Ocean-based climate cooling solutions
Marine Cloud Brightening (MCB) aims to reflect more sunlight back into space by enhancing the reflectivity of clouds over the ocean. The process involves:
- Spraying Seawater: Devices over the ocean surface spray fine mist of seawater.
- Aerosol Formation: These droplets evaporate, leaving salt aerosols that rise into the atmosphere.
- Cloud Interaction: The salt aerosols act as condensation nuclei, making clouds whiter and more reflective.
- Increased Albedo: Brighter clouds reflect more sunlight, reducing the amount of solar energy absorbed by the Earth.
Cloud Brightening Systems’ Spray Salt Over the Ocean
When cloud brightening systems spray salt from seawater over the ocean, the water evaporates, and the extremely light salt aerosols rise into the stratocumulus clouds (1/2 – 2 km). This process causes the clouds to divide their water content into more, smaller droplets, making the clouds whiter and more reflective. These brighter clouds persist longer in the sky, enhancing their reflective properties.
The micro-droplets produced by cloud brightening significantly increase the clouds’ reflectivity and longevity, reflecting more sunlight back into space and thus cooling the Earth. This method is particularly effective over the stratocumulus clouds that cover large oceanic areas, which is the foundation of Marine Cloud Brightening (MCB).
The micro-droplets produced by cloud brightening significantly increase the clouds’ reflectivity and longevity, reflecting more sunlight back into space and thus cooling the Earth.
NASA image by Robert Simmon
Reflecting the Sun’s Energy
MCB aims to reflect more of the sun’s energy into space rather than allowing it to be absorbed by the Earth. By enhancing the natural albedo effect of clouds, MCB helps mitigate global warming.
Inspired by Nature
MCB is ‘biomimetic’, inspired by natural processes. It mimics the natural interactions between waves, wind, and air that occur constantly around the world. Salt particles used in MCB are very small, ensuring they do not form a saline cloud but rather integrate into the cloud microstructure.
A Flexible Technology
MCB is adaptable, capable of creating local or regional effects as needed. It also has a safety mechanism: if unintended consequences arise, the spraying can be stopped immediately. MCB’s effects dissipate within a week, and the first rain shower can eliminate all salt spray efforts.
The Cloudy Trails of SO2
Human activity has inadvertently demonstrated the cooling effect of enhanced reflective cloud cover. Until recently, fuels used by international ships contained sulfur dioxide (SO₂), which led to the formation of condensation trails that increased cloud reflectivity. However, recent environmental regulations have reduced SO₂ levels in ship emissions to combat acid rain, resulting in decreased cloud cover and reflectivity and contributing to a temperature increase of about one degree.
James Hansen noted that “Water vapor, the primary short-term forcing, could only be treated by action to cool and brighten the atmosphere, adding aerosols to cut the temperature rise that increases humidity. However, the aerosol changes required are now going in the opposite direction, with albedo now falling by 1% per decade, amplifying the warming feedbacks from water vapor.”
“Water vapor, the primary short term forcing, could only be treated by action to cool and brighten the atmosphere, adding aerosols to cut the temperature rise that increases humidity. However, the aerosol changes required are now going in the opposite direction, with albedo now falling by 1% per decade, amplifying the warming feedbacks from water vapor.”
James Hansen
Preliminary Conclusions on Oceanic Cloud Brightening
MCB offers a biomimetic, nature-inspired, flexible solution to enhance cloud reflectivity and mitigate global warming. By learning from natural processes and past human impacts on cloud cover, MCB presents a promising temporary measure to cool the planet with immediate impact while long-lasting solutions to reduce greenhouse gas emissions are developed and implemented to address climate change in the long run.