A Scientific Community Vision for an Operational Multi-Tiered, Multi-Decadal Greenhouse Gas Observing System to Support Earth System Science and Climate Action

Greenhouse gas (GHG) emissions are accelerating, while natural carbon reservoirs are becoming increasingly vulnerable to anthropogenic pressures such as land-use and climate change, along with more frequent and intense climate extremes and wildfires. These changes are impacting humans, ecosystems, and natural resources worldwide. While the growing availability of Earth Observation (EO) data is addressing global GHG mitigation goals, its full potential to inform measurable climate action at local-to-global scales remains underutilized. Based on a workshop held in September 2024, we provide the rationale and scientific knowledge to more effectively implement an operational system for GHG monitoring to meet climate action needs of national and international stakeholders in support of the Paris Agreement. This system requires a paradigm shift in how EO data is shared, integrated, and operationalized — akin to advancements in numerical weather prediction. To guide the development of this system, we propose a multi-tiered global observing framework prioritizing: 1) increased temporal and vertical GHG column information (sub-daily vertical profiles) from surface, airborne, and spaceborne constellations; 2) expanded coverage of tropical and high latitude regions; and 3) continuous time series and data fusion from Lidar and SAR for accurate monitoring and mapping of ecosystem disturbance and growth. This operational system should prioritize rapid response, early warning and real-time climate risk assessment, and long-term monitoring of both gradual and abrupt changes in carbon emissions, exchanges, and stocks to inform near- and long-term GHG mitigation efforts. This system should also expand surface networks for oceanic and terrestrial/aquatic ecosystems to address under sampled regions, such as non-forest lands, rivers, wetlands, coastal zones, the Southern and Arctic Oceans, tropics, permafrost areas, and drylands.