Excessive state reliance on carbon dioxide removal is ‘likely inconsistent with international law,’ says Oxford research

22 November 2023

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In the run-up to COP28, new research from a team at the University of Oxford and Imperial College London warns that states which over-rely on future Carbon Dioxide Removal (CDR) to meet Paris Agreement targets could fall foul of international law.

The team - which involves researchers working on various research programmes at the Oxford Martin School - is calling for faster cuts in greenhouse gas emissions to limit countries’ dependence on CDR, and warn that they will otherwise risk legal challenges.

Carbon Dioxide Removal (CDR) means capturing CO₂ from the atmosphere and storing it on land, in the ocean, in geological formations or in products. While some CDR projects have demonstrated progress, the technologies remain in their early stages. Yet the failure of many governments to cut emissions fast enough will leave them heavily reliant on CDR to meet their climate targets. The authors demonstrate how this presents a number of risks, including:

  • CDR not being deployed at expected levels in the future – a risk amplified by the lack of legally-binding commitments to scale up CDR to necessary levels
  • CO₂ removed by CDR leaking back into the atmosphere over time
  • An overreliance on CDR leading to Paris Agreement targets being temporarily overshot, exposing the world to greater climate change impacts and burdening future generations with retrieving excess emissions from the atmosphere while battling increased climate change impacts
  • Social, economic and environmental problems, including competition with agriculture for land.

These risks jeopardise the Paris Agreement target, the authors say, and are not in keeping with countries’ commitments to make ‘fair’ and ‘ambitious’ contributions to net zero ‘in line with the best available science.’ Because of this, countries that rely heavily on CDR may not be aligned with norms and principles of international law.

Lead author Rupert Stuart-Smith, Senior Research Associate at the Smith School of Enterprise and the Environment's Sustainable Law Programme as well as an Oxford Martin Fellow, explains:

‘There is no way to meet the Paris Agreement target of limiting global warming to 1.5 degrees without removing some CO2 from the atmosphere. However, there is a big difference between pathways to net zero that fail to cut emissions adequately in the near term and leave us with little choice but to retrieve vast quantities of emissions from the atmosphere in subsequent decades, and those that entail steep and immediate cuts in emissions - at least 50% this decade - and do not leave such a heavy clean-up burden for future generations. Policymakers must recognise this point, and failing to act accordingly could see climate targets challenged in the courts.’

The study gives examples of previous court cases they believe have already set a precedent for legal action, including Urgenda Foundation v State of the Netherlands, which compelled the Dutch government to reduce emissions by 25%.

Lavanya Rajamani, co-author and Professor of International Environmental Law as well as an Oxford Martin Senior Fellow, notes: ‘States that seek to avoid the hard work of near-term mitigation by relying on extensive removals in future will likely breach the norms and principles of international law. We need to see more ambitious near-term greenhouse gas emission reduction commitments from states, followed by rigorous implementation and robust accountability.’

Thom Wetzer, co-author and Associate Professor of Law and Finance and Director of the Oxford Sustainable Law Programme as well as an Oxford Martin Fellow, adds: ‘Climate policies of many countries are incompatible with the Paris Agreement unless vast quantities of CO2 are removed from the atmosphere in the future. As governments head into the COP28 climate negotiations in December, they should focus on near-term actions to reduce emissions rather than promises of future removals, or risk being challenged in court.’

The paper was published in Science.