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20 October 2018, Carbon Brief, Solar geoengineering may not halt ocean warming, study says. Spraying aerosols high in the stratosphere could dampen global warming over land, but may not prevent the oceans from heating up, new research says. The findings suggest that this type of “solar geoengineering” – a set of techniques that aim to tackle global warming by reflecting sunlight back into space – may not necessarily stem sea level rise or prevent damage to the world’s marine ecosystems. The research indicates that solar geoengineering could carry “major uncertainties and risks”, the lead author tells Carbon Brief. The study also raises the issue of whether global average temperature “is the best metric to control” when addressing the impacts of climate change, another scientist tells Carbon Brief. Scientists have suggested that releasing aerosols into the atmosphere – a technique known as “stratospheric aerosol injection” – could cool the planet in a similar way to a large volcanic eruption. When a volcano erupts, it sends an ash cloud high into the atmosphere. The sulphur dioxide released in the plume combines with water to form sulfuric acid aerosols, which reflect away incoming sunlight, temporarily cooling the Earth. Artificially introducing aerosols into the atmosphere – via a plane or a high-altitude balloon – could have a similar cooling effect, researchers say. The idea has never been tested, but previous research using computer simulations suggests that releasing aerosols could help limit global temperature rise to 1.5C – the aspirational target of the Paris Agreement – and keep rainfall from becoming irregular. However, an aerosol sunshade would not protect the planet from rising CO2 emissions – which is causing oceans to become more acidic and crops to become less nutritious, among other problems. The new study, published in Nature Geoscience, identifies, for the first time, another potential downfall of the proposed technique: it may not be able to limit warming in the deep ocean. Access more here