CMIP6 Historical Simulations, model CESM2 (NCAR)

This dataset features a selection of variables generated by the NCAR-CESM2 Earth system model as part of the Coupled Model Intercomparison Project Phase 6 (CMIP6).

The data covers the historical simulation period 1850–2014. Unlike future projections, this experiment utilizes observed time-varying external forcings to reconstruct the climate evolution of the industrial era.

The data is distributed in a compressed Zarr format with near-zero precision loss. It features a daily temporal resolution and is structurally optimized for high-throughput regional assessments and time-series analysis.

Accessing this dataset requires a Zarr v3-compatible library (e.g., zarr-python >= 3.x). Python users can upgrade via pip install "zarr>3".

How to download the data

The default (and preferred) way to access the data requires accessing the api.earthdatahub.destine.eu domain and a valid API key.

Method 1: quick access

It is possible to include the token directly in the URL.

1import xarray as xr
2
3xr.open_dataset(
4    "https://edh:<your personal access token>@api.earthdatahub.destine.eu/cmip6/NCAR-CESM2-historical-r1i1p1f1-day-gn-v0.zarr",
5    chunks={},
6    engine="zarr",
7    zarr_format=3,
8)

Method 2: advanced access

The Python snippet gather the token from a netrc file.

It's required to before running the code snippet below.
1import xarray as xr
2
3xr.open_dataset(
4    "https://api.earthdatahub.destine.eu/cmip6/NCAR-CESM2-historical-r1i1p1f1-day-gn-v0.zarr",
5    storage_options={"client_kwargs":{"trust_env":True}},
6    chunks={},
7    engine="zarr",
8    zarr_format=3,
9)

Variables

Short NameUnitsDescription
clt
%

for the whole atmospheric column, as seen from the surface or the top of the atmosphere. Includes both large-scale and convective cloud.

hfls
W m-2

The surface called "surface" means the lower boundary of the atmosphere. "Upward" indicates a vector component which is positive when directed upward (negative downward). The surface latent heat flux is the exchange of heat between the surface and the air on account of evaporation (including sublimation). In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.

hfss
W m-2

The surface sensible heat flux, also called turbulent heat flux, is the exchange of heat between the surface and the air by motion of air.

hurs
%

Near-Surface Relative Humidity

huss
1

Near-Surface Specific Humidity

pr
kg m-2 s-1

Precipitation

prc
kg m-2 s-1

at surface; includes both liquid and solid phases.

rlds
W m-2

Surface Downwelling Longwave Radiation

rlus
W m-2

Surface Upwelling Longwave Radiation

rlut
W m-2

TOA Outgoing Longwave Radiation

rsds
W m-2

Surface Downwelling Shortwave Radiation

rsus
W m-2

The surface called "surface" means the lower boundary of the atmosphere. "shortwave" means shortwave radiation. Upwelling radiation is radiation from below. It does not mean "net upward". When thought of as being incident on a surface, a radiative flux is sometimes called "irradiance". In addition, it is identical with the quantity measured by a cosine-collector light-meter and sometimes called "vector irradiance". In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.

sfcWind
m s-1

near-surface (usually, 10 meters) wind speed.

tas
K

Near-Surface Air Temperature

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