Geoengineering schemes for moderating climate change come in two main flavours. First, there are those that aim to increase the amount of sunlight that is reflected away from the Earth (currently about 30 per cent) by a few per cent more. Second, there are some that aim to increase the rate at which [carbon dioxide] is removed from the atmosphere, by enhancing the natural sinks for CO2, and maybe even by deliberately scrubbing it out of the air.
It’s pretty clear that some of the reflection schemes could successfully reduce temperatures because that’s just what happens after major volcanic eruptions. This method acts fast and the effects, like those of volcanoes, would decline after a few years, so it wouldn’t be irreversible. This approach, however, would be treating (only) the symptoms and could be used to allow even more CO2 to build up in the atmosphere. Then, if we were to stop enhancing the reflectivity, all that pent-up global warming would happen very fast indeed and we should be in serious trouble. This method also does nothing to moderate the other CO2 problem, ocean acidification.
The CO2 removal schemes avoid these difficulties since they attack the problem at its source; but they would operate slowly, taking many decades to reduce CO2 to safer levels. They may not be able to achieve enough to make a real difference and they may be very costly. And some CO2 reduction schemes, like ocean fertilisation, involve the large-scale manipulation of natural ecosystems, with effects that are very hard to predict.
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The Australian, 4 May 2009. Full article.
