A Summary of Geoengineering Methods

Before I explore and assess the viability of geoengineering I thought it would be best to review the different types of geoengineering and the science behind them. In general, proposed geoengineering schemes can be classified under two categories: Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR) (Kosugi, 2010).

Figure 1: Visual representations of proposed geoengineering schemes under the two broad management categories (Source: http://rethinkingprosperity.org/tag/global-warming/).

Solar Radiation Management:

1. Space Reflectors:

Also Known As: Solar Shields, Solar Radiation Management, Sunshades

Suggestions have been made to place large reflectors high in the statosphere or even in outer space which reflect incoming solar radiation back out into space. The idea was first introduced by Roger Angel first presented the idea of sunshades in 2006, winning NASA grants for further research in 2008 (EurekAlert, 2006). What was a novel idea is now gaining scientific traction but such aims remain unachievable with current existing technology. Furthermore, the project is expected to be extremely expensive regardless of how successful the outcome.

Figure 2: The graphic highlights proposed plans for these solar shields. The shades are transparent but work to spread out incoming sunlight to prevent to divert it from reaching Earth (Source:http://thefutureofthings.com).

2. Reflective Aerosols:

Also Known As: Aersosol Cooling

Aerosols are fine solid particles or liquid droplets suspended in the air, with both natural and anthropogenic source (Colbeck, 2009). Following large scale volcanic eruptions, scientists notice a short period (months to years) of cooled temperatures. This occurs as the eruption releases aerosols into the atmosphere and stratosphere where they scatter sunlight, reducing the solar energy reaching the earth. For example, following the eruption of Mount Pinatubo in 1991 the ejection of sulphur dioxide led to the production of sulphate aerosols. Following this eruption, global temperatures dropped by approximately 0.6°C for 2 years. Geoengineers see this as an opportunity for reducing global temperatures for a longer time span, through injecting reflective aerosols into the atmosphere. However, there are a wide range of aerosols with some reflecting and others absorbing heat. In the case of black carbon, this aerosol absorbs the suns heat further warming the climate whilst also depositing on white snow surfaces reducing surface albedo and shading the earth's surface. Therefore, a critical understanding of different aerosols is first required before utilising them in geoengineering. Ultimately, reflective aerosols also represent a short term solution which will have little impact on global carbon dioxide levels and dealing with the real issue at hand.

Figure 3: The relationship between large volcanic eruptions and global temperature anomalies indicating the impact of aerosol's on the climate (Source: http://earthobservatory.nasa.gov) 

Carbon Dioxide Removal (CDR):

1. Iron Fertilisation:

Also Known As: Ocean Seeding, Carbon Sinking

Companies such as Planktos and Climos suggest mitigating the global rise in atmospheric carbon dioxide through 'seeding' the world's oceans with Iron. The concept was initially theorised by the renowned biogeochemist John Martin who suggested that adding iron dust to oceans can trigger large scale planktonic booms reducing global atmospheric carbon dioxide levels as the plankton absorb carbon dioxide from the atmosphere in photosynthesis (Martin et al. 1987). Arguments against the method suggest that the granulated iron will act as a pollutant, further deteriorating the oceans. It has also been acknowledged that plankton booms along shorelines can lead to oxygen depletion and ocean acidification, proving devastating for marine biodiversity.

The iron fertilisation process summarised in 4 main steps (Source: http://marinefoodchainsmn.tumblr.com)

2. Artificial Trees:

Also Known As: Carbon Capture, Synthetic Trees

A report by the Institute of Mechanical Engineers led by Dr. Tim Fox suggested the use of large, fly-swat shaped constructions as a viable geoengineering option (Fox et al, 2009). These structures act as artificial trees through capturing passing air and separating and storing CO₂ present through possessing 'sorbent' materials such as sodium hydroxide. This stored CO₂ is later removed and buried deep in the ground where it remains naturally stored in the Earth.  The structures (Figure 3) were estimated in the report to cost approximately $20,000 each whilst requiring land to be built on. However, 100,000 of these 'trees' in the UK was calculated to remove the same amount of carbon dioxide released from the UKs household and transport emissions each year. However, other studies such as that by Lackner, 2009 suggests a total of 10 million units of these structures are required worldwide to mitigate against humanity's total carbon output. Therefore, it is clear that the science behind this scheme remains relatively untested with global estimates remaining rare.

Figure 5: Proposed design for 'artificial carbon absorbing trees'  (Source: http://www.theresilientearth.com).

3. Enhanced Weathering:

Also Known As: Dissolution & Carbonation

Scientists have suggested that exposure of new rocks to weathering can act as a means of sequestering atmospheric carbon dioxide levels. When surface rock is weathered away, new rock is exposed and this absorbs carbon dioxide from the atmosphere as it has not previously been in contact with CO₂ before. This highlights an attractive opportunity in geoengineering where crushing and spreading the magnesium rich rock olivine across land surfaces could speed up the natural carbon sequestering processes. Under natural conditions, olivine absorb atmospheric CO₂ to form magnesium carbonate and silicic acid and in turn removing and storing carbon. The olivine particles can also be deposited on sea beds to deal with issues of ocean acidification.  However, these processes would require large scale projects to have a meaningful impact. Hangx & Spiers (2009) carried out a kinetics study indicating the need for an approximate annual spread of 5 gigatonnes of olivine across beaches to reach a 30% offset of yearly global emissions based on 1990 levels. Despite this, it still remains unknown as to how long it will take for the olivine to sequester the carbon dioxide and whether such a technique will be cost efficient or not.

Figure 6: Olivine broken into small pieces (Source: http://www.nature.com)

Conclusions:

The explored geoengineering schemes represent key projects of interest but it must be noted that other schemes such as cloud seeding, deep sea carbon capture, biochar and forestation to mention a few, are all gaining traction with pros and cons being highlighted for each. Through exploring these options I am beginning to form an opinion of geoengineering as a hopeful yet futuristic concept. If anything, each method requires global efforts and intensive technological and scientific research before implementation. At this stage, I have a positive outlook on geoengineering but yet question its global governance if used in the future. Let me know what you think on last week's poll!

Geoengineering: a destructive strategy or a technological solution?

As I begin writing this blog post, I question which stance I will take on this truly controversial management strategy. Geoengineering has so many signs of being a potential contender to solving (or at least aiding) our global climate change conundrum but at the same time, I wonder if further anthropogenic alterations can really benefit our fragile earth.

The simple truth is that at this very moment, I do not know. However, that alone is what makes this topic so interesting to me. Over 4 years ago, I stumbled across an article which spurred my interest in geoengineering. An article which for me, highlighted the true power of the human race, a species who can manipulate mother nature herself. It made reference to how China dispersed a total of 1,100 rockets around the olympic stadium to prevent it raining during the opening ceremony of the 2008 olympic games. Although expensive, the ceremony was without rain and the method was celebrated by Chinese officials as a successful management of small scale meteorological systems.

China's cloud seeding rocket launcher (Source: http://usatoday30.usatoday.com)

At the time of reading, as a young, naive, geography student I saw this to be a novel and technological answer to our climate change issue. Excited about this new stance, I blogged about geoengineering as a marvel invention in 2013- using examples from Abu Dhabi and how they managed to manipulate rainfall for a 52 day period over a desert. I wrote a blog post highlighting what topics will be of interest to geographers 100 years from now, with geoengineering being at the forefront of my argument.

Ionisers in Abu Dhabi inducing rain (Source: http://www.esquireme.com)

One small article spurred so much interest - yet my questions remained unanswered and my knowledge unsatisfied. Over the coming weeks, I hope to delve into the unknown, dig deep and find some real concrete evidence to build an opinion on. Through reviewing sources, peer reviewed articles and other blogposts I hope to explore the controversies of geoengineering and conclude it's viability in long term climate strategy.