ON APRIL 13th, delegates of the International Maritime Organisation, the UN agency responsible for shipping safety and pollution, announced that 170 of its members had agreed to reduce carbon emissions from shipping to no more than half of 2008 levels by 2050. Shipping in Changing Climates, a research consortium, called the deal “major progress” towards bringing shipping in line with the goals of the 2015 Paris climate agreement. But why has it taken two years after Paris to reach such a deal ?

Shipping and airlines were the only greenhouse-gas-emitting industries not mentioned in the Paris agreement. This was, in part, because assigning emissions is hard. To whom should you designate emissions for shipping Chinese goods, made with South Korean components, across the Pacific to American consumers? But similar problems did not stop airlines agreeing on an industry-wide limit within a year. Diplomats argue the slow progress is because any caps would affect exporters, too. If regulators move too aggressively they may reduce the competitiveness of seaborne trade. For instance, Brazil, a big exporter of iron ore to China, fears overzealous caps will drive shipping costs higher, helping its competitor, Australia, whose ores travel a quarter as far as Brazil’s. The idea of slowing vessels down draws ire from countries that export perishable goods, like cherries and grapes, as Chile does.

Others fear that powerful lobbyists have hijacked the process. Transparency International, an NGO, has raised “serious concerns” about the IMO being unusually influenced, for a UN body, by corporate interests. A report by InfluenceMap, a research firm, found that at a recent meeting of the agency 31% of nations were represented, in part, by direct business interests. The way the IMO is structured exacerbates these problems. The IMO is funded proportionately according to the tonnage shipped under a nation’s flag, so countries running “open registries”, which allow any shipowners to register under their flag (sometimes known as “flags of convenience”), have disproportionate influence. Sometimes this helps those keen to limit emissions, such as the Marshall Islands, a low-lying Pacific nation, where 11% of all ships are registered and which is vociferous in its support of emissions cuts. But for the most part it works against them. Countries are beholden to ship owners, so those nations that are not about to disappear under the water themselves are often averse to any emissions cuts. Panama, where 18% of global ships are registered, supported a much less ambitious deal.

The IMO announcement also faced opposition from countries such as Saudi Arabia and America, who consistently oppose efforts to combat climate change (both refused to sign up to this deal). Even including the agreed cuts, shipping, which currently accounts for almost 3% of total global carbon emissions, will probably see its share of emissions rise in coming years. Technology could help. New design standards are already lowering harmful emissions. Zero-carbon fuels are becoming available. Reducing the speed at which ships travel by 10% could reduce fuel usage by almost a third. Last week’s agreement was a good start to encourage adoption of such changes. As with many such agreements, the implementation is all.