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Climate change necessitates a global effort to reduce greenhouse gas emissions while adapting to increased climate risks. This broader climate transition will involve large-scale global interventions including renewable energy deployment, coastal protection and retreat, and enhanced space cooling, all of which will result in CO 2 emissions from energy and materials use. Yet, the magnitude of the emissions embedded in these interventions remains unconstrained, opening the potential for underaccounting of emissions and conflicts or synergies between mitigation and adaptation goals. Here, we use a suite of models to estimate the CO 2 emissions embedded in the broader climate transition. For a gradual decarbonization pathway limiting warming to 2 °C, selected adaptation-related interventions will emit ∼1.3 GtCO 2 through 2100, while emissions from energy used to deploy renewable capacity are much larger at ∼95 GtCO 2 . Together, these emissions are equivalent to over 2 y of current global emissions and 8.3% of the remaining carbon budget for 2 °C. Total embedded transition emissions are reduced by ∼80% to 21.2 GtCO 2 under a rapid pathway limiting warming to 1.5 °C. However, they roughly double to 185 GtCO 2 under a delayed pathway consistent with current policies (2.7 °C warming by 2100), mainly because a slower transition relies more on fossil fuel energy. Our results provide a holistic assessment of carbon emissions from the transition itself and suggest that these emissions can be minimized through more ambitious energy decarbonization. We argue that the emissions from mitigation, but likely much less so from adaptation, are of sufficient magnitude to merit greater consideration in climate science and policy. 

Abstract. The University of Victoria Earth System Climate Model (UVic ESCM) ofintermediate complexity has been a useful tool in recent assessments oflong-term climate changes, including both paleo-climate modelling anduncertainty assessments of future warming. Since the last official releaseof the UVic ESCM 2.9 and the two official updates during the last decade,considerable model development has taken place among multiple researchgroups. The new version 2.10 of the University of Victoria Earth SystemClimate Model presented here will be part of the sixth phaseof the Coupled Model Intercomparison Project (CMIP6). More precisely it willbe used in the intercomparison of Earth system models of intermediatecomplexity (EMIC), such as the C4MIP, the Carbon Dioxide Removal and ZeroEmissions Commitment model intercomparison projects (CDR-MIP and ZECMIP,respectively). It now brings together and combines multiple modeldevelopments and new components that have come about since the lastofficial release of the model. The main additions to the base model are(i) an improved biogeochemistry module for the ocean, (ii) a vertically resolvedsoil model including dynamic hydrology and soil carbon processes, and (iii) arepresentation of permafrost carbon. To set the foundation of its use, wehere describe the UVic ESCM 2.10 and evaluate results from transienthistorical simulations against observational data. We find that the UVicESCM 2.10 is capable of reproducing changes in historical temperature andcarbon fluxes well. The spatial distribution of many ocean tracers,including temperature, salinity, phosphate and nitrate, also agree well withobserved tracer profiles. The good performance in the ocean tracers isconnected to an improved representation of ocean physical properties. Forthe moment, the main biases that remain are a vegetation carbon density thatis too high in the tropics, a higher than observed change in the ocean heatcontent (OHC) and an oxygen utilization in the Southern Ocean that is too low.All of these biases will be addressed in the next updates to the model.