The goal of this theme is the development of a system for early and accurate assessment of current GHG and SCLF emissions and removals based on observational data (Fig. 1). The theme comprises the following three sub-themes: (1) development of methods for estimating surface fluxes (sources and sinks) by using atmospheric transport models (National Institute for Environmental Studies, NIES); (2) compilation and analysis of observational data generated by monitoring networks centered on the Asia–Pacific region (NIES); and (3) evaluation of air–sea CO₂ fluxes based on measurements of dissolved CO₂ concentrations in seawater obtained by research vessels and other platforms (Meteorological Research Institute, MRI). In addition, this theme seeks to establish an integrated framework for comprehensively assessing fluxes by combining information derived from various models and observations. Distinctive characteristics of this theme include its use of observational data obtained from diverse platforms (including ground stations, towers, ships, aircraft, and satellites), its improvement of model resolution to extract maximum information from those data, and its close integration of observation and modeling.