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.
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.
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
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)
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