23rd Session of the GCOS/WCRP Atmospheric Observation Panel for Climate (AOPC-23) - GCOS-218

This report summarises the discussions and agreed actions of the twenty-third session of the Atmospheric Observation Panel for Climate, held in Darmstadt in March 2018. It reviews progress on the Global Climate Observing System Implementation Plan, updates from related programmes, and the work of task teams on surface reference networks, lightning, radar and upper-air observations. The meeting addressed essential climate variable requirements, harmonisation of observational data, coordination with space agencies, and contributions to the Paris Agreement and the Global Stocktake. It also examined network performance, data policy issues, and development of fact sheets and requirements within the Observing Systems Capability Analysis and Review framework, setting out responsibilities and follow-up actions.