Shipping's CO2 Fell in 2025 — But the Hard Decision Is Still Ahead

A year of verified numbers has given shipping's climate debate something it rarely has: a fact both sides can quote. Analysis of the International Maritime Organization's 2025 fuel-consumption data shows global shipping cut its carbon dioxide emissions by 1.3 percent in 2025 compared with 2024 — even though the fleet grew 2 percent in capacity and sailed 1 percent further. The figures come from the IMO's Data Collection System (DCS), analysed by Drewry, and will be reviewed at MEPC 85 in London, from 30 November to 3 December 2026. Days later, on 4 December, a resumed extraordinary session could decide the fate of the IMO Net-Zero Framework, the draft global fuel standard and emissions price. The numbers say shipping is moving. December will say whether the rules catch up.

1. What the 2025 numbers actually show

Ships reported burning around 221 million tonnes of fuel in 2025, of which alternative fuels accounted for about 18.3 million tonnes. Measured by energy, alternative fuels have risen from 5.9 percent of shipping's energy demand in 2019 to 9.5 percent in 2025: steady growth, not a breakthrough. Biofuels were the year's growth story, with consumption more than doubling to around 2.5 million tonnes, lifting their share of alternative-fuel demand from 6.2 percent in 2024 to around 12 percent. Liquefied natural gas (LNG) remains the largest alternative fuel, stable at just under 15 million tonnes. Methanol is growing but still tiny, at 0.3 percent of alternative-fuel energy. Ammonia, much discussed as a future fuel, has not yet appeared in the DCS reports at all — a useful reminder of the gap between conference panels and engine rooms.

2. Why emissions fell while shipping grew

Two drivers explain the fall: ships generally sailed more slowly, encouraged by the efficiency rules known as EEXI and CII, now in their third year, and more biofuel was burned. Emissions per vessel fell 4 percent and emissions per nautical mile fell 2.3 percent. Shipping's carbon intensity, measured by AER (annual efficiency ratio, emissions against fleet capacity), improved by a further 1.6 percent, reaching 33.1 percent below 2008 levels — within sight of the IMO's target of a 40 percent cut by 2030. Drewry's assessment is that the target looks achievable if the current rate of improvement continues. Treat that as a projection, not a promise: it assumes the pace holds. Container ships and tankers actually sped up in 2025, partly because longer Cape of Good Hope voyages kept demand high.

3. What December has to decide

The Net-Zero Framework was approved in draft form at MEPC 83 in April 2025, but formal adoption was adjourned at an extraordinary session in October 2025. MEPC 84, in April and May 2026, ended without a final agreement, and governments set two intersessional working-group meetings — in September and from 23 to 27 November — to narrow the gaps before MEPC 85. The framework, as drafted, has two pillars: a global fuel standard that tightens the allowed greenhouse-gas intensity of fuel year by year, and a pricing mechanism under which ships that miss their targets buy remedial units — $380 per tonne of CO2 equivalent for the stricter tier and $100 for the base tier in 2028–2030, with revenue going to a new IMO Net-Zero Fund. It would apply to ocean-going ships above 5,000 gross tonnage. None of this is adopted yet, and none of it is in force: approval, adoption and entry into force are three different steps, and the framework has only cleared the first.

Three questions remain open, according to the Maersk Mc-Kinney Moller Center for Zero Carbon Shipping, which followed the September talks. First, should emissions targets be fixed in advance, or linked to whether low-emission fuels are actually available and affordable at ports? Liberia proposes linking targets to commercial viability; Japan proposes fixed targets through 2035 with later targets set after reviews. Second, how should transition finance work? Some delegations question an IMO-managed fund's governance and costs, while Liberia and Panama propose voluntary support, Brazil a facility hosted by an international financial institution, and Japan a voluntary company scheme. Third, how should zero- and near-zero-emission fuels be rewarded? China proposes a multiplier falling from about 1.95 in 2029 to 1.10 in 2035. The framework also faces political headwinds: the United States president criticised it at the UN General Assembly on 22 September, calling it a “global carbon tax” and arguing it could raise shipping costs by 10 to 20 percent or more — a political argument, not a measured outcome. If the text is not ready for adoption, the decision could be deferred to MEPC 86, expected in October 2027.

4. How to read the December outcome

When the London meetings close, judge them by a short checklist. Was the framework adopted, revised, or deferred? Did the Net-Zero Fund survive, or was revenue generation replaced by voluntary contributions? Are targets fixed through the 2030s, or left to future reviews? The 1.3 percent fall is real progress, but it is incremental, driven mostly by slower steaming and biofuel blends rather than the zero-emission fuels the 2050 net-zero goal will eventually require. Efficiency buys time; it does not finish the transition. For readers in Pakistan, the stakes are structural rather than local — no verified local statistic is claimed here — but the ships that call at Karachi, the seafarers who crew them, and the fuel they burn will all be governed by whatever London decides. At AstolixGen, a small Karachi-based company, our contribution is awareness and education, not monitoring or regulation: our free learning book, Maritime Climate Awareness, explains what a changing ocean and changing shipping rules mean for seafarers and coastal families. The sea will not be protected by announcements — it will be protected by rules that survive contact with December's negotiating room.

Sources: Drewry analysis of IMO DCS 2025 data (27 October 2026); Maersk Mc-Kinney Moller Center for Zero Carbon Shipping assessment of ISWG-GHG 22 (September 2026); Ship & Bunker report on MEPC 84 (May 2026). Figures are as reported by those sources from IMO DCS data; Drewry's 2030 assessment is its projection.