AER

The Annual Efficiency Ratio is the default attained CII metric, expressed as grams of CO2 per deadweight-tonne-nautical-mile. It divides total annual CO2 (fuel mass times the fuel carbon factor Cf) by the product of deadweight and distance sailed, capacity-based rather than cargo-based so it does not require cargo tonnage data. The AER feeds the A-to-E rating under MEPC.336(76) and is the carbon-intensity metric the Poseidon Principles and Sea Cargo Charter use to score portfolios against decarbonization trajectories.