b'FLUXES The European Greenhouse Gas Bulletinwe need a model that links these concentra-tion measurements to emissions and natural fluxes at the surface. Then we need additional models for the ocean and terrestrial carbon cycle, and for various kinds of human-induced emissions on land, such as those caused by land use or by burning fossil fuels, for example, says Scholze.Alongside this, directly measuring all types of emissions is a hard task to accomplish, says Dr Richard Engelen, Deputy Director of the Copernicus Atmosphere Monitoring Service (CAMS) at the European Centre for Medi-um-Range Weather Forecasts (ECMWF).While we might be able to make direct observations from point sources, such as facto-ries or heating facilities, this becomes much more difficult when trying to measure emis-sions from cars, for instance, he explains.Running long-term MRV systems that incorporate observations requires high tech-nological knowledge of the personnel. MRV systems also require financial support. In Europe, the EU funds several MRV projects which are moving towards becoming opera-tional systems. Financial support is essential to purchase the supercomputers required for computation, data handling and storing many terabytes of data.When incorporating observations into a global MRV system, these challenges take on a new dimension. Some parts of the world, such as Europe and North America, have well-developed ground-based observation networks and the people to operate them but even these have gaps in their coverage.Meanwhile, some regions would need to find ways to develop networks. This is not just in terms of physical installations but also concerns the development of data pipelines and model-ling systems with well-trained personnel. Photo: Pekka Pelkonen, ICOS RIIn spite of these challenges, the number of independent observation-based MRV projects has grown in recent years. Initiatives like the Global Greenhouse Gas Watch (see page 48) benefit from the significant strides that have been taken already towards establishing observation-based MRV systems.'