Climate Projections

Here, we used the climate input data of the ISIMIP2b simulation round to force the global hydrological models. This was done to enable comparability to ISIMIP2b multi-model ensemble runs in the analysis. Below, we briefly describe how these climate input data were generated.

Historical (1861-2005) and future climate conditions were simulated by multiple general circulation models (GCMs) in the framework of the Coupled Model Intercomparison Project Phase 5 (CMIP5). The output data from the following four GCMs was used for ISIMIP2b:

  • IPSL-CM5A-LR
  • GFDL-ESM2M
  • MIROC5
  • HadGEM2-ES

To account for future human-induced greenhouse gas (GHG) emissions scenarios, the GCMs were forced by the Representative Concentration Pathways (RCPs) adopted by the Intergovernmental Panel on Climate Change for its Fifth Assessment Report (AR5) in 2014:

  • RCP2.6 (lowest GHG emission scenario)
  • RCP4.5
  • RCP6.0
  • RCP8.5 (highest GHG emission scenario)

Each of these pathways is based on a set of assumptions about economic activity, energy sources, population growth and other socio-economic factors, and contains emission estimates up to the year 2100. The aim of including all four RCPs is to increase the number of ensemble members and, in this way, to better represent the uncertainty of future climate projections. For more detailed information concerning the RCPs, please consult The Beginner’s Guide to Representative Concentration Pathways by Graham Wayne.

In the framework of ISIMIP2b, the original output data from the GCMs was bias corrected based on the EWEMBI (EartH2Observe, WFDEI and ERA-Interim data Merged and Bias-corrected for ISIMIP) observational dataset, which covers the entire globe at 0.5° horizontal spatial resolution and daily temporal resolution from 1979 to 2013. For more detailed information concerning the bias correction, please consult the ISIMIP2b Bias Correction Fact Sheet. The resulting ISIMIP2b climate input data set has a daily temporal resolution and a 0.5° horizontal spatial resolution. In the context of CO-MICC, future GCM runs were carried out over 30-year time periods centered from 2020 to 2085 in 5-year time steps.