report touts cloud ships as climate salvation

So-called geo-engineering projects capable of tinkering with the climate could provide a more cost-effective means of lowering global temperatures than cutting carbon emissions, according to a highly controversial new report from Danish think tank the Copenhagen Consensus Centre.

The study, An Analysis of Climate Engineering as a Response to Climate Change (PDF), calculates that proposals for a fleet of 1,900 unmanned ships capable of spraying water into the air to seed clouds would cost just $9bn. The clouds would then reflect one to two per cent of the sun's energy back into space, effectively cancelling out the warming effect generated by the past century's carbon emissions.

However, green groups were quick to downplay the proposals, arguing that geo-engineering projects are unlikely to prove effective and could distract from efforts to cut carbon emissions.

The study, which comes ahead of a similar report from the UK's Royal Society due later this year, looked at a number of different geo-engineering proposals, including releasing particles into the atmosphere to mimic the effects of a volcanic explosion, launching space-based mirrors capable of reflecting back some of the sun's energy, and carbon capture technologies that remove carbon dioxide from the atmosphere, as well as the cloud ships proposal.

It concluded that the cloud ship fleet offered the most cost-effective option, providing $2,000 worth of benefits for each $1 invested. In contrast, it calculated that releasing aerosol particles into the atmosphere would cost $230bn over 25 years and would deliver $15 of benefits for each dollar invested, while space mirrors and carbon capture systems were deemed less attractive still from both a technical and a cost perspective.

The report's authors, Professor J. Eric Bickel and Lee Lane, said that the scale of gains suggested by the cost benefit analysis fully justified further research into geo-engineering, and in particular marine cloud whitening projects. "The results of this initial benefit-cost analysis place the burden of proof squarely on the shoulders of those who would prevent such research," they said.

The report was commissioned by the Copenhagen Consensus Centre as part of its project to assess how the global community should best allocate up to $250bn a year over the next decade to diminish the adverse effects of climate change. The think tank is headed by Bjorn Lomborg, the controversial scientist and author of the book The Sceptical Environmentalist, who has in the past angered green groups as a result of his perceived willingness to downplay the effects of climate change.

Bickel and Lane recommended that $750m a year should be allocated from the hypothetical $250bn budget for research into geo-engineering, with a particular focus on identifying possible side effects that could push up the costs of proposals.

Speaking to, Lomborg said that all the evidence suggested that the cloud ships proposal was technically and economically feasible. "We know it works because you can see that it already happens with clouds formed along shipping lanes," he said. "There's obviously more testing that needs to be done, but it is so cheap that it has to be worth looking at."

However, green groups warned that increased investment in geo-engineering approaches would serve only to distract from efforts to curb carbon emissions, while doing nothing to address related issues such as ocean acidification or energy security.

"Rich countries urgently need to cut our carbon emissions if we are to have any chance of preventing dangerous climate change," said Mike Childs, Friends of the Earth's head of climate. "The tried and tested technology and policy solutions that exist now - such as a large-scale programme to cut energy waste and invest in wind, wave and solar power - could significantly reduce our emissions if we deploy them at the scale and with the urgency that is needed."

His comments were echoed by a spokesman for Greenpeace, who warned that, even if they worked, geo-engineering projects would fail to address other environmental issues associated with carbon emissions. "We are opposed to all geo-engineering," he said. "Even if the cloud ships idea worked we would still have ocean acidification continuing as a result of increased carbon emissions. We would still have a catastrophe in the form of a collapsed marine ecosystem even if the climate was no longer heating up."

But Lomborg insisted that the proposals offered a more effective means of curbing rising temperatures than the current mechanisms for cutting carbon emissions.

"There are well respected models that suggest that if every rich nation meets the target of cutting emissions by 80 per cent by 2050 then it would lower temperatures by just 0.22 degrees centigrade by the end of the century," he said. "[Cloud ships] have the potential to be much quicker at bringing down temperatures and are thousands of times cheaper - that has to be worth looking at."

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