Answer
The Ship Energy Efficiency Management Plan (SEEMP) and the Carbon Intensity Indicator (CII) are two regulatory pillars established under MARPOL Annex VI (Regulations 26, 27, and 28) designed to systematically reduce greenhouse gas (GHG) emissions from international shipping.
The Structural Link: Tool vs. Outcome
The fundamental relationship can be summarized as: SEEMP is the management tool, while CII is the operational outcome metric.
SEEMP Part III (The Plan): Mandated for all ships of 5,000 GT and above engaged in international voyages). It requires a vessel-specific, 3-year rolling implementation plan that details how the ship will achieve its required carbon reduction. This includes technical actions like hull coatings, waste heat recovery, or operational modifications like speed optimization and weather routing
CII (The Metric): Measures how efficiently a ship transports goods or passengers in terms of grams of CO2 emitted per cargo-carrying capacity (DWT or GT) per nautical mile. The actual attained annual operational CII is calculated based on data submitted via the IMO Data Collection System.
The Compliance Feedback Loop: The ship is assigned an annual performance rating from A (Superior) to E (Inferior). If a vessel receives a D rating for 3 consecutive years or an E rating for a single year, the SEEMP Part III must be immediately revised . The revised SEEMP must include a detailed Corrective Action Plan showing exactly how the operational practices will be adjusted to raise the performance back to a compliant 'C' rating or higher.