Methane emissions from solid waste may represent a substantial fraction of the global anthropogenic budget, but few comprehensive studies exist to assess inventory assumptions. We quantified emissions at hundreds of large landfills across 18 states in the United States between 2016 and 2022 using airborne imaging spectrometers. Spanning 20% of open United States landfills, this represents the most systematic measurement-based study of methane point sources of the waste sector. We detected significant point source emissions at a majority (52%) of these sites, many with emissions persisting over multiple revisits (weeks to years). We compared these against independent contemporaneous in situ airborne observations at 15 landfills and established good agreement. Our findings indicate a need for long-term, synoptic-scale monitoring of landfill emissions in the context of climate change mitigation policy.

Anthropogenic carbon dioxide (CO₂) emissions dominate uncertainties in the global carbon budget. Global inventories, such as the National Greenhouse Gas Inventories, have latencies of 12–24 months and may not keep pace with rapidly changing infrastructure, particularly in the developing world. Our work reveals that airborne and satellite imaging spectrometers provide 3–30 m spatial resolution and accurate quantification of CO₂ emissions at the facility scale. Examples from 17 coal and gas fired power plants across the United States demonstrate robust correlation and 21% agreement on average between our remotely sensed estimates and simultaneous in situ measured emissions. We highlight four examples of coal‐fired power plants in India, Poland, and South Korea, where we quantify significant carbon dioxide emissions from power plants where limited public emissions data exist. Leveraging previous work on methane (CH₄) plume detection, we present a strategy to exploit joint CO₂ and CH₄ plume imaging to quantify carbon emissions across widely distributed industrial infrastructure, including facilities that co‐emit CO₂ and CH₄. We show an example of a coal operation, where we attribute 25% of greenhouse gas emissions to coal extraction (CH₄) and the remaining 75% to energy generation (CO₂). Satellite spectrometers could track high emitting coal‐fired power plants that collectively contribute to 60% or more of global coal CO₂ emissions. Multiple revisits and coordinated targeting of these high emitting facilities by multiple spaceborne instruments will be key to reducing uncertainties in global anthropogenic CO₂ emissions and supporting emissions mitigation strategies.

Airborne remote sensing observations were collected at 217 landfills across 17 states in the US in 2023. We used these observations to attribute emissions to major sources, including the landfill work face, where new waste is placed at the landfill and gas-control infrastructure. Methane emissions from the work face appeared to be more prevalent than gas-control infrastructure emissions, with 52 landfills exhibiting work face emissions out of the 115 observed landfills shown to be emitting in 2023. Landfills with work face emissions were often the highest emitters, especially sites with associated renewable natural gas facilities, and the total average site emissions from these landfills accounted for 79% of the observed emissions, indicating inefficient gas capture at these sites. Landfills with work face emissions also displayed the greatest disparity between observed emission rates and hourly emission rates that we estimated using annual emissions reported to the US EPA's Greenhouse Gas Reporting Program. Work face emissions present a major opportunity for methane mitigation: Observed emissions from work face emitting-landfills in this study were equivalent to 15% of US methane emissions from municipal solid waste landfills in 2022, as reported in the 2024 Greenhouse Gas Inventory, though these landfills accounted for only 4% of open sites in the US. As the 217 landfills in this study cover only 17% of open landfills in the US, the total mitigation potential is likely greater. Using remote sensing, we find that the largest contributor to observed methane emissions at US landfills is the landfill work face, an area of the landfill often left out of the required monitoring and traditional emissions accounting methods.

Coral reef ecosystems are rapidly changing, and a persistent problem with monitoring changes in reef habitat complexity rests in the spatial resolution and repeatability of measurement techniques. We developed a new approach for high spatial resolution (<1 m) mapping of nearshore bathymetry and three-dimensional habitat complexity (rugosity) using airborne high-fidelity imaging spectroscopy. Using this new method, we mapped coral reef habitat throughout two bays to a maximum depth of 25 m and compared the results to the laser-based SHOALS bathymetry standard. We also compared the results derived from imaging spectroscopy to a more conventional 4-band multispectral dataset. The spectroscopic approach yielded consistent results on repeat flights, despite variability in viewing and solar geometries and sea state conditions. We found that the spectroscopy-based results were comparable to those derived from SHOALS, and they were a major improvement over the multispectral approach. Yet, spectroscopy provided much finer spatial information than that which is available with SHOALS, which is valuable for analyzing changes in benthic composition at the scale of individual coral colonies. Monitoring temporal changes in reef 3D complexity at high spatial resolution will provide an improved means to assess the impacts of climate change and coastal processes that affect reef complexity.

Satellites are becoming a widely used measurement tool for methane detection and quantification. The landscape of satellite instruments with some methane point-source quantification capabilities is growing. Combining information across available sensor platforms could be pivotal for understanding trends and uncertainties in source-level emissions. However, to effectively combine information across sensors of varying performance levels, the probability of detection (POD) for all instruments must be well characterized, which is time-consuming and costly, especially for satellites. In August 2023, we timed methane-sensing aerial surveys from the Global Airborne Observatory (GAO) to overlap with observations from the NASA Earth Surface Mineral Dust Source Investigation (EMIT). We show how these coincident observations can be used to determine and verify the detection limits of EMIT and to develop and test a multisensor persistence framework. Under favorable conditions, the 90% POD at 3 for EMIT is 1060. We further derive a Bayesian model to infer probabilistically whether nondetected emissions were truly off, and we validate and show how this model can be used to assess the intermittency of emissions with GAO and EMIT. Time-averaged emission rates from persistent sources can be underestimated if POD is not characterized and if differences in POD across multisensor frameworks are not properly accounted for.

Rapid ‘Ōhi‘a Death (ROD) is a disease aggressively killing large numbers of Metrosideros polymorpha (‘ōhi‘a), a native keystone tree species on Hawaii Island. This loss threatens to deeply alter the biological make-up of this unique island ecosystem. Spatially explicit information about the present and past advancement of the disease is essential for its containment; yet, currently such data are severely lacking. To this end, we used the Carnegie Airborne Observatory to collect Laser-Guided Imaging Spectroscopy data and high-resolution digital imagery across >500,000 ha of Hawaii Island in June–July 2017. We then developed a method to map individual tree crowns matching the symptoms of both active (brown; desiccated ‘ōhi‘a crowns) and past (leafless tree crowns) ROD infection using an ensemble of two distinct machine learning approaches. Employing a very conservative classification scheme for minimizing false-positives, model sensitivity rates were 86.9 and 82.5, and precision rates were 97.4 and 95.3 for browning and leafless crowns, respectively. Across the island of Hawaii, we found 43,134 individual crowns suspected of exhibiting the active (browning) stage of ROD infection. Hotspots of potential ROD infection are apparent in the maps. The peninsula on the eastern side of Hawaii known as the Puna district, where the ROD outbreak likely originated, contained a particularly high density of brown crown detections. In comparison, leafless crown detections were much more numerous (547,666 detected leafless crowns in total) and more dispersed across the island. Mapped hotspots of likely ROD incidence across the island will enable scientists, administrators, and land managers to better understand both where and how ROD spreads and how to apply limited resources to limiting this spread.