Last updated: 11 Dec 2023

Addressing climate change is a daunting and urgent task for humanity. While drastically reducing greenhouse gas emissions to mitigate climate change is the cornerstone of the solution, scientists have acknowledged that complementary measures will be needed, due to the unavoidable residual emissions. This has brought increased attention to climate-altering technologies and measures (CATM), also known as geoengineering, which could remove residual emissions or counteract the disruptions and heating they cause. How these instruments will be governed at the global level is an important question in climate governance.

Definition and Rationale of CATM

Climate-altering technologies and measures (CATM) – also sometimes referred to as climate or geo-engineering – refer to a broad set of methods and technologies that aim to deliberately alter the climate system in order to alleviate the impacts of climate change (IPCC, 2014). These methods can be classified into two groups. Carbon Dioxide Removal (CDR) focuses on absorbing carbon from the atmosphere and increasing carbon sinks at a scale sufficiently large to alter the climate. Solar Radiation Management (SRM) aims at limiting the amount of absorbed solar energy in the climate system, for example by increasing the reflectivity of the earth’s surface or injecting aerosols into the stratosphere.

Although mitigation strategies are the heart of global action to tackle climate change, scientists and policymakers acknowledge that even drastic emission reductions over the next years will not be sufficient to keep temperature rise under desired levels. No pathway envisioned by the IPCC could limit global warming under 1.5°C without the use of CDR (IPCC, 2018). Similarly, it is highly unlikely that mitigation efforts alone with be sufficient to stay under the 2°C target set by the Paris Agreement (Edmonds et al., 2013).

This section provides resources to understand the nature and relevance of CATM in the fight against climate change.

The Science behind CATM

In the Fifth Assessment Report (AR5) published in 2014, the IPCC produced several new scenarios which included CDR measures. In the Special Report on Global Warming of 1.5°C Report, scenarios achieving the 1.5°C target include the removal of in the order of 100 to 1,000 billion tonnes of CO2 from the atmosphere in the next 80 years. In both reports, these measures are presented as important to achieving ambitious climate mitigation. Yet, it is underlined that they do not present an alternative to immediate action to reduce greenhouse emissions. Furthermore, there are currently no CDR techniques ready to be deployed at the scale necessary to significantly contribute to meeting the Paris Agreement goals.

SRM is not included in any of the IPCC scenarios, but discussions on its uncertainties, side effects, risks, governance, and ethical implications have been seen in both the AR5 and the 1.5°C Report. However, UNEP’s independent expert review on SRM research and deployment (One Atmosphere: UNEP, 2023) has highlighted new risks caused by SRM deployment at scale, including damages to the ozone layer and increase or redistribution of climate change impacts on society and ecosystems.

The section provides resources on the state of science on CATM.

International Governance of CATM

As CATMs are being developed and tested, there is a growing need for global frameworks to address the issue as the impacts will transcend borders. At the 2017 UN Climate Change Conference (COP23), experts expressed the need to discuss the governance of CATM, especially in relation to stratospheric aerosol injection (SAI), due to the great uncertainties and potential side effects of these measures (UN News, 2017).

Given the numerous unknowns, risks and gaps in research, some have identified a strong need to establish an international scientific review process to identify scenarios, consequences, uncertainties and knowledge gaps (UNEP, 2023). Such research requires an equitable, transparent, diverse and inclusive discussion of the underpinning science, impacts, risks, uncertainties and governance, should they be deployed.

Immediate and meaningful steps may need to be taken to lay a foundation for a decision process regarding the research, policy, regulation, and possible use of CATM. This section outlines current discussions on governance issues among international actors in Geneva and beyond.

Perspectives on Solar Radiation Modification

An event that had taken place ahead of the sixth session of the UN Environment Assembly (UNEA-6) — the world’s highest decision-making body on the environment, taking place from 26 February to 1 March 2023 — aimed to take stock of recent publications referring to SRM. These include the UNEP Independent Expert Review on solar radiation modification research and deployment, the report of the Human Rights Council Advisory Committee on the impact of new technologies for climate protection on the enjoyment of human rights (A/HRC/54/47), the UN Convention on Biological Diversity on certain restrictions on solar insolation activities that may affect biodiversity (CBD/DEC/X/33/8w), and mentions of SRM in reports of the Intergovernmental Panel on Climate Change.

The event, Perspectives on Solar Radiation Modification Governance, organized by Switzerland within the framework of the Geneva Environment Network, brought together stakeholders from different fields to provide their perspectives on solar radiation modification governance. A draft resolution on solar radiation modification was submitted by Guinea, Monaco, Senegal and Switzerland for UNEA-6.

CATM at UNFCCC and the Paris Agreement

The United Nations Framework Convention on Climate Change (UNFCCC) is the main global forum aimed at addressing climate change. The agreements under the UNFCCC could significantly shape the governance of CATM. The 1997 Kyoto Protocol alluded to CDR, as it stated that Parties should promote research, development and increased use of carbon dioxide sequestration technologies (Art. 2.1.a.iv).

The Paris Agreement, adopted by the Parties in 2015, has spurred further interest in CATM in climate policy discussions, although these measures are not explicitly mentioned in the agreement. The ambitious target of limiting global warming under 2°C – which is unlikely to be achieved without substantial implementation of CDR measures –  and the mention of greenhouse gas removal as a potential mean to achieve this target have contributed the growing interest for CATM. There have been to date no discussions of SRM under the UNFCCC.

Parties aim to reach global peaking of greenhouse gas emissions as soon as possible, recognizing that peaking will take longer for developing country Parties, and to undertake rapid reductions thereafter in accordance with best available science, so as to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century, on the basis of equity, and in the context of sustainable development and efforts to eradicate poverty.

Paris Agreement | 2015 | Article 4.1

This section provides additional resources on discussions of CATM under the UNFCCC.

CATM and Biodiversity

Some Nature-Based Solutions (NBS) seek to exploit natural systems capacities to absorb and store carbon through actions such as planting trees and improving soils. The 2019 IPBES Report underscores that nature-based solutions will be ‘indispensable’ to achieving climate targets. It concludes that these may ‘provide 37 per cent of climate change mitigation until 2030 needed to meet the goal of keeping climate warming below 2°C, with likely co-benefits for biodiversity’. It further notes that ‘more transdisciplinary research and sharing of knowledge among appropriate institutions are needed in order to better understand the impacts of climate-related climate engineering on biodiversity and ecosystem functions and services, socio-economic, cultural and ethical issues and regulatory options’. (IRGC/EPFL, 2020)

By significantly altering the earth’s climate, the implementation of CATM would have tremendous impacts on ecosystems and biodiversity. In 2010, the contracting Parties to the Convention on Biological Diversity (CBD) agreed on a temporary moratorium stating that “no climate-related geo-engineering activities that may affect biodiversity take place, until there is an adequate scientific basis on which to justify such activities” (CBD, 2010). While this position was reaffirmed in 2016, it does not cover all forms of carbon storage or small-scale experiments, is not binding, and country participation in the CBD is not universal (e.g. it is not ratified by the United States).

CATM and the Oceans

Marine CATM refers to all activities that intend to manipulate the marine environment, for the purposes of combatting the effects of climate change. One of the most common discussed method is ocean fertilization, the practice of introducing considerable quantities of iron compounds into the ocean to trigger algal bloom across large areas. Debates remain about the potential of such methods to effectively store CO2 and the associated risks.

Since 1999, contracting Parties to the London Convention and London Protocol have taken steps to address ocean fertilization. In April 2013, a proposal to amend the London Protocol to regulate the placement of matter for ocean fertilization and other marine geoengineering activities was accepted. This section offers resources on the various governance mechanisms and discussions around marine climate engineering.

CATM at the UN Environment Assembly

The United Nations Environment Assembly (UNEA) is the world’s highest-level decision-making body on the environment. At the fourth annual meeting of UNEA in March 2019, a resolution on ‘Geoengineering and its Governance’, put forward by Switzerland with the support of several other member States, was discussed. The resolution requested that the Executive Director of the UN Environment Programme prepare an assessment of CATM, in particular CDR and SMR. Although the revised resolution was ultimately withdrawn for lack of agreement, further discussions on the topics can be expected in further UNEA processes. This section provides resources on the negotiations on CATM at UNEA.

CATM and Human Rights

While there is no doubt that climate change itself threatens the effective enjoyment of various human rights, it is equally important to consider the human rights implications of the measures that are to be implemented to address climate change. At its 48th session in October 2021, the Human Rights Council adopted a mandate for a Special Rapporteur on climate change. The resolution also requests the Advisory Committee to conduct a study on the impact of new technologies for climate protection on the enjoyment of human rights and submit a report to HRC54 in September 2023.

In April 2022, the Advisory Committee issued a call for inputs on the matter. At the 28th Session of the committee in August 2022, experts discussed the preliminary outline for the study. NGOs have raised concerns about the terminology used in the report, emphasizing the importance of differentiating CATM from other proven technologies, like renewable energy, and of critically assessing the impacts of CATM on human rights.

Other Resources

  • Solar Geoengineering Non-Use Agreement
    An initiative calls for an International Non-Use Agreement on Solar Geoengineering, highlighting how solar geoengineering deployment at planetary scale cannot be fairly and effectively governed in the current system of international institutions, as it also poses unacceptable risk if ever implemented as part of future climate policy. The Non-Use Agreement now has endorsements by various organizations across the world.
  • Refroidir le climat, une idée qui se réchauffe | Denis Delbecq | Le Temps | 2 March 2023
    Après que des expériences d’injection de soufre dans la stratosphère ont été réalisées en catimini, des voix de plus en plus nombreuses s’élèvent pour défendre – ou contester – les recherches sur le refroidissement du climat