Rising concentrations of the main greenhouse gases, CO2, CH4, and N2O, driven by human activities is the main driver of the currently ongoing climate change. The Paris Agreement of 2015 sets specific goals for maximum rise in global mean temperature, but in spite of very significant efforts devoted to developing accurate national emission reporting, the world does not appear to be in track to meet these goals
One problem is that focusing on anthropogenic emissions alone will not be a sufficient basis for mitigation action. Natural GHG fluxes have even larger uncertainties, and future concentrations are determined by the combined impact of natural and anthropogenic sources and sinks. A second problem is the accounting for negative emissions, in particular involving off-setting, where e.g. emissions related to fossil fuel consumption, are claimed to be “offset” by negative emissions achieved elsewhere. The quantitative rationale for carbon offsetting is often weak, and monitoring of its impact on atmospheric concentrations is rarely done, which leads to risks of overestimation and double-counting of the effect.

Routine top-down estimation of greenhouse gas fluxes using atmospheric observations and models can provide a wealth of quantitative data to help constrain the modelling of the carbon cycle.  and can help put mitigation steps taken by Parties to the Paris Agreement on a solid scientific footing. Top-down flux estimation methodology is mature and borrows heavily from longstanding practices of operational numerical weather prediction. However, in contrast to weather prediction and climate monitoring, the observational basis for top-down GHG flux monitoring is still weak, with only limited international coordination and no routine, timely exchange of data. There is no routine intercomparison of output and no commonly agreed metrics of quality. In order for the methodology to live up to its full potential, these issues must be addressed in international coordination.

In May 2023, the 19th World Meterorological Congress therefore endorsed the Global Greenhouse Gas Watch as am internationally coordinated system that will provide consolidated, near-real time estimates of net GHG fluxes between atmosphere, land, and oceans, calculated on a monthly basis, with global coverage and delivered at a maximum delay of one month. The GGGW builds on WMO's research in greenhouse gas observations and modelling since 1975, and on the operational practices of the global observing network, global data exchange and routine model intercomparison used for more than 50 years for weather forecasting and climate analysis around the world. In this seminar we will introduce the scope, purpose and architecture of the GGGW, and the potential roles of both academia and the private sector in its implementation will be discussed.