Geoengineering promises a technological solution to climate change, but its risks remain deeply uncertain. Photo credit: Kaptured by Kasia via Unsplash.
To limit global warming to 1.5 degrees Celsius, and meet the 2016 Paris Agreement target for 2050, around 8 billion tonnes of carbon dioxide per year must be removed from the atmosphere. With recent developments in carbon dioxide removal technologies, national governments, including the United Kingdom are funding projects that investigate the feasibility of this technology to reduce greenhouse gas emissions. Geoengineering refers to deliberate, large-scale scientific interventions within natural ecosystems that aim to remove greenhouse gases from the atmosphere or cool the Earth’s temperatures. With around 600 research trials planned or undertaken internationally between 1971 and 2023, geoengineering has ceased to be a scientist’s dream. Now, it is being considered by governments worldwide as a viable alternative to further limiting greenhouse gas emissions.
With around 600 research trials planned or undertaken internationally between 1971 and 2023, geoengineering has ceased to be a scientist’s dream.
However, the promise of geoengineering should not be used as a tantalising way to forget the severity of increasing carbon emissions, as it may even cause further damage to the planet’s natural cycles—such as disrupting the hydrological cycle, altering marine ecosystems, and causing biodiversity loss—despite the current research hubristically claiming to have the capability to alter the Earth for the better.
There are three main types of geoengineering: carbon dioxide removal, greenhouse gas removal, and solar radiation modification. Each form comes with separate challenges of implementation, as well as the dangerous potential to instead accelerate both ecosystem collapse and species extinction. This raises the question: why is reducing the amount of greenhouse gases emitted daily not the primary focus of governments and scientific institutions?
Carbon dioxide removal (CDR) and greenhouse gas removal (GGR) encompass low-technology actions such as tree planting as well as more recent technologies such as Bio-Energy with Carbon Capture and Storage (BECCS) and marine carbon dioxide removal. BECCS is the process of capturing CO2 and permanently storing it using biomass energy generation. This functions by burning organic matter (biomass) as a fuel for large steam boilers or furnaces that drive energy generating turbines. After the biomass is consumed, the resulting CO2 is isolated using chemical solvents. Then, the captured CO2 is liquified to be permanently injected into porous rock formations, such as depleted oil fields, that will hypothetically allow the CO2 to become chemically bonded to the rock through mineral storage. Because plants naturally remove carbon from the atmosphere, using BECCS would allow energy-generation at industrial facilities to be carbon-negative.
BECCS is the process of capturing CO2 and permanently storing it using biomass energy generation.
As of 2023, there were 45 commercial facilities globally in the works of implementing or already using BECCS to capture carbon according to the International Energy Agency (IEA). However, there are several flaws with current BECCS models, including requiring a large amount of land to grow the biomass, needing proper geological storage sites to contain the CO2 without it leaking, and being unable to stop other flue gases needed within energy production from being released into the atmosphere. Considering more countries seek to develop this technology in their energy plants, the limitations of BECCS that are yet to be perfected should be carefully considered.
Marine carbon dioxide removal (mCDR) stores CO2 in the ocean through ocean alkalinity enhancement (OAE) or ocean fertilisation. Similar in scale to land-based CDR, both forms of mCDR require several tons of chemicals or alkaline minerals to be added into the ocean to absorb CO2 and other greenhouse gases. On one hand, ocean fertilisation functions by adding nutrients such as iron or phosphorus to stimulate photosynthesis by causing phytoplankton blooms. On the other hand, OAE increases the concentration of alkaline or basic ions in the surface seawater, resulting in a series of chemical reactions that dissolve CO2 within the water into bicarbonate. Then, to keep replenishing dissolved CO2 ions in the water, additional atmospheric CO2 would hypothetically be absorbed when the air comes into contact with the ocean surface. However, by attempting to alter the ocean’s current nutrient cycle, mCDR can lead to toxic algal blooms, ocean acidification, deoxygenation, and nutrient loss, resulting in overall environmental harm.
Although mCDR comes with the risk of altering natural marine ecosystems, experiments are currently being carried out by the US’s National Oceanic and Atmospheric Administration (NOAA) to determine if and how mCDR practices could be carried out with as little damage as possible to marine organisms. However, if speculative technologies like OAE and ocean fertilisation are pushed forward by governments before considering the risks, or before such methods are perfected to avoid inextricably altering the planet’s oceans, atmosphere, and land, geoengineering could cause more harm than good. On the other hand, if governments and scientific organisations wait too long to implement CDR technologies by assessing their safety and effectiveness, it could also be too late to prevent damage from climate change without cutting emissions.
Solar radiation modification (SRM) aims to lower global temperatures by reflecting sunlight into space. One method involves injecting sulphur dioxide particles into the stratosphere to mimic natural cooling effects observed after volcanic eruptions. The other main form of SRM, marine cloud brightening, functions by spraying sea salt aerosols into the clouds to stimulate cooling.
Just as CDR has its dangers, SRM risks major changes in weather and precipitation, with predicted increases of acid rain, and could even cause ozone depletion, given that sulphur particles cause reactions that break down ozone molecules. In addition, if SRM were to be stopped after achieving lower temperatures, a rapid warming of the atmosphere would occur. Although the UK is against deploying SRM practices for now, other countries, including China, have begun to explore SRM as a solution to global warming.
The fundamental danger of geoengineering lies in treating the Earth’s geological systems like a laboratory for testing.
The fundamental danger of geoengineering lies in treating the Earth’s geological systems like a laboratory for testing. As illustrated in the proposed SRM and CDR plans—some of which are already being tested in smaller locations—geoengineering holds the potential to alter the planet’s natural systems without assuredly removing CO2 from the atmosphere.
Furthermore, according to the UN Human Rights Council’s Advisory Committee, a mass deployment of geoengineering systems may disproportionately affect historically marginalised communities such as Indigenous peoples and rural groups. With both the US and UK working to create and execute CDR programs, this technology may not be in place yet, but even the possibility is indicative of a future that neither fully resolves the harms of climate change nor protects those most vulnerable to it.
Geoengineering focuses on removing CO2 on a larger scale than previously unsuccessful carbon offset plans under the 1997 Kyoto Protocol: only 7% of global companies are actually reaching the minimum offset requirements to reach net zero carbon emissions in 2025. But the general failure of governments and large companies to reduce greenhouse gas emissions reveals a deeper, structural avoidance of climate impact. Rather than hitting the root of the problem, the continuing high number of daily emissions, governments are using the promise of geoengineering programs as a solution for offsetting emissions before these technologies are fully in place.
For instance, the UK government’s statement on geoengineering by using GGR technologies is as follows: ‘Our independent advisors, the Committee on Climate Change (CCC), have made it clear that GGRs will be essential to realising this target, to offset remaining emissions in the sectors where it is most difficult to cut them.’ Instead of creating more legislature on reducing emissions by limiting their production from the start, the focus has shifted to creating technologies that may or may not absorb enough CO2.
Instead of creating more legislature on reducing emissions by limiting their production from the start, the focus has shifted to creating technologies that may or may not absorb enough CO2.
The promotion of geoengineering by governments instead becomes a way to propose a high-tech fantasy where global emissions can simply be removed later down the line. As we move into the latter half of this decade, geoengineering proposals, experiments, and practices are undoubtedly happening, but the problems these technologies will create may outweigh their fantastical benefits. While science is a crucial tool in discovering new technologies, we must be careful about how these tools are used and continue to fight for environmental policies which reduce greenhouse gas emissions.
Some ideas expressed in this article are opinion, and may not represent the opinion of The Oxford Scientist as a whole.
Edited by Sebastian Evans, Leah Belson, Eleanor Hamilton Clark, and Sophie Lyne.
