In March 2025, greenhouse gas (GHG) experts met at WMO headquarters in Geneva to advance the Global Greenhouse Gas Watch (G3W) implementation. The workshop covered foundational elements of G3W, including products output requirements, modelling systems and data flow mapping to support system implementation. These elements can initiate the creation of value-added products that are crucial for informed decision-making, helping countries to take effective action to reduce climate-related risks. The workshop's outcomes position G3W for its first operational phase by 2027.
G3W entered pre-operational phase following a decision of the Seventy-eighth Session of the Executive Council (EC-78) , held in June 2024 in Geneva (Switzerland) that approved the G3W Implementation Plan. Priority activities were defined within the context of the pre-operational phase - the first stage of implementation, covering the period 2024 to 2027.
The G3W Advisory Group along with three task teams have been established forming an overall core group of 60 expert that support the coordination of the G3W technical activities in the context of the WMO Integrated Global Observing System ( WIGOS ), the WMO Information System ( WIS ) and the WMO Integrated Processing and Prediction System ( WIPPS ). At their initial meetings, the task teams developed a stepwise approach to delivering the outputs required in the workplan of the Commission for Observation, Infrastructure and Information Systems ( INFCOM-3 ).
Substantial progress toward achieving these objectives was made during the G3W Data Providers Workshop that took place in March 2025 at WMO Headquarter in Geneva, Switzerland. The hybrid-format workshop brought together thirty-three experts, including members of the Task Team on G3W Modelling, the Task Team on G3W Data, and invited specialists.
Data management and modelling systems definitions are essential elements required to deliver monthly net fluxes of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) - initially at 100 km by 100 km resolution with plans to refine further. Participants confirmed that initial specification of the systems pave the way towards transition from the pre-operational phase (approved in June 2024) to the initial operational capability by the end of 2027.
The workshop introduced key components of the WIPPS framework. Discussions emphasized the need to:
- Designate WIPPS centres responsible for specific activities
- Develop detailed manuals and comprehensive guidance on mandatory product specifications, verification protocols and quality control
- Draw on lessons from initiatives such as the Global Carbon Project, particularly on benchmarking, model validation and multi-source data integration
While progress has been made in accelerating satellite retrievals to meet performance targets, concerns remain regarding the latency of in situ datasets that are critical for evaluation of model data products. A tiered approach was suggested, where - for instance - a selected subset of in situ data could be delivered more rapidly to support evolving operational capabilities during the pre-operational phase. Participants also discussed opportunities to operationalize research observing networks, especially over the oceans. The group recognized the value of using existing WMO tools such as the Observing System Capabilities Analysis and Review ( OSCAR ) to conduct systematic observation inventories and gap analyses.
Preliminary results of the observing networks survey were presented highlighting diversity of the observational platforms and governance. The importance of consistent metadata frameworks and quality flagging systems was raised. It was evident that the ocean and satellite domains are significantly more centralized - for example, through the Surface Ocean CO₂ Atlas (SOCAT) database and the coordinated efforts of both the Committee on Earth Observation Satellites (CEOS) and the Coordination Group for Meteorological Satellites (CGMS). The modelling community stressed the need to balance atmospheric observations latency - especially from ocean sites - with other factors such as data quality and spatial coverage when prioritizing resources.
Advanced evaluation metrics for assessing model uncertainty were also discussed, alongside the potential for intercomparison exercises between centres. Plans to incrementally evaluate the data products are developed, both in near real time and annually, with eventual performance results to be published on dedicated platforms.
Workshop discussions also addressed the role of designated centres under the WIPPS. Despite ambitious targets placed on latency and spatial resolution of the products, sufficient attention must be given to reliability and level of service as differentiators for operational modelling centres. Modelling groups have outlined requirements for the output products which will be documented in the WIPPS Manual.
Detailed mapping of data flows - including satellite, in situ, and ocean data - has begun. Efforts are underway to harmonize data aggregation practices at regional and national centres. The importance of meeting WMO standards, such as those for WIS and WIGOS metadata, was underscored to ensure system interoperability. A systems design analysis was proposed to review the operational data flow and to identify where centralized or distributed processing might be necessary.
As a next step, the mapping and documentation of prior data sources and observational networks should continue. Requirements for WIS centres need to be established in the context of the G3W data architecture.
