Attempts to cut carbon emissions to save us from climate change have not been a huge success so far. Could proposed alternatives work any better? Simon Wilson reports.
Cold, isn’t it?
Not everywhere. While the northern hemisphere shivers in a prolonged cold snap, Australians have just had their third-hottest year on record. Worldwide, 2009 was the fifth warmest ever, and the underlying trend remains disturbing. The average temperature during the decade 2000-2009 was 0.4˚C above the 1961-1990 average, while the 1990s decade was 0.23˚C higher. So while the record for the hottest year has not been broken since 1998, data suggests the world is still getting warmer.
What’s the solution?
To date, scientists have focused on ‘mitigation’ – cutting carbon emissions. That remains the top priority. Greenhouse gases play a vital role in keeping the world warm: without them, we would be shivering at an average temperature around -18˚C, instead of comfortably above freezing at +14˚C. But too much of a good thing leaves the climate system vulnerable. Before industrialisation, the atmosphere had a tiny amount of carbon dioxide – ranging between 180 and 280 parts per million. That amount is still tiny, at 387 ppm – but it is much more than the natural state, and is far higher than the level at which temperature rises could be containable.
So where does ‘geo-engineering’ come in?
So far, the world has been remarkably unsuccessful at checking climate change by reducing carbon emissions. So scientists and governments around the world are beginning to look at ways of artificially intervening in the world’s climate – an idea that was until recently viewed as the preserve of eccentrics and wackos. Geo-engineering is a catch-all term for two distinct ways in which some scientists believe we might be able to intervene in the world’s climate to reduce warming. The first is to suck CO2 out of the atmosphere through carbon dioxide removal (CDR) techniques. The second is to cut the amount of sunlight reaching Earth by reflecting a percentage of the sun’s light and heat back into space. This is known as solar radiation management (SRM), or albedo (reflectivity) engineering.
Could these work?
In theory, yes. The Royal Society, which published the UK’s first comprehensive report into the subject in the autumn, found that “geo-engineering of the Earth’s climate is very likely to be technically possible” and called for a £100m fund to foster new research. But their survey is peppered with warnings and caveats. This reflects not just the embryonic stage of research into the practicalities and risks involved, but also the widespread fear among scientists of the moral hazard posed by climate intervention. If policy-makers come to believe that they can engineer their way out of climate change, it risks lowering the drive to cut emissions. No one sees geo-engineering as a panacea, but more a desperate last resort. Overall, the Royal Society concluded that carbon reduction strategies would be preferable, since they tackle the root cause of warming.
How would CDR work?
There are several ways under discussion. A study by the Institute of Mechanical Engineers (IME) found that artificial trees are the most likely to work. Several scientists are working on models – usually resembling huge upright fly-swatters or roadside cabins – which use chemicals to trap CO2 from the air for eventual storage underground. The IME also favours using algae on city buildings to capture carbon. Another proposal is to encourage the growth of algae in the oceans by seeding them with iron.
What about reflecting sunlight?
It’s here that the science gets more debatable and the risks get bigger. Other than painting lots of roofs and roads white (discounted as scarcely worth doing by the Royal Society), the best-known idea for reflecting sunlight is to mimic the cooling effect of volcanic eruptions by pumping sulphur dioxide into the stratosphere, where sulphates form microscopic particles that block sunlight. Such a technique would be relatively cheap, and would take effect more quickly than carbon-cutting.
Is this a good idea?
The world’s most influential atmospheric scientist, the Nobel prize-winning chemist Paul Crutzen, believes that sulphate aerosol techniques could work. But the uncertainties are huge. At present, too little is known about the atmospheric chemistry to be certain about how sulphate particles behave in the stratosphere, even if we devise a method of getting them there. And some scientists think a sulphate haze might actually raise temperatures rather than lower them, or have catastrophic effects on other parts of the climate. So at present, geoengineering as science remains limited and the conclusions tentative.
Where can I find out more?
Start with the Royal Society’s paper. The Society, a fellowship of 1,400 of the world’s most eminent scientists, is also hosting a public lecture on 19 January. Its paper covers all the techniques so far considered and also discusses the implications of geoengineering for public policy and international governance. The January/February edition of MIT’s Technology Review has a wide-ranging survey of the debate, with a particular focus on sulphates. And the January edition of Prospect magazine has a six-page article by The Economist’s energy editor, making the case for geoengineering as one part of the solution to climate change.