As global efforts to reach net-zero intensify, international transport remains a critical puzzle piece in climate policy. Aviation and maritime shipping—two of the hardest sectors to decarbonize—are stepping up to the challenge with global frameworks designed to curb emissions and spur innovation. While often compared side by side, the regulatory landscapes for these sectors offer contrasting lessons and complementary opportunities.
Recent developments in their respective United Nations agencies have ushered in significant policy frameworks—CORSIA for aviation and the IMO Net Zero Framework for shipping. Each scheme tells a unique story of industrial readiness, global collaboration, and the evolving playbook of climate regulation.
Why These Sectors Matter
Aviation and shipping are cornerstones of global trade and mobility. But they also represent stubborn sources of greenhouse gas emissions due to their dependence on energy-dense liquid fuels. Transitioning away from these fuels is not as simple as swapping out technologies. Aircraft, for instance, demand extremely refined fuels that can perform at high altitudes and low temperatures. Ships, on the other hand, offer more leeway in fuel variety but must address fuel compatibility and scalability across a diverse fleet.
This complexity has turned both sectors into laboratories of decarbonization—testing how far policy can go in directing technological progress and investment.
Sustainable Fuels: One Concept, Two Realities
Aviation is currently focused on Sustainable Aviation Fuels (SAF)—drop-in replacements for jet fuel that do not require new infrastructure or aircraft design. However, SAF still accounts for less than 1 percent of global jet fuel consumption. Even with its infrastructure compatibility, the ramp-up is slow due to limited investor confidence, regulatory inconsistency, and supply-chain challenges.
In contrast, maritime transport benefits from a broader fuel palette, including LNG, methanol, and green ammonia. Yet this diversity is both a strength and a weakness. While it allows for tailored solutions, it complicates scale, standardization, and cost-efficiency. Moreover, infrastructure limitations and safety concerns are far from resolved, especially for high-potential fuels like ammonia.
The real insight here is not the diversity of fuels—but the flexibility of policy frameworks to encourage their adoption. By emphasizing harmonized criteria, reliable incentives, and cross-border consistency, emerging regulation plays an outsized role in shaping future fuel ecosystems.
CORSIA: Policy Innovation at Cruising Altitude
Introduced in 2016, the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) remains the only operational, globally agreed climate measure in any industry. It mandates that airlines offset emissions above 85 percent of their 2019 levels through the purchase of eligible emissions units or fuels.
This route-based, market-driven approach is significant. It signals that even in a sector as safety-sensitive and technologically rigid as aviation, there is a path toward accountability and measurable climate finance. As of early 2025, over 60 percent of international air transport emissions are covered under CORSIA, with the figure expected to surpass 85 percent by 2027.
More than compliance, CORSIA fosters transparency and data-based governance. Its Monitoring, Reporting, and Verification (MRV) system ensures that progress is quantifiable, making it one of the most mature climate accountability frameworks today.
IMO’s Net Zero Framework: Maritime Ambition Sets Sail
Shipping is catching up. The International Maritime Organization’s (IMO) Net Zero Framework—adopted in principle in 2023 and slated for implementation in 2028—takes a different, more tiered approach. It includes a bonus-malus pricing system, emissions intensity benchmarks, and financial incentives for ships using zero or near-zero-emission technologies.
By 2028, large ocean-going vessels over 5,000 gross tonnage will be required to track and reduce their greenhouse gas fuel intensity (GFI), with compliance tied to economic penalties or rewards. Unlike CORSIA, which emphasizes offsetting, the IMO approach is grounded in sectoral transformation. Its climate finance model proposes a dedicated fund for innovation, training, and just-transition initiatives.
Though still under negotiation, the IMO framework demonstrates an important shift: regulation that does not just mandate compliance, but also actively redistributes value to build system-wide resilience and equity.
Shared Principles, Diverging Tactics
Despite their differences, both frameworks are unified by key characteristics:
- Global coverage: Both mechanisms are coordinated through international bodies, reducing policy fragmentation and supporting cross-border consistency.
- Climate finance integration: Whether through emissions unit purchases (CORSIA) or a centralized fund (IMO), both sectors embed the polluter-pays principle into their decarbonization strategy.
- Data governance: CORSIA has made strides in public emissions data transparency. The IMO’s Data Collection System is less accessible but signals growing momentum toward similar openness.
This reveals a broader truth: regulatory action in transport is not just about emissions reductions—it is about building institutions that can govern complexity with fairness, clarity, and foresight.
A Subtle Lesson for Policy Designers
Perhaps the most underappreciated insight from these frameworks is the way each sector integrates legacy systems with future ambition. Aviation, limited by infrastructure inertia, leverages drop-in fuels and offset markets. Shipping, with more technological flexibility, aims to reshape its energy and financing landscape over time.
This divergence invites a policy lesson: different sectors require different instruments, but all sectors benefit from alignment on outcomes. Net-zero targets, clear timelines, and financial levers must remain synchronized, even if pathways vary.
Conclusion
The climate frameworks emerging from aviation and maritime transport are not just regulatory tools—they are signals of a new era in international governance. They demonstrate how sector-specific constraints can still yield global coordination. They show that even hard-to-abate industries can move from rhetoric to action when mechanisms are predictable, transparent, and inclusive.
Professionals across sustainability, finance, and transport would do well to study these frameworks—not only for what they mandate, but for how they evolve. Because in the race to net zero, innovation does not just happen in labs or boardrooms. It happens in frameworks.
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Download Document File Here: Climate regulatory frameworks (BRIEF)