Geoengineering – can it combat climate change?

17 December 2021


Geoengineering – can it combat climate change?

Reported by Lizzie Knight, PhD Student at Fitzwilliam College, Cambridge

In December 2021, CSaP’s Horn Fellows gathered at Trinity Hall, Cambridge, for a series of meetings with academics and industry professionals. They discussed geoengineering, which can be described as large-scale interventions to the Earth’s climate system, designed to counteract climate change.

In order to prevent global temperatures rising more than 1.5°C above pre-industrial levels, two main goals from the COP26 summit involved securing net-zero greenhouse gas emissions by 2050 and adapting to protect our natural environments. The Horn Fellows engaged in a timely discussion on how geo-engineering can help achieve these goals and the barriers to its implementation.

The day began with a talk from Professor Sir David King, from the Centre for Climate Repair, Cambridge. Prof King explained that one step towards repairing our global climate involves repairing critical climate systems. The Centre is particularly interested in restoring the stability of major ice sheets, and one such technique being investigated is Marine Cloud Brightening. It is where seawater droplets are sprayed into the atmosphere, and the salt crystals in these droplets “brighten” clouds, encouraging snowfall over polar regions instead of rain and therefore increasing the amount of polar ice. Instead of the term “geo-engineering”, Prof King prefers to describe these technologies as “bio-mimicry”, where the system is designed to replicate natural processes. The Fellows were intrigued by the ingenuity of these technologies, though questions were raised regarding the investment and global governance necessary for such projects. As noted by both Professor King and Professor Hugh Hunt, geo-engineering schemes are not designed to be a permanent solution to climate change, but rather to “buy time” as fossil fuels are phased out.

As emphasised by several of the day’s speakers, carbon dioxide must be directly removed from the atmosphere to offset any remaining carbon emissions by 2050. Dr Amy Ruddock, from Carbon Engineering, introduced the process of Direct Air Capture (DAC), where pure CO2 is captured from the air via a series of chemical reactions, and is then sold to industry or sequestered in the ground. The company has licensed its first plant in the UK, which is expected to be operational in 2026 and aims to remove up to one megatonne of CO2 per year - the equivalent of roughly 40 million trees. Dr Ruddock explained that the main benefits of DAC include the scalability of the operation, and that it requires much less land and water than biological CO2 removal solutions such as reforestation.

Carbon Engineering has recently introduced a carbon removal service, where organisations can pay to offset their carbon emissions and work towards net zero goals. Carbon offset schemes were also the focus of a discussion led by Professor David Coomes and Professor Srinivasan Keshav, who have helped to launch the Cambridge Centre for Carbon Credits. Their goal is to create a trusted, decentralised marketplace where purchasers of carbon offset credits can be confident that they are funding verified nature-based projects. In contrast to bio-mimicry and engineering technologies, nature-based solutions such as reforestation and peatland renewal are designed to not only tackle climate change, but also the global biodiversity crisis. The Fellows were interested in how the Centre will determine the long-term permanence of nature-based solutions and how the pricing of carbon credits will be decided.

A pervasive theme throughout the day was the importance of methane. While methane concentration in the atmosphere is much lower than that of carbon dioxide, Dr Shaun Fitzgerald explained that its concentration is rising at a faster rate, which is concerning as methane has been responsible for approximately 30% of global warming to date. Methane can be removed via photocatalytic oxidation, where metal oxide catalysts help to initiate the combustion of methane into carbon dioxide and water. The Fellows were concerned at how the generation of CO2 would be received by the public, but Dr Fitzgerald noted that the CO2 produced would have much lesser effect on global warming than the methane from which it was generated.

While most of the day’s discussion focused on greenhouse gas removal and repairing the natural environment, Professor Bill Nuttall led the Fellows in a discussion on developments in nuclear power research. Nuclear power forms a key component of the UK Government’s Ten Point Plan for a Green Industrial Revolution, which will involve developing large-scale nuclear projects (e.g. Hinkley Point C in Somerset) and investing in research for small modular reactors, such as those being developed by Rolls Royce.

Public opinion of nuclear power is complex, and this point was revisited in the final roundtable discussion. Dr David Reiner explained that while the public was generally in favour of carbon capture and storage and solar power, public opinion of large-scale geo-engineering projects is much lower. It was raised that there must be greater communication between scientists, policymakers, and the public to help people understand the technologies before any geo-engineering projects can be used to help tackle climate change.