Sunday, 8 November 2015

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

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!


  1. Hi Maria, interesting post as usual! :) Using mirrors as an SRM seems a bit far-fetched to me, and so costly! I think instead of spending trillions of dollars on this method, we need to attack the cause and not the symptom. What about investing more in renewable technology?
    Also I agree with you - hydrological changes may cause conflicts between nations, especially (I'm assuming) it's going to be developed countries such as the US enacting this scheme without much consideration regarding the effects in lower-income countries. In my opinion, it's not worth it!

    1. Hey Celia, thank you for your comment! In what way do you believe are mirrors far fetched? (in terms of seeming too technologically advanced?) To be honest, I am not completely convinced with SRM mirrors, yet the impacts on the hydrological cycle are far less than climate change. I totally agree with you that geoengineering solely is not the solution however it could help climate levels to stabilise and slowly reduced through the use of renewable energy. What do you think in regards to a combination of renewable technology and geoengineering?

    2. I just think they are probably a bit over the top and impractical - I dread to think how much energy it would take to install them in the first place!
      I think perhaps a combination of geoengineering and renewable technology might work, but it depends on the cost and legitimacy of the geoengineering method. I just feel like the focus on geoengineering is distracting scientists away from viable energy alternatives

    3. I agree with you that geoengineering should be used with renewables.

      In regards to if they are being distracted away from viable energy alternatives I'm not completely sure if I agree. as there is a lot of potential in my opinion yet the risks need to be eliminated with geoengineering

  2. As Celia mentioned, the thing I find most shocking about all this is the cost! If people even considered spending that amount of money investing in renewable technologies, the world would be an entirely different state.

    Space mirrors do sound a bit silly, but I agree with you that they are probably less environmentally damaging that some other SRM methods. However, SRM is still fundamentally flawed in treating the symptoms without the cause and really should not be something we even consider, in my opinion.

    1. Thanks for your comment Ben. I totally agree with you in terms of cost. I agree that SRM may be perceived as flawed, however the greatest concern is the global increases in temperatures. SRM would not help solve the reason temperatures are rising yet maybe it can give some time to find efficient methods to reduce carbon dioxide emissions. Though, I believe, this method should be implemented if there are no environmental impacts that may occur. What do you think on the matter in general?

    2. In general I'm more open to CDR geoengineering rather than SRM, as it makes more sense to remove CO2 than to try and limit radiation. Removing CO2 is only working within limits (lower co2 ppm) that the earth has already experienced and can equally help to bide time whilst we find more efficient methods to reduce CO2 emissions, and indeed prevent levels from rising to 500ppm and above.

      By contrast, SRM allowing CO2 to continue to rise whilst reducing radiation pushes the earth into a state we really don't know a lot about. We really don't know for sure what the feedback mechanisms could be if we have an even thicker greenhouse layer but less insolation. We've only seen decreases in incoming radiation to high degrees in association with catastrophic events in the past, which has only been short term - who knows what long term impacts can be. I think its risky for a lot of reasons and as I said before, ultimately flawed by trying to treat the symptoms without the cause.

    3. I totally agree with you! However, I think that SRM and CDR are not mutually exclusive. I believe in order to be successful one must include both, as it may be more effective decreasing CO2 levels yet also decreasing average temperatures (even though CDR may be more successful than SRM).

      Nonetheless, all these suggestions are formulated through modelling highlighting the high degree of uncertainty within these processes.

    4. See, I would disagree with you there - I think they can definitely be exclusive. Whilst the most effective way forward for simply reducing global temperatures may be to use a combination, we are not yet at a point where we need to reduce global temps so rapidly as to throw other environmental concerns out the window. We could use low-risk CDR without SRM easily at the moment to help mitigate climate change, whilst still protecting the other components of the biosphere and taking low risk options.

      The ultimate goal of all of this is to stop climate change altering the biosphere in ways which are negative for humans. So why should we do this by methods (whether they be SRM or CDR) which just degrade different parts of the biosphere we're trying to protect?

    5. I believe that we are at a point where a change is needed as carbon dioxide levels are constantly increasing. I agree that we are still not at a point where global temperatures need to be reduced rapidly. However, if we want to decrease impacts as soon as possible we cannot wait to the last minute. If we want geoengineering processes with low risks and less environmental impacts without degrading the biosphere, we should start soon, as the affects of these processes will take longer to become evident. Hence, if we are using small scale processes of geoengineering, we should use both SRM and CDR to see some change at slightly faster rates. Although, as I have already said previously, I think geoengineering should be used with a combination of renewable processes to reduce climate change impacts and not completely on its own.

  3. Hi Maria, I think that you've provided a really informative overview of the potential power of mirrors to stop global warming. I think I agree with Celia, it's quite a far-fetched notion however I think the theory is does make sense... but in terms of implementation I can't see a future for mirrors in space! I think that despite the potential of this SRM method the fact that it could have negative implications over the hydrological scale which could plunge those in poor climatic and environmental situations further into darkness, there is a significant ethical element obstructing it's progress for the future!

    1. HI Caitlin, thank you for your comment! I am glad you enjoyed this blog-post. I believe it may be perceived as high-fetched, however, if you think about it we are more than capable to send satellites and spacecrafts so why not some kind of mirrors? However, I agree with you! The negative implications are quite high (although not as bad as aerosols) and it may not be the best of way of reducing global temperatures.