It sounds like something from a sci-fi movie, but the artificial manipulation of the Earth’s climate has been touted as a possible strategy to reduce the effects of unmitigated climate change. Thanks to the painfully slow progress that has been made towards reducing our carbon emissions, there has been some surprisingly serious discussion about the prospect of geoengineering the climate in order to suit the needs of humans.
Of the various forms that have been suggested (large machines to suck CO2 from the air, space-borne mirrors to reflect sunlight, iron filings in the ocean), the mostly widely discussed option is the injection of vast quantities of sulphur into the stratosphere. In theory, the airborne particles would have the effect of reflecting solar radiation, and thereby the reducing warming effects of climate change.
Of course, this would do nothing to actually reduce carbon pollution (which would continue to increase with human development), not least anything to reduce the effects of ocean acidification and a myriad of other impacts upon biodiversity, ecosystems and human health. Geoengineering is certainly a drastic option fraught with uncertainty, but advocates of the approach have been considering back-up plans for the worst possible case scenario, while others have been looking into what effects may come if geoengineering became a reality.
A new study published in Nature Geoscience last week has examined the possible consequences of large scale geoengineering on the planet from the baseline year of 2005. The authors simulated a range of geoengineering scenarios by making use of thousands of home computers that were volunteered as part of a large scale climate forecasting experiment.
They found that although the injection of trogospheric sulphur aerosols did in fact reduce global average temperatures compared to the unmitigated climate change scenario, global net precipitation would decrease as a result. The disparity between temperature and precipitation anomalies became increasingly apparent the longer that geoengineering activities were maintained in the modelled scenarios – meaning that over time it would become more and more difficult to regulate temperature and precipitation within “20th century climate conditions” simultaneously.
On top of these effects, the results also indicate that the degree of climate engineering undertaken (i.e the amount of aerosols pumped into the air) would impact upon different parts of the world in different ways. This regional variation in the effects of geo-engineering would make it even more difficult to choose an “optimum” level of climate manipulation – for example, keeping China close to its baseline climate meant undesirable conditions for India, and vice versa.
Although some of these results may be model-specific (such as the specific regional effects), this new study gives a frightening glimpse into the risks and uncertainties of climate geoengineering. The fact that we’re even considering the idea of large scale climate manipulation seems to be indicative of society’s desire to seek technological fixes to treat the symptoms of a problem, instead of addressing the root cause. Clive Hamilton describes the penchant of wealthy Texans to enjoy a log fire despite living in a hot climate, and so likens geoengineering to “responding to overheating by turning up the air-conditioning while continuing to pile more logs onto the file”.
 Ricke, K. L., Morgan, M. G. & Allen, M. R. Nature Geosci. Advance online publication doi:10.1038/ngeo915
 Clive Hamilton. 2010. Requiem for a Species: Why We Resist the Truth About Climate Change
Page photograph from Nature News article “Geoengineering can’t please everyone” doi:10.1038/news.2010.357