"Dr Harrison is developing a technology known as “cloud brightening” – encouraging clouds over the reef to deflect more of the sun’s rays back into space, which would hopefully curb rising sea temperatures that cause coral bleaching."

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"More specifically, the talk focuses on Marine Cloud Brightening, an idea that explores the possibility of "brightening" clouds over the ocean to make them reflect more sunlight away from the Earth. David then encourages the audience to consider the implications of such a drastic and far-reaching solution to global warming, and whether we, as humans, have the right to intentionally perturb our Earth's natural climate systems."

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Ahlm, Lars; Jones, Andy; Stjern, Camilla W.; Muri, Helene; Kravitz, Ben; Kristjánsson, Jón Egill (2017): Marine cloud brightening – as effective without clouds. In Atmos. Chem. Phys 17 (21), pp. 13071–13087. DOI: 10.5194/acp-17-13071-2017.

"Here we present results from coordinated simulations with three Earth system models (ESMs) participating in the Geoengineering Model Intercomparison Project (GeoMIP) G4sea-salt experiment. Injection rates of accumulation-mode sea spray aerosol particles over ocean between 30° N and 30° S are set in each model to generate a global-mean effective radiative forcing (ERF) of −2.0 W m⁻² at the top of the atmosphere. We find that the injection increases the cloud droplet number concentration in lower layers, reduces the cloud-top effective droplet radius, and increases the cloud optical depth over the injection area."

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"In the absence of a sudden and rapid reduction in global greenhouse gas emissions, recovery options are few and tenuous.  In fact, that’s a generous assessment.  We have basically reached the point where anything that provides a glimmer of hope is “worth a crack”. One such proposal is to cool the ocean around the reef by “brightening” clouds overhead.  Modelling and measurements indicate that increasing cloud cover and density would reduce water temperatures around the reef, although whether the effect is sufficient to arrest coral bleaching is uncertain."

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