Code and processed data for "Separating Flight Activity from Emission Intensity: A Source-Level Decomposition of Airport-Attributed Aviation CO₂ in Vietnam"

This record contains the analysis code and processed data for a source-level decomposition of airport-attributed aviation CO₂ emissions in Vietnam from January 2021 to December 2025. All inputs are taken from the Climate TRACE Emissions Inventory V5.5.0 (doi:10.5281/zenodo.19952746): monthly CO₂, fuel and flight records for 23 domestic and 15 international aviation sources, 2,280 source-months in total. The script code/vnm_aviation_lmdi.py (Python 3.12, standard library only) reads the aviation files directly from the inventory's transportation.zip, validates the panel, and applies an additive logarithmic mean Divisia index (LMDI) decomposition of emission change into activity (total airport movements), composition (distribution of movements across airports) and intensity (emissions per movement) components. Sources that move between zero and positive activity are accounted for as separate activation and deactivation terms, without replacing zeros by small constants. Every pair of years from 2021 to 2025 is decomposed along three computational paths (annual totals, sum of same-month comparisons, and a chain of adjacent years), and closure is verified for each. The results/ folder holds the monthly and annual source panels, the decomposition results for all ten year pairs and three paths, source-level contributions, and robustness checks: a comparison of each 2025 source-month with the same month of 2024, the 2024–2025 decomposition with identical records removed, the fields carried by the aviation records, tests of how domestic flights are recorded at their two endpoint airports, and a comparison of the inventory's fuel per movement with the average passenger trip length published by the National Statistics Office of Viet Nam. The figure_data/ folder holds the values plotted in the article's figures. Running the script on the inventory reproduces all published values to within 10⁻⁷ t CO₂. Processed data are released under CC BY 4.0, in line with the source inventory; the code is released under the MIT Licence.