What I think about global warming

A reader wrote:

I am a recent reader of your blog Stoat. I am very interested in the Climate Change issue but I am not a scientist. I read Joe Romm, Island of Doubt and General news about the subject. You are the first expert I have come across that seems to have a balanced opinion on climate change. I have searched through your archives but I can’t really get a complete feel of what your opinion is. I get lost sometimes when you explain the technical stuff or use abbreviations for things that I don’t know what the abbreviations are for. Could you do a blog post (in an untechnical format) of what your opinion of the problem with climate change is? Is it a problem? What are the consequences? etc…

which is the spur to this post. I am conscious occaisionally when I search back through my archives for a source for “of course my opinion about X is quite clear” I then discover that actually my opinion is delivered through so many layers of assumed knowledge that you might well be confused about what I think.

Anyway, in answer, I direct you to Just what is this Consensus anyway? which is a post I wrote for RealClimate (which I usually abbreviate to RC – in celebration of my obscurity I’ve just written a glossary, do peruse it). The reason I wrote it is worth going into, because it illustrates some of the problems in communicating global warming type stuff. And that is, that the people involved in it just know what is going on. There is no formalised system of “stuff you believe in” – you just swim in it. The borders aren’t really clear but the core is obvious. Nowadays the “stuff” is sort-of defined by the IPCC (WGI of course) but no-one can read it all. You just don’t get people in science saying “well I don’t think the world has warmed in the last 50 years you know” because people like that live off in la-la land so people don’t even realise it is supposed to be an item of belief. It is just There.

I’ll quote what I said in 2004:

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The main points that most would agree on as “the consensus” are:

1. The earth is getting warmer (0.6 +/- 0.2 oC in the past century; 0.1 0.17 oC/decade over the last 30 years (see update)) [ch 2]
2. People are causing this [ch 12] (see update)
3. If GHG emissions continue, the warming will continue and indeed accelerate [ch 9]
4. (This will be a problem and we ought to do something about it)

I’ve put those four points in rough order of certainty. The last one is in brackets because whilst many would agree, many others (who agree with 1-3) would not, at least without qualification. It’s probably not a part of the core consensus in the way 1-3 are.

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Yep, all of that remains pretty well true, and remains the core. For point 2 you can see the update; the context of updating point 1 is more interesting: I originally wrote “0.1 oC/decade over the last 30 years” because I didn’t actually know what the true value was and I didn’t much care. It really didn’t matter too much to me at that point, and the exact value still doesn’t matter all that much now. I should probably qualify “the warming will continue and indeed accelerate” – the warming goes up to ~0.2-0.3 oC/decade, depending on scenario (see, I still don’t care about the exact value and didn’t even bother look it up) but doesn’t accelerate thereafter (well, except for SRES A2).

In the years since I wrote that nothing has come along to overturn any of that, and much has come in to buttress it. 1, 2 and 3 are now strong enough to be considered “essentially true”; the arguments that claim any of them are false are now dull and uninteresting and without scientific validity. Pretty well all of the meaningful scientific skeptics have now given up trying to argue that. That doesn’t stop the blogosphere reverberating with nonsense, of course.

However, I still think there is room for honest skepticism and disagreement about point 4. I think it is regrettable that there is so much continuing discussion about 1-3, which is largely sterile and mis-informed (on the septic side). I suppose you could argue that this blog and many others owe their continued existence to this sterile debate :-). The real argument should be about point 4: that it will be a problem and we should do something about it. Some groups – and I’m thinking of the likes of Greenpeace or WWF – are of the sort who will say “global warming is automatically a problem and there is no need even to demonstrate this” [See update]. I think that is wrong.

I don’t know the answer to point 4, and I know that I don’t know :-). If forced to pronounce on it, I would say what has been said before: conducting a giant geophysical experiment with the only defence of “we don’t know what might happen” is really stupidly dangerous and the sort of thing you’d get a clip round the ear for if you tried it in chemistry in a proper old fashioned school. If you see what I mean. On the other hand (and there is another hand) the converse to that is “conducting a giant experiment with the global fuel / financial system isn’t a great idea either” and that is what Doing Something About It amounts to. And left to the lobbyists and politicians some pretty stupid ideas will get a look in, like Cap-n-Trade – I prefer a carbon tax.

The reasons why point 4 might be a problem are obvious enough –

1. our culture and civilisation is adapted to roughly the current temperature and precipitation distribution (despite the emphasis on “warming” it is entirely likely that the major impacts could be hydrology related, since rainfall will shift in hard-to-predict ways as the climate changes),
2. the natural world on which we depend is also so adapted,
3. sea level rise,
4. hurricanes and other natural disasters,
5. ocean acidification [Added later]

Number 3 is an interesting one. Because 1 and 2 are kind of woolly, people often drop down to 3 as an “absolute” of-course-this-is-bad (and I’ve never heard anyone argue that SLR would be anything but bad). But that can lead to people over-emphasising or exaggerating the likely future sea level rise. How big will it be? We don’t know. The IPCC AR4 (4th Assessement Report, see glossary) wimped out of answering fully, and instead said ~70 cm by 2100 [Ahem. See update] but excluding exciting things from the ice sheets. Since Exciting Things from the Ice Sheets was the main point at issue, this was a big wimp out. But it did arguably relfect the science, which is: we really don’t know the answer right now.

[Added later: number 5 might be bad; I’m not sure. I haven’t troubled to find out much about it so far]

1 I’m somewhat dubious about – people are adaptable, as are buildings over a long enough time frame – and I’m inclined to think that most of the trouble will come from point 2. But really a discussion of the impacts has to involve the impacts people and the biologists and so on who deal with the squishy stuff. I don’t know. An obvious counter to 2 is “but climate has changed in the past: it has been much colder (ice ages) and much warmer (errr…)”. The “err…” there is because actually it *hasn’t* been “much” warmer (or at least, the evidence for greater warmth is thin) for a good while, where “a good while” is poorly defined – perhaps millions of years – at least, a time long enough in terms of evolution. The “counter-counter” is usually “ah yes, the climate has changed, but not at this unprecedented rate” and this is where the rate of future climate change becomes important.

Hurricanes became very sexy in the aftermath to Katrina (don’t fail to follow the link to the RC view) but on this issue I’m largely with Roger Pielke Jr (RP Jr) on this – almost all of the increase in damage from hurricanes over the last ~50 years is due to societal changes, not climate changes.

And that happily leads me on to my Spotters Guide to Climate Blogs. But I think I’ll reserve that for another post.

[Updates: I just knew I was going to have to do this…

* SLR: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/spmsspm-projections-of.html#table-spm-3 says “0.21 – 0.48” so my 70 cm is a bit high.
* deconvoluter points out that point 4 is subject to the “inequity problem” – while some areas might gain from climate change, others might lose. Attempting to balance gains and losses would be alegal nightmare and a lawyers troughing dream. The only way to handle it in the real world would be allowing freer movement of people.
* environmental stress: I didn’t mention this before, but if you care about environmental stress the biggest sources are probably not GHG’s but our towns, cities, farms and rainforest destruction. Yes they are all linked.
* “global warming is automatically a problem and there is no need even to demonstrate this” – I forgot one of the reasons – perhaps the strongest – for people believing this, which is the morality argument (thanks cbp): breaking things is Bad. Cutting down old growth forest is Bad. *I* agree with that, but since it is a morality problem it runs slap into the “ah, but my morality is different from (but no worse than) yours” answer.

Refs

* How fast is the earth warming? – Open Mind / Tamino.
* ATTP on some things we should be able to agree about.
* Rates of ancient climate change may be underestimated? [2015]