The overall aim of COUP was to use landscape-scale process understanding to constrain uncertainties in Earth System Model (ESM) projections of the permafrost-climate feedback. The following objectives were addressed: 1. Use landscape-scale system understanding to develop JULES (the land surface scheme of the UKESM1 ESM) to include permafrost-climate feedback processes 2. Provide an estimate of the permafrost-climate feedback in the updated UKESM1 ESM 3. Provide high-resolution quantification of potential permafrost-climate feedbacks at sites covering the full range of pan-Eurasian environmental conditions 4. Constrain uncertainties in a new estimate of the permafrost-climate feedback based on a simplified carbon climate framework tuned to a range of ESMs 5. Open-source publication of circumpolar datasets to support ESM development in the wider research community

As the global climate warms, thawing permafrost may lead to increased greenhouse gas release from Arctic and Boreal ecosystems. Scientists agree that this permafrost-climate feedback is important to the global climate system, but its magnitude and timing remains poorly understood. The overall aim of COUP was to use detailed understanding of landscape-scale processes to improve global scale climate models. Better predictions of how permafrost areas will respond to a warming climate can help us understand and plan for future global change. In recent years much scientific progress has been made towards understanding the complex responses of permafrost ecosystem to climate warming. Despite this, large challenges remain when it comes to including these processes in global climate models. Permafrost ecosystems are highly variable and studies show that very detailed field investigations are needed to understand complexities. Because global scale models cannot run at such high-resolutions, the propose d an approach was to local landscape-scale field studies and modelling to identify those key variables that should be improved in global models. Field studies and high-resolution modelling was used at field sites covering all pan-Eurasian environmental conditions. The system understanding gained from this was then used to (1) scale key variables so they are useful for global models and (2) improve a new global climate model. In the final step, the improved global climate models was used to quantify the impact of thawing permafrost on the global climate.