbit, known as Milankovitch cycles. These change the amount and location of solar energy reaching Earth. However, the correlation is not perfect and the heating or cooling effect of these orbital variations is small. It has also long been recognised that they cannot fully explain the dramatic temperature switches between ice ages and interglacials.
So if orbital changes did cause the recent ice ages to come and go, there must also have been some kind of feedback effect that amplified the changes in temperatures they produced. Ice is one contender: as the great ice sheets that covered large areas of the planet during the ice ages melted, less of the Sun's energy would have been reflected back into space, accelerating the warming. But the melting of ice lags behind the beginning of interglacial periods by far more than the rises in CO2.
Another feedback contender, suggested over a century ago, is CO2. In the past decade, detailed studies of ice cores have shown there is a remarkable correlation between CO2 levels and temperature over the past half million years (see Vostok ice cores show constant CO2 as temperatures fell).

It takes about 5000 years for an ice age to end and, after the initial 800 year lag, temperature and CO2 concentrations in the atmosphere rise together for a further 4200 years.
What seems to have happened at the end of the recent ice ages is that some factor – most probably orbital changes – caused a rise in temperature. This led to an increase in CO2, resulting in further warming that caused more CO2 to be released and so on: a positive feedback that amplified a small change in temperature. At some point, the shrinking of the ice sheets further amplified the warming.
Models suggest that rising greenhouse gases, including CO2, explains about 40% of the warming as the ice ages ended. The figure is uncertain because it depends on how the extent of ice coverage changed over time, and there is no way to pin this down precisely.

The ice ages show that temperature can determine CO2 as well as CO2 driving temperature. Some sceptics – not scientists – have seized upon this idea and are claiming that the relation is one way, that temperature determines CO2 levels but CO2 levels do not affect temperature.

To repeat, the evidence that CO2 is a greenhouse gas depends mainly on physics, not on the correlation with past temperature, which tells us nothing about cause and effect. And while the rises in CO2 a few hundred years after the start of interglacials can only be explained by rising temperatures, the full extent of the temperature increases over the following 4000 years can only be explained by the rise in CO2 levels.

Matt

8th August 2008, 07:39 AM

Finally, can we perhaps rise above reducing the scientific debate to a set of slightly abusive characterisations - "deniers", "warmists" and such are unhelpful away from the public bar.

Deniers exist. Take tobacco denialists for example. From court cases we have very public information detailing an orchestrated campaign to supress evidence. Some of the same names are coming up in relation to global warming denialism. However without resorting to ad hominem it's not so much the same faces as the same actions that are relevant. The patterns of orchestrated denialsim are recognisable. The use of rhetoric and sophistry to shift the debate away from awkward evidence. These are anathema to the true skeptic and should be pointed out as such.

I'm not saying that there aren't valid questions and valid uncertainties. There are. However there are also known things that shouldn't be denied. That can't be denied without deliberate dishonesty. It is important for a skeptic to be able to recognise the difference. Denialism is the appropriate word for such arguments. Denialist is the correct word for a paid advocate charged with denying AGW.

As well as the advocate paid to be dishonest there are people on both sides who have carved a niche. Who've staked their reputation on a proposition and can't back down. On the pro AGW side we have James Hansen who it seems to me has a habit of focussing on worst case scenarios. We have Al Gore's famous presentation being a self confessed polemic rather than a ballanced assessment. On the anti AGW side have the same but we also see evidence of orchestration and funding. Not just with regard to science but PR and lobbying.

However I shall not call you a denialist. I have no reason to believe you're in reciept of money or status that binds you to one proposition or another. So long as you choose to be guided by evidence and rational thught then you're a skeptic in my book.

Take a skeptical look at the "Hockey Stick Graph" and similar temperature reconstructions over the past 1,000 years.

What do you consider it's most important feature relevent to the discussion at hand. Is it the exponential rise in average global temperatures or is it the pressence of the medeval warm period. Mann's proxies for the medeval warm period have been strongly debated. The handle of his hockey stick looks quite straight. Other reconstructions show a defiinite kink. Denialists have made polava about the treatment of the medeval data in Man's reconstruction. Did Mann deliberately flatten the medval portion of his graph to make the contemporay warming look more pronounced? I do't know. Frankly I don't care. I've seen nearly a dozen or so other reconstructions that disagree over the medeval warm period and show a far more pronounced feature. However all of them agree that the present warming is unprecedented in gradient and magnitude. The denialist would want to move the focus away from this unprecidented warming which cannot be denied, and towards the medeval warm period about which some debate may be merited.

I've genuinely encountered climate skeptics who've been so convinced by denialist dogma that when shown any temperature reconstruction graph that shown even ones showing very pronounced temperature increases for the medaval warm period, they denounce it at the "discredited hockey stick graph" SO yes be scpetical but don't allow vested interests to tell you how to be skeptical.

Pebble

8th August 2008, 12:10 PM

An extract from the New Scientist web resource on 'Climate Change for the Perplexed', concerning that "hockey stick":

To repeat, the evidence that CO2 is a greenhouse gas depends mainly on physics, not on the correlation with past temperature, which tells us nothing about cause and effect. And while the rises in CO2 a few hundred years after the start of interglacials can only be explained by rising temperatures, the full extent of the temperature increases over the following 4000 years can only be explained by the rise in CO2 levels.

A single opinion piece, is not what I generally accept as evidence. However, if my reading is correct, nothing presented invalidates the position I outlined above. If anything this supports the position I have outlined.

Allo Allo

8th August 2008, 12:23 PM

. There are many other logical fallacies in the Durkin screed that are explained in this lecture at the University of Edinburgh (http://video.google.com/videoplay?docid=-1656640542976216573).

Thanks for this link - I watched it - couldn't say it was 'good' - as in 'convincing'. I bet a lot of the students went away believing the movie instead. But one thing did strike me as something I don't quite get. What is the difference between an ad hominem attack and pointing out a conflict of interest? This come up right at the very end. Scientists are being suspected of proving global warming so they can get funding is an ad hominem attack????!

I simply want to point out there are good ways to be a skeptic (e.g. Michael Shermer (http://www.sciam.com/article.cfm?id=the-flipping-point), etc) and bad ways to be a skeptic (http://gristmill.grist.org/skeptics) (most anti-AGW blogs I've seen). Michel Shermer changed by watching Al Gore's movie. In Climate change issues one doesn't know how to apply the word skeptic anymore! Who is the skeptic? The 'fors' or the 'againsts'? Or is it just the 'fors' against the 'againsts'?

Or skeptics like me?

As an older person, I can remember looking at my newborn son and thinking 'Poor little shit. When you grow up you will have only one meter of earth to live on, and be starving to death in a ghastly catastrophic Ice Age. What have I done?'

That was what scientists were telling us then.

This has given me an innate suspicion of what Scientists say.

Tim the Mage

8th August 2008, 12:47 PM

I guess there's a point at which we all become convinced of something (I become convinced of the truth of free market economics in September 2007 following a lecture on Adam Smith and nothing I've read since has changed my mind) and Michael Shermer reached that point on 'climate change' (although how anyone could 'deny' the facts of climate change defeats me) after watching Al Gore's film.

I've not reached that point yet nor do I buy the catastrophe theory of global warming that 'demands we act now'.

wagdog

8th August 2008, 12:53 PM

I am sceptical about the claims of those who propose an AWG thesis, if only because some of their evidence has been shown to be flawed - especially on the historical temperature record (that famously wrong 'hockey stick' graph). And I am angry that people wish to use this to break up efficient, scientifically-proven systems and replace them with untried and questionable interventions.

What exactly is "famously wrong" with the hockey stick graph?

It is some of the most scrutinised research in the scientific community. At the behest of the US Congress the National Academy of Sciences examined it in detail (http://www.nationalacademies.org/morenews/20060622.html) and concluded there was high confidence in the surface temperature record for the last 400 years. Not bad given this is 10 year old research, and since then the reconstructions have only improved. Climate denialists love to cherry pick passages from this report and spin them as if the hockeystick has now been broken, but when one reads the actual NAS report as a whole, it confirms the main conclusion that it is hotter now than in the last 400 years, and very probably in the last millennium. Talk about subconscious confirmation bias!

The AGW denialists also like to trumpet the Wegman statistical analysis (http://energycommerce.house.gov/reparchives/108/Hearings/07192006hearing1987/Wegman.pdf) of the principal components method (http://en.wikipedia.org/wiki/Principal_components_analysis) used to produce the hockey stick graph. Closer examination of these criticisms reveals that they're confusing a Principal Component with the final reconstruction - they are not the same (http://www.realclimate.org/index.php/archives/2006/07/the-missing-piece-at-the-wegman-hearing/). Of course the leading critic in all this, Steve McIntyre, would never acknowledge this, and continues in his belief that he's found a major flaw in how the PCA was applied, even though when alternative statistical techniques are applied (http://www.realclimate.org/RuthetalJClim2004.pdf) you still get a hockey stick. According to McIntyre, the hockey stick is an artefact of an interaction between PCA and bristlecone proxy data, so if one replaces PCA and still gets the same result, where does that leave his argument?

As a result those in the AGW denialist camp have to discredit the data itself, and with it the entire field of dendroclimatology (Yes, one of McIntyre's disciples is claiming this in the comments of this blog (http://scienceblogs.com/deltoid/2006/07/hockey_stick_hockey_stick_hock.php).) It is cherry picking in the extreme.

Those who are new to AGW theory and to the hockey stick debate in particular, the climate scientists behind the research have made a primer for laymen (http://www.realclimate.org/index.php/archives/2005/02/dummies-guide-to-the-latest-hockey-stick-controversy/) on the topic of PCA-based temperature reconstructions. They also clarify several myths regarding this piece of research (http://www.realclimate.org/index.php?p=11), namely that AGW relies on the hockey stick (http://www.realclimate.org/index.php?p=114) -- as if disproving it would deal a fatal blow to AGW.

BTW. I use PCA in my work, so maybe I'm biased. It is used not just in climate reconstruction, but virtually every field of science (in my case medicine). It is widely regarded as one of those "efficient, scientifically-proven systems".

wagdog

8th August 2008, 02:09 PM

Thanks for this link - I watched it - couldn't say it was 'good' - as in 'convincing'. I bet a lot of the students went away believing the movie instead.

You're underestimating the university-level students.

For your average non-scientifically minded television viewer, this debunking by Tony Jones (http://www.youtube.com/watch?v=lIjGynF4qkE) (more here (http://www.youtube.com/watch?v=goDsc9IaSQ8)) when Durkin's movie was broadcast in Australia may hold more sway.

What is the difference between an ad hominem attack and pointing out a conflict of interest? This come up right at the very end. Scientists are being suspected of proving global warming so they can get funding is an ad hominem attack?! The ad hominem is the implication that climate scientists are dishonest -- that they would deliberately distort the data to prove a preheld conclusion for monetary gain. And even the conflict of interest claim doesn't hold water. What gets research funding is when the researchers clearly demonstrate to the funding body that there is an interesting and important scientific question for which we have no answer -- i.e. that the conclusion is as yet uncertain. E.g. Will a certain class of vaccine cure malaria? Will a certain architectural design protect against magnitude 7 earthquakes?

Contrast this to the IPCC conclusion of being more than 90% certain that the Earth is warming and humans are causing it. Why would anyone fund science that is already settled? And look who is claiming that the science has not been settled -- all those AGW denialists. Richard Lindzen's contention (http://www.opinionjournal.com/extra/?id=110008220) that climate scientists just want to swell their pockets is unfounded.

In Climate change issues one doesn't know how to apply the word skeptic anymore! Who is the skeptic? The 'fors' or the 'againsts'?You're asking the wrong question. My usage of "Skeptic" refers to Scientific Skepticism (http://www.ukskeptics.com/article.php?dir=articles&article=what_is_skepticism.php). In spoon bending, it is obvious that James Randi is on the side of the scientific skeptic. It is equally clear that the Geller fans are not applying any accepted science but have succummed to psychological tricks -- we cannot prove this, but it is the most likely scientific explanation.

A closer examination of the climate change players reveals a similar break down. The climate scientists who have concluded AGW as fact have been applying rigorous science to reach this conclusion. Those in denial of AGW have not -- they've used psychological arguments and logical fallacy dressed up in scientific jargon, a strategy not very disimilar from that used by Creationists to rebrand themselves as Intelligent Design proponents. The public can be fooled into thinking there's a debate simply by wrapping enough pseudo-scientific jargon around the dissenting opinion.

'be starving to death in a ghastly catastrophic Ice Age. What have I done?'

That was what scientists were telling us then.Correction. That's what the mainstream media were telling you about what scientists were saying back then. The truth behind this 70's ice age hysteria myth (http://environment.newscientist.com/channel/earth/climate-change/dn11643) is more damning of scientific journalism than of the scientific community. Not only was there no consensus that an ice age was imminent, there was virtually no peer reviewed publication claiming this (http://www.wmconnolley.org.uk/sci/iceage/) either.

This has given me an innate suspicion of what Scientists say.You should be suspicious of what everyone says. But we live in a new age now. We can now fact check the arguments of both sides, apply principles of skepticism, and see who comes out worse for wear.

wagdog

8th August 2008, 02:57 PM

I've not reached that point yet nor do I buy the catastrophe theory of global warming that 'demands we act now'.

As you realise, the pro-AGW camp are not as polarised as one would think. This climate blogger (http://scienceblogs.com/stoat/2007/06/the_earth_today_stands_in_immi_1.php) accepts AGW as fact but is skeptical of James Hansen's predictions as to the speed of the collapse of the Greenland and Antarctica ice sheets.

However, you don't have to buy in to the catastrophists' belief to demand we act now. If we ignore all the alarmism coming from the environmentalists and focus only on what the climate science is actually saying, we get a range of outcomes: from moderately bad scenarios occurring at high probability, to catastrophic scenarios occurring at low probability. The environmentalists like to focus on the latter (http://www.youtube.com/watch?v=zORv8wwiadQ) using a sort of minimax decision framework (http://en.wikipedia.org/wiki/Minimax) to justify immediate mitigation. Anti-alarmists like Bjorn Lomborg (http://online.wsj.com/article/SB121720170185288445.html) make sure to focus only on the former to justify market driven adaptation. Both approaches are flawed, but are psychologically convincing to the general public who are not well versed in how to deal with a range of probabilistic outcomes.

The problem lies in how one deals with very costly and highly damaging outcomes occurring at low probabilities. If I were to apply Lomborg's approach to myself, I'd plan my life assuming that I will live exactly to the age of average life expectancy for the whole population. There is no need to take out life insurance, nor save up a pension for living beyond 80 years, etc. In reality there is a small probability of an early death and there also is a small probability one will live to 100, so we pay extra for insurance/pension to cater for these outcomes. We're hedging our bets. The question is how much is society willing to pay to hedge against a 1% chance of a climate catastrophe?

Tony Williams

8th August 2008, 03:34 PM

An extract from the review on my SFF blog of Gilovich's How We Know What Isn't So seems appropriate (//sciencefictionfantasy.blogspot.com/ Ist August):

We are often misled by information we receive second hand, because of the tendency to "sharpen and level", as the author puts it. By this he means that in relaying a news item, for instance, we tend to emphasise the points which we consider to be important (or which we believe) and downplay or omit other aspects. So if a carefully-written report comes to a tentative conclusion which we agree with, but wraps this around with qualifications and caveats, we tend just to relay the conclusions, making the results appear far more definite than the report's authors intended. As people "sharpen" different aspects of information to suit their beliefs, so we get a rapid polarisation of opinions on controversial issues. Even worse, some organisations deliberately "sharpen and level" because they want to turn public opinion in their favour [popular news media and politicians are of course notorious for presenting such selectively slanted information, especially during election campaigns, but so do many organisations with agendas]. Most "urban legends" probably develop as a result of an extreme version of this, with the key points pulled out and exaggerated.

This sharpening effect is exacerbated by the fact that if we hold certain beliefs, we are likely to discuss them only with people who agree with us, and only to read supportive publications. Our beliefs are thereby rarely challenged but instead are constantly reinforced, so we tend to end up with the view that our beliefs are naturally and obviously right. Anyone who disagrees with them must therefore be entirely mistaken and possibly downright stupid if not malevolent. This polarisation is obvious today in politics and in debates about other controversial issues. In reality, of course, situations are rarely as polarised as this: we exaggerate differences.

The way I look at it is this: if you have a big tree overhanging your house, so you ask ten tree specialists if they think there's a risk of it falling on your house in a storm, and nine of them say yep, there is - ranging from possible to very likely - but the tenth says no, don't worry about it: what do you do? Ignore it and hope that the tenth one is right?

Tim the Mage

8th August 2008, 03:59 PM

As you realise, the pro-AGW camp are not as polarised as one would think. This climate blogger (http://scienceblogs.com/stoat/2007/06/the_earth_today_stands_in_immi_1.php) accepts AGW as fact but is skeptical of James Hansen's predictions as to the speed of the collapse of the Greenland and Antarctica ice sheets.

However, you don't have to buy in to the catastrophists' belief to demand we act now. If we ignore all the alarmism coming from the environmentalists and focus only on what the climate science is actually saying, we get a range of outcomes: from moderately bad scenarios occurring at high probability, to catastrophic scenarios occurring at low probability. The environmentalists like to focus on the latter (http://www.youtube.com/watch?v=zORv8wwiadQ) using a sort of minimax decision framework (http://en.wikipedia.org/wiki/Minimax) to justify immediate mitigation. Anti-alarmists like Bjorn Lomborg (http://online.wsj.com/article/SB121720170185288445.html) make sure to focus only on the former to justify market driven adaptation. Both approaches are flawed, but are psychologically convincing to the general public who are not well versed in how to deal with a range of probabilistic outcomes.

The problem lies in how one deals with very costly and highly damaging outcomes occurring at low probabilities. If I were to apply Lomborg's approach to myself, I'd plan my life assuming that I will live exactly to the age of average life expectancy for the whole population. There is no need to take out life insurance, nor save up a pension for living beyond 80 years, etc. In reality there is a small probability of an early death and there also is a small probability one will live to 100, so we pay extra for insurance/pension to cater for these outcomes. We're hedging our bets. The question is how much is society willing to pay to hedge against a 1% chance of a climate catastrophe?

The life insurance question is interesting because it depends on the cost. In truth most of your investment decisions are made on the assumption that you will live up to or beyond the mean life expectancy. You are wrong about the pension of course because the pension calculation has already ractored in the expectation that some will not live to claim and others will exceed the mean age of death. Plus of course the climate change question is about "actions now" rather than "savings now".