Solar Geoengineering: A farfetched expense or foresightful investment?

By Nicole Bortfeld

Stratospheric sulfur injections (SSIs) are a form of solar geoengineering which involve  introducing particles of sulfur into the atmosphere. The tiny particles of sulfur are ideal for reflecting insolation and reduce the Earth’s global average temperature. Humankind  has pushed global temperatures to increase by more than 1°C since the Pre-Industrial Era and as a result, increased occurrences of drought, floods, extreme weather events, sea level change and losses in biodiversity wreak havoc on our planet1. All of these factors pose an incredible risk to the physical and socio-economic security of millions of people worldwide, so it is no surprise that governmental bodies are investing large amounts of capital into their prevention2.  With the Intergovernmental Panel on Climate Change (IPCC) projecting a further and significantly more drastic increase of between 1.8°C to 4.5°C within the next century and no end in sight for our dependence on fossil fuel combustion, preventative measures for the incoming slew of environmental crises are under fervent examination by climate scientists and policy makers alike3. If the efficacy of solar geoengineering depends equally on the technology available at hand and cooperation between nations, the question is: Do we have to tools necessary to geoengineer the Earth’s climate? And if so, at what cost?

Proof by volcano, trial by climate model

Volcanic eruptions provide a natural analogue for SSIs and evidence for their potential success. In 1991, Mount Pinatubo, a volcano in the Zambales Mountains region of the Philippines, erupted and injected approximately 10 megatons of sulfur into the atmosphere. This eruption triggered a sudden global cooling of 0.5°C4. Since then, computational studies using climate models have been conducted in order to simulate how Earth would react if a similar  atmospheric influx of sulfur were to be artificially created. So far, studies point towards success. Various studies confirm that artificially triggering global cooling would indeed be possible, but not without certain drawbacks5. Despite the overwhelming numerical evidence that SSIs lead to global temperature decrease, there is a large level of uncertainty surrounding how exactly climatic impacts are distributed regionally. A 2015 study found that SSIs could potentially lead to a reduced monsoon season in parts of the African Sahel and Southeast Asia – regions where millions of people are economically dependent on heavy summer rains for a prosperous harvest season6. In addition to this, the study identified a positive feedback loop between weakened the monsoon seasons and increased regional temperature, further exacerbating drought conditions7. It is vital to acknowledge the dissimilar (and possibly detrimental) impacts SSIs could have in some of the most vulnerable parts of the world. Furthermore, the spatial inequality of the benefits and drawbacks is potential grounds for conflict between nations in terms of who gets to make this crucial decision on behalf of the others.

Driving a hard bargain

It is estimated that the annual cost of injecting 1 megaton of sulfur, the proposed estimate to keep global warming at bay, into the atmosphere is 1-2 million US dollars8. This is less than 1% of the projected annual cost of remediating the infrastructural and environmental damages caused by climate change, such as combatting sea level rise in coastal and island communities9. However, the development of SSIs will have significant up-front costs – one study suggests that the development of suitable technology (i.e. aircrafts) to carry heavy loads of sulfur into the stratosphere will be as much as 2.25 billion US dollars per year in the first 15 years of development.

Essentially, in comparison to the cost of carbon mitigation and reversing the damage caused by climate change, stratospheric sulfur injections are still an extremely cheap alternative which doesn’t necessitate curbing fossil fuel emissions. When we break down the costs of solar geoengineering, it becomes clear that there is great potential for what economists call the ‘Free Driver Effect’ to take place. The Free Driver Effect describes the phenomenon of a processes’ direct costs being so incredibly cheap that one nation or even person could have the power to implement it on behalf of others. The prospect of one nation’s leader or, simply, a billionaire playing god with the Earth’s climate is a terrifying one. This is why international efforts convened by the British Royal Society, Academy of Sciences for the Developing World, and the Environmental Defense Fund are aiming to create a governance system which would regulate geoengineering research and, ultimately, prevent reckless “free driving”10.

A day late and a dollar short

At first glance, SSIs may seem like an attractive form of climate change mitigation due to their cheap, rapid and reversible nature. The overwhelming evidence that geoengineering the Earth’s climate would be easier than curbing emissions or mitigating future damage makes it simple to overlook the potential for negative changes to regional climate. At their core, SSIs are an inherently flawed strategy because they temporarily and haphazardly mitigate rising global temperatures while simultaneously failing to address the multitude of environmental crises which each have their own price to pay.  In order for SSIs to be implemented with any degree of success, they must be conducted in conjunction with other carbon mitigation strategies and movement away from a fossil fuel dependent economy. Most importantly, geoengineering techniques should only be attempted with the common good as its central goal so that “free driving” is avoided at all costs11. Ultimately, solar radiation management must be viewed as a climate adaptation strategy, rather than a long-term solution12. Otherwise, we are simply delaying the inevitable.

The views expressed in this article are the author’s own, and may not reflect the opinions of The St Andrews Economist.

  1. IPCC 1.5°C Warming Report (2018)
  2. IPCC 1.5°C Warming Report (2018)
  3. Meehl et al. (2007)
  4. Robock et al. (2008)
  5. Crutzen (2006)
  6. Rasch et al. (2008)
  7. Rasch et al. (2008)
  8. Ron Nielson (1992); Crutzen (2006)
  9. McCellan, Keith and Apt (2012)
  10. Wagner and Weitzman (2012)
  11. Heyen et al. (2019)
  12. McCellan, Keith and Apt (2012)


Banks, M., 2013. Individual Responsibility for Climate Change. The Southern Journal of Philosophy, 51(1), pp.42-66

Crutzen, P., 2006. Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma?. Climatic Change, 77(3-4), pp.211-220.

11. Heyen, D., Horton, J. and Moreno-Cruz, J., 2019. Strategic implications of counter-geoengineering: Clash or cooperation?. Journal of Environmental Economics and Management, 95, pp.153-177.

IPCC, 2018: Global Warming of 1.5°C.An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. In Press.

McClellan, J., Keith, D. and Apt, J., 2012. Cost analysis of stratospheric albedo modification delivery systems. Environmental Research Letters, 7(3), p.034019.

Meehl et al., 2007: Global Climate Projections. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

National Academy of Sciences (NAS), 1992. Policy Implications of Greenhouse Warming: Mitiga- tion, Adaptation, and the Science Base, Panel on Policy Implications of Greenhouse Warming, Committee on Science, Engineering, and Public Policy, National Academy Press, Washington DC, 918 pp.

Niemeier, U. and Timmreck, C., 2015. What is the limit of stratospheric sulfur climate engineering?. Atmospheric Chemistry and Physics Discussions, 15(7), pp.10939-10969

Rasch, P., et al., 2008. An Overview of Geoengineering of Climate Using Stratospheric Sulphate Aerosols. Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences,.

Robock, A., Oman, L. and Stenchikov, G., 2008. Regional climate responses to geoengineering with tropical and Arctic SO2injections. Journal of Geophysical Research, 113(D16).

Wagner, G. and Weitzman, M., 2020. Playing God. [online] Foreign Policy. Available at: <; [Accessed 24 October 2020].

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