PML backs call for safeguards on emerging ocean carbon removal technologies 

The recommendations – released today [7th May 2026] – are backed by the latest science, and set out a framework for how experimental mCDR projects should be designed, funded, and regulated, amid growing interest in using the ocean to help remove carbon dioxide from the atmosphere.  

“Premature deployment of marine carbon removal risks harming ocean ecosystems, undermining public trust, and can distract from the emissions reductions that we know are essential – and which must be our first priority,” said PML’s Professor Helen Findlay, who contributed to the joint statement.

“It’s vital we have a staged and gated approach to mCDR. This type of approach allows us to make progress with responsible technology and scaling developments while minimizing unintended consequences. It allows us to feed results back into the regulatory and development process so that potential risks can be mitigated by setting appropriate limits or constraints.”   

How much CO₂ must we remove to limit global warming to 1.5C°? 

Though invisible, greenhouse gases have measurable mass – and amount to billions of tonnes in the atmosphere. 

To meet the Paris Agreement and keep global warming below 1.5°C, CO2 removal needs to happen alongside emissions reductions – scientists estimate that between 7 and 9 gigatonnes of CO₂ will need to be removed from the atmosphere every year by 2050. A gigatonne is one billion metric tonnes. 

Yet current global carbon removal capacity is only around 2 gigatonnes annually – the vast majority coming from traditional land-based approaches such as tree planting, which draw down CO₂ through photosynthesis. 

What will happen if we don’t limit warming to 1.5C°? 

Failing to limit warming to 1.5°C could have profound and irreversible consequences. Recent research involving PML’s Professor Helen Findlay highlights how exceeding this threshold would accelerate global ice loss, driving metres of sea-level rise that could be observed in our lifetime – putting coastal communities at risk worldwide. Melting ice sheets and warming oceans are also expected to disrupt major ocean currents, with far-reaching impacts on climate systems and more frequent extreme weather events.  

At the same time, increasing carbon emissions will worsen ocean acidification – which was found to have crossed its Planetary Boundary in a landmark study led by Prof Findlay last year – which threatens key marine species and entire food webs. 

These findings reinforce both the urgency of deep emissions reductions and the need to consider additional carbon removal strategies alongside them – and so marine carbon dioxide removal has gained considerable interest in recent years. 

Professor Findlay, who is a Biological Oceanographer at PML, and a leading expert in the consequences of carbon emissions – from global warming to ocean acidification – said the ocean’s role as a carbon sink is already under strain. 

“The ocean already plays a critical role in absorbing carbon from the atmosphere – around a quarter of human emissions each year. It is this natural ability to take up and store carbon, which makes the ocean an interesting option for exploring mCDR approaches. The ocean is doing its very best to help us, but this has come at a cost. The ocean is actually losing its capacity to store carbon as a result of rising temperatures, warming seas, and acidification – all driven by emissions.” 

“The ocean is a delicate and complex system. Any large-scale mCDR intervention must be backed by strong evidence of effectiveness and safety – for both marine ecosystems and the communities that depend on them.”  

The joint statement emphasises that while mCDR may eventually contribute to climate mitigation, its role remains uncertain. It warns that premature deployment could damage ecosystems, erode public trust, and distract from emissions reduction efforts.  

Key recommendations include: 

• Independent monitoring and verification  

• Open-access data for transparency and scrutiny  

• Stage-gated testing, with progression only after safety is demonstrated  

• Meaningful consultation with Indigenous Peoples, coastal communities, and fisheries  

• Strong ethical governance and alignment with international best practice  

The statement also stresses that funding for mCDR research must be additional to, not diverted from, existing climate finance. 

Professor Findlay emphasised the importance of trust and inclusion. 

“Building public trust is absolutely crucial. That means engaging communities early, ensuring local knowledge informs decisions, and making data openly available so results can be independently assessed.” 

The recommendations also caution against the early commercialisation of mCDR through carbon credit markets. Until robust scientific evidence and monitoring standards are in place, the statement advises that field trials should not generate carbon credits, warning that premature crediting could undermine confidence in future markets. 

Instead, the document argues that public and government funding should play a leading role in supporting early-stage research, helping to ensure independence and credibility. 

The guidance has been developed collaboratively by ocean, climate and policy experts across multiple organisations and is intended to inform and support regulators, funders, and companies as interest in mCDR continues to grow. 

Access the full statement, ‘Recommendations for Responsible Assessment of Engineered Marine Carbon Dioxide Removal Approaches’ here >> 

While the authors acknowledge that mCDR could eventually form part of a broader climate solution, they stress that its role remains uncertain. 

“We cannot assume these technologies will deliver the outcomes we need. Careful, transparent research is essential to determine whether they can contribute meaningfully to climate mitigation without causing unintended harm.” 

Just last year, Prof Findlay co-authored the first comprehensive study investigating the impacts of Direct Ocean Carbon Capture and Storage (DOCCS) discharge on marine ecosystems – which found that the release of treated, high pH seawater could place stress on certain marine organisms, especially those near to the discharge site. 

Marine carbon removal approaches like these work by electrochemically removing dissolved inorganic carbon from seawater, which can then be stored. The treated, low-carbon, high pH seawater is released back into the ocean, where it naturally draws down more atmospheric CO₂, gradually returning to normal pH and carbon levels. 

This type of mCDR research has further been trialed by Plymouth Marine Laboratory through the SeaCURE project – the UK’s first mCDR pilot facility of its kind – to test the effectiveness of this mCDR approach in real world conditions, but at a small scale, and following the principles outlined in the statement. 

The statement concludes that with strong governance, ethical oversight, and sustained investment in evidence-building, the field of mCDR can advance responsibly – ensuring that any future decisions are grounded in science and in the public interest. 

Access the full statement, ‘Recommendations for Responsible Assessment of Engineered Marine Carbon Dioxide Removal Approaches’ here >>