Black Carbon and Arctic Shipping

Background

What black carbon is, and what it is not

Black carbon isn’t a precise chemical species. It’s an operational class of carbonaceous aerosol, & the choice of definition decides what an instrument reports. The IMO faced this head-on. At its sixty-eighth session in May 2015, the Marine Environment Protection Committee agreed to use the definition from Bond et al (2013), a 232-author scientific assessment, because that definition is measurement-method neutral and is widely supported in the literature. Bond et al describe BC as a distinct type of carbonaceous material formed in flames during combustion of carbon-based fuels, set apart by four physical properties.

Those four properties are what separate BC from look-alikes. It strongly absorbs visible light, with a mass absorption cross-section of at least roughly 5 m2/g at 550 nm. It is refractory, retaining its form to a vaporization temperature near 4000 K. It is insoluble in water and in common organic solvents. And it exists as an aggregate of small carbon spherules. Material that fails any of these tests is something else.

That distinction matters for regulation, because three other terms get used loosely as synonyms. Total particulate matter (PM) is the whole filterable mass of the exhaust aerosol, of which BC is one fraction. Elemental carbon (EC) is a thermal-optical measurement quantity, close to BC but defined by the analysis protocol rather than by physical properties. Organic carbon (OC) is the weakly absorbing organic fraction of soot, which can even cool. A control measure written against PM or EC would not target the same material a BC-specific measure targets, so the IMO’s decision to anchor on Bond et al narrowed the policy object before any limit was discussed.

Black carbon as a climate forcer

Black carbon is the strongly light-absorbing carbonaceous component of fine particulate matter (PM2.5), formed from the incomplete combustion of carbon-containing fuels (diesel, HFO, biomass, coal). It is a primary emission, formed during combustion rather than from atmospheric chemistry, and is removed by wet and dry deposition with an atmospheric lifetime of roughly 5 to 11 days. That short lifetime is the whole point of treating BC as a near-term, regional forcer: cut the emission and the airborne burden clears within weeks, unlike CO2, which persists for centuries.

Bond et al put a number on the stakes. The best estimate of BC’s total industrial-era climate forcing through all mechanisms, including clouds and the cryosphere, is +1.1 W/m2 with a wide bound of +0.17 to +2.1 W/m2. The direct (atmospheric absorption) component alone is +0.71 W/m2 (+0.08 to +1.27). On that estimate BC is the second most important human emission for present-day climate forcing; only CO2 forces more. The wide uncertainty band, more than a factor of ten on the total, is itself a finding: it reflects how hard BC is to measure and to attribute, and it shadows every downstream policy number.

The climate impact of BC works through three mechanisms. Direct absorption: airborne BC absorbs incoming solar radiation and warms the surrounding air. Snow and ice albedo reduction: BC settling on snow or ice lowers the surface reflectivity, so the surface takes up more radiation and melts faster, an effect concentrated in the polar regions where snow and ice cover are extensive. Cloud effects: BC alters cloud microphysics through drop nucleation, the semi-direct effect, and indirect effects, with warming and cooling components whose net sign is the largest source of the +1.1 W/m2 uncertainty.

Translating BC mass into a CO2-equivalent figure requires a global warming potential, and the choice of time horizon changes the answer by more than threefold. The Fourth IMO GHG Study 2020 included the first official inventory of shipping BC and reported it at a GWP-100 of 900. On that basis, including BC raises the voyage-based international shipping GHG total for 2018 by 7%, to 810 million tonnes CO2e, and the CO2 share of the climate impact falls from 98% to 91%. Those are the figures the IMO itself uses when it weighs BC against the CO2-focused work of the IMO Net-Zero Framework.

On a 20-year horizon the weighting is far heavier. The ICCT inventory estimated global shipping emitted 67 thousand tonnes of BC in 2015, which on a GWP-20 basis is more than 20% of the sector’s CO2-equivalent emissions. The contrast between the GWP-100 share (single digits) and the GWP-20 share (over a fifth) is the reason BC policy splits along the choice of metric: the near-term framing makes BC a major lever, the century framing makes it a secondary one. Because BC clears within days, the near-term framing is the physically relevant one for Arctic ice that may pass a melt threshold this decade.

Marine BC emissions

Marine BC emissions vary by fuel type and by engine load. Typical emission factors (g-BC per kg-fuel) under steady-state operation:

The figures above are representative; wide variation is observed between engines, with engine wear, operating profile, and fuel composition. The ICCT has compiled the marine BC inventory used as the basis for IMO and EU policy discussions, and its engine-test programme is the most-cited evidence on how fuel and load drive the emission factor.

The fuel-type result, and why VLSFO is not the answer it looks like

The intuitive ranking holds at typical loads: distillate is the cleanest. ICCT engine tests measured distillate (13 ppm sulphur), high-sulphur HFO (about 32,000 ppm S, 3.2% S), and a desulphurised residual oil (13 ppm S), and found distillate BC emission factors roughly 40 to 50% lower than residual on four-stroke engines and about 80% lower than residual on two-stroke engines, across the 25% to 75% load band that covers most service operation.

The complication is the 0.5% sulphur residual blend that dominated the fleet after the IMO 2020 sulphur cap. The same ICCT work found a 0.5% S residual blend emitted less BC than HFO at 75% load but more BC than HFO at 25% load. One proposed explanation is that the metallic compounds in HFO help complete combustion at low load, an effect the cleaner blend lacks. The practical reading is uncomfortable: switching from HFO to a compliant 0.5% S residual fuel, the cheapest route to sulphur compliance, can raise BC at the low loads typical of ice navigation and manoeuvring. A fuel switch reduces BC only if it goes all the way to distillate or a genuinely paraffinic product, not merely to a low-sulphur residual blend. That finding is the technical core of the case for a distillate-specific Arctic measure rather than a sulphur-specific one, since emission control areas target sulphur, not BC.

Hot-spot operating conditions

BC emissions are concentrated at certain operating conditions:

• Cold start: high BC during the warm-up period when cylinder walls are cold and combustion is incomplete.
• Low load: high BC at part load (typically 25 to 50% MCR) due to longer combustion duration and cooler cylinder temperatures.
• Transient operation: high BC during rapid load changes, particularly load increases.
• Aging engine: progressively higher BC as injection nozzles wear and combustion deteriorates.
• Poor fuel quality: HFO with high asphaltenes, high sulphur or high heavy-metals content tends to produce more BC than well-refined VLSFO or distillate.

For Arctic shipping, the time spent in port (cold-start emissions) and the tendency to operate at low to moderate load (manoeuvring through ice) means that the operational BC emission rate per kg-fuel is typically 30 to 60% higher than the steady-state design value.

The Arctic-specific concern

Arctic warming and the BC role

The Arctic is warming approximately 3 to 4 times faster than the global average (the “Arctic amplification”). The principal drivers of Arctic amplification are:

• Sea ice albedo feedback: as sea ice retreats, the darker ocean below absorbs more incoming radiation, accelerating warming and further sea-ice loss.
• Atmospheric water vapour and cloud feedbacks.
• Reduced atmospheric heat loss to space in the autumn, when warmer ocean retains heat longer.
• Black carbon deposition on snow and sea ice: BC deposition reduces albedo and accelerates melt.

The BC contribution to Arctic warming is estimated at approximately 17 to 25% of the total Arctic warming since 1900 (AMAP - Arctic Monitoring and Assessment Programme), making it the second-largest contributor after CO2 (approximately 60 to 70%).

Marine BC contributes a small but rapidly-growing share of total Arctic BC deposition, currently approximately 1 to 5% but projected to grow to 5 to 15% by 2050 if the Northern Sea Route (NSR) and Northwest Passage (NWP) traffic grows as forecast and if emission controls remain unchanged.

The Northern Sea Route

The Northern Sea Route (NSR) is the shipping route along the Russian Arctic coast from the Bering Strait to Murmansk. Annual transit traffic has grown from approximately 4 vessels in 2010 to approximately 30 to 40 transit vessels in 2024 (excluding the much larger Russian domestic shipping). Western sanctions on Russia following the 2022 Ukraine invasion temporarily reduced NSR traffic but recent quarters show recovery as Russian and Chinese-led traffic has substituted.

The NSR offers significant distance savings versus the Suez Canal route for trades between East Asia and Europe (approximately 40% reduction in voyage distance). The principal constraints on NSR uptake are: ice conditions (reliable ice-free transit only July to October), nuclear icebreaker escort fees, Polar Code compliance requirements, and political constraints associated with Russian sovereignty assertions.

The Northwest Passage

The Northwest Passage (NWP) through the Canadian Arctic Archipelago is shorter than the NSR and is open seasonally for approximately 8 to 10 weeks per year. Commercial traffic remains very limited (typically under 10 transits per year for cargo) due to the difficulty of ice navigation and the limited support infrastructure.

Arctic shipping growth projections

DNV’s Maritime Forecast to 2050 (2023) projects:

• NSR traffic: 50 to 200 transits per year by 2030, 200 to 800 by 2050.
• NWP traffic: 10 to 50 transits per year by 2030, 50 to 200 by 2050.
• Other Arctic traffic: cruise vessels, fishing vessels, scientific vessels, regional cargo. Significant growth driven by tourism and resource extraction.

The growth is sensitive to climate-warming pace (faster warming opens routes for longer per year) and to geopolitical conditions (Russia-NATO relations, China-Western relations, Arctic Council functionality).

Regulatory framework

Polar Code

The International Code for Ships Operating in Polar Waters (Polar Code), adopted by IMO Resolution MSC.385(94) and MEPC.264(68), entered into force on 1 January 2017. The Polar Code is a structured framework covering:

• Part I-A (Safety): mandatory safety provisions including ship structure, stability, machinery, fire safety, life-saving appliances, navigation, radio communication, voyage planning.
• Part I-B (Safety): recommendatory safety provisions.
• Part II-A (Environmental): mandatory environmental provisions covering oil discharge, noxious liquid substance discharge, garbage discharge.
• Part II-B (Environmental): recommendatory environmental provisions.

The Polar Code applies to vessels operating in Polar waters (defined as waters above 60° N for Arctic and 60° S for Antarctic, with some exceptions). Vessels are categorised as Category A (designed for ice up to 0.7 m thickness in winter), Category B (lighter ice) or Category C (occasional ice contact only).

The Polar Code includes a Polar Ship Certificate, a Polar Water Operational Manual, ice-strengthened hull requirements, additional life-saving equipment, voyage planning provisions, and crew training (additional STCW certification for ice navigation).

The Polar Code did not initially include BC controls; the BC discussion has been a parallel and ongoing IMO process.

The Arctic HFO ban: MARPOL Annex I Regulation 43A

The first binding Arctic measure with BC consequences sits in MARPOL Annex I, not Annex VI. Resolution MEPC.329(76), adopted on 17 June 2021, amended the title of Annex I chapter 9 to “Special requirements for the use or carriage of oils in polar waters” and added a new Regulation 43A, “Special requirements for the use and carriage of oils as fuel in Arctic waters.” The amendments were deemed accepted on 1 May 2022 and entered into force on 1 November 2022, with the operative prohibition applying from 1 July 2024.

The regulation defines the banned oils by reference to regulation 43.1.2, the same category used for the Antarctic: oils with a density above 900 kg/m3 at 15 degrees C or a kinematic viscosity above 180 mm2/s at 50 degrees C. So the ban is a physical-property ban, not a sulphur ban, and it captures conventional HFO.

The dates and carve-outs are specific:

• From 1 July 2024: the use and carriage for use as fuel of the listed oils is prohibited in Arctic waters (as defined in regulation 46.2 of Annex I), except for ships engaged in securing the safety of ships or in search and rescue operations, and ships dedicated to oil spill preparedness and response.
• From 1 July 2029: ships fitted with protected fuel tanks under regulation 12A of Annex I, or under regulation 1.2.1 of chapter 1 of part II-A of the Polar Code, must also comply. Until then their double-hull protection earns a deferral, on the logic that the spill risk is lower.
• Coastal-state waiver to 1 July 2029: a Party whose coastline borders Arctic waters may temporarily waive the requirement for ships flying its flag while they operate in waters under that Party’s sovereignty or jurisdiction. No waiver may apply on or after 1 July 2029, and the Party must notify the IMO of each waiver.

Regulation 43A also states that where prior operations used the listed oils as fuel, cleaning or flushing of tanks or pipelines is not required, which lowers the changeover cost. The combination of the 2029 deferral and the coastal-state waiver is why the Clean Arctic Alliance and several Arctic states have criticised the in-force date as leaving most Arctic HFO use legal for years: a large share of the HFO-burning fleet in Russian Arctic waters can fall under the waiver until mid-2029.

The HFO ban is principally an oil-spill-risk measure. Its BC effect is a co-benefit and an indirect one: it forces operators off HFO, but the ICCT result above means the BC benefit is realised only if the replacement is distillate rather than a 0.5% S residual blend. A switch from HFO to a low-sulphur residual blend can leave Arctic BC unchanged or higher at low load. So the headline “HFO ban cuts BC” claim is conditional on the fuel chosen to replace it.

The policy gap: no mandatory black carbon control measure

There is still no IMO regulation that limits BC directly. The PPR Sub-Committee has worked on the question since 2011, adopted the Bond et al definition in 2015, agreed the three candidate measurement methods, and discussed control options. But the only operative output is recommendatory. The IMO has encouraged ships operating in or near the Arctic to switch voluntarily to distillate or other cleaner alternative fuels, and to consider goal-based control measures. None of that is enforceable.

That leaves three reasons BC remains uncontrolled where CO2, sulphur, and increasingly methane are regulated. First, the metric problem: a GWP-100 framing makes BC a 7% issue while a GWP-20 framing makes it a 20%-plus issue, and the IMO has not settled which horizon governs. Second, the measurement problem: until a single reference method with a stated uncertainty is agreed, a numeric emission limit cannot be enforced fairly, since two compliant instruments could disagree. Third, the fuel paradox: the obvious lever, a fuel switch, only works if it reaches distillate, which raises cost and bumps against the same operators the classification society survey regime already stretches in remote waters. A future mandatory measure would most plausibly take the form of a distillate-fuel requirement in defined Arctic areas, an engine BC limit verified by one of the three methods, or both, folded into MARPOL Annex VI. Until then, Arctic BC control is voluntary.

EU and US measures

The EU AFIR Regulation (Alternative Fuel Infrastructure Regulation) for shore power and the EU Deforestation-free Products Regulation indirectly affect Arctic shipping but do not specifically target BC.

The US Environmental Protection Agency (EPA) Tier 4 marine emission standards for new vessel engines (in force from 2014 for engines below certain size thresholds) include particulate matter (PM) limits that effectively control BC. The standards do not extend to large slow-speed two-stroke engines (which dominate the Arctic-operating cargo fleet).

The CARB (California Air Resources Board) rules apply within California state waters and do not extend to Arctic operations.

Voluntary frameworks

The Clean Arctic Alliance (a coalition of NGOs including FUTURE - Fund for the Environment, ICC - Inuit Circumpolar Council, Pacific Environment) has campaigned for Arctic BC controls and for HFO bans since approximately 2017. Several Arctic Council member states (Norway, Sweden, Finland, Canada, USA - inconsistently) have supported the Clean Arctic Alliance positions at IMO.

The Poseidon Principles and Sea Cargo Charter include BC in their environmental scoring but with relatively limited weighting compared to CO2.

Mitigation technologies

Distillate fuel

The simplest and most cost-effective BC mitigation is to switch from HFO or VLSFO to MGO or distillate fuel (LSMGO 0.1% S, ULSMGO 0.001% S). The fuel switch reduces BC emission factor by approximately 50 to 80% versus HFO, with no engine modification required.

The fuel cost premium of MGO vs HFO is typically USD 100 to USD 250/t (variable with crude oil and refinery margin). For an Arctic-operating Capesize bulker burning 35 t-fuel/day for 60 days/year in the Arctic, the additional fuel cost is approximately USD 200,000 to USD 500,000 per year.

Diesel particulate filter (DPF)

A diesel particulate filter is a ceramic or metal filter that physically traps particulate matter (including BC) in the exhaust stream. Marine DPFs are commercially available from several vendors (Boll Group, Hug Engineering, IBIDEN, Nett Technologies, NoNox) and achieve typical 90 to 99% BC reduction.

DPF performance and cost:

• BC reduction: 90 to 99%.
• Pressure drop: typically 1 to 3 kPa, equivalent to 0.5 to 1.5% additional fuel consumption.
• Sulphur sensitivity: requires LSMGO or ULSMGO operation; DPF lifetime is severely shortened by HFO or VLSFO operation.
• Capital cost: USD 100,000 to USD 400,000 per engine depending on engine power.
• Periodic regeneration: required to burn off accumulated soot; achieved by raising exhaust temperature (active regeneration) or by adding fuel-borne catalysts (passive regeneration).

DPFs are widely deployed on land-based heavy-duty diesel applications (trucks, locomotives) since approximately 2007. Marine DPF deployment is at approximately 50 to 200 vessels in 2024, principally smaller vessels operating in low-emission zones. Larger marine engines (slow-speed two-stroke) face more challenging DPF applications because the larger exhaust volumes require larger DPF systems.

Engine combustion redesign

Engine manufacturers have refined combustion design to reduce BC at source. The principal levers are:

• Higher injection pressure: better fuel atomisation reduces BC formation.
• Common-rail injection: variable injection timing and pressure permits optimisation across operating conditions.
• Multi-pulse injection: fuel injected in multiple pulses to allow better mixing.
• Combustion chamber geometry: chambers designed to maintain longer high-temperature residence reduce BC.

These approaches collectively reduce BC by approximately 20 to 50% versus older designs. Modern Tier III-compliant engines have lower BC emissions than older Tier I or Tier II engines, even before accounting for any aftertreatment.

LNG, methanol, ammonia conversion

The fundamental BC mitigation is to switch to a fuel that does not produce significant BC. LNG (essentially methane), methanol and ammonia all produce near-zero BC when properly combusted.

For Arctic operations, the conversion to LNG provides BC mitigation alongside the avoided HFO use under the 2024 ban. Arctic LNG bunker availability is currently limited (a small number of LNG bunker barges in Murmansk and Sabetta); expansion is ongoing.

For biofuels, particularly biodiesel (FAME) and hydrogenated vegetable oil (HVO), BC emissions are typically 20 to 50% lower than petroleum diesel due to the oxygen content of the biofuel improving combustion. Biodiesel blends are increasingly used as a partial BC mitigation.

Operational measures

Several operational measures reduce BC without hardware modification:

• Avoid low-load operation: BC is concentrated at part load. Operators can consolidate loads onto fewer engines at higher load.
• Avoid cold starts: significant BC is emitted during engine warm-up. Operators can use shore power (where available) or auxiliary heating to reduce cold-start emissions.
• Maintain engine condition: worn injectors and turbochargers increase BC. Regular maintenance reduces in-service BC.
• Use high-quality fuel: well-refined VLSFO with low asphaltene content produces less BC than poorly-refined HFO.

These measures collectively deliver 10 to 30% BC reduction; useful but not transformative.

Measurement methodology

Measuring marine BC is harder than measuring CO2 or methane, and the difficulty is the gate on any numeric regulation. CO2 follows directly from fuel carbon and fuel mass. BC does not: it depends on combustion conditions that vary with load, fuel, and engine state, and the measurement quantity itself depends on the instrument principle. The PPR Sub-Committee narrowed the field to three candidate methods and has run a correspondence group on a standardised sampling, conditioning, and measurement protocol, including a traceable reference method and an uncertainty analysis covering all three. Those three are the methods any future Arctic BC limit would be verified against.

Filter Smoke Number (FSN)

FSN is the oldest and cheapest of the three. A measured volume of exhaust is drawn through a clean filter paper, and the darkening of the paper is read optically and reported as a Filter Smoke Number on a standard scale. It’s the method behind most existing marine BC emission-factor data, because smoke meters were already standard engine-test equipment long before BC became a regulatory term. The strength is availability and low cost; the weakness is that FSN is a soot-darkening proxy that must be converted to BC mass through an empirical correlation, and that correlation drifts with fuel type and particle properties.

Photo-Acoustic Spectroscopy (PAS)

PAS measures absorption directly rather than collecting particles. A modulated laser beam passes through the aerosol; BC absorbs the light, heats, and the periodic heating generates a pressure (sound) wave that a microphone detects. The signal is proportional to absorbed light, which is the physical property that makes BC a climate forcer, so PAS measures something close to the policy-relevant quantity. ICCT and other work has found good agreement between FSN and PAS, which is why both stay in the candidate set.

Laser-Induced Incandescence (LII)

LII heats individual soot particles with a high-intensity laser pulse until they incandesce, then measures the thermal-radiation signal, which scales with refractory (elemental) carbon mass. Because it keys on the refractory property, LII is conceptually aligned with the Bond et al definition. It correlated well in the IMO-relevant comparisons, but with more limited experimental data than FSN or PAS, so its track record on marine exhaust is thinner.

How close the three agree

The instrument-comparison work behind the IMO discussion found BC concentrations from the different methods clustered together, with standard deviations between instruments typically in the range of 5 to 15% at BC concentrations below about 30 mg per standard cubic metre. That is tight enough to support a protocol but not so tight that a numeric limit could ignore the spread. A regulation setting a single emission limit would have to state which method is the reference and what tolerance applies, or two technically compliant ships could be ranked differently by two compliant instruments. The unresolved reference-method question is one reason no BC limit has yet been adopted.

Spot measurement versus modelled estimation

For owners not running continuous instruments, periodic spot measurement at engine commissioning and at surveys is the practical route, against the protocol the PPR group is developing. The lowest-cost and lowest-accuracy route is engine-modelled estimation: combining engine bench-test BC data with the vessel’s operating profile. Modelled estimates are adequate for inventory work, like the ICCT and IMO studies, but they’re too coarse to verify a per-ship limit, which is part of why a mandatory measure needs the measurement protocol settled first.

Implications for Arctic-operating owners and charterers

Owners

Owners of Arctic-operating vessels face a regulatory environment that is rapidly tightening: the 2024 HFO ban, the 2029 HFO carriage ban, and the upcoming MEPC 84 BC measure. The principal owner decisions are:

1. Fuel switch: from HFO to MGO/distillate is the most immediate compliance step. Cost: USD 100,000 to USD 500,000 per Arctic season per vessel.
2. DPF retrofit: 90 to 99% BC reduction, USD 100,000 to USD 400,000 per engine plus operational costs. Decision sensitive to the final form of the MEPC 84 BC measure.
3. LNG conversion: most aggressive BC mitigation but USD 5 to USD 30 million per vessel for conversion. Justified for vessels with significant Arctic operating profile.
4. Polar Code compliance: ongoing requirement for ice-strengthened hull, ice navigator certification, additional safety equipment.
5. Charter avoidance: some owners may exit the Arctic charter market if compliance costs exceed the freight premium.

Charterers

Arctic charterers (notably Russian-based oil and gas exporters, Chinese state importers, and a small number of European bulk shippers) face indirect cost passthrough as owner compliance costs increase. The charter premium for Arctic operations is being discounted upward to reflect the new costs.

Insurers

Marine insurers (P&I clubs and hull underwriters) have begun applying Arctic-specific premiums reflecting the elevated environmental and reputational risk of Arctic shipping. The combination of Polar Code compliance, BC controls, and the broader oil-spill risk drives the Arctic premium structure.

Banks and finance

Ship-finance banks signed up to the Poseidon Principles report Arctic shipping exposure separately as part of their portfolio reporting, reflecting the elevated climate-impact-per-fuel-burnt of Arctic operations.

Future outlook

The shape a mandatory measure would take

If the IMO does move from voluntary encouragement to a binding BC measure, the design space is already mapped from the PPR work, and three contested choices would set the cost.

Geographic scope is the first. A “true Arctic” line (above 70 degrees N, say) captures the highest-sensitivity ice surfaces but exempts much of the sub-Arctic shipping that deposits BC onto the same air mass; a polar-waters line (above 60 degrees N, matching the Polar Code) captures far more traffic at far higher fleet cost. The second is the compliance pathway: a distillate-fuel requirement is simple to verify (check the bunker delivery note and tank samples) and sidesteps the measurement problem entirely, while an engine emission limit needs the reference method settled but lets owners keep residual fuel if they fit aftertreatment. The third is the new-versus-existing question: applying a limit only to newbuilds is cheap and slow, applying it to the existing fleet is expensive and fast, and the Arctic-operating fleet skews old.

A distillate requirement in a defined area is the lowest-friction option because it reuses the bunkering paperwork that already supports the sulphur regime, and it directly answers the ICCT finding that only a full switch to distillate guarantees a BC cut. That is the option the Clean Arctic Alliance has pressed. Whichever path is chosen, it would most plausibly be folded into MARPOL Annex VI and move through the standard amendment cycle, so an in-force date trails adoption by at least the tacit-acceptance period the HFO ban itself illustrates: adopted June 2021, in force November 2022, operative July 2024.

Continued NSR growth

If geopolitical conditions permit (Russia-China cooperation continues, Western sanctions ease), NSR traffic may grow more rapidly than the DNV central case, increasing the Arctic BC concern. The Arctic Council framework (currently impaired by Russia’s exclusion) is the principal multilateral forum for managing the growth.

Additional Arctic protections

The Clean Arctic Alliance and several Arctic Council member states are advocating for additional Arctic-specific protections including:

• Heavy fuel oil ban for transit through the Arctic (extending the use ban to include transit-only vessels).
• Speed limits in defined Arctic areas to reduce both BC emissions and underwater noise.
• Mandatory pilotage in defined Arctic areas.
• Ban on HFO carriage as cargo through Arctic (currently the ban is for fuel only, not for cargo).

Convergence with greenhouse-gas frameworks

The Arctic BC work runs in parallel with the IMO Net-Zero Framework and FuelEU Maritime, both CO2-focused. Folding BC into those frameworks at the 4th GHG Study’s GWP-100 of 900 would raise its policy weight from the 7% it carries on a CO2-equivalent basis, and a GWP-20 weighting would raise it much further. The metric choice, not the science, is the live policy question, and it interacts with the same near-term-versus-century-horizon debate that shapes how methane is counted alongside CO2 in the methane-slip and N2O discussions.

Limitations

The figures and rules here come with practitioner caveats. Treat them as the boundaries of the claims, not footnotes.

The radiative-forcing and GWP numbers carry a factor-of-ten uncertainty band. Bond et al’s central +1.1 W/m2 spans +0.17 to +2.1, and the GWP-100 of 900 used by the Fourth IMO GHG Study is one point estimate inside a wide range driven mainly by the cloud-interaction term. Any per-vessel CO2-equivalent figure built on a single GWP should be read as order-of-magnitude, and the answer changes by more than threefold between the 20-year and 100-year horizons. Quote the horizon every time, because a BC tonne is a 7% issue or a 20%-plus issue depending on it.

Emission factors are not transferable between engines without measurement. The fuel-and-load results are from specific ICCT test engines on specific fuels; the direction (distillate cleaner than residual at service loads, the 0.5% S blend worse than HFO at low load) holds across the tests, but the magnitudes shift with engine design, injection condition, turbocharger match, and engine age. An operator planning a fuel switch for BC reasons should verify on the actual machinery, not assume a table value, and should not assume any low-sulphur residual blend cuts BC at the low loads typical of ice operation.

The measurement methods don’t yet agree closely enough for a fair numeric limit. FSN, PAS, and LII cluster within roughly 5 to 15% at low concentration, but FSN is a darkening proxy needing fuel-dependent conversion, PAS keys on absorption, and LII keys on refractory mass, so the three measure related but not identical quantities. Until the IMO settles a single reference method and stated uncertainty, BC numbers from different instruments are not directly comparable, and no enforceable emission limit can be set on them.

The Regulation 43A HFO ban is narrower than it sounds. It bans use and carriage for use as fuel of high-density, high-viscosity oils from 1 July 2024, but protected-tank ships have until 1 July 2029, and Arctic coastal states can waive the requirement for their own flag ships in their own waters until the same date. A large part of the Russian Arctic fleet can keep burning HFO under the waiver through mid-2029. The ban also targets oil-spill risk, not BC, so its BC benefit is conditional on the replacement fuel being distillate, not a residual blend.

There is no mandatory BC control measure, and this article does not predict one. The IMO position is voluntary fuel-switch encouragement plus continuing technical work. Statements about what a future measure might look like are inferences from the published PPR options, not from an adopted instrument, and no in-force date for a BC measure exists.

Finally, the geographic and traffic numbers for the Northern Sea Route and Northwest Passage are sensitive to climate pace and to geopolitics that lie outside any emission model. Route-opening forecasts and transit counts should be read as scenario-dependent, not as fixed planning inputs.

See also

Additional calculators:

• Filter Smoke Number \u2192 Black Carbon
• Marine Black Carbon Calculator
• Marine Engine PM Calculator - PM10 / PM2.5
• HFO Well-to-Wake Calculator

Additional formula references:

• Imo Polar Code
• Polar Ops Ice Class Light Ice

Additional related wiki articles:

• Polar Code

Marine fuels

• LNG as marine fuel
• LNG fuel system
• Methanol as marine fuel
• Ammonia as marine fuel
• Biofuels in shipping
• Heavy fuel oil
• Marine gas oil
• Well-to-wake intensity
• RFNBO under EU rules
• Methane slip from LNG dual-fuel
• N2O emissions from marine engines

Engines, exhaust and machinery

• Marine diesel engine
• Marine gas turbine
• Marine propeller
• Exhaust gas cleaning system
• Bow thruster and stern thruster

Regulatory and reporting frameworks

• MARPOL Annex VI
• IMO Net-Zero Framework
• IMO GHG Strategy
• EEXI, EPL and ShaPoLi
• SEEMP I, II, III
• CII corrective action plan
• EU MRV Regulation
• EU ETS for shipping
• FuelEU Maritime
• FuelEU penalties, pooling and multipliers
• UK ETS for shipping
• China DCS
• IMO DCS vs EU MRV
• CARB at-berth rule
• Emission control areas
• NOx Tier I, II, III
• IMO 2020 sulphur cap

Voluntary frameworks

• Poseidon Principles
• Sea Cargo Charter
• RightShip GHG Rating
• Green Shipping Corridors
• BIMCO CII clauses
• EUA market mechanics for shipping
• Voluntary carbon credits in shipping

Operational and technical efficiency

• Wind-assisted propulsion
• Air lubrication systems
• Just-in-time arrival
• Weather routing
• Trim optimisation
• Slow steaming
• Bulbous bow retrofits
• Energy-saving devices
• Battery-hybrid propulsion
• Onboard carbon capture
• Cold ironing / shore power

Hydrostatics, stability and ship types

• Hull form design
• Block coefficient
• Hydrostatics and Bonjean curves
• Trim and list
• Metacentric height
• Free surface effect
• Intact stability
• Damage stability
• Ship resistance and powering
• Bulk carrier
• Container ship
• Chemical tanker
• LNG carrier
• General cargo ship

Conventions, codes and class

• SOLAS Convention
• MARPOL Convention
• Ballast Water Management Convention
• Hong Kong Convention
• COLREGs Convention
• ISM Code
• ISPS Code
• Classification society

Calculators

• Black carbon emission factor calculator
• Arctic BC deposition calculator
• BC GWP equivalency calculator
• DPF retrofit savings calculator
• Polar Code compliance calculator
• WtW intensity calculator
• GFI compliance calculator
• SEEMP Measures Combined calculator
• EEXI Required calculator
• CII Attained calculator
• Calculator catalogue

References

• IMO Resolution MEPC.329(76): Amendments to MARPOL Annex I (HFO use and carriage in the Arctic). International Maritime Organization, 2021.
• IMO Resolution MSC.385(94) and MEPC.264(68): International Code for Ships Operating in Polar Waters (Polar Code). International Maritime Organization, 2014/2015.
• IMO PPR 9 and PPR 10: Outcome documents on the development of the Arctic black carbon measure. International Maritime Organization, 2022/2023.
• Bond, T. C. et al. Bounding the role of black carbon in the climate system: A scientific assessment. Journal of Geophysical Research, 2013.
• AMAP. Arctic Climate Change Update 2021: Key Trends and Impacts. Arctic Monitoring and Assessment Programme, 2021.
• ICCT. Black Carbon Emissions from International Shipping. International Council on Clean Transportation, 2017.
• ICCT. Black Carbon Emission Inventory and Reduction Potential for the Arctic. International Council on Clean Transportation, 2022.
• Clean Arctic Alliance. The Need for an Arctic Black Carbon Standard. Clean Arctic Alliance, 2023.
• DNV. Maritime Forecast to 2050. DNV Energy Transition Outlook, 2023.
• IPCC. Sixth Assessment Report (AR6). Intergovernmental Panel on Climate Change, 2021/2022.

Further reading

• AMAP. Arctic Marine Ship-Source Pollution Assessment. Arctic Monitoring and Assessment Programme, 2024.
• US EPA. Arctic Black Carbon Strategy. United States Environmental Protection Agency, 2022.
• ICS. Catalysing the Fourth Propulsion Revolution. International Chamber of Shipping, 2022.
• IRENA. A pathway to decarbonise the shipping sector by 2050. International Renewable Energy Agency, 2021.

Related calculators

• IMSBC - Carbon Black
• UK ETS Shipping Liability
• System - Immersion Suit: Polar / Arctic
• IMSBC - Activated Carbon
• IGC - Carbon Dioxide (liquefied)
• IBC - Carbon Tetrachloride
• MCR - Micro Carbon Residue Assessment
• Shipping - Asset Depreciation Schedule

Related formulas

• IMSBC - Carbon Black
• Black Carbon
• uk ets shipping
• System - Immersion Suit: Polar / Arctic
• IMSBC - Activated Carbon
• IGC - Carbon Dioxide (liquefied)
• IBC - Carbon Tetrachloride
• MCR - Micro Carbon Residue Assessment
• Filter Smoke Number → Black Carbon