Input data set: Land Use 15crops (ISIMIP4)

Description:

Annual grid-cell fractions of fifteen ISIMIP crop groups, each split into rainfed and irrigated area, on the ISIMIP 0.25° and 0.5° grids.

LUH3 resolves cropland only into five crop functional types. landuse-15crops downscales those five into the fifteen ISIMIP crop groups (temperate cereals, rice, temperate and tropical roots, four oil crop groups, maize, tropical cereals, pulses, two residual annual groups and the two perennial groups) by imposing a crop composition taken from CROPGRIDS 2020 within each functional type. The fifteen groups sum to the five functional types of landuse-5crops in every cell. The two perennial groups are carried as in landuse-5crops, split into food and feed production and dedicated second-generation bioenergy plantations. The pasture total is carried as well, so a crop model can read cropland and pasture from one file.

Seasonal detail is provided by the separate landuse-subgroups dataset, documented under Land Use Subgroups: it splits temperate cereals into winter wheat, spring wheat and a non-wheat residual, and rice into a first and a second growing season. Those subgroups sum exactly to their parent groups in this dataset.

All fractions are fractions of the whole grid cell, not of its land area.

Derived from the CMIP7 input4MIPs UofMD Land-Use Harmonization (LUH3) dataset, using the multiple-states land-state fractions together with the multiple-management irrigation and bioenergy fractions. Project page: https://luh.umd.edu/

Historical: UofMD-landState-3-1-2
SSP1-VL: UofMD-landState-vl-3-1-1
SSP3-H: UofMD-landState-h-3-1-1

All three were taken at input4MIPs publication version v20260408.

Chini, L. and Hurtt, G.: Land-Use Harmonization 3 v1.2 for CMIP7 Historical (LUH3 v1.2), source_id UofMD-landState-3-1-2, https://doi.org/10.5281/zenodo.19261724 — used for histsoc, 1850soc, 1901soc and 2021soc

Chini, L. and Hurtt, G.: Land-Use Harmonization 3 Future Scenario VL v1.1 for ScenarioMIP (LUH3-VL v1.1), source_id UofMD-landState-vl-3-1-1, https://doi.org/10.5281/zenodo.19353397 — used for ssp1vlsoc-noadapt

Chini, L. and Hurtt, G.: Land-Use Harmonization 3 Future Scenario H v1.1 for ScenarioMIP (LUH3-H v1.1), source_id UofMD-landState-h-3-1-1, https://doi.org/10.5281/zenodo.19354835 — used for ssp3hsoc-noadapt

The crop composition within each functional type is taken from CROPGRIDS v1.08, a global geo-referenced dataset of the harvested and cropped area of 173 crops for the year 2020 at 0.05°:
Tang et al. (2024), CROPGRIDS, Scientific Data, https://doi.org/10.1038/s41597-024-03247-7

References for the LUH methodology:
Hurtt et al. (2020), Geoscientific Model Development, https://doi.org/10.5194/gmd-13-5425-2020
Chini et al. (2021), Earth System Science Data, https://doi.org/10.5194/essd-13-4175-2021

The crop composition within a functional type is static. The shares that split each LUH3 crop functional type into crop groups come from CROPGRIDS 2020 and are applied unchanged to every year and every scenario, in both rounds. Only the functional-type total varies in time. A shift in which crops are grown within a functional type (a region moving from wheat to barley, say) is therefore not represented; changes in the group areas follow changes in the functional-type area alone.

Fractions are of the whole grid cell, not of its land area. Ice and water are held static in LUH3 and already subtracted upstream. Do not renormalize to land area.

Irrigation is a share of the crop area, not of the grid cell. The published irrigated and rainfed variables are already the product of the crop-type area and its irrigated share, so they can be added and compared directly.

Annual values are interpolated. The LUH3 reconstruction is anchored on decadal to centennial steps for much of the historical period. Smooth year-to-year behaviour in the early record is a property of that interpolation, not observed interannual variability.

The two resolutions do not give the same global totals. The 0.5° product is conservatively remapped from the native 0.25° grid and renormalized over the land area of each coarser cell, so a global area total computed from a 30arcmin file exceeds the same total from the 15arcmin file by about 1 %, concentrated in coastal cells. Use the 15arcmin files when the global total matters.

Sums close to within numerical tolerance, not bit-exactly. The fifteen groups reproduce the five functional types to about 1e-6, and the seasonal sub-splits of landuse-subgroups sum back to their parent group here to the same tolerance.

2021soc means different things in the two rounds. Under ISIMIP4b it holds the 2021 state fixed across the 2022–2100 future window; under ISIMIP4a it holds the same state fixed across the full 1850–2025 historical period, as a present-day baseline.

Under ISIMIP4a the value for 2025 repeats 2024, the last observed year.