The Strait of Hormuz has been closed since 28 February 2026, causing one of the most significant disruptions to maritime energy trade in recent years. Roughly a quarter of the world’s seaborne oil flows and a fifth of global LNG trade typically pass through the strait, and the ongoing disruption has triggered energy price spikes and wider supply chain pressures (EIA, 2025; IEA, 2026).
Major shocks to shipping also affect maritime transport emissions: idle vessels burn less fuel, while vessels rerouted onto longer, less efficient routes burn more (De Queljoe et al, 2025).
The OECD’s experimental Maritime Transport CO2 emissions database tracks CO2 emissions for the global fleet, with breakdowns by vessel-type and by country. In this article, we use these data to examine how the current crisis has reshaped the emissions profiles of oil and Liquefied Natural Gas (LNG) tanker fleets most directly affected. We also take a port of departure perspective to show how rerouting can alter the geographic distribution of emissions. Countries with pipeline access can partially bypass the disruption, while others remain fully exposed and see sharper declines in shipping activity and emissions.
Impact on large oil and gas tanker emissions
Using vessel-level CO₂ estimates derived from AIS tracking data combined with ship-specific technical characteristics, we quantify the emissions impact across the two tanker classes most directly affected by the closure: Very Large Crude Carriers (VLCCs), the largest oil tankers on the water; and Q-Flex and Q-Max LNG carriers, the largest LNG vessels in the world, purpose-built for Qatar’s export trade, one of the world’s largest LNG exporters.
Figure 1 tracks daily CO₂ emissions from the global fleets of each class, smoothed with a 7-day moving average. The grey shaded area marks the post-closure period, from 1 March to 31 May 2026, based on the latest available data at the time of writing. Each panel overlays 2026 data (orange line) on top of the same calendar period in 2025 (blue line). This comparison helps distinguish the effect of the closure from past patterns.
Figure 1. CO2 emissions for global tanker fleets; 7-day moving average
Note: The shaded area marks the post-closure period covered in the data, from 1st March to 31st May 2026, based on the latest available data at the time of writing.
Prior to the closure, 2026 emissions closely followed those recorded in 2025 across both fleets. Within the post-closure period, emissions for both fleets declined sharply at first but their paths then diverged: VLCC emissions followed a W-shaped pattern, rebounding through May after a second trough in late April, while large LNG tanker emissions remained near their lows. The magnitude of the contraction also differs across the two vessel types: while VLCC emissions fell by 14% on a year-on-year basis during the post-closure period, emissions from large LNG carriers fell by around 45% (see Table 1 below). At its lowest point, daily LNG tanker emissions were about 60% below their pre-closure peak.
Table 1. Emissions changes for VLCC and large LNG carriers, year-on-year, pre- and post-closure
| VLCC Oil Tankers | Large LNG Tankers |
|---|---|---|
Pre-closure YoY (1 Jan – 28 Feb) | +0.8% | –3.1% |
Post-closure YoY (1 Mar – 31 May) | –13.4% | –44.9% |
Peak-to-trough decline | –19.2% | –59.6% |
Note: VLCC comprise oil tankers with a capacity of 200,000 deadweight metric tonnes or greater. Large LNG tankers have a capacity of 200,000 cubic metres or greater.
Why have LNG tanker emissions fallen so much further?
The sharper decline in CO₂ emissions from large LNG tankers reflects structural differences between the crude oil and LNG export systems.
Some crude oil exports from the Gulf can bypass the Strait of Hormuz via overland pipelines. The International Energy Agency (IEA) notes that Saudi Arabia’s pipeline to the Red Sea and the UAE’s pipeline to the port of Fujairah have a combined capacity of 3.5-5.5 million barrels per day (mb/d), enough to reroute around one-fifth of the oil that was flowing through the strait before the closure (IEA, 2026). The VLCC fleet is also relatively flexible: when Gulf loading ports became inaccessible, some vessels re-positioned to load crude oil from producers in West Africa and the Americas (Kpler, 2026).
By contrast, Qatar’s LNG system has far less flexibility. Unlike crude oil, its LNG cannot be rerouted via long-distance pipelines, leaving maritime shipment as the only viable export option. Moreover, apart from limited deliveries to Kuwait, all Qatari LNG exports pass through the Strait of Hormuz. To compound matters, Qatar’s Ras Laffan facility, the main site of LNG production, sustained damage during the conflict. In addition, the Q-Flex and Q-Max fleet that carries Qatar’s gas are built exclusively for this trading operation. Contracted to QatarEnergy LNG, these ships are effectively tied to one terminal and one route through the strait. With both the facility and the route shut down, the fleet is largely idle, generating only minimal emissions associated with auxiliary operations.
Alternative routes and uneven impacts across Gulf exporters
The presence or absence of overland infrastructure shapes how Gulf producers can sustain or reroute shipments when access to the Strait of Hormuz is disrupted. These differences are reflected in shipping activity and, in turn, in CO2 emissions across Gulf exporters.
Shifting to a regional perspective allows for a closer examination of voyages directly affected by the closure. It is worth noting, however, that these estimates are experimental and subject to measurement errors inherent in the AIS-based methodology, including signal loss from interference and gaps in receiver coverage (Clarke et al, 2023). In the current context, these underlying issues have been compounded by a marked deterioration in data reliability across the region. GPS jamming affected a large number of vessels across the Persian Gulf and the Gulf of Oman in early March (Windward, 2026) while an increased number of vessels turned off their AIS transponders or broadcast false positions. Therefore, emissions estimates for the region should be interpreted with caution. Nevertheless, the data retains sufficient analytical value to identify broad patterns of disruption and cross-country differences.
Figure 2 shows emissions from VLCCs and large LNG tankers exiting the Persian Gulf, which contracted sharply as vessels found themselves stranded and unable to transit to international markets. Compared with the same period in 2025, outbound tanker activity effectively collapsed after the closure. By late April, large LNG tanker activity had ceased almost entirely, though early signs of recovery began to emerge in May. Over the same period, VLCC emissions had fallen to less than 1% of their 2025 level. Throughout the analysed post-closure period, cumulative VLCC and large LNG tanker emissions were only 9% and 11% of comparable 2025 levels, respectively.
Figure 2. CO2 emissions for vessels exiting the Persian Gulf; 7-day moving average
Note: The shaded area marks the post-closure period covered in the data, from 1st March to 31st May 2026. The underlying data is available through 16th May 2026, reflecting the latest completed voyages available at the time of writing.
The aggregate contraction masks important cross-country differences. As shown in Figure 3, emissions associated with departures from Iraq, Kuwait, and Qatar declined sharply, broadly in line with the aggregate trend. This reflects their near-total dependence on the Strait of Hormuz and the absence of viable overland alternatives. The effect is particularly acute for LNG: Qatar, one of the world’s largest LNG exporters, routes about 93% of its volume through the strait (IEA, 2026) and has only limited pipeline deliveries to neighbouring countries, leaving it with virtually no rerouting options. This is corroborated by a separate OECD analysis tracking key maritime indicators, which identifies over 60 LNG tankers stuck within the Persian Gulf between February and March 2026 – a significant share of global capacity for this vessel type.
Figure 3. Average daily CO2 emissions for voyages departing from Persian Gulf countries
Saudi Arabia occupies a different position. Its comparatively moderate decline of around 50% reflects the rapid ramp-up of the East-West crude oil pipeline, which links the Abqaiq processing centre on the Persian Gulf to the port of Yanbu on the Red Sea. This rerouting is directly visible in shipping patterns (Figure 4): tanker emissions from Red Sea terminals increased following the closure (although fell following an aerial attack on the Yanbu port in the second half of March) (Reuters, 2026), while emissions from Persian Gulf ports fell by around 86%. By the end of the analysed post-closure period, outbound emissions from the Gulf had fallen to near-zero levels.
Figure 4. CO2 emissions for VLCC oil tankers departing from Saudi Arabia; 7-day moving average
Note: The shaded area marks the post-closure period covered in the data, from 1st March to 31st May 2026. The underlying data is available through 16th May 2026, reflecting the latest completed voyages available at the time of writing.
The United Arab Emirates (UAE) also operate a bypass pipeline. The Abu Dhabi Crude Oil Pipeline connects inland production to the Fujairah terminal on the Gulf of Oman and, in principle, provides a comparable rerouting option. In practice, however, despite Fujairah’s location outside of the Strait of Hormuz, its proximity to conflict zones prompted several major operators to divert their vessels away from the terminal (Gulf Petro Vision, 2026; Windward, 2026).
Conclusion
The closure of the Strait of Hormuz has led to a sharp but uneven contraction in maritime transport CO2 emissions. At the fleet level, the much larger decline in emissions from large LNG tankers relative to VLCCs reflects the structural differences between the two export systems, with LNG shipments being far less flexible and more exposed to disruptions at a single route and facility.
At the regional level, the availability of overland infrastructure emerges as the key factor shaping outcomes across exporters. Countries with access to bypass pipelines have been able to partially reroute exports and sustain some level of activity, while others remain fully dependent on the strait and have therefore seen emissions fall sharply.
These patterns highlight how infrastructure and supply-chain structure condition both trade resilience, but also the relationship between shipping disruptions and maritime transport CO2 emissions, an area that remains relatively less explored in existing analysis.
References
- Clarke, D. et al. (2023), “CO2 emissions from global shipping: A new experimental database”, OECD Statistics Working Papers, No. 2023/04, OECD Publishing, Paris, https://doi.org/10.1787/bc2f7599-en.
- De Queljoe, M. et al. (2025), “Analysing recent trends and drivers of maritime transport CO₂ emissions: Insights from a decomposition analysis for the OECD and the world”, OECD Statistics Working Papers, No. 2025/03, OECD Publishing, Paris, https://doi.org/10.1787/6bb2bd69-en.
- EIA (2014). “Oil tanker sizes range from general purpose to ultra-large crude carriers on AFRA scale.” U.S. Energy Information Administration. https://www.eia.gov/todayinenergy/detail.php?id=17991
- EIA (2025). “Amid regional conflict, the Strait of Hormuz remains critical oil chokepoint.” U.S. Energy Information Administration, June 2025. https://www.eia.gov/todayinenergy/detail.php?id=65504
- Gulf Petro Vision (2026). “Fujairah Avoidance: Shifting Gulf tanker routes.” Gulf Petro Vision, April 2026. https://gulfpetro.om/fujairah-avoidance-shifting-gulf-tanker-routes/
- IEA (2026). “Strait of Hormuz — About.” International Energy Agency, February 2026. https://www.iea.org/about/oil-security-and-emergency-response/strait-of-hormuz
- Kpler (2026). “When the strait closes: how tanker charterers navigate the Hormuz crisis.” https://www.kpler.com/blog/when-the-strait-closes-how-tanker-charterers-navigate-the-hormuz-crisis
- Reuters (2026). “Saudi Aramco-Exxon refinery SAMREF in Saudi Arabia's Yanbu targeted, source says.” Reuters, March 2026. https://www.reuters.com/business/energy/saudi-red-sea-port-yanbu-targeted-aerial-attack-minimal-impact-source-says-2026-03-19/
- Windward (2026). “GPS Jamming Rises 55% in a Week in the Middle East Gulf.” Windward, March 2026. https://windward.ai/blog/gps-jamming-surges-in-the-middle-east-gulf-1650-ships-hit/
