Journal Article

The global energy balance as represented in CMIP6 climate models

Wild, Martin

2020

Overview

A plausible simulation of the global energy balance is a first-order requirement for a credible climate model. Here I investigate the representation of the global energy balance in 40 state-of-the-art global climate models participating in the Coupled Model Intercomparison Project phase 6 (CMIP6). In the CMIP6 multi-model mean, the magnitudes of the energy balance components are often in better agreement with recent reference estimates compared to earlier model generations on a global mean basis. However, the inter-model spread in the representation of many of the components remains substantial, often on the order of 10–20 Wm −2 globally, except for aspects of the shortwave clear-sky budgets, which are now more consistently simulated by the CMIP6 models. The substantial inter-model spread in the simulated global mean latent heat fluxes in the CMIP6 models, exceeding 20% (18 Wm −2 ), further implies also large discrepancies in their representation of the global water balance. From a historic perspective of model development over the past decades, the largest adjustments in the magnitudes of the simulated present-day global mean energy balance components occurred in the shortwave atmospheric clear-sky absorption and the surface downward longwave radiation. Both components were gradually adjusted upwards over several model generations, on the order of 10 Wm −2 , to reach 73 and 344 Wm −2 , respectively in the CMIP6 multi-model means. Thereby, CMIP6 has become the first model generation that largely remediates long-standing model deficiencies related to an overestimation in surface downward shortwave and compensational underestimation in downward longwave radiation in its multi-model mean.

• Publisher: Springer Berlin Heidelberg,Springer,Springer Nature B.V
• Subject: absorption / Analysis / Atmospheric absorption / Atmospheric models / Budgets / Climate / Climate change / Climate models / Climatology / Components / Computer simulation / dynamics / Earth and Environmental Science / Earth Sciences / Energy / Energy balance / Geophysics/Geodesy / Global climate / Global climate models / Global water balance / Heat flux / Heat transfer / Intercomparison / Latent heat / Long wave radiation / Oceanography / Radiation / Representations / Short wave radiation / Simulation / terrestrial radiation / Water balance / water budget