Thursday, February 27, 2014

Floods: more please?

Are the UK floods a sign of climate change? According to a recent poll, 46 percent of people think so, 27 percent think not. The invitation is to regard this as a proxy poll for a general belief in the reality of climate change, and perhaps in humankind’s key causative role in it.

But in fact, any information embedded in this poll is complicated and difficult to entangle. If any climate or weather scientists were quizzed, it seems likely that they will have gravitated, like me, towards the “undecided” category. As they have been repeating insistently and now a little wearily, no single extreme-weather event (and this one certainly qualifies as that) can yet be unequivocally attributed to climate change. This of course is manna for the climate sceptics, who use it to argue that we still don’t know if climate change is really happening, and that this uncertainty reflects a serious limitation, perhaps a fundamental flaw, of the whole basis of climate modelling. It matters little that climatologists say such extreme weather is fully consistent with what the models predict – the misguided but widespread notion that science provides “yes/no” answers to questions, decided by the data, is here proving a burden.

That situation is changing, however. As Simon Lewis points out in Nature this week, it is now becoming possible to make some definite links between specific extreme weather events and anthropogenic climate change. Such analyses are complicated and the conclusions tentative, but they already give grounds for saying a little more than merely “it’s too early to tell”.

What the flood poll really probes, however, is public perceptions about what an altered climate would mean. The effect of the floods is likely to be not so much convincing undecided voters that climate change is already upon us, but showing them what is really at stake in this temperate zone: not balmy Mediterranean-style summers, not distant news of drowned Pacific island states, but Verdun-style mud and sandbags, and images of this green and pleasant land under glittering, muddy water from horizon to horizon. We have finally got a feeling for what it might be like to live in a world a degree or two warmer, and it seems uncomfortably close to home, and not at all pleasant. Shivering east coast Americans are having a somewhat different kind of awakening.

As wake-up calls go, it is pretty mild. But it is also likely to shift perceptions, not just of what to expect but of what the social and economic consequences will be. The more intelligent, or perhaps just cannier, sceptics have ceased questioning the science or the evidence but instead contest the economics: it will cost more, they say, to mitigate climate change, for example via taxes on fossil fuels or expensive green technologies, than to accept and adapt to it. This, for example, is the line taken by the science writer Matt Ridley, who laid out his case last October in an article in the Spectator.

The Viscount Ridley, immensely wealthy Eton-educated Conservative hereditary peer whose Darwinian attitude to economics was notoriously suspended when it came to the bailout of Northern Rock under his chairmanship, is an easy villain. But the Ridley I know (slightly – we sit on the same academic advisory committee), who happens to be an exceptionally good science writer and a clever thinker, is harder to caricature. His argument – in which a warmer world results in fewer net deaths, for example, though winter hypothermia – can’t be casually waved away. The dismantling needs more care.

The economic case is hugely complicated, and plagued by many more uncertainties than the science. It depends, for example, on making projections about nascent or even as yet undeveloped technologies. Even the research on which Ridley almost exclusively draws – by economist Richard Tol – mostly just points out these lacunae, and Tol advises nonetheless that “there is a strong case for near-term action on climate change”. (Ridley jettisons that bit.)

But of course economic figures paper over a multitude of woes. Imagine, for example, that an ice-free summer in the Arctic (which begins to look likely sooner than we expected) leads to the extinction of the economically insignificant polar bear (I’ll come back to that) but creates a fertile new breeding ground for fish stocks, with large economic benefits for fisheries. How would you feel about that? Or if the inundation of a few island states with trivial GDP, leaving the populations homeless, were massively offset by improved wheat yields in a warmer US Midwest? I’m not saying these things will happen, just that GDP is only a part of the story.

More importantly, perhaps, one can’t really put an economic figure on consequences of climate change such as the mass human migration that is predicted from north to south, which could very readily lead to social unrest and even war. Or the drastic changes in ecosystems likely to result, for example if ocean acidification from dissolved carbon dioxide wipes out corals. It isn’t hard to dream up such disasters, and Ridley is right that we need to think carefully, not just reactively, about what the real consequences would be – but economics, let alone highly uncertain economics, doesn’t give a full answer. All we can really agree on is that there seem unlikely to be any net benefits beyond 2070 or so, by which time things are getting really bad – especially if you have ploughed on merrily with business as usual, which Ridley seems to recommend. (He offers no alternative plan.) I won’t be around to see that; with good luck, my children will be. I don’t think theirs will be a problem that can be solved with wellies and sandbags.

All the same, I wish I could trust the arguments Ridley brings to the table. But, surprised by his passing suggestion that polar bears are fine and might even benefit from a bit of polar warming, I decided to check. The US Geological Survey in Alaska says “Our analysis of those data has shown that longer ice-free seasons have resulted in reduced survival of young and old polar bears and a population decline over the past 20 years. Recent observations of cannibalism and unexpected mortalities of prime age polar bears in Alaska are consistent with a population undergoing change.” The National Wildlife Federation says “The chief threat to the polar bear is the loss of its sea ice habitat due to global warming.” It’s impossible to generalize, however: studies suggest that many polar-bear populations will be wiped out within a few decades without human intervention, but some seem to be doing OK and may survive indefinitely (although climate change may introduce other threats, such as disease). If I were a polar bear, I’d feel decidedly less than sanguine about these forecasts. I’d also suspect that Ridley is less the “rational optimist” he styles himself, and more the wishful thinker.

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