Statistically Downscaled CMIP6 Projections Show Stronger Warming for Germany

Frank Kreienkamp,Philip Lorenz,Tobias Geiger

doi:10.3390/atmos11111245

Frank Kreienkamp, Philip Lorenz + Show 1 more

Open Access

https://doi.org/10.3390/atmos11111245

Copy DOI

Journal: Atmosphere	Publication Date: Nov 18, 2020
Citations: 16	License type: CC BY 4.0

Affiliation: German Meteorological Service

Abstract

Climate modelling output that was provided under the latest Coupled Model Intercomparison Project (CMIP6) shows significant changes in model-specific Equilibrium Climate Sensitivity (ECS) as compared to CMIP5. The newer versions of many Global Climate Models (GCMs) report higher ECS values that result in stronger global warming than previously estimated. At the same time, the multi-GCM spread of ECS is significantly larger than under CMIP5. Here, we analyse how the differences between CMIP5 and CMIP6 affect climate projections for Germany. We use the statistical-empirical downscaling method EPISODES in order to downscale GCM data for the scenario pairs RCP4.5/SSP2-4.5 and RCP8.5/SSP5-8.5. We use data sets of the GCMs CanESM, EC-Earth, MPI-ESM, and NorESM. The results show that the GCM-specific changes in the ECS also have an impact at the regional scale. While the temperature signal under regional climate change remains comparable for both CMIP generations in the MPI-ESM chain, the temperature signal increases by up to 3 °C for the RCP8.5/SSP5-8.5 scenario pair in the EC-Earth chain. Changes in precipitation are less pronounced and they only show notable differences at the seasonal scale. The reported changes in the climate signal will have direct consequences for society. Climate change impacts previously projected for the high-emission RCP8.5 scenario might occur equally under the new SSP2-4.5 scenario.

Highlights

Climate change across the globe is driven by changing forcings and it is shaped by versatile processes in and interactions between the spheres of the Earth system on various spatial-temporal scales
While the temperature signal under regional climate change remains comparable for both CMIP generations in the MPI-ESM chain, the temperature signal increases by up to 3 °C for the RCP8.5/SSP5-8.5 scenario pair in the EC-Earth chain
The increases in Equilibrium Climate Sensitivity (ECS) and corresponding stronger warming signal for some of the updated climate models contributing to CMIP6 are confirmed for the area of Germany

Summary

Introduction

Climate change across the globe is driven by changing forcings (e.g., solar irradiance; chemical compositions of the atmosphere; volcanic outbreaks) and it is shaped by versatile processes in and interactions between the spheres of the Earth system on various spatial-temporal scales. Models (GCMs, see e.g., [1,2,3,4,5]), which simulate the evolution of climate states under prescribed forcings, constitute the main tool to analyse potential changes in the climate system. GCMs are capable of picturing climate states on global to continental scale, but not on regional scales. The latest Coupled Model Intercomparison Project (CMIP6) provides simulations from a new generation of climate models, which —in comparison to CMIP5—are based on a new scenario framework [6]. These changes will be fully documented in the IPCC’s upcoming Sixth Assesment Report (AR6). The first analyses of the newest GCM output show that the Equilibrium Climate Sensitivity (ECS)

Methods

Results

Discussion

Conclusion