Ports are major sources of greenhouse gases (GHGs) and air pollution, emitting pollutants from ships, trucks, industrial activities, and port operations. These emissions disproportionately harm nearby disadvantaged communities. While strategies like electrification—planned for the Ports of Los Angeles and Long Beach—are expected to reduce pollution, no methane (CH₄) reductions were detected in satellite data during the COVID-19 shutdown, underscoring the need for robust monitoring.

A NASA-supported monitoring system combined satellite data (2018-), airborne remote sensing, and mobile air quality lab data (2019-) to characterize methane emissions. Key findings:

• Port-area methane emissions totaled 7.3 gigagrams/year, with 71% from oil production and 25% from refineries.


• Refineries emitted much more methane than reported in California's official inventory, with satellites detecting unreported transient release events.

The study reveals significant gaps between reported and observed emissions, demonstrating how satellite monitoring validated by ground measurements can improve accountability. This approach enables more effective policy decisions to reduce emissions and protect vulnerable communities.