IMO Approves Mandatory Carbon Ratings for Ships

Carbon intensity regulations have gotten complicated with all the rating thresholds, compliance options, and enforcement timelines flying around. The IMO just made it real — mandatory carbon ratings starting July 2025. Ships rated D or E for three years straight face operational restrictions.

How the Rating System Works

The Carbon Intensity Indicator (CII) measures grams of CO2 emitted per cargo-carrying capacity and nautical mile traveled. Vessels receive annual ratings from A (best) to E (worst). Rating thresholds tighten each year through 2030. Thats what makes this different from previous regulations — the goalposts keep moving.

What Owners Can Do

Ship owners can improve CII scores through slow steaming, hull cleaning, propeller polishing, and route optimization. More substantial improvements require engine modifications or alternative fuel adoption.

Industry Reality

Shipping associations warn that older vessels may become economically unviable under the new regime. Some owners are already scrapping tonnage rather than investing in upgrades for ships with limited remaining lifespan.

The rules accelerate the fleet renewal cycle, benefiting newbuild orderbooks at major shipyards. Probably should have led with that — this regulation reshapes the entire secondhand market.

Captain Tom Bradley

Captain Tom Bradley

Author & Expert

Captain Tom Bradley is a USCG-licensed 100-ton Master with 30 years of experience on the water. He has sailed across the Atlantic twice, delivered yachts throughout the Caribbean, and currently operates a marine surveying business. Tom holds certifications from the American Boat and Yacht Council and writes about boat systems, maintenance, and seamanship.

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