ZEMBA v1.0: An energy and moisture balance climate model to investigate Quaternary climate

Abstract. A Zonally-Averaged Energy and Moisture BAlance Climate Model (ZEMBA) is introduced as a simple and computationally efficient tool for studies of the glacial-interglacial cycles of the Quaternary. The model is based on an energy balance model comprising an atmospheric layer, a land component and a two-dimensional ocean transport model with sea ice. In addition, ZEMBA replaces temperature with moist static energy for calculations of diffusive heat transport in the atmospheric layer and includes a hydrological cycle for simulating precipitation and snowfall. Prior to coupling with an ice sheet model, we present and evaluate equilibrium simulations of the model for the pre-industrial period and the Last Glacial Maximum, using prescribed land ice fractions and elevation. In addition, we test the sensitivity of ZEMBA to a doubling of the atmospheric CO₂ concentration and a 2 % increase in solar radiation at the top of the atmosphere. Compared to a global climate model (NorESM2) and reanalysis data (ERA5), ZEMBA reproduces the zonally-averaged climate of the pre-industrial period with reasonable accuracy, capturing features such as surface temperature, precipitation, radiative fluxes, snow cover, sea ice cover and meridional heat transport. The response of ZEMBA to increasing CO₂ concentrations is qualitatively similar to the observational record and climate models of higher complexity, including a polar amplification over the northern hemisphere and during the winter months. The globally-averaged rise in surface air temperature for a doubling in CO₂ is 3.6 °C. Finally, ZEMBA shows success in emulating changes in surface temperature and precipitation during the Last Glacial Maximum when compared to reconstructions and global climate models.