Spreading iron at sea can bury carbon for centuries, study shows

Iron filings and carbon burialDumping iron into the sea can bury carbon dioxide for centuries, potentially helping reduce the impact of climate change, according to a major new study. The work shows for the first time that much of the algae that blooms when iron filings are added dies and falls into the deep ocean.

Geoengineering – technologies aimed at alleviating global warming – are controversial, with critics warning of unintended environmental side effects or encouraging complacency in global deals to cut carbon emissions.

Prof Victor Smetacek, at the Alfred Wegener Institute for Polar and Marine Research in Germany, who led new research, said: "The time has come to differentiate: some geoengineering techniques are more dangerous than others. Doing nothing is probably the worst option."

Ocean iron fertilisation could bury at most 1 gigatonne of CO2 per year compared to annual emissions of 8-9Gt, of which 4Gt accumulates in the atmosphere. But sequestering some CO2 could make the difference between crossing a climate "tipping" point, where feedback effects lead to runaway global warming