The NASA-GISS ModelE2.1-CC2 ESM: development and simulations

Abstract. This paper describes the NASA Goddard Institute for Space Studies (GISS) ModelE2.1-Carbon Cycle version 2 Earth System Model (NASA GISS E2.1-CC2 ESM), assesses its skill against observations and reports on its performance under future climate scenarios. The first version of GISS ESM (GISS‐E2.1‐G‐CC) was introduced in CMIP6, and therefore ModelE2.1-CC2 is a post CMIP6 release that includes the same physical climate model E2.1-G, updated ocean and land carbon cycle and longer equilibrium simulations. While the focus here is on the land and ocean carbon components and their interactions with atmosphere and ice, we also describe in detail the physical coupled model for consistency and ease of reference. We detail parameterizations, tuning, and conservation diagnostics that are relevant to the global (land & ocean) carbon cycle. We also describe a full suite of simulations performed with this model, including pre-industrial control, historical, and future climate scenarios. The model is an improvement to prior releases, has been better tuned and exhibits smaller drifts. However some persistent biases remain, particularly with regards to low ocean and land primary production. Results shown here are compared to previous versions of the model, as well as the state-of-the art in Earth system modeling via community intercomparisons.