Preface to Special Topic on Atmospheric Greenhouse Gas Measurement and Application in China

China initiated a national carbon trading market in December 2017. Commitments and actions to reduce greenhouse gas (GHG) emissions require consistent, reliable and timely information on GHG emissions. GHG monitoring and model-ing studies provide GHG emission estimates to evaluate and guide progress towards emission reductions. GHG monitoring has mainly focused on global-scale background networks over the last few decades, while recent efforts have been made on regional and urban scales, such as projects in the Beijing-Tianjin-Hebei city cluster, in Paris, Washington-Baltimore, Indi-anapolis, and Los Angeles. These"top-down" atmospheric observations, together with"bottom-up" GHG emissions inventor-ies and biosphere fluxes, are integrated into GHG monitoring and application information systems. The Integrated Global Greenhouse Gas Information System (or IG3IS) was established by WMO/UNEP to facilitate such efforts after the 17th World Meteorological Congress. As one of the countries heavily impacted by climate change, China has implemented many actions to respond to climate change. Atmospheric GHG measurement techniques have been developed rapidly in China over the last decade, and this work has been applied in evaluating GHG emissions, identifying GHG sources, quantifying GHG fluxes, and supporting GHG-related policymaking.