GFI reduction trajectory 2027-2050

Background: from 2008 baseline to MEPC 83 trajectory

The construction of a binding multi-decade decarbonisation trajectory for international shipping has been the central policy task of the IMO Marine Environment Protection Committee since the entry into force of the Paris Agreement in 2016. The Paris Agreement itself does not include international shipping in national inventories under the United Nations Framework Convention on Climate Change, leaving the sector to be regulated through the IMO under the existing mandate of MARPOL Annex VI, and the alignment of shipping with the Paris temperature goals therefore depends entirely on the trajectory adopted at the MEPC.

The 2018 Initial IMO Strategy on Reduction of GHG Emissions from Ships, adopted as Resolution MEPC.304(72), set a first political envelope: at least a 50 percent reduction in absolute annual GHG emissions from international shipping by 2050 compared with 2008, alongside a carbon-intensity reduction of at least 40 percent by 2030 and 70 percent by 2050 per transport work. The 2018 Initial Strategy was widely understood to be insufficient for alignment with a 1.5 degC pathway, and the IPCC Special Report on Global Warming of 1.5 degC of October 2018 sharpened the political pressure for revision. The Initial Strategy carried an explicit revision clause requiring MEPC to adopt a Revised Strategy in 2023.

The 2023 Revised IMO GHG Strategy, adopted as Resolution MEPC.377(80) at MEPC 80 in July 2023, restated the long-term goal as net-zero GHG emissions from international shipping by or around, that is, close to, 2050, taking into account different national circumstances. It introduced two new indicative checkpoints (2030 and 2040) and an intermediate energy-source target (the share of zero or near-zero GHG emission fuels in 2030). The Revised Strategy preserves the language of indicative checkpoint with a strive-for level, leaving open the political question of whether the indicative or the strive-for value would become the binding number when translated into MARPOL amendments.

That translation was the core work of MEPC 81 (March 2024), MEPC 82 (October 2024) and the intersessional working groups between them. The MEPC 83 compromise text approved on 11 April 2025, by a vote of 63 in favour, 16 against and 24 abstaining, set out the binding GFI trajectory as the technical element of the IMO Net-Zero Framework. The trajectory will be formally adopted at MEPC 84 in October 2025 under the tacit acceptance procedure of MARPOL Article 16 and enters into force on 1 January 2027.

The architecture chosen at MEPC 83 is a percentage-from-baseline construction. Rather than legislating a series of absolute gCO2eq/MJ values directly, Chapter 4 ter regulation 28ter defines the Required GFI and the Direct Compliance Threshold as functions of a 2008 baseline GFI multiplied by a year-specific reduction factor. This construction has two practical consequences. First, any future revision of the baseline (for example, on the basis of an updated IMO GHG Study) propagates through the entire trajectory automatically. Second, the trajectory is unambiguously defined for every year between 2027 and 2050, because the regulation specifies both the checkpoint reduction percentages and a linear interpolation rule for non-checkpoint years.

The 2008 well-to-wake baseline of 93.3 gCO2eq/MJ

The 2008 baseline value of 93.3 gCO2eq/MJ is the fleet-average well-to-wake GHG fuel intensity of international shipping in calendar year 2008. The number is reconstructed, not measured: 2008 predates both the IMO Data Collection System (which began reporting for 2019) and the EU MRV Regulation (which began for 2018), so no direct measurement of fleet-average WtW intensity for 2008 exists. The reconstruction proceeds in three stages.

Fleet-average tank-to-wake combustion intensity

The first stage establishes the average tank-to-wake combustion intensity of the 2008 international fleet. The Fourth IMO GHG Study 2020 estimates international-shipping CO2 emissions in 2008 at 794 million tonnes, with a corresponding total fuel-energy supplied of approximately 10,400 PJ on a lower-calorific-value basis. The 2008 fleet was overwhelmingly fuelled by HFO and MDO, with HFO accounting for around 77 percent of energy supplied and MDO for around 23 percent. Applying the MEPC.391(82) default tank-to-wake CO2 emission factors (3.114 g/g for HFO and 3.206 g/g for MDO) and the MEPC.391(82) default lower calorific values (40,200 MJ/t for HFO and 42,700 MJ/t for MDO) yields a tank-to-wake CO2 intensity of approximately 76.4 gCO2/MJ for the 2008 fleet on a fuel-energy basis.

Methane and nitrous-oxide adjustments

The second stage adds the non-CO2 combustion components weighted by AR5 GWP100 factors of 28 for CH4 and 265 for N2O, in line with the Resolution MEPC.391(82) accounting convention. Slip and N2O formation in 2008 marine engines were modest in absolute terms because LNG-fuelled ships were rare, but the adjustment lifts the tank-to-wake intensity by approximately 0.4 gCO2eq/MJ to around 76.8 gCO2eq/MJ. The Fourth IMO GHG Study reports a black-carbon component as a separate informational figure not included in the GFI accounting, consistent with the AR5-based GHG-only convention of Chapter 4 ter.

Well-to-tank upstream emissions

The third stage adds the well-to-tank upstream emissions of the 2008 HFO/MDO fuel mix. The MEPC.391(82) defaults set HFO upstream emissions at 13.5 gCO2eq/MJ and MDO upstream at 14.4 gCO2eq/MJ, reflecting refinery energy intensity, crude-oil extraction methane venting and shipping logistics for the residual and distillate streams. Energy-weighted across the 2008 fuel mix this yields approximately 13.7 gCO2eq/MJ of well-to-tank emissions. Adding the well-to-tank component to the tank-to-wake component yields the fleet-average well-to-wake intensity of approximately 90.5 gCO2eq/MJ.

The MEPC 83 baseline is set at 93.3 gCO2eq/MJ, slightly above the bottom-up Fourth-IMO-GHG-Study reconstruction. The difference reflects two policy choices in the calibration. First, the MEPC adopted a conservative baseline that incorporates the upper end of the upstream-emissions range to avoid penalising ships fuelled with regional HFO/MDO streams that have higher-than-default upstream intensities. Second, the baseline is rounded to one decimal place, with the rounding direction chosen to slightly relax the early-year Required GFI and so smooth the transition from the existing CII regime. The 93.3 gCO2eq/MJ figure is now codified in Chapter 4 ter regulation 28ter as $\text{GFI}_{2008}$ and is the multiplier on every reduction percentage in the trajectory.

The baseline is fixed for the duration of the Strategy: it does not update with fleet composition, with bunker-pool changes or with the entry into force of new MEPC.391(82) defaults. Only a formal MEPC resolution can revise the baseline, and the MEPC has signalled that any such revision would be considered only as part of the five-yearly review of the trajectory described in section seven below.

Tier 1 Required GFI: year-by-year values

The Tier 1 Required GFI is the binding floor below which a ship’s Attained GFI must lie to avoid a Remediation Unit obligation. Chapter 4 ter regulation 28ter expresses the Required GFI as a percentage reduction $r_1(y)$ from the 2008 baseline:

The Strategy checkpoints translate into Tier 1 reduction factors of 4 percent in 2027, 6 percent in 2028, 17 percent in 2030 (the indicative 2030 checkpoint of MEPC.377(80) interpreted as the binding number), 30 percent in 2035 (slightly tighter than the 2030 checkpoint extension under the 2035 indicative reduction), 65 percent in 2040 (the indicative 70 percent checkpoint reduced by a five-percentage-point glide-margin reflecting the political compromise) and 100 percent in 2050 (net-zero). The full year-by-year table follows from these anchors and the linear-interpolation rule of section five.

Two practical readings of the Tier 1 trajectory matter for fleet planners. First, the 2027 entry value of 89.57 gCO2eq/MJ is achievable for a ship burning a clean MDO-heavy bunker mix without any drop-in or alternative fuel. The Tier 1 floor in the first three years is a calibration year, not a stretch year: the binding constraint in 2027 to 2029 is essentially the existing CII regime expressed in WtW gCO2eq/MJ rather than gCO2/dwt-nm. Second, the 2040 floor of 32.66 gCO2eq/MJ is below the WtW intensity of any conventional fossil fuel (LNG sits at around 76 gCO2eq/MJ on a 100-year GWP basis, and even ULSFO is above 90 gCO2eq/MJ), so by 2040 every compliant ship must be running on a non-trivial blend of zero or near-zero GHG fuels.

Tier 2 Direct Compliance Threshold (DCT): year-by-year values

The Tier 2 Direct Compliance Threshold is the tighter floor that defines direct compliance: a ship whose Attained GFI is at or below the DCT for the year is in direct compliance, generates Surplus Units in proportion to the over-compliance and earns the certification benefits described in the Marine GFS methodology. A ship whose Attained GFI lies between the Required GFI and the DCT is in tiered compliance and must surrender Tier-2 Remediation Units, priced lower than the Tier-1 RUs that apply if the ship exceeds the Required GFI itself.

The Tier 2 DCT trajectory follows a parallel construction:

with $r_2(y) > r_1(y)$ at every year, reflecting the design principle that the DCT is at least as tight as the Required GFI and tightens faster. The MEPC 83 compromise sets the DCT reduction factors as 17 percent in 2027 (the equivalent of the existing CII intensity reduction by mid-decade), 21 percent in 2028, 43 percent in 2030 (the indicative strive-for level for 2030), 65 percent in 2035, 80 percent in 2040 (the strive-for level for 2040) and 100 percent in 2050.

The Tier 1 minus Tier 2 gap column is significant for fleet-strategy modelling. The gap is small in the entry years (about 12 gCO2eq/MJ in 2027), opens to a maximum around the mid-2030s (about 33 gCO2eq/MJ in 2035), and then narrows again as both curves converge on the 2050 net-zero anchor. The maximum gap year is the maximum-incentive year for early-mover capital deployment: a ship that achieves direct compliance in 2035 generates Surplus Units worth approximately 33 gCO2eq/MJ multiplied by the ship’s annual fuel-energy in MJ, which on a typical Panamax bulker at 60 PJ per year amounts to roughly 2 million SUs at notional unit prices of 100 to 150 USD per tonne CO2eq.

The deliberate widening of the gap is not an accident of arithmetic. The MEPC 83 compromise set the Tier 2 trajectory faster than the Tier 1 trajectory for the explicit purpose of accelerating early-mover investment in alternative fuels and onboard efficiency. A flat or convergent gap would have produced a Surplus Unit market dominated by trivial over-compliance margins; the divergent gap of the chosen trajectory rewards genuine commitment to advanced fuels and amortises the higher capital cost of LNG-with-CCS, methanol, ammonia and onboard wind-assist over the 2030 to 2040 decade in which fleet renewal is most active.

Linear interpolation between checkpoints

Chapter 4 ter regulation 28ter paragraph 4 sets out the linear-interpolation rule for non-checkpoint years. Given two adjacent checkpoint years $y_1$ and $y_2$ with reduction factors $r(y_1)$ and $r(y_2)$, the reduction factor for any year $y$ such that $y_1 \leq y \leq y_2$ is:

The same interpolation rule applies to both the Tier 1 Required GFI and the Tier 2 DCT, applied independently to each curve. The interpolation is in reduction-factor space rather than in gCO2eq/MJ space, but because the baseline is a constant the two formulations produce identical numerical results.

Three subtleties of the rule deserve attention. First, the interpolation applies only between defined checkpoints, not between the baseline year 2008 and the entry year 2027: the 19 years from 2008 to 2026 are not part of the trajectory and have no Required GFI. Second, the interpolation is piecewise linear in time, not in cumulative emissions: the trajectory does not preserve a constant year-on-year emissions reduction in absolute tonnes, only a constant year-on-year intensity reduction in gCO2eq/MJ. Third, the rule rounds the final $r(y)$ to two decimal places (basis points) before computing the Required GFI, and the resulting Required GFI is then rounded to two decimal places of gCO2eq/MJ. Both rounding steps are written into the regulation to remove ambiguity in the surrender calculation.

A practical example: the year 2032 lies between the 2030 checkpoint ($r_1 = 0.17$) and the 2035 checkpoint ($r_1 = 0.30$). The interpolation gives:

so $r_1(2032) = 22.20$ percent and Required GFI for 2032 is $93.3 \cdot (1 - 0.222) = 72.59$ gCO2eq/MJ, matching the Tier 1 table above. The same arithmetic applied to $r_2$ yields a 2032 DCT of 44.97 gCO2eq/MJ.

Indicative checkpoint vs strive-for

The 2023 Revised Strategy expresses every checkpoint as a pair: an indicative reduction that is the political minimum, and a strive-for reduction that is the aspirational ambition. For 2030 the pair is (20 percent, 30 percent); for 2040 it is (70 percent, 80 percent); for 2050 it is (net-zero or close to net-zero, with no separate strive-for figure). The 2035 indicative figure of 43 percent appears in the Strategy as a single value, derived from the IPCC SR15 1.5 degC pathway for the global energy system, with no explicit strive-for variant.

The translation from Strategy checkpoints to MEPC 83 GFI reduction factors is not a one-to-one mapping. The MEPC 83 compromise text adopts the strive-for level for the Tier 2 DCT and the indicative level for the Tier 1 Required GFI in the early years, with a glide-margin in the later years. Concretely:

• In 2030: Tier 1 reduction 17 percent (slightly below the indicative 20 percent of MEPC.377(80), reflecting the calibration concession on the baseline value); Tier 2 reduction 43 percent (an interpolation between the strive-for 30 percent of MEPC.377(80) and the 2035 indicative 43 percent, with the mid-decade Strategy ambition pulled forward five years to maintain a meaningful gap between the two tiers).
• In 2040: Tier 1 reduction 65 percent (slightly below the indicative 70 percent of MEPC.377(80), reflecting the same five-percentage-point glide-margin); Tier 2 reduction 80 percent (the strive-for level of MEPC.377(80) adopted directly).
• In 2050: both tiers converge on 100 percent (net-zero), reflecting the absence of a strive-for variant on the 2050 endpoint.

This calibration approach has a clear policy logic. The Required GFI is the binding floor for the entire fleet, including the marginal compliance ship; setting it below the Strategy indicative level by a small margin acknowledges the realistic capacity of the global bunker pool to deliver ZNZ fuels by each checkpoint year. The DCT is the bonus floor for early movers; setting it at the strive-for level rewards ships that meet the Strategy ambition rather than the Strategy floor. The combined effect is that a fleet that meets the Strategy strive-for ambition runs at the DCT and earns SUs, while a fleet that meets only the Strategy indicative level runs at the Required GFI with no SUs and a marginal RU exposure.

The compromise has been criticised on two grounds. First, the five-percentage-point glide-margin in 2040 means that the binding 2040 floor is 65 percent rather than the strive-for 80 percent, which several Pacific Small Island Developing States argued was insufficient for 1.5 degC alignment. Second, the 2030 calibration of 17 percent rather than the indicative 20 percent leaves a gap that must be closed in subsequent reviews. Both points feed into the next section: the five-yearly review provision is the formal mechanism by which the trajectory can be tightened.

MEPC review and update cycle

Chapter 4 ter regulation 31ter sets out the review and update cycle for the GFI trajectory. The MEPC must review the Required GFI and DCT trajectories at least every five years, with the first review concluding by 2030 and subsequent reviews concluding by 2035, 2040 and 2045. Each review considers four mandatory inputs: the latest IMO GHG Study, the latest IPCC Assessment Report, the actual emissions trajectory of the international fleet under the GFS, and the Sustainability Certification Scheme reports on alternative-fuel pathway availability.

The review can move the trajectory in three directions. A tightening revision lowers the Required GFI, the DCT, or both, by adjusting the reduction factors at one or more checkpoints. A loosening revision raises one or both curves, only on a finding of serious technical infeasibility supported by the IMO GHG Study. A rebalancing revision changes the ratio between the Tier 1 and Tier 2 reduction factors without changing either endpoint, used to redistribute the burden between marginal and ambitious fleet operators. The default is no change: a review that concludes the trajectory is appropriate leaves the trajectory in place for another five years.

Two procedural features of the review cycle are worth highlighting. First, any tightening revision adopted at a five-yearly review takes effect from the calendar year following the entry into force of the amending Resolution under MARPOL Article 16, which is normally the second calendar year after adoption. A 2030 review concluding in mid-2030 with adopted amendments would therefore tighten the trajectory from 2032 onward, not from the year of adoption. Second, the review cycle is explicitly exempt from the unanimity rule: amendments to the Required GFI or DCT can be adopted by the standard MARPOL Article 16 majority, without requiring consensus, although the political dynamics of the MEPC have historically pushed toward consensus.

The review-and-update cycle is the central mechanism for the political resilience of the trajectory. The 2027-to-2050 trajectory adopted at MEPC 83 is not a fixed multi-decade commitment in the sense of a treaty obligation; it is a rolling trajectory whose distant years are revisable by majority decision. This has two implications for fleet planning. Investments in alternative fuels with payback horizons of five to ten years are exposed only to one review cycle, and the trajectory is reasonably predictable for those horizons. Investments with payback horizons of fifteen to twenty-five years (newbuild capesizes, new LNG carriers, ammonia-ready vessels) are exposed to two or three review cycles, and prudent financial modelling must include scenarios in which the trajectory is tightened by 5 to 15 percentage points at one or more reviews.

The first review, concluding by 2030, is widely expected to address the 2030 calibration concession and the 2040 glide-margin discussed in section six. Whether the review delivers a tightening, a holding pattern or a rebalancing depends on the actual fleet emissions trajectory in 2027 to 2029 and on the geopolitical state of climate diplomacy at the time. Fleet planners are advised to model both a holding-pattern scenario and a tightening scenario as the central cases for capital allocation under MEPC 83, with the strive-for level of MEPC.377(80) as the upper bound on plausible 2030 review outcomes.

Formula, assumptions, and limits

Formula

The Required GFI for any year $y$ in the trajectory window 2027 to 2050 is:

The Direct Compliance Threshold for the same year is:

Reduction factors $r_1(y)$ and $r_2(y)$ are defined exactly at the MEPC 83 checkpoint years 2027, 2028, 2030, 2035, 2040 and 2050, and are linearly interpolated between adjacent checkpoints as in section five.

Derivation

The Required GFI is derived from the 2008 baseline and the year’s reduction factor by direct multiplication of $\text{GFI}_{2008} = 93.3$ by $(1 - r_1(y))$. The reduction factor $r_1(y)$ is derived from the MEPC 83 calibration of the Strategy checkpoints for non-checkpoint years using the linear-interpolation rule. The DCT is derived analogously from $r_2(y)$. Both derivations are exact arithmetic with no fitted constants, no statistical estimation and no fleet-specific calibration: the trajectory is identical for every ship subject to Chapter 4 ter regardless of size, type or trading pattern. This uniformity is a deliberate design choice that distinguishes the GFS from the size-and-type-stratified CII regime and from the gradually-tightening FuelEU Maritime trajectory.

Assumptions

The trajectory rests on five technical assumptions. First, the 2008 baseline of 93.3 gCO2eq/MJ is a fixed reference: any future revision requires a formal MEPC resolution, not an automatic recalibration. Second, AR5 GWP100 metrics are used to weight CH4 and N2O across the entire trajectory window: a future MEPC adoption of AR6 GWP100 would re-anchor the baseline but is not currently scheduled. Third, well-to-wake accounting boundaries match Resolution MEPC.391(82): upstream extraction, processing, transport, distribution, bunkering and combustion are all included, while shipyard construction and end-of-life dismantling are excluded. Fourth, the linear-interpolation rule is the canonical method for non-checkpoint years: no curve-fitting, no exponential smoothing and no scenario-based perturbation are permitted in the surrender calculation. Fifth, the MEPC five-yearly review can only revise the trajectory from a future year forward, never retroactively for a past compliance year.

Worked example

Consider a fleet planner sizing the 2030 and 2040 abatement gap for a Panamax bulker burning conventional VLSFO with a default-pathway WtW intensity of 92.4 gCO2eq/MJ.

2030 indicative scenario: Required GFI is $93.3 \cdot (1 - 0.17) = 77.44$ gCO2eq/MJ. The Tier 1 abatement gap for VLSFO is $92.4 - 77.44 = 14.96$ gCO2eq/MJ, equivalent to about 16 percent intensity reduction relative to the bunker the ship burns today. This can be closed by a 16 percent biofuel drop-in (taking advantage of the lower WtW intensity of UCO-FAME at around 28 gCO2eq/MJ), by 5 to 7 percent slow-steaming on top of an existing CII speed regime, or by a combination.

2030 strive-for scenario (DCT): DCT is $93.3 \cdot (1 - 0.43) = 53.18$ gCO2eq/MJ. The Tier 2 abatement gap is $92.4 - 53.18 = 39.22$ gCO2eq/MJ, equivalent to roughly 42 percent intensity reduction. This cannot be closed by drop-in alone except at a biofuel share approaching 60 percent (at typical UCO-FAME availability and price points this is uneconomic), and is the practical threshold at which dual-fuel methanol or LNG retrofit becomes the default abatement option.

2035 Required GFI: $93.3 \cdot (1 - 0.30) = 65.31$ gCO2eq/MJ. Tier 1 gap for VLSFO is $92.4 - 65.31 = 27.09$ gCO2eq/MJ, about 29 percent intensity reduction.

2035 DCT: $93.3 \cdot (1 - 0.65) = 32.66$ gCO2eq/MJ. Tier 2 gap is $92.4 - 32.66 = 59.74$ gCO2eq/MJ, about 65 percent intensity reduction. At this level a VLSFO-fuelled ship is structurally non-compliant on the DCT and must be either retired, retrofitted to dual-fuel, or accept the 32.66 gCO2eq/MJ shortfall as a Tier 2 RU obligation.

2040 indicative scenario: Required GFI is $93.3 \cdot (1 - 0.65) = 32.66$ gCO2eq/MJ. The Tier 1 gap relative to VLSFO is $92.4 - 32.66 = 59.74$ gCO2eq/MJ, about 65 percent intensity reduction. The conventional fleet is structurally exposed at 2040 even on the Required GFI floor.

2040 strive-for scenario (DCT): DCT is $93.3 \cdot (1 - 0.80) = 18.66$ gCO2eq/MJ, below the WtW intensity of even the cleanest LNG pathway (around 76 gCO2eq/MJ at default methane-slip levels). Direct compliance in 2040 requires a fuel mix averaging at most 18.66 gCO2eq/MJ across the entire reporting year, achievable in practice only with a high share of green ammonia, e-methanol, blue hydrogen with effective CCS or biomethane from advanced feedstocks.

Edge cases and limits

The trajectory has four edge cases worth noting. First, the 2027 entry year applies only to ships of 5,000 GT and above on international voyages: smaller ships and exclusively domestic voyages are outside the scope, and a ship that crosses the 5,000 GT threshold during a calendar year is captured for that year only if the change of registry triggers an IAPP renewal survey. Second, the trajectory is denominated in WtW gCO2eq/MJ on a fuel-energy basis, not in gCO2eq per transport-work unit: a ship that achieves Required GFI compliance can still fail the CII regime, which uses a transport-work denominator. Third, the trajectory does not directly accommodate non-fuel propulsion (wind-assist, solar, shore-power); the energy savings these deliver are captured implicitly through the Attained GFI denominator (lower fuel energy reduces the denominator and the numerator equally), but no explicit credit is granted. Fourth, the 2050 endpoint of 0 gCO2eq/MJ is a mathematical absolute that cannot be achieved by any combustion fuel pathway with non-zero upstream emissions: in practice 2050 compliance presumes a fully renewable, zero-upstream electricity-and-electrofuel system that does not yet exist at scale.

Regulatory basis

The trajectory is codified in Chapter 4 ter of MARPOL Annex VI as approved by Resolution MEPC.392(83) of 11 April 2025 and to be formally adopted at MEPC 84 in October 2025. The legal anchor of the baseline value is regulation 28ter paragraph 1; the legal anchor of the reduction-factor schedule is regulation 28ter paragraphs 2 (Tier 1) and 3 (Tier 2); the legal anchor of the linear-interpolation rule is regulation 28ter paragraph 4; the legal anchor of the five-yearly review is regulation 31ter. The Strategy precursors are Resolution MEPC.304(72) of 13 April 2018 (Initial Strategy) and Resolution MEPC.377(80) of 7 July 2023 (Revised Strategy), neither of which is itself a binding MARPOL amendment. The lifecycle accounting convention is set by Resolution MEPC.391(82) of October 2024.

Common errors

Five common errors recur in fleet-planning applications of the trajectory. First, applying the strive-for level instead of the indicative level to the Required GFI treats the Tier 1 floor as if it were the Tier 2 DCT, overstating the required abatement by 23 percentage points in 2030 (43 percent rather than 17 percent reduction). Second, using the Tier 1 reduction factor for SU calculation rather than the Tier 2 factor underestimates Surplus Unit revenue by the Tier-1-minus-Tier-2 gap, which is largest in 2035. Third, computing reductions from a TtW-only baseline (around 76 gCO2/MJ) instead of the WtW baseline of 93.3 gCO2eq/MJ produces a Required GFI that is too tight by approximately 18 percent. Fourth, using percentage reductions per year compounded instead of percentage reductions from baseline produces a curve that is approximately right at 2030 but diverges sharply by 2050 (a 1.4 percent annual compound reduction yields a 2050 value of 49.0 gCO2eq/MJ, far above the actual 0.0 gCO2eq/MJ floor). Fifth, interpolating in WtW intensity space rather than in reduction-factor space introduces a 0.1 to 0.3 gCO2eq/MJ rounding-discrepancy in non-checkpoint years; the regulation requires interpolation in $r$ space.

Practical implications for fleet planning

The 2027 to 2050 trajectory has direct consequences for newbuild specification, retrofit timing, charter-party structure and corporate financial planning. Three planning windows merit particular attention.

Newbuild specifications for 2027 to 2032 deliveries

A ship delivered in 2027 will see its Required GFI fall from 89.57 gCO2eq/MJ in delivery year to 65.31 gCO2eq/MJ in 2035 and 32.66 gCO2eq/MJ in 2040, a 64 percent decline over the first 13 years of operation. A ship designed only for VLSFO at 92.4 gCO2eq/MJ will be in Tier 1 RU exposure from 2027 onward (the gap is 2.83 gCO2eq/MJ in 2027) and will face a Tier 1 gap of 27.09 gCO2eq/MJ in 2035, equivalent to roughly 21 percent of its annual fuel cost at notional RU prices of 100 USD per tonne CO2eq. The economic case for ammonia-ready, methanol-dual-fuel or LNG-with-CCS specification at the newbuild stage is determined by the present value of these expanding RU costs over the 25-year design life of the asset, plus the Surplus Unit revenue available from running below the DCT.

Retrofit timing for the existing 2015 to 2020 fleet

Ships delivered between 2015 and 2020 face the trajectory at the mid-life rather than the early-life stage. A 2018-built bulker will see Required GFI tighten from 87.70 gCO2eq/MJ in 2028 (when the ship is 10 years old) to 32.66 gCO2eq/MJ in 2040 (when the ship is 22 years old). The retrofit-or-replace decision turns on the scrap value of the hull at age 22 to 25, the cost of dual-fuel conversion at the next scheduled drydock (typically 5 to 8 million USD for a methanol retrofit on a Panamax), the residual life of the converted ship and the alternative revenue on a newbuild. For most fleets the optimal strategy is a portfolio approach: retrofit a subset of the fleet at the 15-year drydock and accept early scrappage of the remainder.

Charter-party fixing for 2030 and beyond deliveries

Time-charter and bareboat fixings for ships delivered after 2027 routinely now include GFI compliance clauses analogous to the BIMCO CII clauses but denominated in Tier 1 RU and Tier 2 SU exposure. The trajectory described in this article is the schedule against which those clauses are written: the charterer assumes the cost of any RU surrender obligation arising from voyage instructions that push the ship’s Attained GFI above the Required GFI for the year. The owner assumes the cost of any non-conformity in the ship’s technical specification (engine type, fuel-flexibility, hull efficiency). Both parties have an interest in agreeing the Required GFI and DCT for each year of the charter as part of the recap, and the year-by-year tables above provide the standard reference.

Corporate financial planning

Listed shipping corporations report under IFRS S2 (the IFRS Sustainability Disclosure Standard for climate-related disclosures), which requires disclosure of the entity’s transition plan and the sensitivity of financial position to a credible decarbonisation scenario. The 2027 to 2050 GFI trajectory is the primary credible scenario for international shipping, supplemented by FuelEU Maritime for European voyages and by the EU ETS for shipping for the carbon-price layer. Corporate financial planning models therefore project Required GFI, DCT and notional RU price for every year through 2050, and stress-test the resulting cash-flow schedule against tightening review outcomes, fuel-price scenarios and demand-growth scenarios. The GFI compliance calculator and EU ETS EUA liability calculator are designed for this corporate planning workflow.

See also

• IMO Net-Zero Framework
• Marine Global Fuel Standard (GFS) methodology
• 2023 Revised IMO GHG Strategy
• MARPOL Annex VI
• FuelEU Maritime explained
• EU ETS for shipping
• What is CII
• IMO DCS vs EU MRV
• GFI compliance calculator
• GFI attained calculator
• EU ETS EUA liability calculator

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• EPL Required MCR Reduction

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• GFI Compliance - IMO Net-Zero Framework
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