Published March 5, 2025

By Mary Church, Geoengineering Campaign Manager at the Center for International Environmental Law

This is the second analysis in a multipart series exposing the threats and risks connected to geoengineering and why these technologies must not be considered effective climate action.

Geoengineering — the large-scale manipulation of Earth’s climate — is often framed as an unregulated new frontier, where a lack of rules leaves the door open to dangerous experimentation. But this is simply not true. Across international law, human rights frameworks, and United Nations environmental agreements, a strong foundation for geoengineering governance already exists — and it is highly restrictive.

The real issue is not the absence of governance but the growing disregard for the restrictive framework that already exists. In recent years, geoengineering proponents have attempted to push forward research and field experiments despite clear international decisions that prohibit or severely limit its development. Even worse, the voluntary carbon markets and decisions at the 2024 UN Climate Conference (COP29) risk creating a backdoor for geoengineering commercialization, undermining climate action while benefiting polluters.

Existing restrictive governance that prevents geoengineering development and deployment must be upheld and enforced in the immediate term. Looking forward, this precautionary framework must be the basis for developing any additional agreements and rules and ultimately build up to a global ban or nonuse agreement. 

Existing International Agreements Already Restrict Geoengineering

‘The CBD reaffirmed its longstanding moratorium in 2024

One of the most robust restrictions on geoengineering comes from the United Nations Convention on Biological Diversity (CBD). Recognizing the grave and potentially irreversible harm geoengineering could cause to biodiversity, the CBD had the foresight to address geoengineering as early as 2008 with a decision that put in place an effective moratorium on ocean fertilization and was quickly followed by a wider decision for a de facto moratorium on all geoengineering in 2010. 

The decision is clear: no geoengineering activities should be allowed unless there is robust scientific justification and appropriate consideration of the environmental risks and broader social impacts. Countries have repeatedly reaffirmed the moratorium. In 2016, the CBD first reaffirmed its longstanding moratorium and again in 2024 at the 16th Conference of the Parties (COP16) to the CBD due to concerns over the proliferation of outdoor experiments — particularly in the marine environment. Furthermore, over 100 organizations supported a statement calling on States to prevent such geoengineering experiments. 

The only exception under the CBD moratorium is for small-scale scientific research studies conducted in a controlled setting, but even this is heavily caveated and requires that research be: 

• Fully justified by the need to gather specific scientific data 
• Subject to environmental impact assessment
• Not cause transboundary harm

Furthermore, the decision imposing the moratorium stresses that it is “in line and consistent with” the earlier decision on ocean fertilization, which explicitly rules out any commercial purpose, such as carbon offsetting in such research studies.

It is doubtful that any of the outdoor field experiments proposed or executed in recent years meet the required threshold. At COP16, countries explicitly cited concern at the increase in outdoor field experiments in negotiations. 

The London Convention/London Protocol Also Restricts Marine Geoengineering

Emerging in parallel to the CBD moratorium is a restrictive regime for marine geoengineering at the London Convention/London Protocol (LC/LP), which regulates pollution and dumping at sea. In 2008, the LC/PC effectively prohibited the deployment of ocean fertilization, and in 2013, it amended the Protocol to allow for the regulation of marine geoengineering. 

Countries under the LC/PC have further indicated their intention to include four additional categories of marine geoengineering that should be restricted due to their potential for widespread harm: 

• Biomass cultivation and dumping
• Ocean alkalinity enhancement 
• Marine cloud brightening
• Microbubbles

In 2023, governments stated that activities “other than legitimate scientific research should be deferred,” as these techniques had “the potential for deleterious effects that are widespread, long-lasting or severe” and “there is considerable uncertainty regarding their effects on the marine environment, human health, and on other uses of the ocean.”

While the Protocol and its amendment have yet to enter into force, decisions of the LC/LP have been approved by resolution and clearly ought to be implemented by countries. Like the CBD, the LC/LP also has an exemption for what it refers to as “legitimate scientific research” and has adopted pre-screening criteria for experiments. Importantly, this exception excludes any projects with a commercial aspect — a critical safeguard that should prevent marine geoengineering from being used for carbon credit schemes. 

Geoengineering Contravenes Wider International Law and Human Rights Obligations 

The Precautionary Principle and the Obligation to Prevent Harm

Both the CBD and the LC/LP decisions are based on the precautionary principle enshrined in the UN Rio Declaration. The precautionary principle states that where there is scientific uncertainty, actions that could cause severe or irreversible harm should not be taken. This approach is highly applicable in the context of geoengineering technologies because they are unprecedented.,  These technologies can never be fully tested other than via large-scale deployment — with the many novel risks this would generate. 

The obligation not to cause transboundary harm is highly relevant in relation to geoengineering and, again, is referenced in related decisions of the CBD. This is particularly true in relation to solar and marine approaches — since the oceans and atmosphere know no political borders — and because of the scale at which these technologies would have to be implemented to achieve their intended impact on the climate. For example, around 10 percent of the ocean’s surface would be required for various marine geoengineering interventions to theoretically have any meaningful climate impact, while stratospheric aerosol injection proposes massive-scale pollution of the atmosphere over hundreds of years. Furthermore, modeling shows that techniques such as marine cloud brightening and stratospheric aerosol injection would cause harmful impacts that far surpass mere intervention, for example, interfering with monsoons. Moreover, such technologies raise concerns about the challenges of determining attribution.  This is particularly relevant in the context of loss and damage: how do we determine the contribution of climate change as opposed to any potential future deployment of solar geoengineering to a specific extreme weather event?

UNCLOS and ITLOS Advisory Opinion

Under the UN Convention on the Law of the Sea (UNCLOS), governments have an obligation not to pollute the marine environment. In 2024, the International Tribunal for the Law of the Sea (ITLOS) issued an Advisory Opinion emphasizing that marine geoengineering could violate UNCLOS if it introduces pollutants to the marine environment, as well as if it has the effect of converting one form of pollution into another. Indeed, proposals to dump biomass, minerals, and chemicals into the oceans and sequester or store carbon dioxide in the marine environment clearly have the potential to do precisely that.

Human Rights Law Exposes Geoengineering’s Global Risks

In highlighting “the urgency to implement actions aligned with the best available science, respecting the human right to a healthy environment and other human rights,” last year, the UN Special Rapporteur on the human right to a clean, healthy and sustainable environment identified geoengineering as “worsening the situation, threatening climate safety and thus a healthy environment.”

Geoengineering runs counter to a wide range of human rights obligations, including:

• The right to a clean, healthy, and sustainable environment
• The right to life, food, water, and health
• Indigenous Peoples’ right to Free Prior and Informed Consent (FPIC)
• The rights of future generations

A 2023 Human Rights Council Advisory Committee report warned that “because [geoengineering approaches] are meant to be applied on a global scale, they have the potential to affect everyone indiscriminately,” which could adversely impact the human rights of “millions or perhaps billions of people.” 

The report also highlighted that Indigenous Peoples, peasants, rural communities, and people on the front lines of the climate crisis were most at risk and that “potential deployment … would have a massive and disproportionate impact on Indigenous Peoples whose traditional lands and territories are particularly exposed and at risk of experimental uses.”

This points to the importance of upholding the principle of Free, Prior, and Informed Consent of Indigenous Peoples, while broader rights of access to information and participation in decision-making are also worth noting, as is the implausibility of ever fully implementing these in relation to geoengineering given its nature and scale.

Meanwhile, the Maastricht Principles on the Rights of Future Generations, a comprehensive framework for understanding how international law applies to the human rights of future generations, highlights geoengineering as one of a number of areas that “pose[s] a reasonably foreseeable and substantial risk to the human rights of future generations.”

The Dangerous Proliferation of Geoengineering Experiments

Taken together, international agreements, international customary law, and human rights law create a broad range of principles, norms, and obligations squarely applicable to geoengineering, all of which are restrictive and precautionary.

However, in practice, what we are seeing is a proliferation of outdoor experiments — open-air and open-water — that are planned or underway. An analysis of data aggregated by the Heinrich Böll Foundation and ETC Group and presented through the Geoengineering Monitor Map shows that: 

• At least 598 outdoor geoengineering experiment trials have been proposed since 1971.
• Over 90 percent were proposed between 2004 and 2023, and more than half were proposed between 2019 and 2023.
• Between 2019 and 2023, proposed marine carbon dioxide removal field experiments quadrupled — compared to the period from 2014 to 2018 — and solar geoengineering experiments tripled. 

A key risk of small-scale outdoor experiments is that they tend to lead to technology development and potentially a slippery slope to deployment. 

Carbon Markets an Open Door for Risky Geoengineering Technologies

This acceleration, particularly of marine carbon dioxide removal experiments, is largely driven by voluntary carbon markets and the false promise of carbon offsets, with many projects pre-selling carbon credits despite a lack of evidence that such techniques are effective in the long-term removal and storage of carbon dioxide. 

At COP29, under questionable circumstances, rules for a decade-long contested carbon market mechanism were approved that could permit the trading of greenhouse gas removals and risks further fuelling the growth of commercial geoengineering schemes. 

However, both the CBD and the LC/LP clearly rule out projects with a commercial element or those that sell carbon credits, and Member States to the UN Framework Convention on Climate Change must interpret their obligations under that regime in alignment with their obligations under other treaties, as well as the wider principles, norms, and obligations of international law. This means that credits generated through geoengineering experiments should not be allowed to be traded under the climate regime. 

What Policymakers Should Do to Stop Geoengineering 

Geoengineering can never be meaningfully tested for its intended impact on the climate other than through large-scale deployment. These highly speculative technologies do nothing to tackle the root causes of the climate crisis and, in fact, risk delaying action to cut emissions by presenting the false possibility of a quick fix. The proposition, therefore, is to turn the Earth into a laboratory, risking a range of new, unpredictable, and potentially irreversible impacts and putting essentially everyone’s fundamental human rights at risk. Existing governance is highly precautionary and restrictive, for very good reason, but it is being undermined by those pushing research and experiments. 

Momentum is growing to build on and strengthen the existing governance framework towards Non-Use. More than 500 leading academics from over 50 countries are calling for an International Non-Use Agreement on Solar Geoengineering, on the basis that such an undertaking would be impossible to ever fairly and effectively govern. A non-use agreement would reject deployment, outdoor experiments, and patenting and stop taxpayer funds from supporting the development of solar geoengineering technologies. 

Political support for Non-Use is increasing, with the African Ministerial Conference on the Environment and the European Parliament calling for a non-use mechanism, along with support in the Pacific Islands, led by Vanuatu and Fiji. Germany has also expressed its willingness for dialogue on a non-use agreement, while the EU backed the Africa Group’s position during the controversial negotiations on solar radiation management resolution at the sixth session of the United Nations Environment Assembly earlier this year. Nearly 2000 civil society organizations also endorse a non-use agreement. 

Building on this momentum, governments should:

• • Implement and enforce the CBD’s de facto moratorium on geoengineering at the national and regional levels and uphold decisions of the CBD on geoengineering in other international fora.
  • Support the development of strong precautionary regulatory controls under the LC/LP.
  • Ban all outdoor field geoengineering experiments.
  • Withhold public support — including funding — and stop granting patent rights for geoengineering technologies.
  • Work toward a solar geoengineering non-use agreement. 

Other analysis pieces in this series include:

• Why Geoengineering is a False Solution to the Climate Crisis
• The Risks of Geoengineering on Biodiversity [coming soon]