Year: 2026
Type: article
Abstract: Cities around the world have united to form coalitions, like the C40 network, in pursuit of ambitious climate goals. These efforts often include reducing methane emissions. However, sources and magnitudes of urban methane emissions are not well known, and there is not currently a method to evaluate implementation of mitigation measures. Here, we fill this observational gap with a tracer–tracer approach using space-based observations of methane and carbon monoxide from the TROPOspheric Monitoring Instrument satellite instrument. We measure methane emissions of 92 global cities, including their broader metropolitan area, and find aggregate emissions of 31.2 Tg CH 4 /y (95%CI: 22.3, 40.4 Tg CH 4 /y) in 2023, equivalent to ∼ 10% of the global anthropogenic methane budget. We track emissions for 72 of these cities (51 C40 cities and 21 non-C40 cities) from 2019–2023. Methane emissions from these cities weakly declined in 2020 followed by steady growth, with a 2.3 Tg aggregate increase over 4 y. This growth contributes minimally to the recent atmospheric methane surge. While C40 cities have largely pledged 34% reductions by 2030, we observe significant growth from 2020 to 2023 (10%, 95%CI: 2%, 17%), similar to growth observed in non-C40 cities (12%, 95%CI: − 1.5%, 25%). Inventories fail to capture observed growth, suggesting urban emissions are not well characterized, and mitigation approaches may not be optimally designed. For the C40 network to achieve its methane target (34% by 2030), steep, rapid reductions will be needed. Emission reductions of this magnitude would be detectable with the space-based approach used in this work.
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
Open Access status: hybrid
Awards: PURPOSE: THIS AWARD WILL DEVELOP METHODS TO QUANTIFYING URBAN METHANE EMISSIONS USING SATELLITE-BASED AND SURFACE NETWORK MEASUREMENTS ALONG WITH EVALUATION OF APPROACH EFFECTIVENESS. THE RESEARCH WILL PROVIDE THE ABILITY TO QUANTIFY AND TRACK METHANE EMISSIONS FROM U.S. CITIES, AND THOSE AROUND THE GLOBE, WITH INDEPENDENT GROUND-BASED EVALUATION TO PROVIDE CONFIDENCE IN THE ANALYSIS METHODS AND THEIR RESULTS.ACTIVITIES TO BE PERFORMED: THIS RESEARCH UTILIZES SATELLITE DATA DERIVED FROM CURRENT AND ONGOING MISSIONS. IT WILL ALSO BE TRANSLATABLE TO FUTURE SPACED-BASED SENSOR TECHNOLOGIES. THERE ARE THREE OBJECTIVES:[1] DEVELOP METHOD FOR EVALUATING SPACE-BASED APPROACHES LEVERAGING WELL-INSTRUMENTED CITIES.[2] USING NEW SPACE-BASED METHODS TO QUANTIFY EMISSIONS IN CITIES WITH LITTLE TO NO EXISTING OBSERVATIONAL QUANTIFICATIONS OF URBAN METHANE.[3] DEVELOP APPROACHES THAT EXPAND SPACE-BASED METHODS USING ATMOSPHERIC MODELING AS WELL AS METHODS OF MERGING SATELLITE AND GROUND-BASED DATA IN HIGHLY INSTRUMENTED CITIES SUCH AS THOSE OF NIST'S GHG URBAN MEASUREMENTS TESTBED SYSTEM.EXPECTED OUTCOMES: THIS RESEARCH WILL ADVANCE MODELING CAPABILITIES SUPPORTING MEASUREMENT OF METHANE EMISSIONS BY ADDRESSING SEVERAL ISSUES ASSOCIATED WITH LINKING GROUND-BASED OBSERVATIONAL DATA WITH THAT TAKEN FROM SATELLITES. THE FOLLOWING TASK AREAS ARE THE FOCUS OF THE RESEARCH.* COMPARE SPACE-BASED ESTIMATES WITH TOWER CONSTRAINTS FOR THE NORTHEAST CORRIDOR.* EXTEND THE APPROACH TO LOS ANGELES* EXTENSION TO SELECTED CITIES GLOBALLY* EXPLORE THE XSTILT MODEL APPLICABILITY FOR SPACE-BASED OBSERVATIONS.* EXPLORE INTEGRATION OF TOWER AND SATELLITE OBSERVATIONS* CONSIDER THE APPLICABILITY OF THESE APPROACHES TO FUTURE ATMOSPHERIC COMPOSITION MEASURING SATELLITES.INTENDED BENEFICIARIES: FEDERAL AGENCIES, LOCAL AND STATE GOVERNMENTS, AND THE PRIVATE SECTOR SEEKING TO USE SATELLITE DATA TO DETERMINE EMISSIONS.SUBRECIPIENT ACTIVITIES: THE RECIPIENT DOES NOT INTEND TO SUBAWARD FUNDS., G8465241429
OpenAlex ID: W7154019250