Geo-engineering in vogue…

There was an interesting article in the NY Times this week on possible geo-engineering solutions to the global warming problem. The story revolves around a paper that Paul Crutzen (Nobel Prize winner for chemistry related to the CFC/ozone depletion link) has written about deliberately adding sulphate aerosols in the stratosphere to increase the albedo and cool the planet – analogous to the natural effects of volcanoes. The paper is being published in Climatic Change, but unusually, with a suite of commentary articles by other scientists. This is because geo-engineering solutions do not have a good pedigree and, regardless of their merit or true potential, are often seized upon by people who for various reasons do not want to reduce greenhouse gas emissions. However, these ideas keep popping up naturally since significant emission cuts continue to be seen as difficult to achieve, and so should be considered fairly. After all, if there was a cheaper way to deal with the CO2 problem, or even a way to buy time, shouldn’t we take it?

First a little history [Update: See Spencer Weart’s essay on the history of climate modification ideas]. Geo-engineering ideas first reached the public in the 60s when there was still a lot of enthusiasm for technical fixes of the world’s problems. One example was suggested by the Soviets who wanted to melt the Arctic (either using soot or nuclear devices) in order to warm up their frozen North. More recently, there was a proposal to dam the Straits of Gibraltar in order to prevent more saline Mediterranean Sea water (because of the Aswan Dam) from affecting the North Atlantic conveyor circulation (no, it didn’t make sense to us either). With such a pedigree, geo-engineering is generally seen as fringe entertainment at best, although some of the new ideas concerning atmospheric carbon dioxide sequestration are being looked into seriously.

Edward Teller is the scientist most associated publicly with the idea of creating a stratospheric shield to prevent excessive global warming, though he built on an idea from Freeman Dyson (who has subsequently become a bit of global warming contrarian)*. However, as Teller’s collaborator Stanislaw Ulam once said after discussing some new ideas with him: “Edward is full of enthusiasm about these possibilities; this is perhaps an indication they will not work”. And given Teller’s estrangement from the scientific community in his later years, it was not likely that the concept would be taken very seriously, and indeed it hasn’t been.

*Which in turn built on a idea from Budyko…(see comment below).

But now Paul Crutzen has stepped into the fray. He has a much more solid reputation amongst climate scientists than Teller, and thus his ideas will be taken more seriously. I haven’t seen the new paper yet (it’s out in August) but there are a number of questions that need to be addressed before any geo-engineering proposal combatting global warming should be thought of as anything more than an interesting idea. First, the idea has to actually work, second, the side effects need to be minimal, and third, it has to be able to keep up with an increasing forcing from ever higher greenhouse gas levels, and fourth, it has to be cheaper than the simply reducing emissions at source. These are formidable hurdles.

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