Martin, indeed I didn't answer you before (top of page 10), but if you think what I said was "vehement" protest, I suggest a trip to the bookshop to buy a dictionary would be in order.

But anyway, it was not a bad question. I cannot respond to everything that is said against me in detail in any reasonable amount of time, but since you asked again... No, evidence of a physical phenomenon is clearly not the same as 'evidence' given by a model.

I have actually come around to your view that the word 'evidence' should be avoided when talking about the future in the climate field. The same can be said of acidification, another sceptic bugbear, and there are other problematic words too that escape me right now. Other words less open to attack can be used. And 'evidence' should probably also not be used in relation to evolution, secondary smoking or asbestos. But in any field that lacks a constituency that has an interest in picking holes in terminology in order to delegitimize what it dislikes, I think evidence is a fine word. Everyone will understand what is meant and nobody will try to impose their own narrow meaning on the word.

Talking about non-answered questions, you never did tell me your pdf for temperature. You said you just don't know, or some such. But as I suggested, this implied that you thought the global average temperature in say 100 years might be any value from zero K to infinity. That is clearly nuts and you are clearly not, so please give me an idea of the probability of any particular temperature. For example you might think it would be a normal distribution around the current temperature. You clearly are not certain that it will actually *be* the current temperature (as you said you just don't know) and it seems unlikely that you think +1 (from now) is as likely as +2 and +3, -4, -10 etc. So what is your pdf and how do you calculate it? How much less (or more) likely is +1 than 0, +2 than +1 etc.

Martin A
QED on your theory I;d say.

Radical, I surrender the word 'evidence' to you and your friends. Use it wisely. I hope you are happy together. I shall be content to say that models provide strong grounds for belief that climate will change; that they support the assertion that CO2 is responsible for climate change; that they have allowed us to conclude that doubling CO2 will raise global average temperatures by one or more degrees celcius; that they indicate problems ahead if CO2 is not controlled. I could go on. English is flexible.

I'll throw in 'acidification' and content myself with decreasing ocean pH, falling ocean pH, plummeting pH, souring.

I'll even give you, your Bishop and your friends 'evolution'. It is enough for me to say that all dogs have descended from a common ancestor, that they have been modified genetically to reach their present form, that genomes of bacteria, insects, all animals and plants change in response to selection pressure such that new species arise. I need 'evolution' not.

Those who must censure words to defend their opinion are like a regime that censures opinion to protect their power - doomed to fail eventually.

Blimey.

I don't know about you, but if I asked someone to give me a "vehement protest" I'd expect at the very least an exclamation mark. I guess vehement is another word from the sceptic lexicon that I shall have to avoid.

And "demanding" is a stretch too; I just asked. Add "demand" to the list I guess...

But really you cannot possible claim that you "haven't a clue". I mean I might say that "haven't a clue" what color socks you are wearing but I can in fact estimate some probabilities (none would behigh on the list given the time, but followed by black, navy and grey with a non-zero chance of white and an infinitessimal chance of pink). For temperature you clearly do have some data to go on. Not much different from today would be the obvious central value for someone sceptical of AGW. Or "a bit warmer" would be a sensible central value for someone who doesn't reject GHG physics outright. A deal colder would be a good answer for someone who favors force X and multi-megabyte Excel models, but I guess that is not you. So now that you have your most likely value you can sketch the shape of the curve. The chance is obviously less as you move away from the center value and the rapidity of decline reflects your degree of certainty that you understand the constraints. So however little you think you know (and I don't get the impression that you think you know only a little) you can sketch out a curve of some sort.

Radical, I was asking for a pdf, no dot. You say, "every model shows that as the levels of CO2 rises, so will the heat. CO2 levels have gone up; the heat has not." It is generally accepted that the earth's heat content has gone up. Clearly I don't expect that you believe that, but your sentence also clearly has little weight if it is based upon a reading of available information shared only by you and relatively few others.

I'll throw in 'acidification' and content myself with decreasing ocean pH, falling ocean pH, plummeting pH, souring.

Jul 25, 2014 at 5:25 PM | Unregistered CommenterRaff

Ohhhh nooooo!!!!!!! The oceans are plummeting towards the pH of pure neutral water. [Even though we don't have enough fossil fuels to come even close to that end point if we burned them all.]

That's right Raffles, throw in the "acid" word because you think it will frighten people. This is fun.

Mickey H Corbett: ‘Raff, your insistence that Matt Ridley is implying that you can use models as "evidence" in his piece about Richard Tol.
This piece in the Spectator
Ridley does nothing of the sort. He simply points out that if you consider the "consensus" and various economic models that use AGW as a basis - the overall message is that warming is mostly beneficial.’

I think there’s a fine line there. Ridley is not just claiming that the prognosis for future climate is more positive than the IPCC makes out, he is also, at least implicitly, appealing to the authority of models to support his case, and ultimately making a positive claim about the future.

There are a couple of aspects to this. Ridley begins by claiming: ‘There are many likely effects of climate change...’ The key phrase here is ‘likely effects’ (ie what may happen). Nevertheless, he’s basing his claim on work done collating the output of models.

The second aspect is that, while Ridley begins his article in the hypothetical, by the end he has morphed to making factual claims: ‘So we are doing real harm now to impede a change that will produce net benefits for 70 years’.

It’s not difficult to see how lesser writers could morph from claims of possible harm to be caused by climate change, to claims of actual future harm.

That aside, if evidence is something that can be used to support an assertion/claim, then Ridley certainly seems to be appealing to evidence. But the assertion in this case is, at least initially, only about what may happen. That is, he is using evidence to support forecasting/projection rather than prediction.

Has Raff actually answered any questions with anything other than opinions? When present with evidence countering these opinions has he done anything other that throw in a new question, the latest being ocean acidification currently being countered by michael hart?

Anyway, as it seems that digressions are OK, how about throwing this in the pot. From Wiki

Submarine volcanoes are underwater vents or fissures in the Earth's surface from which magma can erupt. They are estimated to account for 75% of annual magma output.

Some estimates put CO2 from volcanoes into the atmosphere at 300+ million tonnes (Guardian article). Therefore assuming the ratio for CO2 is the same as magma then ~1000 M tonnes is going straight into the sea along with large amounts of sulphur, potential sulphuric/sulphurous acid, and HCl. The amount of submarine Vulcanicity must vary over time just as it does on land and we've no idea about exactly how many there are, what they produce and it what quantity then we can't possibly say what effect they are having on oceanic pH and certainly not by how much.

Are there any models that account for this?

Micky, I missed your comment last night, sorry. Brendan has already nailed it really - Ridley concludes his piece with "will", not "might" or "could" or "maybe". He presents the model results fact.

Radical, you keep asking for evidence, but the problem is that you don't *accept* the available evidence as evidence. To me it is fairly obvious that if you have one or more systems that you can represent numerically, that running a model incorporating those systems generates output that shows more than just the equations. That is what numerical analysis is all about and has always been about. GCMs take that further but the principle is the same.

Mickey H Corbett: ‘He doesn't say that he accepts models as evidence ...’

Here is what Ridley says: ‘There are many likely effects of climate change ... if you aggregate them all, the overall effect is positive today – and likely to stay positive until around 2080.

‘That was the conclusion of Professor Richard Tol of Sussex University after he reviewed 14 different studies of the affects of future climate trends’.

Ridley is telling the reader that he is basing his views about the future on the results of scientific studies. And since we’re talking about possible future events, we’re talking models.

‘He is using a logical argument - it sounds like Reductio Ad Absurdum.’

A reductio takes one’s opponents claims and stretches them to absurdity to hold them up to ridicule. Ridley is not doing that. On the contrary, he is attempting to make a strong case for a view that he himself supports.

‘I believe he was making a point that we shouldn't jump the gun based on what a model says.’

No, he’s telling us to chill based on what a bunch of models are claimed to say. He is trying to persuade the reader to accept that the models tell us that everything will be fine.

No I don't think he missed it. Ridley was saying "You can choose not to believe the studies Prof Tol has collated. Or you can say the net benefit is small...etc". He then concludes with his own opinion, using "will". It is quite clear what he thinks.

Mickey H Corbett: ‘You missed this’

No, I got that. I understand that Ridley is trying to turn the consensus argument against the warmers, so is taking a position, apparently for the sake of argument.

But it doesn’t matter whether or not he is taking a position for the sake of argument. All that matters is whether he is appealing to models in support of his views, and whether he takes the models seriously. He certainly appears to be doing both.

‘From the above Ridley is clearing saying that if you accept that the temperature models are correct ... then it does not lead to catastrophe. In other words the good news if you assume all the pieces are correct is in the data.’

Except that the good news is not just in the data -- some of the good news is in projections about the future. Ridley is not claiming clairvoyance, so he must be getting his good news information from some other source.

The only sources he mentions are work by an economist on the immediate past climate record (the ‘gaze backward’), and a study that reviews studies of the effects of ‘future climate trends’.

And keep in mind the opening paragraph of the article: ‘Climate change has done more good than harm so far and is likely to continue doing so for most of this century’. That sentence sets the scene for the rest of the article and gives us a clear indication of the intentions of the writer.

Radical, I cannot give you an example that will illuminate you in one leap. You'll have to get there yourself - read about numerical analysis, which can be used to determine solutions to systems for which the answer cannot simply be calculated but must be arrived at through a large series of computations. The solution is more than just a representation of the coding of algorithm, in that it is the process of executing the algorithm that delivers the solution. That is not to say that the coding doesn't matter - of course it does.

Numerical methods are part of math, science and engineering and have been forever. They have always been used to deliver results where other analytical methods are impractical or unavailable. Radiative physics models that calculate the effect of GHG in the atmostphere by calculating the effects on many layers is a standard way of treating such problems. This is not an abomination of climate science and nobody serious would argue that it cannot deliver a soltion which can be relied upon. Equally, everybody knows that the accuracy of the solution delivered depends upon many factors including the level of approximation (how thin are the layers, for example) and of course fundamentally upon the correctness of the implementation. As the approximation is made more realistic the accuracy improves (narrowing in, not changing radically). The model is delivering evidence (oops, sorry, strong grounds etc).

For the numerical analysis of climate (GCMs), the principle is the same.

----

Micky, you said that the debate has been "bogged down in semantics and not about the bigger picture", but bogging down in semantics is Ridley's creation (and Martin A's as he introduced it here). Nobody in any other field of science, math or engineering would get worked up about a colleague developing a model to represent what they were studying because the colleague dared to use the word 'evidence' when discussing the result. They might point out, well let's not get carried away, the result is evidence of a sort but we need more xyz..., etc. But they would accept that it is an appropriate word and discuss the xyz instead.