illuminating science

There’s a pretty interesting, if controversial, article in the latest edition of Science, on a proposal to deliberately pollute our atmosphere to counteract global warming.

Global warming refers to the recent increase in temperature of our planet, and all of the indications are that it’s because of human activities, most notably the emission of lots of green house gas, particularly carbon dioxide. The rise in temperature of our planet, far greater than has been seen in many thousands of years, coincides very closely with the industrial revolution, and there’s almost no question now that humans are responsible for it. The outcomes are many, but include the destruction of our reefs, change in world climate, droughts, storms, and rising sea levels wiping out costal areas. Unfortunately, because of the costs involved with reducing our CO2 output, many governments (particularly the U.S.) are reluctant to take any action.

One highly controversial proposal is some sort of “geoengineering” strategy, whereby we change our planet in some other way to counteract these effects. In this case, the basic idea is to replicate some effects of a volcanic eruption, which spews millions of tons of sulfur into the atmosphere. This sulphur (and other emissions?) act to form more clouds, which in turn blocks out sunlight, producing cooling. It’s conceivable that by appropriately injecting compounds like sulphur dioxide into the stratosphere, we could cool the Earth enough to counteract the rise in temperature predicted by global warming. Apparently, after the Mount Pinatubo explosion, there was measurable short term cooling afterwards, so there is at least in-principle evidence that this could work.

The recent article (subscription required) presents climate models which suggests that this type of cooling might actually work, and hold off the effects of global warming indefinitely. It would involve somehow duplicating a massive Pinatubo-level contribution every two years, and the practical difficulties in actually doing this enormous (suggestions include using balloons, giant guns or massive planes), but according to researchers from the National Center for Atmospheric Research, “all the simulations have suggested it would basically work”.

Other scientists are not so impressed - they worry that instead of addressing the real problem (our greenhouse gas emissions) we’re coming up with bandaid solutions. Biogeochemist Meinrat Andreae of the Max Planck Institute for Chemistry in Mainz says “You’re papering over the problem so people can keep inflicting damage on the climate system without having to give up fossil fuels.” Carbon dioxide emissions also produce effects such as acid rain and increased acidity of the oceans, which seemingly wouldn’t be addressed by such a scheme. There’s also the issue that although “the Mount Pinatubo eruption…did not seriously disrupt the climate system”, this is a frightfully complicated system we’re messing with. It’s worth noting, however, that we do currently have very good models of our climate which are able to reproduce most of the the large scale climate effects we currently see (which is why we trust their predictions of global warming), and these models should, thefore, be trusted for this new scenario too.

Obviously, a lot more modelling needs to be done before real conclusions can be reached (a number of conferences and workshops are scheduled for next year, and I suspect this will increase). I’m not sure how I feel about the idea - current models of global warming suggest that we’ve already done irreversible damage to our planet which will destroy at least half our reefs, for example, over the next 50 years. If a “global shading” program like this could actually counteract that, then that could be a good thing. But surely it’s not a good solution for the next thousand years? I just can’t help but think with fossil fuels running out anyway that we’re better to look towards a sustainable economy rather than ways of maintaining our bad habits. The cost and time required for such an operation might be better spent on developing solar power technology (similarly, the massive amounts of money going into finding ways of storing carbon or making fossil fuels cleaner is disturbing). I’d also worry that just when everyone’s starting to take notice of the issues of climate change, if an easy solution like this is suddenly on the table, that people will just thank science and ignore the issue. Besides, I like sunshine!