Marine Cloud Brightening

What is it?

Marine Cloud Brightening involves spraying superfine particles of seawater into clouds- specifically clouds over the sea where its harder for clouds to form, to brighten them. This utilises an effect called the Twomey effect- if the size of particles in clouds are smaller, they reflect more light.

If clouds reflect more sunlight, less sunlight is available to warm up the earth, so in theory, this could reverse warming up to 3 degrees Celsius by just spraying seawater into the air.

Any problems?

Climatically, yes. There could be a reduction in global rainfall, especially over the Amazon, according to one study, although this is considerably less than unabated climate change, however, this is enough to cause serious ecological and social consequences. Even so, this could be avoided by spraying in different places. Another study found increased rainfall over land even though there was an overall global reduction.  

The key problem, however, is research- we don't have enough research yet to ensure their won't be dangerous unintended consequences of Marine Cloud Brightening, and it is this lack of research which is what would make large scale implementation today so dangerous.  Even over something like rainfall amounts, there is no real consensus.  This is why we need research.

Politically, there's the issue of control. If it were used on a large scale, the question of which countries or individuals controls the global thermostat is very pressing. This question could heighten tensions between countries and potentially reinforce global inequalities if not done in the right way.

Also, if we decide to stop, or what we use to do it gets destroyed, the effects will be unravelled, leading to faster climate change than we would have seen without using it in the first place.

Potential Benefits

  • Could reverse global warming potentially by up to CO2 doubling point

  • Could help retain Arctic Ice at current levels, stopping the huge impact if it melted

  • Could be used to stop mass coral bleaching events as Marine Cloud Brightening could be implemented locally

  • Could be switched off and effects reversed if serious problems detected

  • Many areas  where warming would make the most difference (Africa and India for example) would be protected the most by Marine Cloud Brightening

  • Can be implemented locally rather than globally

  • By cooling waters, reduces the chances of hurricanes

  • Cheap

  • All of this is deeply theoretical, based solely off computer modelling- field trials are necessary to prove all of this, and it could disprove a lot of these 'benefits'


Climate impacts of geoengineering marine stratocumulus clouds. Jones et al. 2009

Marine Cloud Brightening  Latham et al 2012 (review of research up to that point)    project to discern whether could be used on coral reefs

Geoengineering by cloud seeding: influence on sea ice and climate system  Rasch et al 2008

Sea-going hardware for the cloud albedo method of reversing global warming  Salter et al 2008  about costs

Marine cloud brightening: regional applications  Latham et al 2014