Climate cooperation is under real strain in 2026. The US has withdrawn from the Paris Agreement and rolled back major domestic climate policies. When the US, one of the world's largest emitters, steps back from its own climate commitments, the EU and the other governments still trying to make frameworks like CORSIA work are left carrying more of the weight, and it becomes politically easier for other governments to justify withdrawing their own commitments.

Aviation shows this dynamic particularly clearly. Flights routinely cross borders, regulatory systems, airspace, fuel markets, and national interests within a single journey, making the sector unusually dependent on international cooperation.

That is why CORSIA, the Carbon Offsetting and Reduction Scheme for International Aviation and the only global framework requiring airlines to offset emissions on international routes, has become an important test case. In July 2026, the European Commission proposed extending the EU Emissions Trading System, the EU's own carbon market, which requires companies to buy allowances for the emissions they produce, to some international flights from 2029, while allowing airlines to deduct relevant CORSIA offsetting costs.

Rather than choosing between its own regional carbon market and the global framework, the Commission is trying to combine them, an attempt to strengthen a shared global mechanism rather than abandon it at exactly the moment other major players are stepping away. The detail is genuinely technical, deduction mechanisms, route thresholds, offsetting calculations, but the underlying question is not. Holding a fragile international mechanism together where possible needs patience, political discipline, and people willing to do the slow work of cooperation.

CORSIA Is Imperfect, But It Is Still the Global Framework

CORSIA is administered by the International Civil Aviation Organization (ICAO), the UN's specialised agency for international civil aviation, and requires airlines to offset emissions above an agreed baseline on covered international routes.

Environmental groups including Transport & Environment and Carbon Market Watch have criticised CORSIA because it relies on offsetting rather than forcing absolute emissions cuts, arguing this lets aviation's emissions keep growing rather than actually falling, on a baseline they say is too weak to begin with. Carbon Market Watch has gone as far as calling it a distraction.

CORSIA's defenders point to a different value. It remains the only globally harmonised market-based measure applying to CO₂ emissions from international flights, and for a sector where a single flight routinely crosses several countries' borders and regulatory systems, that matters. Without one shared framework, different jurisdictions could impose their own overlapping carbon charges on the same flights, leaving airlines paying twice for the same emissions.

The European Commission's proposal recognises both realities. The proposal would place a stronger regional carbon price on more flights without abandoning CORSIA entirely. It has not satisfied everyone. Transport & Environment and Carbon Market Watch argue the compromise still doesn't go far enough, and that the EU should extend its own carbon market to all departing flights rather than continuing to lean on a scheme they consider fundamentally flawed.

On the other hand, defenders of this approach would argue that serious climate leadership is not always about announcing the toughest possible rule and pursuing it alone. A maximalist rule that collapses cooperation entirely can end up achieving less in practice than a workable one that holds together and can be strengthened over time. Whether that trade-off is worth making, or whether it simply lets weaker action pass as pragmatism, is a genuinely open question.

The Hard Choice Is Between Strength and International Climate Participation

The EU has tried going it alone before. In 2012, it attempted to apply its ETS to all international flights and faced such fierce opposition, from more than 20 countries including the US, China, and Russia, that it was forced to retreat within the year, confining the scheme to flights within Europe. It extended that retreat repeatedly over the following decade, and once CORSIA was created in 2016, continued deferring to it for flights beyond Europe.

In the years since, the debate has often been framed as a choice between two extremes: keep deferring to CORSIA entirely, or expand the EU's own system to every departing flight and risk a repeat of 2012.

Instead, the European Commission has proposed a limited expansion of the EU ETS, covering departing flights to destinations within 5,000 kilometres of the EU's geographical centre. If adopted, it would place a stronger carbon price on more flights without going as far as the approach that failed in 2012.

Setting a climate target is the easy part. It becomes far harder once it has to survive contact with diplomacy, markets, national interests, and the people expected to actually make it work.

The US Pullback Makes Multilateral Climate Cooperation Harder

The US pullback from climate cooperation makes this balancing act more difficult. The European Commission is not abandoning the multilateral route, but it no longer considers CORSIA sufficient on its own.

The more the US rolls back its own climate policy, the higher the cost of cooperation becomes for everyone still trying to make shared mechanisms work. The EU, ICAO, and airlines all have to work harder to keep those mechanisms alive as the US steps back.

The dynamic will be familiar to companies dealing with competitors who haven't made the same environmental commitments and can therefore undercut them on cost, or to professionals working with a colleague or department pulling in the opposite direction. When others stop pulling their weight, it becomes tempting to stop trying too. Holding the line anyway, continuing to invest in cooperation precisely when it has become harder and more expensive to do so, is what leadership actually looks like in that moment.

Multilateralism can look soft from the outside, closer to diplomacy than delivery. Those still doing the slow work of keeping shared systems alive would argue it is the opposite: the least visible, hardest-won part of making any of this function at all.

Climate Leadership Means Holding the System Together

Working to manage the effects of climate change can mean many things, from writing policy documents to developing new technology. Even within policy itself, setting a target is one part of the work. Keeping that target alive once other countries start pushing back, negotiating the detail, adjusting it, holding it together over years, is another.

The valuable skill is keeping progress moving when the incentives are messy. As climate politics fragments, the people who can hold rules, markets, and organisations together will become much harder to replace.