Solar Geoengineering to Reduce Global Warming—The Outlook Remains Cloudy

In March 2021,Australia’s Great Barrier Reef played host to a rare field test of marine cloud brightening(MCB)technology.Blasting a seawater mist into the air from the aft of a research ves-sel using a turbine outfitted with novel spray nozzles,researchers watched the resulting white plume rise into the sky(Fig.1)[1].Over the last five years,the Reef has suffered multiple mass bleaching events because of ocean warming caused by climate change[2].The MCB project,led by senior lecturer Daniel Harrison of Southern Cross University,Coffs Harbour,Australia,is part of the Reef Restoration and Adaptation Program[3],a government-backed research and development initiative that aims to“develop,test and risk-assess novel interventions to help keep the Reef resilient.”