With the integration of non-CO₂ effects into aviation climate reporting, airlines are required to choose a standardized methodology for calculating emissions. The two approved approaches—Method C and Method D—differ in complexity, data needs, and eligibility.
Selecting the right method is crucial for regulatory compliance, cost efficiency, and data credibility. This article breaks down the differences and helps you determine which method applies to your operation.
What Are Method C and Method D?
Both methods are approved under the EU’s MRV framework for non-CO₂ aviation effects. They serve the same goal—translating flight data into CO₂-equivalent (CO₂e) emissions—but follow different approaches.
Method C: Weather-Based Monitoring (Default for Large Emitters)
What it is:
A detailed, flight-specific monitoring approach that incorporates actual weather and operational data.
Key characteristics:
- Requires real-time trajectory and meteorological inputs
- Uses high-resolution data such as aircraft mass, engine configuration, and fuel properties
- Models emissions and impacts using tools like CoCiP (for contrails) and aCCF (for NOx and water vapour)
- Integrated via platforms like NEATS or approved third-party systems
Best for:
- Operators emitting above a regulatory threshold
- Airlines with access to granular flight and fuel data
- Those looking for precise, science-aligned emissions profiling
Pros:
- Highest accuracy
- Fully aligned with MRV requirements for large emitters
Cons:
- Higher data and IT infrastructure requirements
- More complex to implement and maintain
Method D: Climatological Monitoring (For Small Emitters)
What it is:
A simplified approach using pre-calculated emission response surfaces based on average climatological data.
Key characteristics:
- Uses OpenAirClim datasets
- Does not require live weather or flight-specific inputs
- Appropriate for operators with fewer covered flights or limited data systems
Best for:
- Small operators with emissions below a defined threshold
- Organizations seeking a low-cost, low-effort compliance solution
Pros:
- Easier to implement
- Minimal data handling
Cons:
- Less precise than Method C
- Cannot adjust for actual atmospheric or operational conditions
Can You Use Both?
Yes—mixed-method monitoring is allowed for operators with diverse fleets or route profiles. For example, you can apply Method C for high-traffic or high-emission routes, and Method D for low-frequency operations.
This hybrid approach must be fully documented in the Monitoring Plan and approved by the Competent Authority.
Key Factors for Method Selection
To decide between Method C and Method D, consider the following:
- Annual emissions volume: Are you a small or large emitter?
- Data availability: Do you capture engine IDs, fuel composition, and actual trajectories?
- Tool readiness: Can you integrate NEATS or approved modeling software?
- Verification strategy: Are you prepared for deeper scrutiny if using Method C?
How Vurdhaan Supports Your Method Choice
Vurdhaan specializes in helping operators determine and implement the right monitoring method. Whether you’re a large network carrier or a regional operator, we help you align your MRV strategy with your operational reality.
Our services include:
- Emitter status evaluation and method eligibility assessment
- Monitoring Plan development for Method C, D, or hybrid approaches
- Tool selection, NEATS integration, and approval guidance
- Verification preparation and evidence pack design
- Long-term roadmap planning for scalable MRV systems
With Vurdhaan, you don’t just choose a method—you adopt a future-proof compliance solution. Unsure which monitoring method fits your operations? Contact Vurdhaan for a tailored assessment and implementation strategy.