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.

Thoughts

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?

'Colouring' roofs

Today I would like to discuss with you 3 main types of roofs: the typical white roof, the green roof and the PV roof.  Keep on reading to find out more…

With a rapidly increasing population, and a rise in global economies, urbanisation is expanding. This increases the amount of roads and buildings, creating dark surfaces that reduce solar reflection and the Earth’s albedo.

A geoengineering method that could enlarge albedo reflectance is through painting roofs and human settlements white, bringing about a net increase in albedo of 0.1 in urban areas (The Royal Society 2009). The increase in albedo increases solar reflectance and reduces global temperatures.  This may lead to a decreasing rate of glacial ice melting and less of an impact on the environment.  Although this geoengineering process may take a few decades to be implemented worldwide, once complete, effectiveness should be highly apparent (Table 1). Furthermore, there are very low risks with the white roof method compared to other SRM processes.

 

Table 1: White Roof Evaluation Summary
Source: The Royal Society 2009

Criticism of White Roofs

Jacobson and Hoeve (2011) may disagree suggesting that local temperatures will decrease by 0.02K, however, global temperatures will increase by approximately 0.07K.  The white roofs reduce temperatures near the surface air.  However, there is a reduced sensible heat flux (i.e. heat energy transferred from the Earth’s surface to the upper atmosphere).  Consequently, due to a reduction in the sensible heat flux, cold air cannot be transported further up in the atmosphere, hence leading to a local cooling but a global warming.

Furthermore white roofs are accumulated in specific areas, causing small changes in cloud optical depths and winds.  Therefore, clouds intensify over the northern hemisphere making the area cooler and increasing surface albedo.  However in the Southern Hemisphere, temperatures increase, causing global temperatures to rise.  Hence there will be less clouds in the Southern Hemisphere leading to a decrease in precipitation events such as snow and rain (Jacobson and Hoeve 2011).   Consequently the hydrological cycle may be negatively impacted in the southern latitude.

Another disadvantage is that a high amount of carbon dioxide aerosols in the atmosphere absorb upward solar radiation from the reflection of white roofs and trap heat within the atmosphere, increasing global temperatures (Jacobson and Hoene 2011).

Lastly, white roof reflections are effective in warm areas, this causes energy efficiency when using electrical cooling appliances, saving energy (Cubi et al 2015).  However, if an area is cold and becomes cooler due to an intensification in surface albedo, such as Canada, this increases energy demand and more fossil fuels need to be burnt for electricity.  It is suggested that cold areas would consume more electricity than in warm areas, therefore increasing carbon dioxide in the atmosphere (Jacobson and Hoeve 2011).

An alternative suggestion

Cubi et al 2015 suggests an alternative method in cold climates; green roofs and Photovoltaic (PV) roofs.  Green roofs (or eco-roofs) are vegetated roofs, where organic material is grown.  This is aesthetically appealing, can create sound and heat insulation and can be a good way in preserving habitats.  Although the reflectance will be less compared to white roofs, there may be some reduction in carbon dioxide due to photosynthesis of plants.  Furthermore little maintenance is required and less heat will be needed for buildings in cold environments.  The PV roofs are photovoltaic panels placed on the roof of buildings, creating renewable energy with no carbon emissions, reflecting some solar energy and decreasing environmental impacts.  However, PV roofs, would not be sufficient during cloudy days with no sunlight for energy (Cubi et al 2015). 

Consequently, PV roofs are preferred overall, as it is the highest performing amongst all categories (Table 2).  PV roofs reduce carbon dioxide levels and save energy to a higher degree compared to any other type of roof. However, it may be argued that Green roofs are cheaper and a longer lasting method which also conserves environmental habitats to some degree.  Furthermore white roofs have significant negative impacts on ecosystems.  When modelling the white roofs process, it is suggested that the expected outcome will not be achieved, as global temperatures will increase rather than decrease.

 

Table 2: A summary of the 3 types of roof reflectance
Source: Cubi et al 2015

Thoughts

I think PV roofs would be the most beneficial in terms of reducing carbon dioxide emissions and declining climate change impacts.  Even though green roofs cannot be disregarded due to their many advantages.  In general, PV roofs and green roofs could be a success and a safe, cost-effective process.  I believe this may be the first indication of alternative small-scale geoengineering that could be successful in the long term, reduce global carbon dioxide emissions and global temperatures without many (or any) risks.  What do you think?

Mirrors: not for just looking at your appearance?

During 1989, Seifritz was the first to propose placing mirrors in the Lagrange orbit, where the gravitational powers of the Sun and Earth counteract (Figure 1).  This would reflect sunrays away from the Earth (Humphreys et al 2011).  Angel (2006) suggested building a ‘cloud’ of small sunshades in the Lagrange orbit, requiring around 25 years to build at the cost of ‘a few trillion dollars’.

 

Figure 1: The positioning of small mirrors in the Lagrange orbit (L1)
Source: Angel 2006

Physical Implications

The installation of space mirrors may be advantageous, as Lunt et al 2008 suggest that global temperatures may decrease to pre-industrial climate and prevent glacial ice melting.  This is emphasised by the Geo model, which suggests a cooling in the Barrents Sea, due to an increase in sea ice.

In contrast a decrease in temperatures may influence the hydrological cycle, causing lower evaporation rates and a decrease in precipitation levels, leading to a decrease in water availability and a degradation of aquifers.   It is suggested that precipitation levels will decrease by 5%, especially near the tropics (Lunt et al 2008).  Additionally ENSO intensity may decrease due to the tropics becoming cooler.  This may be problematic as ENSO events cause the main groundwater recharge in some semi-arid and arid countries, such as Tanzania (Taylor et al 2013). 

Contrariwise, it is argued that the reduction in precipitation may not be as severe compared to climate change impacts (Lunt et al 2008).  The impacts on the hydrological cycle may not be as critical as expected, since it should not lead to a decrease in soil moisture, creating less problems for crop growth (Lunt et al 2008).

Public Concerns

When public surveys are undertaken, it is suggested that people are reluctant to space mirrors (Figure 2).  They feel that it is an unknown process with high levels of uncertainty, it may be very risky and is perceived a quick fix (Wright et al 2014).  Hence, people are reluctant to reducing global temperatures through this process.

Figure 2: Public Perception in Mirrors in space concept image. Percentage point deviations from expected attribute counts
Source: Wright et al 2014

Thoughts

I believe that mirrors in space may be a better SRM method compared to artificial aerosols, as I feel it may cause less environmental and health issues.  Nonetheless, I am reluctant to use space mirrors, due to the hydrological impacts.  Hence, changes in the water distribution may create water stress in countries and lead to conflicts between nations.  Consequently, I believe this may not be the best approach of decreasing global temperatures.

I look forward to hearing your thoughts on the matter!

SPICE, oh my! -The Public Perception

Last week I focused on one of the main SRM processes, the input of artificial aerosols in the atmosphere and its impacts.  This blog post aims to assess people’s concerns and the uncertainty of artificial aerosols through a case study, the SPICE project.

The SPICE project investigates the building difficulties of raising  aerosols through a 20km pipe (Figure 1), held in the air by a giant helium-filled balloon (Pidgeon et al 2013).  However, before this project takes place, SPICE aims to test this SRM method in the real world and wanted to know people’s response on the matter through a public dialogue.

Figure 1: The SPICE Project planned test proposal
Source: Pidgeon et al 2013

Pidgeon et al 2013 suggest the public is relatively unaware about geoengineering.  However, when given basic knowledge people have high levels of uncertainty and concerns and relate the SPICE project to the Hinderburg disaster and the Chernobyl explosion.  Furthermore many people feel that geoengineering is unnatural, and will ‘push nature beyond its limits’, as it is a manmade response to solve atmospheric irregularities which may lead to health issues, such as respiratory problems (Corner et al. 2013).  Additionally the artificial input of aerosols may not help reduce carbon dioxide levels in the atmosphere.  It may be perceived as a ‘quick fix’, where temperatures are reduced but the initial carbon dioxide problem remains unresolved (Davies2011). Moreover, artificial aerosols will need to be constantly inputted in the atmosphere and long-term management would be required.  If neglected this may cause dramatic climatic changes causing great concerns (Pidgeon et al 2013).

Oppositely, some people may argue that the inputs of aerosols may be beneficial.  The input of aerosols is relatively a cheap method, hence being a cost effective solution for governments to resolve climate change issues (Pidgeon et al 2013).   After the first day of debating in the SPICE public dialogue many people became less reluctant to the SPICE project.  It is evident that under the precondition that the artificial input of aerosols are safe, and will be managed correctly people are less reluctant to use them.

Artificial aerosols may be highly effective, yet with many negative consequences.  I am not sure that anthropogenic interference such as aerosols is the solution.  However, other geongineering processes may be more effective and with less environmental impacts. What do you think?