After D-for-three-years or a single E rating, owners submit a SEEMP Part III plan projecting how to return to at least C.
Formula
$$ r_\text{annual} = 1 - \left(\frac{d_3 \cdot I_\text{required}^\text{end}}{I_\text{attained}^\text{now}}\right)^{1/N} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $r_\text{annual}$ | Required annual CII reduction | fraction | result |
| $d_3$ | C-band upper boundary (type-specific) | - | MEPC.339(76) |
| $I_\text{required}^\text{end}$ | Projected Required CII at plan end (Z-tightened) | g CO₂ / (dwt·nm) | MEPC.338 |
| $I_\text{attained}^\text{now}$ | Current Attained CII | g CO₂ / (dwt·nm) | DCS |
| $N$ | Plan horizon (years) | - | typically 3 |
Sources
- IMO MEPC.339(76) - rating boundaries + triggers.
- IMO MEPC.347(78) / MEPC.376(80) - SEEMP Part III.