- Updated 11:12 09 April 2009 by Catherine Brahic
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Update: John Holdren, the chief scientific adviser to Barack Obama, has said drastic measures to tackle climate change using massive technological measures should be considered. Holdren's statement is a "personal opinion", he says, but this is the strongest statement yet from within the Obama administration that geoengineering is being taken seriously. As we reported earlier in the year, the proposal has now moved into mainstream scientific and political thought.
IN A room in London late last year, a group of British politicians were grilling a selection of climate scientists on geoengineering - the notion that to save the planet from climate change, we must artificially tweak its thermostat by firing fine dust into the atmosphere to deflect the sun's rays, for instance, or perhaps even by launching clouds of mirrors into space.
Surely the scientists gave such a heretical idea short shrift. After all, messing with the climate is exactly what got us into such trouble in the first place. The politicians on the committee certainly seemed to believe so. "It is not sensible, is it? It is not a serious suggestion?"
Had the question been posed a few years ago, most climate scientists would have agreed. But the mood is changing. In the face of potentially catastrophic climate change, the politicians and scientists all agreed that since cuts to carbon emissions will likely fall short we need to be exploring "Plan B". Climatologists have hit a "social tipping point" says Tim Lenton of the University of East Anglia, UK.
What's more, respected scientists, including Nobel laureate Paul Crutzen, and groups such as the UK's Royal Society, are already assessing the risks and benefits. Are we ready to try to turn down the thermostat? Who will have the authority to push the button? And what would happen if one nation or well-intentioned "green finger" individual decided to go it alone?
Geoengineering schemes range from the low-tech, such as planting trees, to sci-fi, such as placing mirrors in orbit between Earth and the sun. All would work either by diverting solar energy away from Earth or by sucking carbon dioxide out of the atmosphere to dampen the greenhouse effect
Previously, the idea of tweaking the climate in this way was anathema to most scientists. Apart from the technical challenges and environmental risks, many argued that endorsing the concept might scupper international negotiations for a post-Kyoto protocol to reduce global emissions. But it's becoming clear that moves to cut global carbon emissions are too little and too late for us avoid the worst effects of climate change. "There is a worrying sense that negotiations won't lead anywhere or lead to enough," says Lenton. "We can't change the world that fast," says Peter Liss, who is scientific adviser to the UK parliamentary committee investigating geoengineering. Extraordinary measures may now be the only way of saving vulnerable ecosystems such as Arctic sea ice.
What's more, geoengineering could turn out to be relatively cheap. Early estimates suggest some schemes could cost a few billion dollars, small change compared to the cost of slashing emissions - estimated by former World Bank chief economist Nicholas Stern to be at least 1 per of global GDP per year. In his testimony to the UK politicians last year, John Latham of the National Center for Atmospheric Research in Boulder, Colorado, argued that all of the above reasons make it "irresponsible" not to examine geoengineering.
While no one advocates deploying fleets of ships or launching space mirrors tomorrow, we need to know how Plan B is going to work, which means doing field tests. "If you wait for a climate catastrophe then you need to deploy fairly full-scale fairly quickly which means you won't have time to look at the risks," says Ken Caldeira of the Carnegie Institution of Washington in Stanford, California.
Yet, as with genetically modified crops, field testing has already sparked public resistance. This has been made clear with the various attempts in recent years over ocean fertilisation experiments. In 2007, a commercial firm called Planktos announced a plan to dump iron filings into the ocean off the Galapagos Islands. More recently, a research ship set off to seed iron in the Southern Ocean. Both generated protests from environmentalists, such as ETC group, which feared they would damage ocean ecosystems.
In many ways ocean fertilisation shows how other geoengineering schemes might be regulated. After the Planktos furore, the London Convention on marine pollution - ratified by over 80 countries - extended its remit to include geoengineering, and imposed a ban on commercial fertilisation. It has also announced its intention to strictly regulate scientific experiments. On 9 February, interested parties met to begin setting up experimental standards.
Yet how we would implement geoengineering schemes on a global basis is less obvious, says lawyer David Victor of Stanford University's programme on energy and sustainable development. "Whether all governments would need to OK a scheme in international waters or outer space is unclear," he says. "Who would decide? And who would be responsible for redressing any unintended consequences?"
For an example of the problems that would need to be ironed out, take a look at one of the more mature geoengineering schemes that could provide us with instant cooling today - pumping sulphate particles into the atmosphere to reflect the sun's rays back into space. If one country forged ahead, it could have detrimental effects on others. A 2007 study suggested sulphate sunshades could trigger catastrophic drought in some regions. "There would inevitably be winners and losers, as there is not a single global thermostat which will bring about universal and consistent cooling," says David Santillo, senior research scientist at Greenpeace Research Laboratories in Exeter, UK. "By its very nature, if there is to be any purpose in geoengineering, it would have to exert an impact over a vast proportion of the planet."
Victor estimates only a handful of nations or groupings - including Australia, Brazil, China, India, Russia, the European Union and possibly Japan - have the capability to unilaterally deploy atmospheric sunshades. Only one of these has come close so far. In November 2005, Yuri Izrael, former vice-chair of the Intergovernmental Panel on Climate Change and head of the Russian Global Climate and Ecology Institute, tried to persuade his president, Vladimir Putin, that Russia should release 600,000 tonnes of sulphur aerosol particles into the atmosphere immediately.
If any nation seriously considered going it alone, "there would almost certainly be an international diplomatic incident", says Santillo. If a sunshade triggered drought elsewhere, this could be interpreted as "hostile use" of weather modification, in which case the action would fall foul of the UN Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD). During the Vietnam war, the US experimented with rain seeding to disrupt the Ho Chi Minh trail, which eventually led 70 nations, including the US, to ratify the treaty. But for it to be of any use, a drought-stricken nation would have to prove that a stratospheric sunshade was to blame and this could be difficult at best.
"Almost everyone agrees that some form of international regulation and authorisation is necessary," says John Shepherd, a deputy director of the UK Tyndall Centre for Climate Change Research and chair of the Royal Society working group investigating geoengineering. But as for how, "we just don't know", he says.
The obvious choice would be for the UN to regulate geoengineering. However, when New Scientist enquired, the UN Framework Convention on Climate Change was unable to comment. According to Joan Ruddock, a UK minister serving in the Department of Energy and Climate Change, a powerful UN treaty on geoengineering in the wake of failed emissions talks is unlikely. "If we have entirely failed to bring the world community together to do the rather simpler things which we already understand very well," she says, then devising a geoengineering agreement would be even more difficult.
Even if no nation did go it alone and governments couldn't agree on global action, that still leaves the alarming possibility of an individual deciding to modify the climate on their own - a so-called "green finger". Science historian James Fleming of the Wilson Center in Washington DC describes a gathering he attended at NASA's Ames Research Center in California in November 2006. Astrophysicist Gregory Benford of the University of California, Irvine, announced that he wanted to "cut through red tape and demonstrate what could be done" by injecting a chalk-like substance into the Arctic stratosphere to reflect sunlight, using private funding. And Planktos would have forged ahead with ocean fertilisation had no one stepped in.
There is little doubt that planetary tinkering presents governments with huge challenges. But living in a much warmer world will be even more unpleasant (see "Surviving in a warmer world"). For now we have time. It will be a couple of decades before we know if international negotiations to wean ourselves off high carbon fuels have had any success.
If not, we may have no choice but to start tweaking the climate ourselves. "Only fools find joy in the prospect of climate engineering," says Caldeira. "There is a sense of despair that we are not seeing deep emissions cuts quickly, and that is pushing us to consider these things."
Dump the Sunshade at our Peril
What happens if we tinker, then change our mind? Will all of humanity be doomed? Not necessarily. Most methods that absorb carbon dioxide would take decades to work so stopping them is unlikely to have sudden undesired effects.
In the most worrying scenario, sunshades would be deployed then removed. Preliminary results suggest aerosols would naturally have a stratospheric life of about one year, making them reversible if needed. But there is a big catch.
If they were deployed as an excuse to continue burning fossil fuels, the masked greenhouse effect would build up and other effects such as ocean acidification would continue. Sunshades would have to be replenished or the planet would be hit with the full force of pent-up warming. Victor Brovkin of the Max Planck Institute for Meteorology in Hamburg, Germany, calculates that if a sunshade were kept up for 200 years, then dismantled, the planet could warm by between 5 °C and 10 °C within decades. Such an event would trigger massive belches of methane from thawing permafrost and the breakdown of entire ecosystems.
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