Combining ground, atmosphere and space-based measurements to create metrology tools and frameworks to support a climate observing system able to support improved understanding of drivers of climate change. Themes Level 1 satellite traceability Developing highly accurate, cost-effective, sensors for space-based climate observations, suitable for pre-and in-flight measurements, including TRUTHS and FORUM mission studies. Atmospheric ECVs Developing SI traceable measurement methods for bio-geophysical parameters, considering optical and Synthetic Aperture Radar sampling techniques. Biophysical ECVs Developing satellite-derived SI traceable measurement methods of greenhouse gas emissions and natural carbon sinks, including robust monitoring of carbon emissions reduction policies. Radiation ECVs Developing instrumentation and standards for traceable climate quality measurements, from surface-based networks operated by the WMO and UN. Projects MetEOC is an NPL coordinated series of collaborative European metrology projects supporting Earth Observation applications by establishing metrological techniques, including pre-flight calibration, post-launch on-board and vicarious calibration, and validation of higher level products. MetEOC-4 September 2020 – August 2023 MetEOC-3 September 2017 – February 2021 MetEOC-2 September 2014 – August 2017 MetEOC-1 October 2011 – September 2014 These European Metrology Research Programme (EMPR) and the European Metrology Programme for Innovation and Research (EMPIR) projects are supported by EURAMET’s European Metrology Research Programmes.