Friday, November 27, 2009

Why am I an AGW sceptic?

This is in response to an e-mail, which asks: "I wonder if you could enlarge on your global warming scepticism?
1. Is it not a fact that there is less ice over the North Pole, and that glaciers are retreating all over the world?
2. CO2 is a greenhouse gas, and as a result of burning fossil fuels over the last 200 years we have increased the proportion of CO2 in the atmosphere by 50%.
Does it not seem likely that 2 has contributed to 1?"

I say:
- no denial that there has been significant warming, esp. through the second half of the twentieth century, the issue is about the A of the AGW (ie how far is it anthropogenic);
- the level of CO2 in the atmosphere has been rising consistently since industrialisation;
- the temperature has not displayed anything like a linear relationship with CO2;
- the temperature has fluctuated significantly in previous centuries without any regard to CO2 (and, I believe, has been warmer than today eg in the Medieval Warm Period);
- I'm therefore dubious about the anthropogenic element, and I haven't seen very much that convincingly links the temperature shifts to human activity. It's a reasonably plausible hypothesis which I find, at present, 'not proven'.

I could well be wrong. I don't think that AGW is a 'hoax', I think that there is a perfidious industry of 'climate change denial' and I am quite open to the idea that human activity has indeed had an effect on the climate change. However, even if AGW is true, I see it as largely irrelevant because a) the peaking of fossil fuels places an absolute limit on emissions (at a much lower level than the IPCC expect, and which will achieve vastly more than any inter-governmental agreements like Kyoto or Copenhagen) and b) we need to change our behaviour (we will be forced to change our behaviour) anyway due to the many other limits to growth.

In other words, I'm starting to see all the fuss about climate change as being like an engineer rushing up to tell the captain of the Titanic that he needs to shut down the engines because if he doesn't, they are likely to blow up in a day or two, and the captain says 'Engineer, we've just struck an iceberg!'

I'm also getting more sceptical about the way that the church is latching on to the issue (and, indeed, on to Peak Oil). I think that we miss the point of our calling if we hitch our behaviour to contemporary issues. We need to live sub specie aeternitatis whatever the science tells us.

6 comments:

  1. the temperature has not displayed anything like a linear relationship with CO2
    In a system as complex as the climate, why would we expect it to? Has anyone claimed that it ought to have? There are many forcings on climate and different forcings have been dominant during different periods. The claim is not that the GW is all A (which would indeed be silly), simply that the lion's share of the recent warming (last three decades) has been.

    the temperature has fluctuated significantly in previous centuries without any regard to CO2 (and, I believe, has been warmer than today eg in the Medieval Warm Period);
    It has fluctuated somewhat within a fairly narrow band in previous centuries of human existence, but not by the amount we're currently seeing. I know you don't accept the mainstream reconstruction, but even without that (i.e. granting for a moment that perhaps the global anomaly during the middle ages was a little greater than the present observed warming), it is still not greater than the presently observed warming added to the warming already "baked in" (due to lags in response), and even with the most pessimistic forecast of peak oil, humanity will still be emitting quite significant amounts of carbon for some time to come, taking us further into uncharted waters.

    I'm therefore dubious about the anthropogenic element, and I haven't seen very much that convincingly links the temperature shifts to human activity. It's a reasonably plausible hypothesis which I find, at present, 'not proven'.
    In the light of your most recent post, have you shifted on this particular point? It is a matter of the most likely explanation. Are there any serious candidates still standing apart from AGW? There were some contenders a decade or two ago, but they have failed to account for all the evidence.

    I do agree that PO is likely to hit sooner and harder (initially) than CC, but I don't think they fall under exactly the same response strategies. There is some common ground, but a crucial difference is in the exploitation of non-conventional fossil fuels and whether the reserves of coal are a boon or a dire threat. CC is also more significant than PO in the long term because its effects are likely to last for millennia, whereas PO might simply see off industrial society as we currently know it. ("simply"!)

    Thus, to modify your analogy along a highly improbable line, perhaps it is like the engineer rushing up to the captain and saying "we've just realised that the water is highly acidic and is going to breach the hull", and the captain says, "No time to worry about that, we've just hit an iceberg!" And then they both realise that the life rafts are also susceptible...

    I also agree that the church ought to live sub specie aeternitatis, but part of how we are to live is by attentive love to our neighbour, and so understanding our neighbour's situation and the threats (spiritual and otherwise) and opportunities that belong to it is an important aspect of Christian discipleship.

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  2. Hi Byron - there was I thinking my latest post was a conciliatory offering ;-)

    Taking your points in order:
    - 'the lion's share' - that's what I think has not yet been fully quantified. I'm thinking in particular of the link with things like
    the Pacific Oscillation;
    - I think we disagree on what counts as the 'mainstream reconstruction' - as I understand it, it's not just the MWP that was warmer, the Roman period was warmer still, and the period about 5,000 BC was even warmer than that - in so far as we can know such things with any confidence. See in particular the context-setting video showing the temperature record of the Greenland ice-cores
    here;
    - have I shifted on this one? yes, probably. I now understand the physics much better than I did (mainly thanks to this site which I think is great: http://scienceofdoom.com/ I think I'd say now that I'm persuaded of the link, it's the extent of the link that I remain to be convinced of.

    Some time back I used to say that coal was
    the enemy of the human race. Now I'm not so sure; that is, I think that there is room for arguing about the trade-off between burning (some) coal and helping the present population vis-a-vis getting renewables going. My views on coal have become much more nuanced - this, of course, is very relevant to your last point.

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  3. Should have added - that is, (to pursue the analogy) - it's like someone telling the captain that in order to save the ships (or stop it sinking so quickly) we have to destroy some lifeboats. At least, that is where the discussion lies, so it seems to me.

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  4. PPS - I tag you with the seven links meme!!

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  5. Conciliatory offering - Yes, that's how I took it, though sorry for not acknowledging that more clearly and if I came across a little abruptly! I've been quite busy recently and some of my comments might have been a little quick.

    Lion's share: not precisely quantified, since there remain reasonable uncertainties about the scale of aerosol forcing. See here for the IPCC's summary of where things were in 2007. I haven't seen this updated, though I know a lot more work on aerosols has been done since then. But compare the scale of the anthropogenic forcings to the natural forcings.

    Pacific Oscillation - here is what I understand of this, though I've read less on it than some other things.

    Greenland - One of many reconstructions, and not a particularly representative one. To get a global picture, check all the data here. The uncertainties in the reconstructions obvious increase fairly rapidly the further back you go. Wikipedia has one global graph that is now about six years old, but you can see the variation amongst the proxies (and that graph doesn't show uncertainty bars). The average (black line) is currently at its highest point during the Holocene (just, and with the degrees of uncertainty involved for thousands of years back, this may not mean much either way). I don't really put any value on that graph, it was just an example of the scale of the variations and so of the uselessness of looking only at Greenland. This page is very helpful in setting out the uncertainties and highlighting what is almost certainly very unusual about the current and projected temp rise, namely its pace. You can of course read the whole chapter if you want to get a broader understanding. I've read bits of it.

    Ah - I saw the seven links meme and thought about just tagging myself. I'm about to go away for a week or so, thus won't get to it when I get back

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  6. A quickie re: Greenland - I think it's useful to concentrate on that one series because of the focus on Greenland itself in some presentations (eg those that talk about it melting). A temperature record for Greenland seems quite a useful focus (in the same way that the record in Siberia also shows previous warm periods which puts a bit of a question mark against the 'permafrost melting will lead to catastrophic positive feedback' meme.

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