1. Quick Summary
Methane absorbs infrared radiation strongly, so it can be detected by measuring sunlight reflected from the surface and atmosphere in specific wavelength bands.
Satellite instruments trade coverage against resolution: some observe the whole globe coarsely, others resolve individual facilities over narrow swaths.
Finding an emission is only the first step. Attributing it to a specific source and estimating its rate require additional information.
2. What It Means
Spectroscopy identifies methane by its absorption pattern. Comparing measured spectra with known absorption features gives the amount of gas along the light path.
Column measurements report the total amount in a vertical path, which must be separated from the background to identify an enhancement from a source.
Retrieval requires knowing the surface and the atmosphere. Surface reflectivity, aerosols, clouds and topography all affect the measurement, and errors there propagate into the estimate.
Emission rate estimation uses the measured enhancement together with wind information, because the plume’s shape and dilution depend on how fast air is moving.
3. Why It Happens
Detection thresholds limit what is visible. Small or low-altitude emissions may be indistinguishable from background noise, so absence of detection is not evidence of absence.
Clouds and aerosols block the measurement. Many observations are unusable in cloudy conditions or over bright, variable surfaces, so revisit rates matter.
Water surfaces are difficult. Sun glint and low reflectivity complicate retrieval over water, where a meaningful share of infrastructure emissions occur.
Attribution needs context. A plume indicates methane but not its origin; identifying the responsible equipment requires facility knowledge or ground confirmation.
Temporal coverage is sparse. An instrument passing overhead once every few days will miss intermittent releases, which are common in some industries.
4. Real Examples
Wide-swath instruments with moderate resolution survey large regions and can identify persistent regional patterns rather than individual sites.
High-resolution instruments can resolve plumes from individual facilities, and have revealed a small number of very large sources responsible for a disproportionate share of emissions.
Aircraft and ground surveys are used to confirm satellite detections and to locate the specific component responsible.
Continuous monitoring systems installed at facilities provide a different kind of data — frequent but local — that complements satellite coverage.
5. How It Affects Us
Identifiable large leaks are the cheapest to fix, so improved detection changes the economics of mitigation substantially.
Measurement-based inventories differ from self-reported ones, which creates pressure for reporting standards to converge with observations.
Regulation increasingly specifies measurement and repair intervals, which only works where detection capability exists.
Data transparency determines who can act: public data enables independent verification, while restricted data limits it to operators and regulators.
6. Key Takeaways
- Satellites detect methane by its infrared absorption, and resolution determines whether sources or regions are visible.
- Non-detection does not mean zero emissions; thresholds and coverage set real limits.
- Estimating a rate requires wind data, and attribution requires ground knowledge.
- The biggest practical value is finding the small number of very large, fixable sources.