Every silver lining has a cloud

A freelance science writer asks why greens seem so opposed to one scientist’s proposal for stabilising global temperatures.

Stuart Blackman

Topics Politics

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Little is certain in the field of global climate prediction. But one thing is for sure: if all those worst-case scenarios made so much of by environmentalists come true, we really are screwed.

So you might expect those same environmentalists to be rather excited by a project that claims to be able to stabilise global temperatures at the push of a button, and keep them stable while the world makes the transition to energy sources of the future. Except that they’re not. In fact, if their reaction to the project is anything to go by, either they don’t believe their own press releases, or trying out new things in order to save the planet is not one of their top priorities.

There has been no shortage of suggestions over recent decades for large-scale ‘engineering fixes’ for global warming, some more outlandish than others. They have ranged from seeding the oceans with iron filings to draw down atmospheric CO2, to the launching of billions of aluminised balloons to reflect the sun’s rays away from the Earth, to the installation of giant mirrors in space that intercept those rays before they reach us. Atmospheric physicist John Latham’s idea is perhaps more down-to-Earth than most, although whether it can provide a ‘solution’ to climate change remains very much up for debate. In the 1980s, Latham, professor emeritus at Manchester University, and now at the National Center for Atmospheric Research in Colorado, realised that the Earth already had the hardware in place for reflecting sunlight back into space.

While some types of cloud have an insulating effect on the planet, others, such as the low-altitude stratocumulus variety that covers much of the world’s oceans, reflect incoming sunlight. Latham’s idea, which he first published in the science journal Nature in 1990, is to make the silver linings of those stratocumulus clouds a little bit more silvery, by injecting salt crystals into the atmosphere to seed the formation of the water droplets that comprise them. In this way, he claims, ‘one can produce a degree of cooling in a controlled way, to try and balance the warming produced by the burning of fossil fuels’. He calculates that to achieve the desired effect on cloud reflectivity would require treating them with ‘a cupful’ of salt per km2 per hour.

‘It’s a very interesting idea, and one that is based on sound cloud physics’, says Alan Gadian, climate scientist at the University of Leeds. He is impressed that, because the technique would be augmenting a natural process (breaking waves are constantly throwing vast quantities of salt up into the atmosphere), it carries relatively little risk. And should things go awry, he says, ‘you could just stop producing these salt crystals and the system would return to its normal state’. John Shepherd, director of the University of Southampton’s Earth System Modelling Initiative, agrees. ‘In principle, the idea is sound’, he says. ‘The big question is whether they can get enough sea salt nuclei into the atmosphere.’

And that’s down to Stephen Salter, professor of engineering at the University of Edinburgh, who is best known for his invention of ‘Salter’s duck,’ a device for harnessing energy from waves. For the current project, he has designed a fleet of specialised ocean-going yachts. ‘They’ll look like steam ships with big funnels’, he says. But these are no ordinary funnels. They will be spinning rapidly on their vertical axis, a feature that serves two important functions.

The first is propulsion. When wind hits a spinning cylinder, it generates a sideways thrust. As well as allowing the boats to be positioned optimally, this force would propel them fast enough to drive a water turbine that powers the conversion of seawater into a very fine mist. As the mist rises, the water evaporates from the droplets to leave the airborne salt crystals. To do their job, the crystals must be within a narrow size range, which means producing droplets that are consistently about one millionth of a metre in diameter. This will involve vibrating the surface of a seawater reservoir to create a network of fine ripples. ‘If you make these ripples big enough, drops are thrown off’, says Salter. The size of those drops is determined by the frequency of the vibrations.

And there lies another technical challenge. To produce the ripples, the surface of the seawater reservoir must be smooth – not easy to achieve on a pitching, rolling boat. This is where the spinning funnels really come into their own. They will be filled with seawater, which gets thrown against the walls by centrifugal force, producing a smooth, vertical surface on which the ripples can be generated. Fans inside the funnels will then blow the resulting mist up into the sky like smoke rising from a chimney.

The yachts will carry no crew, but will be controlled via satellite. Salter estimates that a fleet of up to 40,000 of these hi-tech Mary Celestes would be required to offset the temperature rise predicted to result from a doubling in atmospheric CO2. Even if CO2 concentrations were to increase according to worst-case scenarios, this, he estimates, would provide several decades’ respite – which might provide time to develop non-carbon energy sources; research the intricate workings of climate systems; and plan long-term strategies to cope with a changing climate.

It would also be relatively cheap. ‘I can’t see these things being more than a million quid a go’, says Salter. That still adds up to £40billion. However, the investment would be spread over the time it takes for CO2 to double. ‘You’d only need to spend perhaps three per cent of that every year to stabilise things’, says Salter. ‘That would be an incredible bargain.’ Indeed, it is a tiny fraction of the expense of the Kyoto Protocol, for example, which is expected to shave off just a few tenths of a degree of temperature rise over the next hundred years.

Stabilisation of global temperatures? Little risk? At a fraction of the cost of Kyoto? It sounds like it at least worth trying, and it sounds like an environmentalist’s wet dream. So why are green organisations so unimpressed with the idea? ‘It’s one of those crazy engineering solutions to climate change that we ignore really’, says Friends of the Earth (FoE) climate campaigner Bryony Worthington. ‘It’s not something we think we should be spending money and time on.’ Worthington denies she’s being dismissive. ‘It’s not a question of being dismissive; it’s a question of whether this is worth any time and effort even thinking about.’

Over at Greenpeace, Mark Strutt, who was until recently senior climate campaigner at Greenpeace UK (he’s now Greenpeace International’s agriculture spokesperson), takes a similar stance. ‘Greenpeace wouldn’t be interested in this sort of thing. We’re looking for reductions in the use of fossil fuels rather than these technologies that in all likelihood would come to nothing.’

Of course, the project might indeed come to nothing. There are good reasons to think that we cannot control the climate – a chaotic system influenced by a host of inputs – by tweaking a single variable. And yet tweaking a single variable – CO2 emissions – is precisely what environmentalists are themselves urging us to do. However, the environmentalist case against engineering fixes for global warming does not rest on the underlying science. It has more to do with a view of science as the cause of the world’s problems, and not something that might provide a solution. ‘We don’t take these ideas very seriously because the idea that we’ll somehow come up with a man-made fix is fanciful’, says Worthington. This sentiment is echoed by Charlie Kronick, Greenpeace UK’s climate change coordinator. ‘The idea of interfering with another natural system to compensate for the nearly catastrophic interference we’ve already done is not an enticing prospect’, he says.

Despite these seemingly Luddite sentiments, Worthington claims to have science on her side. ‘The models are showing that reducing the concentrations of greenhouse gases is the only sensible response to climate change.’ Really? Latham has been collaborating with the UK Meteorological Office to test the theory behind his project using their powerful computer model of global climate. This suggested that treating clouds covering just three per cent of the Earth’s surface would cool the planet sufficiently to compensate for a doubling of CO2. Alan Gadian is sufficiently impressed that he is now embarking on a project to replicate that study.

It is at this point that Worthington is forced to express her discomfort with the very models on which the environmental case depends. ‘But he can’t be certain’, she says, ‘they’re only models.’ Yes, and green activists’ predictions of climate change disaster are also based on models.

There may be other reasons for FoE and Greenpeace’s discomfort with such projects. After all, a successful engineering fix would deprive the green movement of its most valuable political currency – urgency. If the world were to have a few decades of stable temperatures, the urgency of green politics would have to give way to a genuine, rational political debate. Their discomfort also points to a lack of faith in man-made solutions; we are seen as giving rise to climate chaos and thus must apparently take a hands-off approach from nature.

Engineering the climate might yet prove impossible, for scientific or practical reasons. Latham’s team is now planning a small-scale pilot experiment further to explore the project’s viability. ‘We don’t know yet what fraction of the drops we make will actually get up to where the clouds are’, says Salter. But there is surely something noble about the aspiration to control the climate. We don’t need climate models to tell us that Mother Nature has plenty to throw at us, whether or not the planet warms as predicted. And in that respect, projects such as Latham’s could be seen as valuable developments, regardless of whether the elements have even more nasty surprises in store for us.

No doubt environmentalist groups would abhor the prospect of controlling the Earth’s climate on the basis that, in the words of Kronick, we’d be interfering in a ‘natural system’. Environmentalists’ aspirations are very different: through rain or shine, they seem determined to stick to the mantra that we should be reducing CO2 emissions and, in doing so, leave us even more vulnerable to the whim of Mother Nature. Worthington and Strutt both claim that the search for engineering fixes for global warming only serves as a distraction, making people and governments less inclined to reduce CO2 emissions. And yet Worthington herself doesn’t seem to have much faith that reducing emissions will be particularly effective: ‘If we can see global CO2 emissions peak and decline in the next 10 to 15 years, we’ve still got a slim chance of holding [temperature increases] down to two degrees’, she says.

A slim chance of avoiding climate catastrophe? Environmentalists, it seems, don’t need any help when it comes to disinclining the world to reduce carbon emissions.

Stuart Blackman is a freelance science-writer.

Read on:

J Latham (1990), ‘Control of global warming’, Nature, vol 347, pp330-340; J Latham (2002), ‘Amelioration of global warming by controlled enhancement of the albedo and longevity of low-level maritime clouds’, Atmospheric Science Letters, vol 3, pp52-58.

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