An Introduction to Geoengineering

by Ben Williams

Geoengineering involves artificially intervening with natural processes and weather systems with the aim of offsetting or even reversing climate change [1]. The term encompasses a range of concepts both small- and large-scale, some of which are mainstream (e.g. afforestation) and some of which are more radical. The first official mention of geoengineering as a method to combat climate change was accredited to the US Science Advisory Committee under President Johnson in 1965 but, with the notable exception of carbon capture, most ideas have since remained purely theoretical [2].

More recently, the National Academy of Sciences proposed investing $100m in research on solar irradiation management, a pillarstone of geoengineering [3]. So, why would we consider it and what are the possible approaches?

The argument for geoengineering is that we may now, or in future, be at a point of no return. In this case, reducing emissions is not enough – we need to actively reverse climate change [1]. Carbon capture and storage (CCS) is the most widely researched option for this i.e. taking CO2 produced by power generation or other industrial processes, then storing it rather than releasing into the atmosphere. If done at a large scale, CO2 can be compressed into liquid form and stored long-term far underground [4]. The commercial viability of this has so far been hampered by a high cost for processing and transportation, but the technology involved is admittedly very immature [4]. More widely adopted is afforestation and making use of biomass for carbon storage. CCS may be an essential part of the global strategy against climate change in coming decades [5]. 

The alternatives largely focus on reducing the net heating effect from sunlight. The eruption of Mount Pinatubo in June 1991 is credited with cooling the Earth’s surface by an average of 0.5°C for several years, due to the large-scale injection of SO2 into the upper atmosphere [6]. We can recreate a similar effect by injecting sulphate particles into the upper atmosphere, although it is unclear how this could physically be achieved. Cloud reflectivity can also be boosted by spraying particles over the sea to encourage droplet formation [2]. Even more unconventional is to encourage growth of phytoplankton in the ocean, which would assist in carbon capture (but can cause serious ocean damage if the phytoplankton dies off) [2].

Clearly there are significant cons to geoengineering. On a political level – since its effects are cross-border – widespread international consensus would be required for effective implementation, particularly if one result could be reduced crop harvests in unpredictable locations.

Without precise engineering CCS presents the risk of large-scale leaks. Away from CCS we have very little understanding of the possible side effects. Sulphate particles projected into the atmosphere reverse heating, but have been shown to result in increased premature deaths and environmental damage through acid rain [6]. Other substances may risk ozone layer damage.

Aside from these, solar irradiation management only reverses heating; it does not do so for ocean acidification or other ecological impacts from fossil fuels (which if left unchecked, could be irreversible on human timescales) [7].

What to look out for

Ever more large companies are announcing investment in carbon capture technologies spread over the next 10 years. Their aim is to improve the commercial offerings to make the process economically viable (e.g. by synthesising useful chemical products) [8].

Geoengineering is crucially not a substitute for rapid emission reduction. Away from CCS, it is a last resort to counteract catastrophic warming rather than a safety net. The fact remains that such technology may still be necessary, and future investment will reflect this. 


[1] Oxford Martin School, “What is Geoengineering”, (accessed on 23/06/2021
[2] James Temple, “What is Geoengineering – And Why Should You Care?”, MIT Technology Review, (accessed 23/06/2021)
[3] Damian Carrington, “Dimming the sun: $100m geoengineering research programme proposed”, The Guardian, (accessed 23/06/2021)
[4] Vincent Gonzales and Others, “Carbon Capture and Storage 101”, Resources for the Future, (accessed 23/06/2021)
[5] Gasser, T., Guivarch, C., Tachiiri, K. et al. Negative emissions physically needed to keep global warming below 2?°C. Nat Commun 6, 7958 (2015).
[6] Crutzen, P.J. Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma?. Climatic Change 77, 211 (2006).
[7] Robert McSweeney, “Geoengineering is no substitute for cutting emissions, new studies show”, Carbon Brief, (accessed 23/06/2021)
[8] Emily Pickrell, “We Can Capture Carbon, But What Then? Turning A Profit Will Be Key”, Forbes, (accessed 23/06/2021)

Ben Williams is one of the ClimaTalk Webmasters. He has a Master’s degree in Electrical and Information Engineering and a passion for green innovation, which he hopes to combine in his career to work on the technological solutions that will help drive social and environmental change. He currently works for Ocado Technology, a groceries and logistics company that supplies cutting-edge retail automation around the world.

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