“Geoengineering” is a catch-all term for approaching climate change from the other side of the too-much-gas-too-much-heat side of the equation. One of the early promising schemes was iron fertilisation, where mixing iron with waters in oceanic ‘deserts’ would cause algal blooms. The theory was that such blooms would come and go so fast that when they died, they’d sink to the bottom of the ocean and take their carbon with them.
It doesn’t seem to work that way. But at least iron fertilisation could show a way to improve fisheries without destroying fish stocks.