EAST LANSING, June 13 -- A new study by researchers at Michigan State University and the Climate Intervention Biology Working Group, published this week in Environmental Research: Climate, models what stratospheric aerosol injection would do to marine heat waves under three deployment scenarios and finds that even the most aggressive intervention would leave about a quarter of the world's oceans facing longer and hotter heat waves than they do today. The headline number is the one the solar-geoengineering community has been working toward. The footnote number is the one the climate-justice community will be reading.

The substantive findings are the part to track. Under the current emissions trajectory, the study finds, average ocean temp...