Decadal decrease in Los Angeles methane emissions is much smaller than bottom-up estimates

Zhao-Cheng Zeng ¹, Thomas Pongetti ², Sally Newman ^3,4

¹Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA. zcz@gps.caltech.edu.
²Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
³Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
⁴Planning and Climate Protection Division, Bay Area Air Quality Management District, San Francisco, CA, USA.
⁵Earth from Space Institute, Universities Space Research Association (USRA), Columbia, MD, USA.
⁶Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD, USA.
⁷Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.
⁸School of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff, AZ, USA.
⁹School of GeoSciences, University of Edinburgh, Edinburgh, UK.
¹⁰Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA. stanley.p.sander@jpl.nasa.gov.
¹¹Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. stanley.p.sander@jpl.nasa.gov.

⁰Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA. zcz@gps.caltech.edu.

Nature Communications +

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September 2, 2023

View abstract on PubMed

Summary

Methane emissions from Los Angeles (LA) natural gas leakage decreased from 2011-2020. This study highlights discrepancies between atmospheric measurements and utility estimates, offering insights for future methane reduction strategies.

Area Of Science

Atmospheric Science
Climate Change Research
Environmental Monitoring

Background

Methane is a potent greenhouse gas with a short atmospheric lifetime, making emissions reductions impactful for climate forcing.
Natural gas leakage is a significant methane source in megacities like Los Angeles.
Quantifying fugitive natural gas emissions is crucial for verifying emission reduction targets.

Purpose Of The Study

To quantify methane emission trends in the Los Angeles area from 2011-2020.
To compare top-down (remote sensing) and bottom-up (utility calculations) estimates of methane emissions.
To assess the effectiveness of emission reduction strategies in a major urban area.

Main Methods

Utilized atmospheric remote sensing data to monitor methane concentrations.
Analyzed emission trends over a decade (2011-2020).
Compared satellite-derived emission data with natural gas utility reported data.

Main Results

Los Angeles area methane emissions showed a decreasing trend of (-1.57 ± 0.41)%/yr from 2011-2020.
This top-down trend contrasts with the observed global increase in methane emissions.
A significant discrepancy exists between the measured emission reduction rate and the much larger negative trend reported by the natural gas utility (-5.8%/yr).

Conclusions

Top-down measurements reveal a moderate decrease in LA's methane emissions, suggesting some success in reduction efforts.
The disparity between top-down and bottom-up trends underscores uncertainties in emission estimation and reporting.
LA's experience provides a potential model for other cities and international efforts, such as COP28, aiming to curb methane emissions.

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