The principle of multilateralism – the bedrock of international climate diplomacy – is facing its most severe test in decades. Amid a rising tide of populism and geopolitical conflict, the collaborative spirit essential for tackling the planetary crisis is under unprecedented strain. The recent Cop30 summit in Belém, Brazil, laid bare these tensions, offering a fragile compromise that satisfied no one but narrowly averted total collapse.
A Fragile Deal in Belém
The negotiations at the Cop30 UN climate summit last November were a stark demonstration of the challenges facing global cooperation. The resulting Belém deal was, at best, a weak agreement. It failed to mandate the deep cuts in greenhouse gas emissions scientists say are necessary and relegated the critical discussion on phasing out fossil fuels to a voluntary side agreement. Yet, in a world of dire geopolitics, the fact that a deal was reached at all was seen by some as a minor victory for multilateralism, proving nations could still find slivers of common ground.
However, a significant and ominous silence hung over the talks: the absence of the United States. Donald Trump, having begun the process of withdrawing from the Paris Agreement in January at the start of his second term, sent no official delegation. While figures like California Governor Gavin Newsom attended independently, the shadow of US disengagement was long. Delegates were acutely aware that American influence could still be felt, and for good reason.
The Shadow of "Thuggery" and Unilateral Pressure
Weeks before Cop30, at a crucial International Maritime Organisation (IMO) meeting in October, the US state department unveiled aggressive tactics that shocked delegates from poorer nations. Officials reported receiving threatening phone calls and emails from US representatives, which included threats of visa revocations, trade sanctions, and personal retaliation. Australian billionaire and clean shipping campaigner Andrew Forrest condemned the behaviour as "thuggery." The IMO talks, intended to finalise a new carbon levy on shipping, nearly collapsed, and the levy was delayed for a year.
This aggressive unilateralism did not directly surface at Cop30, but the threat it represents to future cooperation remains potent. As talks resume at the IMO and look ahead to Cop31 in Turkey in 2026, nations are braced for further pressure. The 2026 summit carries immense weight, as governments must confront the stark reality that their current national emissions plans are woefully inadequate and would lead to a catastrophic 2.5C of global heating.
New Tools and New Tensions: The EU's Green Tariff
Further testing the limits of multilateralism is the European Union's pioneering Carbon Border Adjustment Mechanism (CBAM), which comes into force this month. This "green tariff" will penalise high-carbon imports like steel from countries with lax emissions controls. The EU insists the tool is meant to encourage global cooperation, with Climate Chief Wopke Hoekstra stating, "The best CBAM is one you don't have to use."
Yet many developing countries, led by China, view it as a unilateral and unfair trade barrier. They attempted, largely unsuccessfully, to have it formally censured during the Cop30 negotiations. This clash highlights the delicate balance between incentivising climate action and provoking protectionist disputes that could fracture the cooperative framework further.
Despite the setbacks, alternative pathways for action are emerging. Over 80 countries at Cop30 pushed for a binding resolution on fossil fuel phase-out roadmaps. While they failed, a "coalition of the willing" is moving forward with a Plan B. Colombia will host a pivotal conference on the fossil fuel phase-out this April, creating a parallel forum for ambitious nations. Such coalitions may lack the universality of the UN process, but they represent a pragmatic form of multilateralism in action, increasing pressure on laggard states to justify their inaction.
With 2026 poised to be another record-breaking hot year, reliance on the slender reed of multilateralism may seem a frail hope. Yet the alternative – abandoning the field to the vagaries of individual governments, opaque autocracies, and unfettered capital markets – offers no viable path to averting climate breakdown. A decade on from the Paris Agreement, the need for common solutions to our common problem has never been more urgent, nor more under threat.
