What if one rogue nation dimmed the Sun to avert climate disaster? – BBC.com

Yet in the three years since the publication of Robinson’s novel, global emissions have continued to rise, exacerbating everything from unprecedented heatwaves to deadly floods. This summer in the Northern hemisphere was the hottest on record, and September’s global temperature jumped again by a huge margin.

Amid these rises, some researchers suggest there could be a case for emergency solar geoengineering as an accompaniment to decarbonisation. In the US, the National Academies of Sciences, Engineering and Medicine last year recommended a national research programme on Solar Radiation Modification [SRM] – as the technology is also known. This year, the White House issued a report that examined what a federally-funded research programme might entail. And in the private sector, money from US tech giants and billionaires is flowing towards further investigation.

This February, dozens of scientists published an alternative open letter, organised by Sarah Doherty of the University of Washington, arguing more research is needed. And there are growing calls for a clearer international consensus on rules – one way or the other. The UN Environment Program has noted a “dearth of data” on impacts, and the EU has called for international talks about its risks.

As for Robinson, whose novel has helped foment so much discussion, he stressed to BBC Future that his book was not proposing a plan: “I abjure prediction, or even prescriptions”. Yet he also pointed to the need to take “emergency actions” to reduce the damage caused by burning carbon – from finding new ways to pay for decarbonisation, to exploring options for non-solar geoengineering. “I object to anyone saying ‘Oh we can’t try to fix things because it will encourage fossil fuel promoters to keep breaking things!’ We’re past that moment now. The sense of emergency is intensifying year by year.”

So what might it look like in reality?

Alternative methods of solar geoengineering are all now competing for their moment in the spotlight, from marine cloud brightening (which would inject sea salt aerosols into low-lying clouds to increase their reflectivity), to cirrus cloud thinning (which would inject ice nuclei into high clouds, shortening their life-span and allowing more heat to escape into space). But stratospheric sulphate aerosol injection by aeroplane remains the best-studied proposal for global impact. The technology could potentially lower temperatures at speed, and with relatively low finance. One 2013 estimate equates start-up costs to “the price of a Hollywood blockbuster“. A more recent calculation of running costs comes in at around $18bn (£16bn) a year.

Research supports a slightly different technical vision than in Robinson’s novel, however, with scientists suggesting a much slower ramp up, deployment and decline. One paper recommends that if stratospheric injections begin around 2030, they should peak 50 years later before tapering-off over two centuries. Another study has injections starting in 2035 and running at least until 2100; another estimates a duration of 245-315 years.