Another warning light for the biosphere has just started flashing. The increasing acidification of the ocean - a process driven by the burning of fossil fuels - has crossed its safe limit for the first time ever, putting all marine life and ecosystems at risk. Ocean acidification is the 7th of 9 natural processes that regulate Earth’s #biosphere to exceed safe boundaries. The scientist who led the team behind this work, Johan Rockström, director of Potsdam Institute for Climate Impact Research,