This dataset contains MPI-ESM-1.2-LR output from the work package 1 (WP1) IRR scenario of idealized constant global cropland expansion with irrigation. Similar to the CROP scenario, the simulation branches from the 2014 CMIP6 historical concentration-driven simulation and spans 160 years (2015-01-01 to 2174-12-31), with anthropogenic (trace gases, aerosols, population density) and natural forcings (solar radiation, wildfire, lightning, natural aerosols) held constant at 2014 levels.
In the IRR scenario, irrigation water is added to those grid cells which were also changed to 100% cropland in the CROP scenario. Since there is no native irrigation scheme in JSBACH3.2, we have implemented a rather simple scheme as follows: The soil moisture of the first (0–0.065 m) and second
(0.065–0.319 m) soil layers (out of five) is filled at each simulation time step (20–30 min) to field capacity if the field capacity was not reached and if enough irrigation water is available in the irrigation water storage. Irrigation water is stored in a virtual reservoir at each time step when the reservoir drops below 0.2 m and is filled up with all available water from (surface) runoff and drainage during that time step. Generally, we ran the land model JSBACH3.2 with the following options:
- use_dynveg = false
- use_disturbance = true
- lcc_forcing_type = transitions
- lcc_scheme = 2
This approach mimics cropland expansion with irrigation across all vegetated, cropland and urban areas but avoids cropland being established in e.g. desert, high-altitude and tundra regions (unhospitable land). The checkerboard-like pattern, with its homogeneous distribution of changed and unchanged grid cells, allows the application of an established method to separate local and nonlocal biogeophyiscal as well as biogoechemical effects of this land management change to be compared to the scenario of cropland expansion without irrigation (CROP) (see Winckler et al., 2017 (doi: 10.1175/JCLI-D-16-0067.1), De Hertog et al., 2023 (doi: 10.5194/esd-14-629-2023), and Guo et al., 2025 (doi: 10.5194/esd-16-631-2025)).