Development of Tools for Marine Cloud Brightening (Invited)

Last year, 2024, a new record for the hottest year on record was set and the highest level of CO₂_eq in the atmosphere. The last ten years have been the hottest years on record. Yet CO₂_eq emissions continue to climb putting the planet on a pathway between SSP2-4.5 and SSP3-7.0 and expected global average temperatures of between 2.5 to 4.0^o C above pre-industrial temperatures by 2100. This global warming is likely to result in dire consequences for the planet and humanity. Since neither decarbonization nor carbon sequestration is proceeding at a fast enough pace to prevent some of the worst damages due to global warming, several climate interventions have been proposed to cool the planet while we eliminate CO₂_eq emissions. One of the most promising is Marine Cloud Brightening (MCB).

This talk will briefly describe the motivation for studying MCB technology and the various droplet generation methods that might be used with possible application scenarios. We will discuss the work that has been ongoing in our lab to design the most efficient technique that could make MCB a reality. Nozzle designs and their various tradeoffs include Rayleigh-jets, Taylor-cone jets, supercritical sprayers, effervescent atomization, and superheated water atomization. The first liftoff of sprayed MCB plumes, which supposedly also joined the cloud base has been observed over the GBR in Australia. Also, the observed supersaturation in marine clouds over the oceans is now estimated to be larger than previously thought, which would allow the use of smaller salt nuclei, which could substantially reduce the energy requirements.