Sunday, 22 November 2015

Marine Cloud Brightening

This week’s blog aims to assess another SRM process, the marine cloud brightening (MCB), first suggested by Latham (2002).  This process aims to add small particles of seawater vapour in the atmosphere.  In 2010, Bill Gates decided to expand his cloud building from Microsoft applications to the real world!  He donated $300,000 to the Silver Lining to develop machines able to convert seawater to very small vapour particles.  These particles will be sprayed in the atmosphere, to form stratocumulus white clouds, outlining the main MCB principle (Morton 2009).   Researchers suggest ships to distribute these particles in the atmosphere using Flettner rotors, rather than a conventional diesel engine (Latham et al 2012).  A Flettner rotor is a vertical cylinder that rotates to provide electricity, hence creating movement in these ships that would spread the seawater vapour in the atmosphere to form these white clouds (Figure 1).  Therefore, once these white clouds are formed, less solar reflection reaches the Earth’s surface, creating cooler climate conditions.

Figure 1: Illustration of Marine Cloud Brightening with Flattener rotors
Source: Latham et al 2012
 The MCB process, is nicely described by the researchers, using the following video:

Effectiveness and world Impacts

It is expected precipitation rates will decrease in some areas of the world.  This will be disadvantageous in areas highly dependent on water for agriculture.  It is expected that the precipitation in South America will decrease by 50% (Latham et al 2012).  Thus, the Amazonian region will face a decline in rainfall, drastically influencing the Amazon rainforest.  A decline in rainfall could substantially decrease this rich tropical ecosystem, deteriorating biodiversity (Figure 2).  Nonetheless, it is important to acknowledge that dry areas which are expected to suffer the most from climate change, such as Africa and India may benefit with increasing precipitation (Jones et al 2009).

Figure 2: Land Precipitation and Vegetation approximations from 2030-2059
Source: Modified figures from Jones et al 2009

The above deductions were made using the Hadley Centre Global Environment Model Version 2, (HadGEM2).  However, Rasch et al (2006) uses the Community Climate System Model (CCSM) and suggests no changes in rainfall globally.  This difference in the two models may have occurred due to two reasons.  Firstly, this difference may be due to Rasch et al (2006) seeding a larger amount of the ocean compared to the HadGEM2 model.  Secondly, this difference may occur, as each model takes into account different factors and simulates the Earth in a different way. Hence, making this observation highly variable to model discrepancies and highlighting the uncertainties of theoretical assumptions.

 Another negative impact is that cooling in MCB is non-uniform and occurs regionally.  There is significant warming  which occurs mostly in high latitudes.  However, the lower latitudes have a decreased temperature (Jones et al 2011).  Therefore, it is questionable to what degree the MCB process is globally effective.

Furthermore both models (HadGEM2 and CCSM) show sea ice melting will decrease during the summer months and sea ice thickness will increase near the polar regions in the Northern Hemisphere (Latham et al 2012).  They also expected that sea-ice will increase by 0.9 and 0.5 million km2 in the Arctic and Antarctic regions respectively (Jones et al 2011).  Therefore, due to the ice not melting, there is a declining rate of sea-level rise.


I believe the MCB process may have less negative environmental impacts than the artificial aerosols.  It may also seem more plausible than the space mirrors although it may not be as safe as white/green/PV roofs it may be more effective.  The MCB process once applied, can delay global warming for approximately 25 years, thus reducing temperatures to levels 25 years ago (Jones et al 2009).  However, as the Silver Lining research group suggests, this process should be used to delay climate change impacts, to give some breathing space to develop renewable energy and also reduce carbon dioxide levels in the atmosphere.  The MCB may be very effective and has been highly discussed.  However, I am unsure if this is a correct approach.  As population rates are continuously increasing, they become highly dependent on water as a source of hygiene and sustenance of crop growth.  Hence, a decrease or a shift in the amount of rainfall in specific areas may lead to political tension between nations that may share a water source.  Despite these negative implications, MCB will be seriously considered by all nations taking part in the United Nations Framework Convention on Climate Change (UNFCCC), which will occur in Paris (COP21).  Have we come to the point where such drastic changes are essential to reduce climate change impacts and each country is incapable of reducing their own emissions? Do you believe it is a viable process?


  1. Interesting post Maria - I agree with what you say in your thoughts section that there are a lot of potentially risky consequences in terms of water security around the world. I also don't like the uncertainty between models which shows we clearly do not have a solid grasp on the repercussions that MCB will have for the planet - so how can we justify going ahead with it? 50% loss of rainfall in Amazonia, if it did happen, would be completely disastrous for biodiversity, the ecosystem and the services it provides.

    1. Hi Ben, Thank you for your comment. I could not agree more. I feel concerned that nations are seriously considering the use of geoengineering, specifically, MCB. Imagine how many remedies could be lost if the Amazon rainforest was destroyed due to a lack of rainfall (especially since it is highly reliant on rainfall as a source of water uptake). Also the fact that two models are so different between them is a concern as you don't know which one to believe or if any of them are correct. To be honest, I think the only SRM process that I would feel comfortable with until now would be the green roofs or PV roofs as there are almost no negative consequences.

    2. Same here - the rest are far too risky and far too uncertain to be viable in my opinion!

    3. the scary thing is though, that this process (MCB) will be discussed during the COP21 conference, as it has been suggested by the University of Washington.

  2. Hi Maria, I think I agree with Ben's sentiments on this topic, I think the potential for an impact on water security is too risky to justify using this method. After reading this post, I am going to be looking at COP21 with a new interest, to see the consensus on MCB. It's scary to think that this is going to be discussed, and there has been so few information on it given to the public!

    1. Hey Celia! Thank you for your comment! I agree water security is a highly sensitive subject (especially since they predict major wars in regards to water). I totally agree, COP21 should be very interesting. I am really looking forward to what they have to say and I am hoping they do not propose any type of process which may influence the globe negatively.