For over 30 years scientists and engineers have theoretically pondered whether it was possible to mitigate global warming by atomising seawater over the ocean to ‘brighten clouds’. Given the current plight of the Great Barrier Reef, cloud brightening is now being considered as a regional strategy to reduce environmental stress on coral reefs during bleaching events. Atmospheric, biogeochemical and ecological modelling of cloud brightening undertaken by the Reef Restoration and Adaptation Program suggest that if employed appropriately, it could reduce light and thermal stress during marine heatwaves. As a result, Australia is now leading the world, conducting the first field program to empirically test the concept of marine cloud brightening. From its inception the research has involved consultation and participation of indigenous traditional custodians of the reef and proceeded within the regulatory oversight of one of the world’s most actively managed marine estates. Here, we present the results from summer field campaigns undertaken in the summers of 2020/21 and 2021/22. The results show tantalising evidence that the cloud brightening concept could work as suggested by the theory. The implications of these results, as well as the strengths and limitations of marine cloud brightening to reduce coral bleaching, are further discussed.