A bank that lent 30 million dollars against a ten-year-old bulk carrier in 2015 cared about one number on the climate side: nothing. The loan was priced on the steel, the charter, and the borrower’s balance sheet, and the ship’s carbon intensity sat outside the credit memo. That is no longer true. Thirty-six banks that together hold roughly three-quarters of the world’s ship-finance loans now measure every vessel in their books against a decarbonization trajectory and publish the gap once a year, and the charterers who fix those same ships score the carbon intensity of each voyage on the same yardstick. This article is the hub for the climate-finance and GHG-ratings cluster: it explains how capital and commercial pressure, not only the IMO rulebook, push a ship to decarbonize, and routes down to the two deep-dive articles and four calculators that run the arithmetic. The Poseidon Principles climate alignment calculator and the portfolio adherence calculator score a lending book, the RightShip GHG Rating calculator places a ship on the A-to-E scale, and the ESI score calculator sizes the port-fee rebate.
The cluster has one organizing idea worth stating once. The IMO sets the rules a ship must obey; the schemes in this cluster set the conditions on which a ship gets money, gets fixed, and gets a discount at the berth. A poorly rated ship is not illegal, but it costs more to finance, it is passed over by climate-conscious charterers, and it pays full dues where a clean ship gets a rebate. That is a market pushing the same direction as the regulator, sometimes ahead of it. The schemes split by where they bite: the Poseidon Principles bind the lenders, the Sea Cargo Charter binds the charterers, the RightShip GHG Rating prices the ship in the vetting market, the Environmental Ship Index prices the port call, and voluntary carbon credits sit at the edge of the system, offering an offset that the regulated instruments do not recognize. This cluster sits one level down from decarbonization and alternative fuels and runs alongside the regulatory machinery in the IMO Net-Zero Framework and GHG Fuel Intensity and the design-and-operational metrics in ship efficiency indices.
The Annual Efficiency Ratio: the number under both finance schemes
The Poseidon Principles and the Sea Cargo Charter rest on one metric, and it is worth fixing before the schemes that use it. The Annual Efficiency Ratio (AER) is a ship’s annual carbon intensity expressed as grams of CO2 per deadweight-tonne nautical mile: the total CO2 the ship emitted in a year divided by its deadweight tonnage multiplied by the distance it sailed. It is a supply-side metric, built on the ship’s capacity rather than the cargo it actually carried, which is the same simplification the IMO operational metrics make. The AER is deliberately cruder than the cargo-carried EEOI because it can be computed from data every ship already reports: fuel burned (which fixes the CO2 through the fuel’s carbon factor), deadweight from the ship’s particulars, and distance from the noon reports.
That choice is what makes the AER usable as a portfolio yardstick. A bank financing 120 ships across six segments cannot collect cargo-tonnage data for every voyage, but it can pull the deadweight, the fuel, and the distance for each ship, so the AER scales to a whole loan book in a way a cargo-based metric does not. The cost is precision: a ship sailing half-empty looks more carbon-intensive on the AER than a cargo-based metric would show, so the AER penalizes low utilization and rewards full ships and slow steaming. The schemes accept that trade-off because the alternative, a metric that cannot be computed at portfolio scale, would defeat the purpose. The same AER feeds the Annual Efficiency Ratio calculator and underlies the operational-intensity story told in what is CII.
The decarbonization trajectory: the line every score is measured against
A score is meaningless without a line to measure it against, and that line is the decarbonization trajectory. The trajectory is a year-by-year path for the average carbon intensity of a ship type and size, declining over time so that the fleet reaches the IMO’s emission-reduction goals by the target dates. Each scheme computes, for a given ship in a given year, the AER the trajectory allows; the ship’s actual AER above or below that allowance is its alignment. Aggregate that across a portfolio and weight it by exposure and you get the climate alignment score.
The trajectories were re-cut after the IMO adopted its revised greenhouse-gas strategy in July 2023, which steepened the ambition to net-zero emissions from international shipping by or around 2050, with indicative checkpoints to cut total annual emissions by at least 20 percent striving for 30 percent by 2030, and at least 70 percent striving for 80 percent by 2040, all against 2008. Both finance schemes re-based their trajectories to the 2023 strategy, so a portfolio that looked aligned against the gentler 2018 trajectory can show a gap against the steeper one. This is the direct link between the regulatory hub at the IMO Net-Zero Framework and GHG Fuel Intensity and the finance schemes: the regulator sets the destination, the schemes turn it into a yearly line a banker can score against.
The Poseidon Principles: climate on the lending side
The Poseidon Principles for Financial Institutions became public on 18 June 2019 with eleven founding banks holding around 100 billion dollars of shipping loans and a single mechanism: a signatory measures the carbon intensity of its shipping portfolio against the IMO-aligned trajectory and discloses the result every year. The founders included Citi, Societe Generale, DNB, ABN AMRO, Credit Agricole, Danske Bank, Danish Ship Finance, ING, Nordea, NordLB, and Amsterdam Trade Bank, and the framework was built with the Global Maritime Forum, the Rocky Mountain Institute, and the University College London Energy Institute. The signatory base has grown to 36 institutions holding around three-quarters of the global ship-finance loan book, and the framework now extends beyond traditional senior secured lenders. In December 2025 it opened an associate-member category to draw in lessors and lenders that finance ships on an unsecured basis, widening the share of the market under the discipline. The mechanics of a single bank’s calculation sit in the Poseidon Principles article and run in the climate alignment calculator.
What the Principles commit a bank to is measurement and disclosure, not a lending ban. A signatory can finance a poorly aligned ship; what it cannot do is hide the misalignment, because the AER of every financed vessel rolls up into a portfolio score the bank publishes by name in the Annual Disclosure Report. The discipline is reputational and competitive rather than contractual: a bank carrying a large positive alignment gap is publicly behind its peers, and the loan book it builds next year is the lever it has to close the gap. The Sixth Annual Disclosure Report, published in 2025, recorded the average gap against the minimum trajectory narrowing from just over 19 percent to just under 12 percent in a year, and reported that signatories disclosed 95 percent of their eligible portfolio against 93 percent the year before, with nine signatories hitting 100 percent coverage.
How a bank’s portfolio score is built
The portfolio score is a weighted aggregation, and the weighting is the part that decides what the headline number means. Each ship in the loan book gets its AER for the year and its trajectory allowance for that year and ship class; the percentage difference is the ship’s alignment. The bank then weights each ship’s alignment by the institution’s outstanding exposure to it, so a 40 million dollar loan against a misaligned tanker moves the portfolio score more than a 5 million dollar loan against an aligned coaster. The portfolio adherence calculator runs that exposure-weighted roll-up across a book of ships.
The weighting choice matters because it shapes the incentive. An exposure-weighted score tells a bank that the fastest way to improve its number is to lend more against efficient ships and less against inefficient ones, or to refinance the worst emitters out of the book. That is the intended pressure: the score is designed so that the commercially rational response, growing the clean side of the book, is also the decarbonizing response. A bank that wanted to game the headline could in principle shed its worst loans to an unsigned lender, which is one reason the framework’s December 2025 expansion to unsecured and associate members matters, since it narrows the pool of finance that sits outside any disclosure.
The Sea Cargo Charter: climate on the chartering side
The Sea Cargo Charter is the Poseidon Principles’ mirror on the demand side of the freight market. Launched in October 2020 and governed alongside the Poseidon Principles through the Global Maritime Forum, it binds charterers and shipowners (the parties that move cargo) rather than the banks that finance ships, and it scores the carbon intensity of the voyages a signatory actually charters against the same AER metric and the same IMO-aligned trajectories. A commodity trader, a mining house, or an energy major that fixes hundreds of voyages a year reports the alignment of that chartering activity, which captures a slice of the market the lending schemes never touch: the ship a charterer hires but no signatory bank financed.
The reach is narrower than the finance side, by design. The 2025 Sea Cargo Charter Annual Disclosure Report covered 37 signatories representing over 17 percent of the total bulk cargo moved by sea each year, against the roughly three-quarters of ship finance the Poseidon Principles cover. The two schemes were built to interlock: a ship can be pushed from the lending side by the bank that financed it and from the demand side by the charterer that hires it, and a vessel that is misaligned on both is squeezed twice. The 2025 charterer report recorded signatories on average 12 percent behind the minimum climate trajectory and 18 percent behind the striving targets for 2024, with most signatories cutting emission intensity year on year. Over 90 percent of signatories now use third-party verification of the underlying data, which is the quiet half of any disclosure scheme: a self-reported number nobody audits is worth little.
The RightShip GHG Rating: the ship in the vetting market
Where the finance schemes score portfolios, the RightShip GHG Rating scores the individual ship, and it does so in the place a charterer looks before fixing: the vetting screen. RightShip rates a vessel’s design efficiency on a letter scale and publishes it into the platform that dry-bulk and other charterers use to screen ships on safety and environmental performance, so a poor letter can cost a ship a fixture before any commercial term is discussed. The RightShip GHG Rating calculator places a ship on that scale from its design figures.
The detail that trips people up is the scale. The current RightShip GHG Rating runs A to E, with A the most efficient and E the least. RightShip moved to that five-point scale on 6 December 2023, replacing the older seven-point A-to-G scale; in the transition, old As and Bs broadly became A, and old Fs and Gs became E. So a “RightShip A-to-G” reference describes the pre-December-2023 scheme, not the current one, and a ship’s letter from before that date does not map one-to-one onto the new band. The rating is a relative, not an absolute, measure: it compares a ship against a peer group of vessels within plus or minus 10 percent of its deadweight, so a ship’s letter can shift as the comparison fleet changes even if the ship itself does not.
Three indices behind one letter
The GHG Rating is the only vessel-focused environmental rating that folds three efficiency indices into one index, and which one applies depends on the ship. For ships built from 2013 it can use the IMO Energy Efficiency Design Index (EEDI), the regulatory design metric set at delivery. For existing ships without an EEDI it uses RightShip’s own Existing Vessel Design Index (EVDI), which RightShip built to mirror the EEDI for the pre-2013 fleet, measuring theoretical CO2 per tonne nautical mile. It also incorporates the Energy Efficiency Existing Ship Index (EEXI), the retrofit-design metric the IMO made mandatory from 2023. All three are design or theoretical-design metrics, measuring how efficiently the ship was built or de-rated, not how it is actually operated, which is the line that separates the GHG Rating from the operational CII. The design side of these indices is the subject of what is EEXI, what is EEDI, and the wider ship efficiency indices hub.
The 2.0 rating that took effect on 6 December 2023 also changed how the rating handles speed. The older method scored a ship from its installed engine power, which broke once thousands of ships fitted engine power limitation (EPL) or shaft power limitation (ShaPoLi) to meet the EEXI: a de-rated ship looked artificially clean on a power basis. RightShip moved to a speed-corrected method that compares a ship’s CO2 emissions at a common reference speed, drawn from the Fourth IMO GHG Study 2020 and cut by 10 percent to reflect the fleet slowdown that EEXI power limits forced. So a ship can no longer buy a better letter by limiting power on paper while sailing at the same speed; the rating asks what the ship actually emits at the speed it runs.
The Environmental Ship Index: a discount at the berth
The Environmental Ship Index (ESI) turns clean performance into cash at the port, not in the loan or the charter. The IAPH has run the scheme since 2011: a ship scores from 0 to 100 on how far its NOx, SOx, and CO2 performance and its onshore-power-supply capability beat the current MARPOL Annex VI baseline, with the cleaner ship scoring higher. Ports that join as incentive providers grant a discount on tonnage or berthage dues to ships above a chosen threshold and scale the rebate with the score. More than 100 ports offer ESI-linked incentives and over 6,800 vessels are registered; the IAPH governs the index and externalized its administration to OceanScore on 1 January 2026, adding a professional onboard verification step and a registration fee. The ESI score calculator computes a ship’s score and the rebate it earns at a given port.
The threshold is where the scheme bites. A common cut is a score of 25 or higher: a ship below it earns nothing, a ship above it earns a rebate that rises with the score, so the index rewards the marginal improvement rather than only the cleanest hull. The Port of Rotterdam and many others publish their own ESI tariff, and because each port sets its own threshold and rebate schedule, the same ship earns different money at different berths. The amounts are modest against a ship’s fuel bill, so the ESI works less as a primary economic driver than as a tie-breaker and a public signal: a ship that maintains a high ESI score is documenting its environmental performance to every port it calls, which feeds back into the charterer’s and the lender’s view of the same vessel.
The scheme is also changing under its new administrator. The IAPH has trailed an ESI Core update that enters force in 2027, the largest revision of the index since it launched in 2011, which alongside the 1 January 2026 move to OceanScore adds the onboard verification step and the registration fee. The direction is the same as the rest of this cluster: the index is tightening its evidence requirements so that a high score documents real performance rather than a self-declared figure, the same audit problem the finance schemes solved with third-party verification.
Voluntary carbon credits: the offset at the edge of the system
A voluntary carbon credit offers a shipowner or charterer a different path: instead of cutting the ship’s own emissions, pay for a tonne of CO2 reduced somewhere else and claim the ship’s footprint net of that credit. The appeal is obvious on a hard-to-abate asset, where the in-sector reduction is slow and expensive. The problem is that a credit only cancels a real tonne if the project behind it is additional (it would not have happened anyway), not double-counted, and durable, and the voluntary market has a documented record of credits that fail one of those tests. The voluntary carbon credits in shipping article works through the quality question in full.
The quality concern is not abstract. Academic and market reviews have characterized the voluntary carbon market as suffering persistent failures: imperfect information about credit quality and conflicts of interest in the certification chain, where the verifier is paid by the project it verifies. The Integrity Council for the Voluntary Carbon Market published its ten Core Carbon Principles as a high-integrity benchmark, and in August 2024 it ruled that eight renewable-energy crediting methodologies were not eligible for the Core Carbon Principles label on additionality grounds, a decision that took roughly a third of the market’s supply, about 236 million unretired credits, out of the high-integrity pool. The Council’s reasoning was that the cost of renewables has fallen far enough that most projects now make money without credit revenue, so the credits fail the test that the reduction would not have happened anyway. For a shipowner, the governance lesson is to buy only Core-Carbon-Principles-aligned credits and to treat them as a supplement to, not a substitute for, real reductions.
Why a credit does not move a regulated score
The structural limit on credits in shipping is that the regulated instruments do not recognize them. A ship’s Carbon Intensity Indicator rating is computed from the fuel it actually burned; buying a credit does not change the fuel burned, so it does not change the CII letter. The same holds under the EU’s FuelEU Maritime regulation, where compliance turns on the greenhouse-gas intensity of the energy used on board, and under the EU Emissions Trading System, where a ship surrenders EU allowances for its in-scope emissions, not arbitrary voluntary credits. So a credit can support a corporate or charterer net-zero claim under a framework like the Science Based Targets initiative’s maritime guidance, which sets corporate target-setting and reduction priorities for ship operators, but it cannot buy a ship out of a poor CII rating or a FuelEU deficit. That is the boundary line of this cluster: credits live in the voluntary, claim-making layer, while the CII, EEXI, and FuelEU metrics live in the compliance layer, and the two do not net against each other.
There is one place where market and regulation converge on a real cash flow, and it is worth keeping distinct from the voluntary schemes. Under the EU Emissions Trading System a ship calling at European ports surrenders EU allowances (EUAs) bought on a regulated exchange for a share of its in-scope CO2, phased in from 40 percent of 2024 emissions to 100 percent from 2026; under FuelEU Maritime a ship that exceeds the greenhouse-gas-intensity limit pays a penalty or pools with cleaner ships. Those are compliance instruments with a hard price, not voluntary credits, and a ship cannot meet either by buying an offset. So a poorly rated ship faces the disclosure pressure of the voluntary schemes in this cluster and, separately, a direct regulated cost under the EU instruments, and the two reinforce rather than substitute. The detail of those EU instruments sits outside this cluster, but the lesson here is the separation: an ICVCM-grade carbon credit can support a corporate net-zero claim, yet it buys the ship nothing against an EUA surrender obligation or a FuelEU deficit.
The five schemes side by side
The schemes are easy to confuse because they all measure carbon and all push the same direction, but they bite at different points in a ship’s commercial life and on different parties. The table sets out who is rated, the scale or metric, and who acts on the result.
| Scheme | Who is rated | Scale or metric | Who uses the result | Governing body |
|---|---|---|---|---|
| Poseidon Principles | A bank’s ship-finance portfolio | Climate alignment score (% above/below the AER trajectory) | Lenders, the market, and the bank’s own loan strategy | Poseidon Principles Association / Global Maritime Forum |
| Sea Cargo Charter | A charterer’s or shipowner’s chartered voyages | Same AER alignment score, on the demand side | Charterers, cargo owners, the market | Sea Cargo Charter Association / Global Maritime Forum |
| RightShip GHG Rating | The individual ship’s design efficiency | Letter A to E (A best); EEDI / EVDI / EEXI | Charterers and cargo owners at the vetting stage | RightShip |
| Environmental Ship Index | The individual ship’s emissions performance | Score 0 to 100 vs MARPOL Annex VI baseline | Ports, as a dues rebate above a threshold | IAPH (administered by OceanScore from 2026) |
| Poseidon Principles for Marine Insurance | A marine insurer’s hull and machinery portfolio | Same AER alignment score, on the insurance side | Hull and machinery underwriters, the market | Poseidon Principles Association / Global Maritime Forum |
| Voluntary carbon credits | A project’s claimed emission reduction | Tonnes CO2e, against the Core Carbon Principles | Shipowners/charterers making voluntary net-zero claims | ICVCM (integrity benchmark); various registries |
The pattern in the table is the substance of the cluster. Three schemes (the Poseidon Principles for lenders, the Sea Cargo Charter for charterers, and the Poseidon Principles for Marine Insurance for hull underwriters) rate a portfolio of activity on a common AER trajectory and discipline through annual disclosure; two (the GHG Rating and the ESI) rate an individual ship and discipline through the vetting screen and the dues sheet; one (carbon credits) sits outside the rating logic entirely, offering an offset the compliance instruments ignore. A single ship can feel all of them at once: financed by a Poseidon bank, insured by a Poseidon underwriter, chartered by a Sea Cargo signatory, screened on its RightShip letter, and either earning or missing an ESI rebate at each berth.
How the schemes interact with CII and lending
The schemes do not run in separate boxes; they feed one another, and the operational CII rating is the thread that connects them. A ship’s CII letter, the IMO’s annual operational-intensity grade from A to E, is computed from much the same fuel-and-distance data as the AER, so a ship sliding toward a D or E CII is almost certainly drifting away from the finance trajectories at the same time. A charterer reading a poor RightShip design letter and a poor CII operational rating sees the same ship as a fixture risk on two axes, and the financing bank sees it as a drag on the portfolio alignment score it must publish. The pressure compounds rather than adds. The CII machinery itself sits in what is CII and the operational side runs in the CII rating calculator and the AER calculator.
The lending consequence is the sharpest end of the chain. A bank under the Poseidon Principles that watches a financed ship slide to a poor CII and a widening alignment gap has three moves: re-price the loan to reflect the higher transition risk, attach sustainability-linked covenants that tie the margin to the ship’s carbon intensity, or decline to refinance at maturity and let the loan run off. Sustainability-linked ship loans, where the interest margin steps up or down with the borrower’s measured emissions performance, are the contractual form this pressure increasingly takes, turning the disclosure score into a cash cost on the borrower’s interest line. A ship that cannot attract competitive finance and cannot attract climate-conscious charterers loses value, which is the transition-risk channel that links a soft disclosure framework to a hard number on a ship’s balance sheet.
The Poseidon Principles for Marine Insurance: the third side of the loan
The lending and chartering schemes are the two best known, but they are not the only place capital touches the same ship. Six marine insurers launched the Poseidon Principles for Marine Insurance on 15 December 2021: Swiss Re, Gard, Hellenic Hull Management, SCOR, Victor International, and Norwegian Hull Club, with brokers and trade bodies as affiliate members. The scheme is the insurance analog of the finance framework, applying to hull and machinery portfolios rather than loan books, and it asks the same question of an underwriter that the original Principles ask of a lender: how does the carbon intensity of the ships you cover stack up against the IMO-aligned trajectory.
The mechanism is identical in spirit. A signatory insurer measures the climate alignment of its hull and machinery portfolio against the same trajectory the lenders use, and discloses it annually, so a ship that fails the trajectory now sits inside a third disclosure that an underwriter must publish, alongside the loan a bank discloses and the voyage a charterer discloses. The insurance side reaches ships the lending side can miss, because a vessel financed by an unsigned lender or owned outright can still need hull cover from a signatory underwriter. The three schemes together close more of the gap than any one alone: a ship that escapes the bank can still be caught by the charterer or the insurer, and the December 2025 expansion of the finance side to unsecured and associate lenders was the same logic applied to the financing end.
The insurance scheme matters most for ships that fall outside the lending discipline. A vessel owned outright, financed by an unsigned regional bank, or carried on a lease still needs annual hull and machinery cover, and a signatory underwriter scoring its book picks up that ship where no Poseidon lender did. The reach is still partial: the marine-insurance signatory base is smaller than the finance one, and a ship insured in a market with no signatory underwriter sits outside it entirely. As with the lending and chartering sides, the discipline is disclosure rather than refusal, so an insurer can write cover for a misaligned ship and report the misalignment rather than decline the risk.
Why all five rest on one data backbone
The schemes look like five separate disciplines, but they draw on a shared data backbone, and that is why they line up rather than contradict one another. The IMO Data Collection System (DCS), mandatory since 2019, requires every ship above 5,000 GT on international voyages to report its annual fuel consumption, distance sailed, and hours under way to its flag administration, which forwards the data to the IMO. The EU Monitoring, Reporting and Verification (MRV) regulation collects a parallel verified dataset for ships calling at European ports. Those two reporting regimes are the raw material from which the AER, the CII, and a Poseidon or Sea Cargo alignment score are all computed, so a ship that reports honestly to the DCS has, in effect, already supplied the numbers every voluntary scheme needs.
That shared backbone is the quiet reason the schemes interlock so cleanly. The same fuel-and-distance figure that fixes a ship’s CII letter under the IMO rulebook fixes its AER under the finance schemes, and a discrepancy between the two would be visible to a verifier holding both. The Global Maritime Forum, which hosts the secretariats of both the Poseidon Principles and the Sea Cargo Charter, designed the two schemes to share the AER metric and the trajectory precisely so that a banker and a charterer scoring the same ship reach the same number. The cost of that consistency is the cost of the DCS itself: a ship that under-reports fuel to flatter its CII flatters its AER by the same amount, so a fraudulent figure helps the owner everywhere at once, which is why the third-party verification rate, over 90 percent on the charterer side, matters as much as the headline alignment.
One ship through every scheme
Trace a single vessel to see how the layers stack. Take a 75,000 deadweight-tonne Panamax bulk carrier built in 2011, financed by a Poseidon-signatory bank, hull-insured by a Poseidon marine insurer, and routinely chartered by a Sea Cargo Charter commodity house. The ship reports its 2024 fuel and distance to its flag under the DCS; that single dataset produces its CII letter for the IMO, its AER for the finance schemes, and the input to its RightShip rating speed correction. Say the figures put it at a CII grade D and an AER around 12 percent above the trajectory for its size and year.
That one set of numbers now bites in five places. The bank that financed it records the ship as a positive (misaligned) contributor to its portfolio alignment score and must publish that fact in next year’s Annual Disclosure Report. The hull underwriter does the same on its side. The Sea Cargo Charter commodity house, scoring the voyages it fixed on this ship, books the same misalignment against its own disclosure. The charterer’s vetting desk, pulling the ship up on the RightShip screen, sees a poor design letter that the speed-corrected 2.0 method will not let the owner fix by limiting power on paper. At the berth, the ship’s middling ESI score earns little or no rebate where a cleaner competitor collects one. None of these is a fine, and none is illegal, but together they raise the ship’s cost of capital, narrow its charter market, and shrink its resale value. The arithmetic that drives each of these sits in the cluster’s calculators: the climate alignment calculator and portfolio adherence calculator for the finance side, the RightShip GHG Rating calculator for the vetting letter, the ESI score calculator for the berth rebate, and the AER calculator and CII rating calculator for the common intensity figure underneath them all.
Limitations
This article maps how climate finance and GHG-rating schemes push ship decarbonization; it is not the rule text of any scheme, and the controlling document is always the scheme’s own published methodology and the contract a party signs. The Poseidon Principles and the Sea Cargo Charter trajectories are re-based as the IMO strategy and the underlying science move, so the alignment figures quoted here are from the 2025 disclosure reports and shift each year; the current trajectory and the current signatory list are the ones on the scheme’s own site, not a figure carried in prose. The AER is a capacity-based metric that penalizes low utilization and does not capture cargo actually carried, so a ship’s alignment score reflects its deadweight and distance, not the social value of the voyage.
The RightShip GHG Rating is a relative design metric scored against a moving peer group, so a ship’s letter can change without any change to the ship, and the A-to-E scale described here replaced the older A-to-G scale on 6 December 2023; a letter quoted from before that date is on the old scale. The ESI rebate is set port by port, so the threshold and the amount quoted here are common conventions, not a universal tariff, and the controlling figure is the individual port’s published ESI schedule. Voluntary carbon credits do not change a ship’s CII, EEXI, FuelEU, or EU ETS position; they live in the voluntary claim layer and must meet a high-integrity standard such as the Core Carbon Principles before they carry weight, and a credit that fails the additionality test offsets nothing. None of the linked calculators replaces a scheme’s own reporting tool, a verifier’s assessment, or a port’s tariff for a specific ship.
See also
- Poseidon Principles: the lending-side framework, the AER measurement, and the climate alignment score in detail.
- Voluntary carbon credits in shipping: the additionality, double-counting, and permanence tests, and the Core Carbon Principles.
- Decarbonization and alternative fuels: the parent hub for how shipping cuts its carbon intensity.
- IMO Net-Zero Framework and GHG Fuel Intensity: the regulatory machinery the finance trajectories are aligned to.
- Ship efficiency indices: the EEDI, EEXI, EVDI, and CII metrics the ratings are built on.
- What is CII: the operational carbon-intensity rating that runs alongside the design ratings.
- Poseidon Principles climate alignment calculator: scores a financed ship against the trajectory.
- Poseidon Principles portfolio adherence calculator: the exposure-weighted roll-up across a loan book.
- RightShip GHG Rating calculator: places a ship on the A-to-E design-efficiency scale.
- ESI score calculator: the Environmental Ship Index score and the port-fee rebate it earns.
- AER calculator: the Annual Efficiency Ratio that underlies both finance schemes.
- CII rating calculator: the operational carbon-intensity letter for a ship-year.