Methane (CH₄) is a powerful greenhouse gas, second only to carbon dioxide (CO₂) in its contribution to global warming. Despite its relatively short lifespan in the atmosphere (around a decade compared to centuries for CO₂), methane has over 80 times the warming potential of carbon dioxide over a 20-year period.
This makes accurate tracking and reduction of methane emissions critical for slowing climate change. Recent advances in methane mapping, driven by new satellite technologies and improved analytical methods, are transforming how scientists identify and quantify emissions. However, satellite-based monitoring also comes with limitations, necessitating a multi-source approach for comprehensive methane tracking.
The historic challenge of methane emissions
Methane emissions originate from both natural and human-made sources. Key natural sources include wetlands, which account for about 30% of global emissions. On the human side, agriculture, particularly livestock farming, landfill decomposition, and fossil fuel extraction are the largest contributors. Unlike carbon dioxide, which spreads uniformly in the atmosphere, methane forms concentrated plumes that are difficult to detect and measure without advanced tools.
Historically, monitoring methane emissions relied heavily on ground-based sensors and aircraft, which provided localized but incomplete data. This made it challenging to identify large-scale emission sources or track sudden leaks from industrial facilities.
Recent advancements in satellite technology have significantly enhanced our ability to detect and monitor methane emissions, a potent greenhouse gas contributing to climate change. These developments provide comprehensive global coverage and improved spatial resolution, enabling precise identification of emission sources.
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The role of hyperspectral imaging
Satellites such as MethaneSAT, Sentinel-5P, and GHGSat use hyperspectral imaging to capture detailed data across various wavelengths. Methane absorbs sunlight in specific infrared bands, allowing these satellites to measure absorption patterns and determine methane concentrations.
- MethaneSAT: Launched in March 2024, MethaneSAT is designed to detect methane emissions from oil and gas fields with a precision of 2 parts per billion (ppb). Its targeted approach enables scientists to focus on known emission hotspots.
- GHGSat: This satellite has been instrumental in identifying super-emitting facilities—locations where methane leaks or emissions occur at unusually high rates—worldwide. In 2023, GHGSat’s satellites detected approximately 20,000 super-emitter sites, a significant increase from the previous year.
- Sentinel-5P: Operated by the European Space Agency, Sentinel-5P provides near-daily global methane measurements, focusing on detecting large-scale plumes. Its data has been crucial in identifying and monitoring significant methane emissions globally.
Limitations of satellite-based methane mapping
While satellite technology has revolutionized global methane detection, it is not without limitations. Relying solely on satellites for methane monitoring can create gaps and inaccuracies due to the following challenges:
1. Atmospheric interference Methane detection relies on observing infrared absorption patterns, but atmospheric factors such as clouds, water vapor, and aerosols can obstruct satellite sensors. Cloud cover, in particular, can reduce the ability to capture consistent measurements in certain regions, such as the tropics or during monsoon seasons.
2. Challenges over water bodies Measuring methane emissions over water bodies poses a unique challenge for satellites. Water surfaces reflect sunlight differently compared to land, which interferes with the infrared absorption signals that satellites use to detect methane. This makes it harder to differentiate methane plumes from background signals over lakes, rivers, and oceans. Additionally, methane emissions from sources like offshore oil rigs or natural seeps may be underestimated or missed entirely if the satellite’s resolution or detection capabilities are insufficient
3. Spatial resolution constraints While modern satellites offer improved resolution, they may still struggle to identify small-scale or highly localized emission sources. For example, methane leaks from smaller oil and gas facilities or isolated agricultural areas may go undetected unless combined with ground-based or airborne sensors.
4. Temporal limitations Satellites provide periodic measurements, which may miss short-lived or intermittent emissions. Some satellites only revisit the same location once every few days, making it difficult to monitor rapid changes, such as sudden methane releases from pipeline failures.
5. Validation requirements Satellite data must be validated with measurements taken from the ground or aircraft to ensure accuracy. Ground-based sensors provide critical, high-resolution data that can calibrate and confirm satellite observations. Without this validation, satellite measurements may produce false positives or underestimate emissions.
6. Coverage gaps Some regions, such as dense urban environments or heavily forested areas, pose challenges for methane detection due to physical obstructions or land surface reflectance. These coverage gaps limit the ability of satellites to provide complete global data.
Enhancing methane mapping with a multi-source approach
To overcome the limitations of satellite-only data, scientists advocate for a multi-source approach to methane mapping. By combining satellite observations with ground-based sensors, aircraft surveys, and AI-driven analysis, researchers can achieve a more comprehensive understanding of methane emissions.
A recent Nature article by astrophysicist Lorna Finman recommends that methane monitoring systems integrate data from various platforms to achieve a balance between global coverage and local precision. Combining real-time satellite measurements with on-the-ground validation is particularly important for identifying and mitigating methane super-emitters effectively.
Ground-based sensors provide continuous, localized data that complement satellite measurements. Networks of methane detectors installed near oil and gas fields, agricultural zones, and landfills can identify emission hotspots missed by satellites.
Aircraft-based surveys offer flexibility and high-resolution measurements, particularly for detecting small-scale or intermittent leaks. Aircraft equipped with methane-detection sensors can fly over specific regions to validate satellite data and provide additional coverage.
Closing the methane gap
While advances in satellite-based methane mapping are significant, their limitations highlight the need for integrated monitoring systems. Combining satellites with ground-based and airborne measurements ensures greater accuracy and coverage. This multi-source approach allows scientists to close the methane gap—the discrepancy between reported and actual emissions—and target high-emission sources more effectively.
References
Finman, L. (2024). To monitor methane emissions, combine satellites with boots on the ground. Nature. DOI: 10.1038/d41586-024-03987-x
Schuit, B. J., Maasakkers, J. D., Bijl, P., Mahapatra, G., Van den Berg, A. W., Pandey, S., … & Aben, I. (2023). Automated detection and monitoring of methane super-emitters using satellite data. Atmospheric Chemistry and Physics Discussions, 2023, 1-47. DOI: 10.5194/acp-23-9071-2023
