Researchers used measurements from the TROPOMI instrument on a Sentinel satellite to estimate urban methane over 92 major cities. For 72 cities there were enough observations to track changes from 2019 to 2023. The analysis found global urban methane emissions in 2023 were about 6% higher than 2019 and 10% higher than 2020, while emissions tended to fall in European cities.
Bottom-up accounting methods, which add estimates from individual sources, showed a smaller rise of roughly 1.7% to 3.7% since 2020. The difference between satellite and accounting estimates suggests that policies based on those inventories may underperform.
The study included more than half of the C40 network of cities aiming for net-zero by 2050. Total methane across the studied C40 cities in 2023 was 10% higher than in 2020, adding about 2 teragrams per year, or roughly 30% of their emission reduction targets.
Difficult words
- instrument — device used to make scientific measurements
- estimate — a calculation of an approximate amountestimates
- observation — a recorded measurement or sighting in a studyobservations
- emission — gas released into the air from sourcesemissions
- accounting — method of adding and reporting individual data
- inventory — a list or record of sources and amountsinventories
- underperform — to do worse than expected or planned
- teragram — unit of mass equal to one trillion gramsteragrams
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Discussion questions
- Which data would you trust more for city policy: satellite measurements or bottom-up inventories? Why?
- What actions could a city take to reduce methane emissions in the next few years?
- How would a 10% increase in methane affect a city's emission reduction targets?
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