Space agencies play a key role for Global Greenhouse Gas Watch
Satellites play a key role in tracking greenhouse gases (GHG) around the world, helping scientists understand where emissions come from and where they go. Significant “sources” and “sinks” of Atmospheric Carbon, both natural and anthropogenic, are still not fully quantified or fully understood and thus introduce substantial uncertainties. The World Meteorological Organization (WMO) recognized the importance of space-based GHG operational monitoring in its Global Greenhouse Gas Watch (G3W) initiative, aiming to provide objective estimates of global Carbon fluxes on a continuous basis.
As part of this effort, G3W modelling centres space agencies are working more closely to deliver accurate, science-based data by combining satellite views with ground-based measurements and numerical modeling. Space-based Earth observations play a decisive role in characterizing the sources, sinks, and atmospheric concentrations of major GHG – such as carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O).
By improving the integration between satellite observations, in situ measurements and models, G3W will generate valuable insights to refine global Carbon estimates and thus support climate action. This work is reinforced through strengthened collaboration between agencies. It supports informed decision-making and enables countries to take targeted action for climate change mitigation.
Endorsed in 2023 by the WMO congress, G3W continues to grow with strong support from the Committee on Earth Observation Satellites (CEOS) and the Coordination Group for Meteorological Satellites (CGMS). In March 2025, CEOS and CGMS recognized G3W as
a transformative initiative that will unite scientific and operational communities1.
Reaffirming their early commitment towards the initiative, both organizations acknowledged WMO as
uniquely positioned to lead this effort, in collaboration with organizations with space-based assets in orbit or in development for global coordination of greenhouse gas monitoring.
They also called for the establishment of an effective structure to ensure the continuity and development of G3W activities and recognized the critical importance of strengthening the in situ observational networks. Both elements are essential for the overall success of G3W and for ensuring continuous calibration and validation of space-based measurements.
CEOS and CGMS’s commitment is further expressed through the 2024 Greenhouse Gas Roadmap, which supports space-based observations and modelling efforts. Under this roadmap, the Joint CEOS-CGMS Working Group on Climate and the Greenhouse Gas Task Team will continue to work with WMO to develop fit-for-purpose GHG data products for global use.
Footnotes:
- 1CEOS, CGMS, "Official", 03.2025, available at: 2.4 Global Greenhouse Gas Watch_CEOS CGMS WG Climate March 2025.pdf.
