Governments are under growing pressure to tackle the huge climate impact of the shipping industry, before a key International Maritime Organization (IMO) meeting in the summer. With talks about regulating the sector’s greenhouse gas emissions coming up, the world maritime court has been told that states are legally responsible for tackling the climate impact of shipping. The shipping industry is well behind others when it comes to addressing its climate impact, having failed to cap greenhouse gas emissions more than six years ago. It contributes about 3% of global emissions but this could rise significantly if no action is taken. The international tribunal for the law of the sea has been asked by a group of island nations to give its opinion on the climate crisis and marine responsibilities. Like the international court of justice, which was tasked with giving its view on states’ legal duties on the climate emergency earlier this year, the tribunal’s opinion will not be legally binding, but it will be highly influential. In its submission to the tribunal, seen by the Guardian, the NGO Opportunity Green argues that the law of the sea already obliges all countries to combat vessel pollution and therefore hold the shipping industry accountable for its greenhouse gas emissions. Carly Hicks, the legal director of Opportunity Green, said states had largely delegated their environmental responsibilities over shipping to the IMO. Last year, the UN body finally agreed that some form of action was needed and said that would include a market-based economic element, such as a levy, cap and trade scheme or a reward system, and a technical element, most likely a global fuel standard. There is growing support for the idea of a levy among states and the shipping industry. But IMO members still do not agree on what form it should take, or whether the money should be spent solely on decarbonising the industry or to further climate action elsewhere. The IMO will discuss a revised greenhouse strategy in July. A spokesperson, Natasha Brown, said it “certainly” expected the meeting to agree on the way forward for technical and economic measures. IMO member states are also expected to agree the first net zero target for the sector in July, probably for 2050, although clean shipping organisations are pushing for an earlier goal with additional interim action. Opportunity Green argues that if the IMO comes up with a weak idea or fails to agree one at all, countries are obliged to act on the problem unilaterally. “The IMO meetings in July this year are the final opportunity for the global shipping sector to demonstrate a meaningful commitment to playing its part in the fight against climate change at a global regulatory level,” said Hicks. “If it doesn’t, then a favourable opinion from the tribunal could become even more important as a potential lever to hold countries to account for their inaction.” The International Chamber of Shipping, which represents the industry at the IMO, maintains that a global agreement is the only realistic way to regulate shipping’s environmental impact. Its deputy secretary general, Simon Bennett, told the Guardian: “The UNFCCC [United Nations framework convention on climate change] has quite clearly given the mandate to the IMO to regulate shipping permissions – as it has with aviation – primarily because it’s very difficult to attribute the emissions from shipping to one particular country.” Pressure will continue to grow after the leaders’ summit being held in Paris this week, where heads of state are considering how a levy on shipping could raise money to supplement climate finance. With promises by wealthy governments to provide $100bn (£78bn) a year in climate finance to poorer countries still falling far short, a variety of innovative ways of raising cash are being discussed, to fund climate mitigation and adaptation and tackle the growing problem of loss and damage around the world. The French president, Emmanuel Macron, who is co-hosting the summit, is understood to support a shipping levy as the most advanced option on the table.