I wrote a longish feature for Nature this week on geoengineering. It goes into various details perhaps a little deeper than some accounts have, and of course also leaves out stuff that in an ideal world it would have got in. The bottom line is that lowering the earth’s average temperature by putting long-lived particles of some sort into the stratosphere is, as has long been known, technologically feasible, and would alter the course of, but not completely stop, climate change. Crucially, as yet we cannot predict with any confidence what the net changes under a warming+cooling regime would be, and though there are signs they might be a little smaller than was once thought they could easily be large enough to be complete showstoppers. The article gives, I think, full voice to the uncertainties and risks involved (though I suspect some will differ, especially since the article has served as a springboard for the AEI, which makes this comment peculiarly ironic).

There are some things it doesn’t do: it doesn’t go into the fact that we have no way of deciding, as a world, whether to do this, nor of setting up reliable systems for managing a century long geoengineering strategy. (I say century long because the people I was talking to all seemed to be thinking about geoengineering as either a time-limited stop-gap to buy time for mitigation to get into full swing or as a way to take the edge off the worst of the warming that would accompany an “overshoot” in greenhouse gas levels before they settled down to a stabilisation plateau. No one, as I understood it, was talking about an open ended commitment that would allow emissions to go unchecked forever.) Nor does the article explore the fact that it would be conceivable for a country to embark on such a scheme unilaterally. It certainly doesn’t advocate doing anything along these lines, unilaterally or multilaterally. (It also doesn’t know its history, and lamentably gave Ralph Cicerone a Nobel prize that he doesn’t have. I am a fool.)

What I did try and do, at least a little, was explore the reasons why many researchers don’t even want to look at this issue. There’s a fairly widespread feeling that even studying it lends it a certain legitimacy, and that that legitimacy could be used as a rhetorical tool — or even as a basis for real-world programs — by people who have no interest in reducing CO2 emissions. I can understand this as a position; people obviously have a right to avoid doing research that they believe will be misappropriated. But that said I think that this view is at least somewhat on the wane. One reason is Paul Crutzen‘s intervention last year (see further discussion in the journal Climate Change). Another, I think, is increasing consciousness of ocean acidification, though this is speculation on my part, and didn’t as I recall make it into the finished article. Ocean acidification provides a really strong argument for cutting carbon dioxide emissions that geoengineering can do nothing about. Its acknowledgement may thus, in a strange way, provide people with a license to speculate about such ideas, since it allows all such speculation to carry the firm proviso that even if you did try geoengineering, you’d have to cut emissions anyway — that there’s no either/or.

Predating this, though, I suspect there’s been a feeling that even if there were no practical drawbacks to such schemes — and again, let me stress, there are — they would be inherently inferior solutions to the problem than limiting emissions. The idea is that changing human economies and societies (and for some more fundamentalist greens, human nature) is inherently preferable to changing the natural world. I followed David Keith in mapping these ideas onto the distinction Simon makes between natural science and the sciences of the artificial. Here’s where I ended up:

Although in the past two decades climate scientists have been confronted with the social, technological and economic implications of their work, they are not scientists of the artificial. Hans Feichter, a climate modeller at the Max Planck Institute for Meteorology in Hamburg, speaks for the vast majority of his colleagues when he says “the role of a geoscientist is to understand nature, not to change it.” Climate scientists have proved themselves happy to advocate massive changes aimed at shifting the climate. But they are massive changes in technology, in geopolitics, in social norms — changes that require the sciences of the artificial. Not changes in the workings of the stratosphere. Not changes in the natural.

In the past year, climate scientists have shown new willingness to study the pathways by which the Earth might be deliberately changed, although many will do so in large part simply to show, with authority, that all such paths are dead-end streets. But they are not willing to abandon the realm of natural science, and commit themselves to an artificial Earth.

It may be that that is overstated. For one thing, it’s clear that geoengineering, like mitigation, would also involve a large political intervention. Anyway, I’d be interested to hear your views.