This is the latest in a series of implementation plans produced by the Global Climate Observing System (GCOS) programme since its inception in 1992. It provides a set of high priority actions which if undertaken will improve global observations of the climate system and our understanding of how it is changing. Climate observations have been very important: they have unequivocally shown that anthropogenic climate change is occurring, and they have informed the verification of the models and the projections needed to successfully adapt to and mitigate climate change. Climate services are underpinned by robust, accurate and timely climate observations. This plan is mainly based on the following: • The latest 2021 GCOS Status Report1, released in 2021, that identified the successes and gaps in the existing observing systems. • The United Nations Framework Convention on Climate Change (UNFCCC) Paris Agreement that has highlighted the importance of both adaptation and mitigation. This puts additional requirements on the global climate observing system to support these climate services. • The implications arising from the Intergovernmental Panel on Climate Change (IPCC) 6 th assessment report and recent special reports. • Recent scientific studies of how well the climate cycles of carbon, water and energy are monitored have identified additional observational needs that if addressed would improve scientific understanding, models and projections. This plan aims to identify the major practical actions that should be undertaken in the next 5- 10 years. It identifies six major themes that should be addressed. Within each theme, several actions are identified that are described below with the full details in the main body of the report. The GCOS panels will continually assess the implementation of each of the actions and report on progress in the next status report. The themes are: A. Ensuring Sustainability. Sustained funding is essential to ensure the continuity and the expansion needed for many in situ observations of Essential Climate Variables (ECVs). While some observations have sustained long-term funding, many are supported through short-term funding, with a typical lifetime of a few years, leaving the development of long-term records extremely vulnerable. Satellite observations have been a major success in monitoring many ECVs, but the long-term continuity of some satellite observations is not assured. It is essential that consistent time-series are available across many missions. This theme, in particular, identifies those in situ and satellite observations that are particularly at risk. However, all current observations of ECVs need to be sustained. B. Filling Data Gaps. This theme addresses gaps that have been identified in the existing observing system. In general, the current observations fulfil many requirements and provide the basis for many useful datasets and products of ECVs. However, in situ observations for almost all the ECVs are consistently deficient over certain regions, most notably parts of Africa, South America, Southeast Asia, in the deep ocean and polar regions, a situation that has not improved since the 2015 GCOS Status Report (GCOS-195). 1 GCOS (2021). The Status of the Global Climate Observing 2021: The GCOS Status Report (GCOS-240) 2022 GCOS Implementation Plan - x - C. Improving data quality, availability and utility, including reprocessing. Many climate observations are currently underexploited because of the lack of consistency in their processing and usability. This theme looks at how the original observational data is transformed into user- relevant information. Standards are required throughout the phases of the processing chain that transform observations into user-relevant products. These should address uncertainty, the use of uniform metadata and quality attributes and also support the generation of sensor-agnostic gridded datasets. Further effort is required towards ensuring data could be readily used in reanalysis and is fit for purpose. D. Managing Data. To address and understand climate change, the longest possible time series need to be preserved and made available in perpetuity. Every ECV needs to have one or more recognized global data repositories that are well-curated, provide free and open access to data, are sustainable and have clear guidance for users. Global Climate Data Centres should abide by defined principles such as the TRUST Principles2 and FAIR Principles3. Data rescue from hard copy or archaic digital formats allows data series to be extended in the past and needs to be adequately planned and funded with the results openly and freely available. This theme aims to organise more efficiently data rescue, data sharing, data curation and data provision. E. Engaging with Countries. Many climate observations are made by national bodies; however, these efforts need support and coordination. Some countries have national programmes that need to be connected regionally and globally to share and communicate issues and solutions. GCOS can help by linking these national efforts into the global system, providing information on observing needs, promoting needs for support and access to global information. Ultimately the benefits of climate observations need to be widely understood and the contributions of national observations to global datasets enhanced. F. Other Emerging Needs. Stakeholder needs are evolving, and the actions in this theme address some of these needs. The GCOS Expert Panels have already identified several areas where emerging needs arising from response measures such as adaptation and mitigation need to be addressed in the short term. GCOS is looking at how observations more generally can support adaptation and will report these findings in coming years. Global climate observations are made by a wide range of actors. Satellite observations are vital and are coordinated by the Joint Committee on Earth Observations Satellites/Coordination Group on Meteorological Satellites CEOS/CGMS Working Group on Climate (WGClimate). Ocean observations are performed by many countries coordinated thorough the Global Ocean Observing System, GOOS. The World Meteorological Organization coordinates National Meteorological and Hydrological Services (NMHSs) which provide many of the observations needed for monitoring the climate. Other observations are provided by a wide range of international and national bodies, and academia. This implementation plan will be followed by the publication of a series of supplements focusing on each of these constituencies providing guidance on the actions that they can implement. Table 1 provides links between the actions and the bodies expected to implement the actions. The benefits of climate observations far exceed their cost. While no complete and comprehensive cost-benefit analysis of the global climate observing system has been conducted, analysis of its component parts shows its extensive benefits. 2 Lin, D., J. Crabtree, I. Dillo, et al., 2020: The TRUST Principles for digital repositories. Scientific Data 7, 144, DOI:10.1038/s41597- 020-0486-7 3 Wilkinson, M.D., et al., 2016: The FAIR guiding principles for scientific data management and stewardship. Scientific Data, 3, DOI:10.1038/sdata.2016.18 2022 GCOS Implementation Plan - xi - Revised observational requirements for the ECVs are provided in document ‘The 2022 GCOS ECVs Requirements’, (GCOS-245).