The irrational optimist

Matt Ridley, who regards himself as a rational optimist, had an OpEd in the Wall Street Journal yesterday titled Science is about evidence, not consensus. Indeed, I agree, I just think that what Matt Ridley suggests in his article is, at best, a strawman argument.

Phil Plait very nicely rebutted Matt Ridley’s article in a Bad Astronomer post called You’re Getting Warmer: Another Wall Street Journal Global Warming Article Misses the Target. Matt Ridley has now updated his own blog to rebut Phil Plait’s rebuttal, but sadly seems to simply reinforces his own ignorance. There’s something that I suspect I will be repeating many times on this blog and it is this: if you think you’ve noticed something that a large number of professional, highly-trained, experienced scientists have missed, you should typically take a large step back and consider the possibility (quite likely) that you are the one who is mistaken, not the scientists.

So, what does Matt Ridley claim. He quotes Phil Plait and then adds

“First, it’s true that in the distant past (hundreds of thousands of years ago) a rise in carbon dioxide sometimes did follow a rise in temperature.” Actually, this is invariably the pattern in the ice core record, not “sometimes”.

I believe Phil is correct. The Vostok ice core is from Antarctica and in this ice core temperature leads CO2. However, I believe that there are Arctic ice cores for the same period in which CO2 leads temperature. So, CO2 doesn’t always lag temperature. I should probably try and finds these, but have to go and give a lecture in 20 minutes, so happy to be corrected if I’m wrong.

Matt goes on to say,

the inconvenient truth is that at the end of the Eemian interglacial temperature fell steadily for thousands of years before CO2 levels fell at all. The argument that a small warming at the start of an interglacial causes a CO2 release which causes a large warming is one that has been tested and found entirely wanting.

So, yes at the end of the last interglacial the temperature did fall quite quickly while CO2 levels dropped more slowly. However, what Matt Ridley seems to think is that the argument is that a small temperature change driven by orbital variations is then amplified significantly by increased atmospheric CO2 concentrations. During the Milankovitch cycles, temperatures varied by about 10oC. The CO2 forcing varied by about 3 Wm-2. Given an equilibrium climate sensitivity of about 3oC per doubling of CO2, this implies that the CO2 contributed 2 to 3oC of the warming (maybe 30% of the total). The total temperature change cannot be explained without including the influence of CO2, but CO2 wasn’t – as far as I can tell – the dominant forcing. Also, the variation of solar insolation is not nice and simple across the Milankovitch cycles. Sometimes the change is large and rapid, other times smaller and slower. The Eemian may simply be a period where the solar forcing dropped quickly by a large amount and it simply took much longer for the CO2 levels to drop.

Matt Ridley then adds

If we assume that the CO2 is giving 3° per doubling of warming per the IPCC hypothesis, then the problem is that raises the rate of thermal outgassing up to 17 ppmv per degree of warming instead of 15 ppmv. This is in the wrong direction, given that the cited value in the literature is lower at 12.5 ppmv.”

This comes from this Watts Up With That (WUWT) post. During the Milankovitch cycles CO2 varied between about 180 and 280 ppm and the temperature changed by about 10oC. The WUWT post estimates that CO2 increased by 15ppm for every 1oC of warming, quite close to other estimates of 12.5ppm for every 1oC. Matt Ridley seems to have confused the thermal outgassing with the radiative forcing.

Matt Ridley then goes on to criticise Phil Plait for mentioning Michael Mann’s hockey stick and the more recent paper by Marcott et al., both of which – according to Matt – have been discredited. No they haven’t. The hockey stick shape has been recovered in many independent studies including the most recent that involved 78 researchers, from 24 different countries, 60 different institutions, and which used 511 proxies. When Steve McIntyre tried to discredit Michael Mann’s hockey stick, he apparently forgot to remove the hockey stick from what he claimed was simply random noise. When Steve McIntyre recovered hockey stick shapes from his test data, he claimed that this indicated that one could get hockey stick shapes from random noise. Maybe, but only if the random noise already has a hockey stick shape in it. There are numerous blog posts that have attempted to discredit the Marcott et al. work but, as far as I’m aware, none have actually done so, despite the clear desire for this to be true.

So, this has got rather long, but as far as I can tell, the rational optimist is somewhat irrational when it comes to interpreting the evidence for anthropogenic global warming. Maybe he should spend a bit more time talking to actual climate scientists rather than relying on Watts Up With That and Climate Audit, neither of which are particularly well regarded within the climate science community.

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12 Responses to The irrational optimist

  1. bratisla says:

    Just read the Ridley “rebuttal”

    The arrogance is so palpable I could have made a sour cream out of it. “Go back to your journalistic studies, you know nothing” – this is quite litteraly what he wrote at the end.

    And of course he got everything wrong.

  2. Yes, a remarkably arrogant rebuttal. I’m sometimes amazed by how some can continue with their rhetoric when so many have been pointing out their errors, especially when they aren’t even remotely qualified to make the kind of statements that they’ve made in the first place.

  3. dana1981 says:

    The worst part was that after Ridley had cited denier blogs and Phil had citied peer-reviewed studies like Marcott, Ridley told Phil he needed to do better research. Yeah Phil, why aren’t you reading WUWT where the best science is done?!?!

    Regarding the CO2-temp lag issue, Shakun did some really good research, which I summarized here.

    *As we already knew, the Earth’s orbital cycles trigger the initial warming (starting approximately 19,000 years ago), which is first reflected at the highest latitudes (i.e. Greenland and the Arctic – see “Onset of seesaw” in Figure 4).

    *This Arctic warming melted large quantities of ice, causing fresh water to flood into the oceans.

    *This influx of fresh water then disrupted the Atlantic meridional overturning circulation (AMOC), in turn causing a seesawing of heat between the hemispheres. The Southern Hemisphere and its oceans warmed first, starting about 18,000 years ago.

    *The warming Southern Ocean then released CO2 into the atmosphere starting around 17,500 years ago, which in turn caused the entire planet to warm via the increased greenhouse effect.

    According to the Shakun et al. data, approximately 7% of the overall glacial-interglacial global temperature increase occurred before the CO2 rise, whereas 93% of the global warming followed the CO2 increase.

  4. Thanks, I actually found your skeptical science post after I’d written this post. It is amazing that Ridley can quote, without irony, blogs like WUWT and ClimateAudit and then criticise Phil Plait for quoting peer-reviewed research. Quite remarkable really.

  5. BBD says:

    What infuriates me – as much as the buffoons at the WSJ inviting Ridley and others to contribute error-riddled nonsense *yet again* – is that these strident non-experts are taken seriously by far too many people. Dishonest memes like “Marcott is broken” are insinuated into the public discourse. Scientists are smeared; good work is misrepresented. Fake uncertainty is spread and spread again. We all know this is about politics and ultimately, money, not science. Profit before people. That’s what makes it so vile.

  6. Yes, I was somewhat taken aback by Ridley’s comments about the hockey stick and about Marcott et al. As you say, it’s completely unfounded but still enters the public discourse to be repeated by those who either don’t want to or can’t be bothered to check the details for themselves.

  7. dana1981 says:

    Yes, this is the problem with ‘news’ outlets like the WSJ, Forbes, Fox, CNBC, etc. Generally those with a right-wing political lean and/or with business reporting, that see it in their best interest to deny AGW. They’re always looking for people with some sort of apparent science credibility like Ridley, Michaels, Lomborg, Bastardi, Happer, etc. to tell them what they want to hear. And there’s no penalty for getting the science completely wrong – on the contrary, they’re giving their audience what they want.

    Denial is an ugly thing.

  8. When Steve McIntyre tried to discredit Michael Mann’s hockey stick, he apparently forgot to remove the hockey stick from what he claimed was simply random noise.

    And here is where he forgot to do it (excerpted from McIntyre’s R-code at:

    tree<-read.table(file.path(url.source,"NOAMER.1400.txt"),header=TRUE,sep="\t") #collated AD1400 network
    dates<-tsp(tree)# [1] 1400 1992 1
    tree<-ts( tree[(1400-tsp(tree)[1]+1):(end0-dates[1]+1),] ,start=1400,end=end0)
    dim(tree) #581 70


    The first line in the above code snippet is where Mann’s tree-ring data is read in. There’s some data-housekeeping done (marking invalid/missing samples, etc.) in the following lines. The last line in the snippet is where the noise-model coefficients are calculated.

    Note that *nowhere* between where the data gets read in and where the noise-model coefficients are calculated is there any attempt to filter out the “hockey-stick” signal in the data.

    And yes, if you take that data, variance-normalize it, and then just average the time-series together, you will see an underlying “hockey-stick” shape. It’s noisy, but it’s there.

    That “hockey-stick” signal ended up going right into McIntyre’s noise-model right along with everything else. That’s a major boo-boo, and that alone invalidates this particular aspect of his attack on Mann’s work.

    The “hockey-stick” signal in the data is a slowly varying “low frequency” signal. Its autocorrelation length will be significant relative to the data-set length (duration). Process data with autocorrelation times that are significant relative to your time-series duration and you will often see spurious “trends”.

    What McIntyre *should* have done is detrend the tree-ring data first (or apply some sort of high-pass filter) to get rid of the low-frequency long-term climate signal before using the data to generate his noise model. But he didn’t do that. That’s a major oversight that a truly competent scientist like Michael Mann wouldn’t let slip by.

  9. In the first part of McIntyre and KcKitrick’s code there is a section with a function called sd.detrend. Do you know what this does. Also, do you know if it is possible to actually run this code?

  10. Pingback: Debunking the Hockey Stick | Wotts Up With That Blog

  11. Nick Stokes says:

    “The last line in the snippet is where the noise-model coefficients are calculated.”

    I can’t see that. It seems to be just assigning a string constant, which will later tell the noise program to generate arfima noise.

    The snippet does just seem to be cleaning up the table and collecting the valid bits.

  12. Indeed, you’re correct. The last line is simply assigning a string constant that is then used in Part 1 of the code to decide which method to use. You seem to know about these things. Is the basic claim, though, correct? I did find other evidence that what M&M were doing is producing Auto-Correlation Functions from the MBH data without first removing the signal. I appreciate that this isn’t quite the same as simply leaving the signal in the data (because the analysis isn’t directly analysing the MBH data, the MBH data is being used to produce noise using the ARFIMA function and using this package called hosking.sim – which I haven’t been able to find all that much about). It does seem, however, that not removing the signal makes it more likely that the analysis will produce a hockey stick than if one was using trendless (or signal-less) red noise.

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