Cloud spraying and hurricane slaying: how ocean geoengineering became the frontier of the climate crisis

Around the world, dozens of ingenious projects are trying to trick' the ocean into absorbing more CO₂. But critics warn of unforeseen consequences

Tom Green has a plan to tackle climate change. The British biologist and director of the charity Project Vesta wants to turn a trillion tonnes of CO₂ into rock, and sink it to the bottom of the sea.

Green admits the idea is audacious". It would involve locking away atmospheric carbon by dropping pea-coloured sand into the ocean. The sand is made of ground olivine - an abundant volcanic rock, known to jewellers as peridot - and, if Green's calculations are correct, depositing it offshore on 2% of the world's coastlines would capture 100% of total global annual carbon emissions.