Hi there,

I'm using xarray's open_zarr() function to analyse CMIP6 data:

```python

Function to load data: df_data has the catalogue of the variable of interest

def load_data(df_data, source_id, expt_id): """ Load data for given variable, source and expt ids. """ uri = df_data[(df_data.source_id == source_id) & (df_data.experiment_id == expt_id)].zstore.values[0]

gcs = gcsfs.GCSFileSystem(token='anon')
ds = xr.open_zarr(gcs.get_mapper(uri), consolidated=True)
return ds

Just test with 1 model for now:

source_ids_tmp = ['CESM2']

for model_name in source_ids_tmp: print('\n\nStarting ' + model_name +'\n') ds_hist = load_data(df_mon_tas, model_name, experiment_ids[0]).sel(time=slice('1976', '2005')) ```

Problem Description

However, the time slicing fails with the following error:

TypeError: cannot compare netcdftime._netcdftime.DatetimeNoLeap(1932, 7, 15, 12, 0, 0, 0, 1, 196) and '1976'

Looking at the Dataset metedata, the time variable is described as follows:

• time (time) object 1850-01-15 12:00:00 ... 2014-12-15 12:00:00 time_bnds (time, nbnd) object dask.array<chunksize=(1980, 2)>

For another CMIP6 model (MIROC6), the time slicing works fine. That model has the following metadat for time:

• time (time) datetime64[ns] 1850-01-16T12:00:00 ... 2014-12-16T12:00:00 time_bnds (time, bnds) datetime64[ns] dask.array<chunksize=(1980, 2)>

When the time variable is converted to a datetime[ns] object, time slicing seems to work. Any idea what the problem is?

Thanks,

Mike

Output of xr.show_versions()

INSTALLED VERSIONS ------------------ commit: None libhdf5: 1.10.1 libnetcdf: 4.4.1.1 xarray: 0.14.0 pandas: 0.25.1 numpy: 1.16.2 scipy: 1.2.1 netCDF4: 1.3.1 pydap: installed h5netcdf: 0.5.0 h5py: 2.7.0 Nio: None zarr: 2.3.2 cftime: None nc_time_axis: None PseudoNetCDF: None rasterio: None cfgrib: None iris: None bottleneck: 1.2.1 dask: 0.15.3 distributed: 1.19.1 matplotlib: 3.0.0 cartopy: 0.16.0 seaborn: 0.9.0 numbagg: None setuptools: 36.5.0.post20170921 pip: 19.0.3 conda: 4.4.6 pytest: 3.3.0 IPython: 6.1.0 sphinx: 1.6.3