A University of Michigan study funded by NASA and the National Institute of Standards and Technology, published in April 2026, delivers a stark warning: cities are emitting significantly more methane than governments have reported — and the gap is growing. Using the TROPOMI instrument aboard the European Copernicus Sentinel-5 Precursor satellite, researchers measured atmospheric methane over 92 major cities worldwide between 2019 and 2023, tracking changes over time for 72 of those cities.
Global urban methane emissions in 2023 were 6% higher than 2019 levels and 10% higher than 2020 levels. Official government "bottom-up" accounting methods, by contrast, suggest urban methane has only risen between 1.7% and 3.7% over the same period — a discrepancy of two to three times. The researchers also found that urban areas account for 10% of all human methane emissions, and that city methane as a category emits nearly four times more than the oil and gas "ultra emitters" that have historically been the primary focus of methane reduction policy and satellite monitoring programs.
The study covered cities from more than half of the C40 network — 97 cities worldwide that have committed to reaching net-zero emissions by 2050. This group represents some of the most climate-ambitious cities globally, yet their methane accounting appears to be systematically underestimating actual emissions.
The discrepancy between satellite observations and bottom-up accounting stems primarily from measurement methodology. Traditional emissions inventories rely on activity data — the number of cars, gas connections, waste volumes — combined with assumed emission factors for each source category. Satellite measurements, by contrast, observe the actual atmospheric methane concentration above a city and work backwards to determine total emissions. The Sentinel-5P TROPOMI instrument has sufficient spatial resolution to pinpoint individual cities, making it the first satellite system capable of conducting this kind of systematic global urban methane survey.
The study's authors note that the gap is likely driven by underestimated emissions from urban gas distribution networks, wastewater treatment, and landfills — all diffuse sources that are notoriously difficult to measure with on-the-ground methods. As cities age, gas infrastructure leakage rates increase, but these changes are rarely captured in official emissions factors.
The findings have direct implications for urban climate commitments and carbon market integrity. Cities that have committed to net-zero targets based on official inventory data may be significantly off-track — not because they have failed to implement policies, but because their starting baselines were incorrect. This creates a credibility problem for city-scale carbon credit programmes, green bonds, and sustainability-linked financing instruments that reference official urban emission inventories.
For the voluntary carbon market, the study reinforces the case for satellite-calibrated measurement as a verification layer for any project claiming to reduce urban methane emissions — whether through upgraded gas infrastructure, landfill gas capture, or wastewater management. A project that demonstrates genuine methane reduction against a satellite-verified baseline will be far more defensible to buyers and auditors than one relying solely on activity-data accounting.
This study validates what TrustVal has argued since our founding: the MRV gap is not a rounding error — it is a structural problem that undermines the credibility of emissions reduction claims at scale. Satellite-based monitoring does not replace ground-level sensors, but it provides an independent cross-check that makes manipulation or methodological error visible. At TrustVal, our dMRV platform integrates satellite observation layers alongside IoT sensor networks to provide exactly this kind of multi-source verification. For cities and project developers seeking to issue carbon credits backed by credible, defensible data, high-frequency dMRV is no longer optional — it is the baseline expectation.
Primary sources: Michigan Engineering News — April 2026 | Phys.org — Satellites reveal city methane emissions
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