Agri Kultuur December / Desember 2018 - Page 34

New plane can show geoengineering works Tim Radford With new aircraft, humans could potentially mimic volcanic action, dim the sunlight and slow global warming, showing that geoengineering works. It’s a controversial idea. N obody knows for sure whether we shall ever see if geoengineering works. But now somebody knows how to do it. Engineers have designed an aircraft that could lift a cargo of sulphur dioxide to an altitude of 20 kilometres and spray it into the stratosphere to darken the skies, dim the sunlight and damp down climate change driven by emissions from factory chimneys, power stations and vehicle exhausts. The aircraft – already dubbed SAIL, or the stratospheric aerosol injection lofter, could cost no more than $2.35 billion a year for airframe and engine, and the first eight could be rolling down the runway 15 years from now to begin flying 4,000 missions a year. By the end of another 15 years, a fleet of 100 high-flying sulphate dumpsters could be in business, making 60,000 high altitude deliveries a year to combat global warming. US scientists report in the journal Environmental Research Letters that they addressed the costs and practicalities of what is certainly the most-frequently invoked and hotly disputed form of climate engineering on a global scale. Possible catastrophe It is considered necessary because, if humans go on burning fossil fuels at the present rates, greenhouse gas build-up in the atmosphere could increase planetary average temperatures to a catastrophic 3°C or more by 2100. AgriKultuur |AgriCulture Darkened skies do lower planetary temperatures: violent volcanic eruptions have in recent history injected cubic kilometres of fine ash, smoke and sulphur into the upper atmosphere on scales that lower global average temperatures measurably. For more than a decade, researchers have argued that – since humankind collectively still shows no great sign of drastically reducing greenhouse gas emissions – some radical form of solar geoengineering might be necessary. Others have opposed the case, citing possible unwelcome consequences. But the first question was: could it be done at all? The latest answer is that it can, but not with existing hardware. “This plan is a distraction that may well encourage weaker action on emissions reduction by governments in the hope they will no longer be necessary” “While we don’t make any judgment about the desirability of SAI, we do show that a hypothetical deployment programme, starting 15 years from now, while both highly uncertain and ambitious, would be technically possible from an engineering perspective,” said Gernot Wagner, of Harvard University. “It would also be remarkably inexpensive, at an average of around $2 bn to $2.5 bn per year over the first 15 years.” His co-author Wake Smith, who moved from the aviation business to lecture at Yale College, and who led the study, said he had become intrigued by research that suggested 34