The new Max Planck Institute Grand Ensemble with CMIP6 forcing and high-frequency model output

Abstract

Single-model initial-condition large ensembles are powerful tools to quantify the forced response, internal climate variability, and their evolution under global warming. Here, we present the CMIP6 version of the Max Planck Institute Grand Ensemble (MPI-GE CMIP6) with 30 realisations for the historical period and five emission scenarios. The power of MPI-GE CMIP6 goes beyond its predecessor ensemble MPI-GE by providing high-frequency output, the full range of emission scenarios including the highly policy-relevant low emission scenarios SSP1-1.9 and SSP1-2.6, and the opportunity to compare the ensemble to complementary high-resolution simulations. First, we describe MPI-GE CMIP6, evaluate it with observations and reanalyses and compare it to MPI-GE. Then, we demonstrate with six novel application examples how to use the power of the ensemble to better quantify and understand present and future climate extremes, to inform about uncertainty in approaching Paris Agreement global warming limits, and to combine large ensembles and artificial intelligence. For instance, MPI-GE CMIP6 allows us to show that the recently observed Siberian and Pacific North American heatwaves would only avoid reaching 1-2 year return periods in 2071-2100 with low emission scenarios, that recently observed European precipitation extremes are captured only by complementary high-resolution simulations, and that 3-hourly output projects a decreasing activity of storms in mid-latitude oceans. Further, the ensemble is ideal for estimates of probabilities of crossing global warming limits and the irreducible uncertainty introduced by internal variability, and is sufficiently large to be used for infilling surface temperature observations with artificial intelligence.

Decadal Prediction along the Western Irish Coast

“…In this study, we use the first 16 members of the CMIP5 MPI Grand Ensemble (Maher et al, 2019), with CMIP5 historical external forcing until 2005, and CMIP5 scenario RCP4.5 external forcing starting with 2006. We also use the first 16 members of the CMIP6 MPI Grand Ensemble (Olonscheck et al, 2023), with the same CMIP6 external forcing as in assimilation and hindcasts. We analyse the hindcasts and both uninitialised simulations ("CMIP5", "CMIP6") for both potential temperature and salinity at depth.…”