Evidence that deliberate marine cloud brightening can be more effective than previously thought

Abstract

With global warming currently standing at approximately + 1.2 °C, climate change is a pressing global issue. Marine cloud brightening (MCB) proposes injecting aerosols into marine clouds to enhance their reflectivity and thereby planetary albedo. However, because it is unclear how aerosols influence clouds, especially cloud cover, both climate projections and the effectiveness of MCB remain uncertain. Here, we use volcanic eruptions to quantify the aerosol fingerprint on tropical marine clouds. We observe a large enhancement in reflected sunlight, mainly due to an aerosol-induced increase in cloud cover. This observational evidence of a strong aerosol impact suggests that the Earth’s climate is highly sensitive to external forcing mechanisms, but also that mitigation of global warming via MCB is more plausible than current climate models suggest. Our results suggest that the best efficacy for MCB practice is to seed clouds in humid and stable meteorological conditions.