Climate and carbon cycle changes from 1850 to 2100 in MPI‐ESM simulations for the Coupled Model Intercomparison Project phase 5

TLDR

The study reviews MPI‑ESM configurations, forcings, and initialization, and reports on simulated climate and carbon‑cycle changes. MPI‑ESM is run in CMIP5 through CO₂‑only and RCP‑based experiments, with detailed model set‑ups and forcing specifications. Results show global warming of 1.5–4.4 °C (RCP2.6–RCP8.5), with temperature and precipitation patterns largely independent of warming, reduced ocean heat‑uptake efficiency accelerating warming, increasing oceanic carbon uptake, land acting as a net sink (especially boreal), and tropical carbon sources disappearing in RCP4.5 due to reforestation.

Abstract

The new Max‐Planck‐Institute Earth System Model (MPI‐ESM) is used in the Coupled Model Intercomparison Project phase 5 (CMIP5) in a series of climate change experiments for either idealized CO 2 ‐only forcing or forcings based on observations and the Representative Concentration Pathway (RCP) scenarios. The paper gives an overview of the model configurations, experiments related forcings, and initialization procedures and presents results for the simulated changes in climate and carbon cycle. It is found that the climate feedback depends on the global warming and possibly the forcing history. The global warming from climatological 1850 conditions to 2080–2100 ranges from 1.5°C under the RCP2.6 scenario to 4.4°C under the RCP8.5 scenario. Over this range, the patterns of temperature and precipitation change are nearly independent of the global warming. The model shows a tendency to reduce the ocean heat uptake efficiency toward a warmer climate, and hence acceleration in warming in the later years. The precipitation sensitivity can be as high as 2.5% K −1 if the CO 2 concentration is constant, or as small as 1.6% K −1 , if the CO 2 concentration is increasing. The oceanic uptake of anthropogenic carbon increases over time in all scenarios, being smallest in the experiment forced by RCP2.6 and largest in that for RCP8.5. The land also serves as a net carbon sink in all scenarios, predominantly in boreal regions. The strong tropical carbon sources found in the RCP2.6 and RCP8.5 experiments are almost absent in the RCP4.5 experiment, which can be explained by reforestation in the RCP4.5 scenario.