Archive for climate change

Can We Actually Even Tell if Humans Are Affecting the Climate? What if we did nothing at all?

Posted in Bad Statistics with tags , , on June 26, 2013 by telescoper

telescoper:

Reblog of a post about the doctrine of falsifiablity and its relevance to Climate Change….following on from Monday’s post.

Originally posted on Watts Up With That?:

Essay by Charlie Martin

We know, with great certainty, that the overall average temperature of the Earth has warmed by several degreees in the last 400 years, since the end of the Little Ice Age. Before that was a period called the Medieval Warm Period; before that was another cold period, and back at the time of the Romans there was a long period that was significantly warmer — Southern Britain was a wine-growing region. What we’re a lot less certain about is why?

Of course, the “why?” here has been, shall we say, pretty controversial. It’s worth wondering about the controversy and about the social mechanisms through which science is done — I wrote about them during the Climategate controversy as the “social contract of science” — but that’s not what I want to talk about today. Instead, let’s talk about how a scientist thinks about these sorts of…

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Skepsis Revived

Posted in Politics, The Universe and Stuff with tags , , , , , , , , on November 14, 2012 by telescoper

I appear to be in recycling mode this week, so I thought I’d carry on with a rehash of an old post about skepticism.  The excuse for this was an item in one of the Guardian science blogs about the distinction between Skeptic and sceptic. I must say I always thought they were simply alternative spellings, the “k” being closer to the original Greek and “c” being Latinised (via French). The Oxford English dictionary merely states that “sceptic” is more widespread in the UK and Commonwealth whereas “skeptic” prevails in North America. Somehow, however, this distinction has morphed into one variant meaning a person who has a questioning attitude to or is simply unconvinced by what claims to be knowledge in a particular area, and another meaning a “denier”, the latter being an “anti-sceptic” who believes wholeheartedly and often without evidence in whatever is contrary to received wisdom. A scientists should, I think, be the former, but the latter represents a distinctly unscientific attitude.

Anyway, yesterday I blogged a little bit about dark energy as, according to the standard model, this accounts for about 75% of the energy budget of the Universe. It’s also something we don’t understand very well at all. To make a point, take a look at the following picture (credit to the High-z supernova search team).

 What is plotted is the redshift of each supernova (along the x-axis), which relates to the factor by which the universe has expanded since light set out from it. A redshift of 0.5 means the universe was compressed by a factor 1.5 in all dimensions at the time when that particular supernova went bang. The y-axis shows the really hard bit to get right. It’s the estimated distance (in terms of distance modulus) of the supernovae. In effect, this is a measure of how faint the sources are. The theoretical curves show the faintness expected of a standard source observed at a given redshift in various cosmological models. The bottom panel shows these plotted with a reference curve taken out so the trend is easier to see. Actually, this is quite an old plot and there are many more points now but this is the version that convinced most cosmologists when it came out about a decade ago, which is why I show it here.

The argument drawn from these data is that the high redshift supernovae are fainter than one would expect in models without dark energy (represented by the \Omega_{\Lambda}  in the diagram. If this is true then it means the luminosity distance of these sources is greater than it would be in a decelerating universe. Their observed properties can be accounted for, however, if the universe’s expansion rate has been accelerating since light set out from the supernovae. In the bog standard cosmological models we all like to work with, acceleration requires that \rho + 3p/c^2 be negative. The “vacuum” equation of state p=-\rho c^2 provides a simple way of achieving this but there are many other forms of energy that could do it also, and we don’t know which one is present or why…

This plot contains the principal evidence that has led to most cosmologists accepting that the Universe is accelerating.  However, when I show it to first-year undergraduates (or even to members of the public at popular talks), they tend to stare in disbelief. The errors are huge, they say, and there are so  few data points. It just doesn’t look all that convincing. Moreover, there are other possible explanations. Maybe supernovae were different beasties back when the universe was young. Maybe something has absorbed their light making them look fainter rather than being further away. Maybe we’ve got the cosmological models wrong.

The reason I have shown this diagram is precisely because it isn’t superficially convincing. When they see it, students probably form the opinion that all cosmologists are gullible idiots. I’m actually pleased by that.  In fact, it’s the responsibility of scientists to be skeptical about new discoveries. However, it’s not good enough just to say “it’s not convincing so I think it’s rubbish”. What you have to do is test it, combine it with other evidence, seek alternative explanations and test those. In short you subject it to rigorous scrutiny and debate. It’s called the scientific method.

Some of my colleagues express doubts about me talking as I do about dark energy in first-year lectures when the students haven’t learned general relativity. But I stick to my guns. Too many people think science has to be taught as great stacks of received wisdom, of theories that are unquestionably “right”. Frontier sciences such as cosmology give us the chance to demonstrate the process by which we find out about the answers to big questions, not by believing everything we’re told but by questioning it.

My attitude to dark energy is that, given our limited understanding of the constituents of the universe and the laws of matter, it’s the best explanation we have of what’s going on. There is corroborating evidence of missing energy, from the cosmic microwave background and measurements of galaxy clustering, so it does have explanatory power. I’d say it was quite reasonable to believe in dark energy on the basis of what we know (or think we know) about the Universe.  In other words, as a good Bayesian, I’d say it was the most probable explanation. However, just because it’s the best explanation we have now doesn’t mean it’s a fact. It’s a credible hypothesis that deserves further work, but I wouldn’t bet much against it turning out to be wrong when we learn more.

I have to say that too many cosmologists seem to accept the reality of dark energy  with the unquestioning fervour of a religious zealot.  Influential gurus have turned the dark energy business into an industrial-sized bandwagon that sometimes makes it difficult, especially for younger scientists, to develop independent theories. On the other hand, it is clearly a question of fundamental importance to physics, so I’m not arguing that such projects should be axed. I just wish the culture of skepticism ran a little deeper.

Another context in which the word “skeptic” crops up frequently nowadays is  in connection with climate change although it has come to mean “denier” rather than “doubter”. I’m not an expert on climate change, so I’m not going to pretend that I understand all the details. However, there is an interesting point to be made in comparing climate change with cosmology. To make the point, here’s another figure.

There’s obviously a lot of noise and it’s only the relatively few points at the far right that show a clear increase (just as in the first Figure, in fact). However, looking at the graph I’d say that, assuming the historical data points are accurate,  it looks very convincing that the global mean temperature is rising with alarming rapidity. Modelling the Earth’s climate is very difficult and we have to leave it to the experts to assess the effects of human activity on this curve. There is a strong consensus from scientific experts, as monitored by the Intergovernmental Panel on Climate Change, that it is “very likely” that the increasing temperatures are due to increased atmospheric concentrations of greenhouse gas emissions.

There is, of course, a bandwagon effect going on in the field of climatology, just as there is in cosmology. This tends to stifle debate, make things difficult for dissenting views to be heard and evaluated rationally,  and generally hinders the proper progress of science. It also leads to accusations of – and no doubt temptations leading to – fiddling of the data to fit the prevailing paradigm. In both fields, though, the general consensus has been established by an honest and rational evaluation of data and theory.

I would say that any scientist worthy of the name should be skeptical about the human-based interpretation of these data and that, as in cosmology (or any scientific discipline), alternative theories should be developed and additional measurements made. However, this situation in climatology is very different to cosmology in one important respect. The Universe will still be here in 100 years time. We might not.

The big issue relating to climate change is not just whether we understand what’s going on in the Earth’s atmosphere, it’s the risk to our civilisation of not doing anything about it. This is a great example where the probability of being right isn’t the sole factor in making a decision. Sure, there’s a chance that humans aren’t responsible for global warming. But if we carry on as we are for decades until we prove conclusively that we are, then it will be too late. The penalty for being wrong will be unbearable. On the other hand, if we tackle climate change by adopting greener technologies, burning less fossil fuels, wasting less energy and so on, these changes may cost us a bit of money in the short term but  frankly we’ll be better off anyway whether we did it for the right reasons or not. Of course those whose personal livelihoods depend on the status quo are the ones who challenge the scientific consensus most vociferously. They would, wouldn’t they?

This is a good example of a decision that can be made on the basis of a  judgement of the probability of being right. In that respect , the issue of how likely it is that the scientists are correct on this one is almost irrelevant. Even if you’re a complete disbeliever in science you should know  how to respond to this issue, following the logic of Blaise Pascal. He argued that there’s no rational argument for the existence or non-existence of God but that the consequences of not believing if God does exist (eternal damnation) were much worse than those of behaving as if you believe in God when he doesn’t. For “God” read “climate change” and let Pascal’s wager be your guide….

Dare to Be Dumb (via Climate Denial Crock of the Week)

Posted in Politics with tags , on September 5, 2011 by telescoper

I came across this interesting polemic about climate change denialism and because I’m going to be too busy today to post anything original I thought I’d reblog it here.

Someone told me off last week for my “Academic Journal Racket” post, arguing that polemics never advance an argument. I disagree, actually. Polemics are good, as long as they’re good polemics.

Dare to Be Dumb In “Confessions of a Climate Change Convert”, D. R. Tucker explained the change in consciousness that came to a conservative writer after seriously looking at the evidence for  anthropogenic climate change. Today, he offers another insight into the conservative's climate quandary. The amusement parks I visited when I was a child had signs indicating that one had to be “this tall” in order to go on a ride. Viewing the endless stream of op-eds and … Read More

via Climate Denial Crock of the Week

Hard Decisions, Easy Targets

Posted in Science Politics, The Universe and Stuff with tags , , , , , , on January 25, 2011 by telescoper

Just back from a day trip to London – at the Institute of Physics to be precise – to wrap up the proceedings of this years protracted STFC Astronomy Grants Panel (AGP) business. The grant letters have already gone out, so no real decisions were made relating to the current round, but we did get the chance to look at a fairly detailed breakdown of the winners and losers. Perhaps more significantly we also discussed issues relating to the implementation of the brand new system which will be in place for 2011/12.

I’m not exactly sure at the moment how much of what we discussed is in the public domain, so I won’t write anything about the meeting here. Tomorrow there is a meeting of the RAS Astronomy Forum at which department representatives will also be briefed about these issues. I will, however, in due course, on as much information as I can through this blog in case there is anyone out there who doesn’t hear it via the Forum.

Not being able to blog about AGP business, I thought I’d comment briefly on a couple of recent things that sprang to mind on the train journey into London. Last night there was a programme in the BBC series Horizon called Science under Attack, presented by Nobel laureate Sir Paul Nurse. I didn’t watch all of it, but I was fortunate (?) enough to catch a segment featuring a chap called James Delingpole, whom I’d never heard of before, but who apparently writes for the Daily Torygraph.

My immediate reaction to his appearance on the small screen was to take an instant dislike to him. This is apparently not an uncommon response, judging by the review of the programme in today’s Guardian. I wouldn’t have bothered blogging about this at all had I wanted to indulge in an ad hominem attack on this person, but he backed up his “unfortunate manner” by saying some amazing things, such as

It’s not my job to sit down and read peer-reviewed papers, because I don’t have the time; I don’t have the expertise

Yet he feels qualified to spout off on the subject nevertheless. The subject, by the way, was climate change. I’m sure not even the most hardened climate skeptic would want Mr Delingpole on their side judging by his performance last night or, apparently, his track-record.

Anyway, this episode reminded me of another egregious example of uninformed drivel that appeared in last week’s Times Higher. This was a piece purporting to be about the limits of mathematical reasoning by another person who is quite new to me, Chris Ormell, who appears to have some academic credentials, if only in the field of philosophy.

Ormell’s piece includes a rant about cosmology which is on a par with Delingpole’s scribblings about climate change, in that he has absolutely no idea what he is talking about. Jon Butterworth and Sean Carroll have already had a go at pointing out the basic misunderstandings, so I won’t repeat the hatchet job here. If I had blogged about this at the weekend – which I might have done had my rodent visitor not intervened – I would have been considerably less polite than either of them. Ormell clearly hasn’t even read a wikipedia article on cosmology, never mind studied it to a level sufficiently deep to justify him commenting on it in a serious magazine.

I’m still amazed that such a pisspoor article could have made it through the Times Higher’s editorial procedures but more worrying still is the ract that Ormell is himself the editor of a journal, called Prospero, which is “a journal of new thinking of philosophy for education”. The last thing education needs is a journal edited by someone so sloppy that he can’t even be bothered to acquire a basic understanding of his subject matter.

What’s in common between these stories is, however, in my opinion, much more important than the inadequate scientific understanding of the personalities involved. Rubbishing the obviously idiotic, which is quite easy to do, may blind us to the fact that, behind all the errors, however badly expressed it may be, people like this may just have a point. Too often the scientific consensus is portrayed as fact when there are clearly big gaps missing in our understanding. Of course falsehoods should be corrected, but what science really needs to go forward is for bona fide scientists to be prepared to look at the technical arguments openly and responsibly and be candid about the unknowns and uncertainties. Big-name scientists should themselves be questioning the established paradigms and be actively exploring alternative hypotheses. That’s their job. Closing ranks and stamping on outsiders is what makes the public suspicious, not reasoned argument.

In both climatology and cosmology there are consensus views. Based on what knowledge I have, which is less in the former case than in the latter, both these views are reasonable inferences but not absolute truths. In neither case am I a denier, but in both cases I am a skeptic. Call me old-fashioned, but I think that’s what a scientist should be.


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Publish or be Damned

Posted in Science Politics, The Universe and Stuff with tags , , , , , , , , , on August 23, 2010 by telescoper

For tonight’s post I thought I’d compose a commentary on a couple of connected controversies suggested by an interestingly provocative piece by Nigel Hawkes in the Independent this weekend entitled Peer Review journals aren’t worth the paper they’re written on. Here is an excerpt:

The truth is that peer review is largely hokum. What happens if a peer-reviewed journal rejects a paper? It gets sent to another peer-reviewed journal a bit further down the pecking order, which is happy to publish it. Peer review seldom detects fraud, or even mistakes. It is biased against women and against less famous institutions. Its benefits are statistically insignificant and its risks – academic log-rolling, suppression of unfashionable ideas, and the irresistible opportunity to put a spoke in a rival’s wheel – are seldom examined.

In contrast to many of my academic colleagues I largely agree with Nigel Hawkes, but I urge you to read the piece yourself to see whether you are convinced by his argument.

I’m not actually convinced that peer review is as biased as Hawkes asserts. I rather think that the strongest argument against  the scientific journal establishment  is the ruthless racketeering of the academic publishers that profit from it.  Still, I do think he has a point. Scientists who garner esteem and influence in the public domain through their work should be required to defend it our in the open to both scientists and non-scientists alike. I’m not saying that’s easy to do in the face of ill-informed or even illiterate criticism, but it is in my view a necessary price to pay, especially when the research is funded by the taxpayer.

It’s not that I think many scientists are involved in sinister activities, manipulating their data and fiddling their results behind closed doors, but that as long as there is an aura of secrecy it will always fuel the conspiracy theories on which the enemies of reason thrive. We often hear the accusation that scientists behave as if they are priests. I don’t think they do, but there are certainly aspects of scientific practice that make it appear that way, and the closed world of academic publishing is one of the things that desperately needs to be opened up.

For a start, I think we scientists should forget academic journals and peer review, and publish our results directly in open access repositories. In the old days journals were necessary to communicate scientific work. Peer review guaranteed a certain level of quality. But nowadays it is unnecessary. Good work will achieve visibility through the attention others give it. Likewise open scrutiny will be a far more effective way of identifying errors than the existing referee process. Some steps will have to be taken to prevent abuse of the access to databases and even then I suspect a great deal of crank papers will make it through. But in the long run, I strongly believe this is the only way that science can develop in the age of digital democracy.

But scrapping the journals is only part of the story. I’d also argue that all scientists undertaking publically funded research should be required to put their raw data in the public domain too. I would allow a short proprietary period after the experiments, observations or whatever form of data collection is involved. I can also see that ethical issues may require certain data to be witheld, such as the names of subjects in medical trials. Issues will also arise when research is funded commercially rather than by the taxpaper. However, I still maintain that full disclosure of all raw data should be the rule rather than the exception. After all, if it’s research that’s funded by the public, it is really the public that owns the data anyway.

In astronomy this is pretty much the way things operate nowadays, in fact. Maybe stargazers have a more romantic way of thinking about scientific progress than their more earthly counterparts, but it is quite normal – even obligatory for certain publically funded projects – for surveys to release all their data. I used to think that it was enough just to publish the final results, but I’ve become so distrustful of the abuse of statistics throughout the field that I think it is necessary for independent scientists to check every step of the analysis of every major result. In the past it was simply too difficult to publish large catalogues in a form that anyone could use, but nowadays that is simply no longer the case. Astronomers have embraced this reality, and it is liberated them.

To give a good example of the benefits of this approach, take the Wilkinson Microwave Anisotropy Probe (WMAP) which released full data sets after one, three, five and seven years of operation. Scores of groups around the world have done their best to find glitches in the data and errors in the analysis without turning up anything particularly significant. The standing of the WMAP team is all the higher for having done this, although I don’t know whether they would have chosen to had they not been required to do so under the terms of their funding!

In the world of astronomy research it’s not at all unusual to find data for the object or set of objects you’re interested in from a public database, or by politely asking another team if they wouldn’t mind sharing their results. And if you happen to come across a puzzling result you suspect might be erroneous and want to check the calculations, you just ask the author for the numbers and, generally speaking, they send the numbers to you. A disagreement may ensue about who is right and who is wrong, but that’s the way science is supposed to work.  Everything must be open to question. It’s often a chaotic process, but it’s a process all the same, and it is one that has servedus incredibly well.

I was quite surprised recently to learn that this isn’t the way other scientific disciplines operate at all. When I challenged the statistical analysis in a paper on neuroscience recently, my request to have a look at the data myself was greeted with a frosty refusal. The authors seemed to take it as a personal affront that anyone might have the nerve to question their study. I had no alternative but to go public with my doubts, and my concerns have never been satisfactorily answered. How many other examples are there wherein application of the scientific method has come to a grinding halt because of compulsive secrecy? Nobody likes to have their failings exposed in public, and I’m sure no scientists likes see an error pointed out, but surely it’s better to be seen to have made an error than to maintain a front that perpetuates the suspicion of malpractice?

Another, more topical, example concerns the University of East Anglia’s Climatic Research Unit which was involved in the Climategate scandal and which has apparently now decided that it wants to share its data. Fine, but I find it absolutely amazing that such centres have been able to get away with being so secretive in the past. Their behaviour was guaranteed to lead to suspicions that they had something to hide. The public debate about climate change may be noisy and generally ill-informed but it’s a debate we must have out in the open.

I’m not going to get all sanctimonious about `pure’ science nor am I going to question the motives of  individuals working in disciplines I know very little about. I would, however, say that from the outside it certainly appears that there is often a lot more going on in the world of academic research than the simple quest for knowledge.

Of course there are risks in opening up the operation of science in the way I’m suggesting. Cranks will probably proliferate, but we’ll no doubt get used to them- I’m a cosmologist and I’m pretty much used to them already! Some good work may find it a bit harder to be recognized. Lack of peer review may mean more erroneous results see the light of day. Empire-builders won’t like it much either, as a truly open system of publication will be a great leveller of reputations. But in the final analysis, the risk of sticking to our arcane practices is far higher. Public distrust will grow and centuries of progress may be swept aside on a wave of irrationality. If the price for avoiding that is to change our attitude to who owns our data, then it’s a price well worth paying.


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Skepsis

Posted in Politics, The Universe and Stuff with tags , , , , , , on May 1, 2010 by telescoper

This past week was the final week of proper teaching at Cardiff University, so I’ve done my last full lectures, tutorials and exercise classes of the academic year. Yesterday I assessed a bunch of 3rd-year project talks, and soon those students will be handing in their written reports for marking.  Next week will be a revision week, shortly after that the examinations begin. And so the cycle of academic life continues, in a curious parallel to the  football league season – the other routine that provides me with important markers for the passage of the year.

Anyway, this week I gave the last lecture to my first-year class on Astrophysical Concepts. This is a beginning-level course that tries to introduce some of the theory behind astronomy, focussing on the role of gravity. I cover orbits in newtonian gravity, gravity and hydrostatic equilibrium in extended bodies, a bit about stellar structure, gravitational collapse, and so on. In the last part I do a bit of cosmology. I decided to end this time with a lecture about dark energy as, according to the standard model, this accounts for about 75% of the energy budget of the Universe. It’s also something we don’t understand very well at all.

To make a point, I usually show the following picture (credit to the High-z supernova search team).

 What is plotted is the redshift of each supernova (along the x-axis), which relates to the factor by which the universe has expanded since light set out from it. A redshift of 0.5 means the universe was compressed by a factor 1.5 in all dimensions at the time when that particular supernova went bang. The y-axis shows the really hard bit to get right. It’s the estimated distance (in terms of distance modulus) of the supernovae. In effect, this is a measure of how faint the sources are. The theoretical curves show the faintness expected of a standard source observed at a given redshift in various cosmological models. The bottom panel shows these plotted with a reference curve taken out so the trend is easier to see.

The argument from this data is that the high redshift supernovae are fainter than one would expect in models without dark energy (represented by the \Omega_{\Lambda}  in the diagram. If this is true then it means the luminosity distance of these sources is greater than it would be in a decelerating universe. They can be accounted for, however, if the universe’s expansion rate has been accelerating since light set out from the supernovae. In the bog standard cosmological models we all like to work with, acceleration requires that \rho + 3p/c^2 be negative. The “vacuum” equation of state p=-\rho c^2 provides a simple way of achieving this but there are many other forms of energy that could do it also, and we don’t know which one is present or why…

This plot contains the principal evidence that has led to most cosmologists accepting that the Universe is accelerating.  However, when I show it to first-year undergraduates (or even to members of the public at popular talks), they tend to stare in disbelief. The errors are huge, they say, and there are so  few data points. It just doesn’t look all that convincing. Moreover, there are other possible explanations. Maybe supernovae were different beasties back when the universe was young. Maybe something has absorbed their light making them look fainter rather than being further away. Maybe we’ve got the cosmological models wrong.

The reason I show this diagram is precisely because it isn’t superficially convincing. When they see it, students probably form the opinion that all cosmologists are gullible idiots. I’m actually pleased by that.  In fact, it’s the responsibility of scientists to be skeptical about new discoveries. However, it’s not good enough just to say “it’s not convincing so I think it’s rubbish”. What you have to do is test it, combine it with other evidence, seek alternative explanations and test those. In short you subject it to rigorous scrutiny and debate. It’s called the scientific method.

Some of my colleagues express doubts about me talking about dark energy in first-year lectures when the students haven’t learned general relativity. But I stick to my guns. Too many people think science has to be taught as great stacks of received wisdom, of theories that are unquestionably “right”. Frontier sciences such as cosmology give us the chance to demonstrate the process by which we find out about the answers to big questions, not by believing everything we’re told but by questioning it.

My attitude to dark energy is that, given our limited understanding of the constituents of the universe and the laws of matter, it’s the best explanation we have of what’s going on. There is corroborating evidence of missing energy, from the cosmic microwave background and measurements of galaxy clustering, so it does have explanatory power. I’d say it was quite reasonable to believe in dark energy on the basis of what we know (or think we know) about the Universe.  In other words, as a good Bayesian, I’d say it was the most probable explanation. However, just because it’s the best explanation we have now doesn’t mean it’s a fact. It’s a credible hypothesis that deserves further work, but I wouldn’t bet much against it turning out to be wrong when we learn more.

I have to say that too many cosmologists seem to accept the reality of dark energy  with the unquestioning fervour of a religious zealot.  Influential gurus have turned the dark energy business into an industrial-sized bandwagon that sometimes makes it difficult, especially for younger scientists, to develop independent theories. On the other hand, it is clearly a question of fundamental importance to physics, so I’m not arguing that such projects should be axed. I just wish the culture of skepticism ran a little deeper.

Another context in which the word “skeptic” crops up frequently nowadays is  in connection with climate change although it has come to mean “denier” rather than “doubter”. I’m not an expert on climate change, so I’m not going to pretend that I understand all the details. However, there is an interesting point to be made in comparing climate change with cosmology. To make the point, here’s another figure.

There’s obviously a lot of noise and it’s only the relatively few points at the far right that show a clear increase (just as in the first Figure, in fact). However, looking at the graph I’d say that, assuming the historical data points are accurate,  it looks very convincing that the global mean temperature is rising with alarming rapidity. Modelling the Earth’s climate is very difficult and we have to leave it to the experts to assess the effects of human activity on this curve. There is a strong consensus from scientific experts, as monitored by the Intergovernmental Panel on Climate Change, that it is “very likely” that the increasing temperatures are due to increased atmospheric concentrations of greenhouse gas emissions.

There is, of course, a bandwagon effect going on in the field of climatology, just as there is in cosmology. This tends to stifle debate, make things difficult for dissenting views to be heard and evaluated rationally,  and generally hinders the proper progress of science. It also leads to accusations of – and no doubt temptations leading to – fiddling of the data to fit the prevailing paradigm. In both fields, though, the general consensus has been established by an honest and rational evaluation of data and theory.

I would say that any scientist worthy of the name should be skeptical about the human-based interpretation of these data and that, as in cosmology (or any scientific discipline), alternative theories should be developed and additional measurements made. However, this situation in climatology is very different to cosmology in one important respect. The Universe will still be here in 100 years time. We might not.

The big issue relating to climate change is not just whether we understand what’s going on in the Earth’s atmosphere, it’s the risk to our civilisation of not doing anything about it. This is a great example where the probability of being right isn’t the sole factor in making a decision. Sure, there’s a chance that humans aren’t responsible for global warming. But if we carry on as we are for decades until we prove conclusively that we are, then it will be too late. The penalty for being wrong will be unbearable. On the other hand, if we tackle climate change by adopting greener technologies, burning less fossil fuels, wasting less energy and so on, these changes may cost us a bit of money in the short term but  frankly we’ll be better off anyway whether we did it for the right reasons or not. Of course those whose personal livelihoods depend on the status quo are the ones who challenge the scientific consensus most vociferously. They would, wouldn’t they? Moreover, as Andy Lawrence pointed out on his blog recently, the oil is going to run out soon anyway…

This is a good example of a decision that can be made on the basis of a  judgement of the probability of being right. In that respect , the issue of how likely it is that the scientists are correct on this one is almost irrelevant. Even if you’re a complete disbeliever in science you should know  how to respond to this issue, following the logic of Blaise Pascal. He argued that there’s no rational argument for the existence or non-existence of God but that the consequences of not believing if God does exist (eternal damnation) were much worse than those of behaving as if you believe in God when he doesn’t. For “God” read “climate change” and let Pascal’s wager be your guide….

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