To assess marine cloud brightening's technical feasibility, we need to know what to study—and when to stop

To avoid the worst impacts of climate change, it’s paramount that we decarbonize the economy and preserve and restore natural ecosystems. Unfortunately, pledges made from countries thus far will not limit warming to below 1.5 °C, even after accounting for the more ambitious targets set at the recent COP26 climate summit in Glasgow. Meeting the 1.5 °C Paris Agreement goal will likely require a massive deployment of CO2 removal technologies that remain unproven at scale. As a result, many scientists—including an expert panel recently convened by the US National Academies of Science, Engineering, and Medicine (NASEM)—have advocated for research into solar climate interventions that would offset some effects of greenhouse gas-driven warming by reflecting more sunlight back to space. This would temporarily cool the Earth, giving mitigation and adaptation efforts more time to scale up. One such approach, marine cloud brightening (MCB), would seed low-altitude clouds over the ocean with salt particles to produce more and smaller cloud droplets, leading to brighter clouds.