Xarray merge warning in process_isimip_data

[lilianschuster]

I am getting a xarray warning when running process_isimip_data that xarray will change its xr.merge behaviour. When running future simulations it results in a lot of warning which is cluttering the slurm files. Probably we should add join='outer' to preserve the old behaviour on these two lines

oggm/oggm/shop/gcm_climate.py

Line 287 in dfca928

temp_a = xr.merge([temp_a_gcm, temp_a_hist],

and

oggm/oggm/shop/gcm_climate.py

Line 306 in dfca928

precip_a = xr.merge([precip_a_gcm, precip_a_hist],

?

For more info: Here is the warning that I am getting ...
FutureWarning: In a future version of xarray the default value for join will change from join='outer' to join='exact'. This change will result in the following ValueError: cannot be aligned with join='exact' because index/labels/sizes are not equal along these coordinates (dimensions): 'time' ('time',) The recommendation is to set join explicitly for this case. temp_a = xr.merge([temp_a_gcm, temp_a_hist], ...

--> and here are the xarray changes described: https://docs.xarray.dev/en/v2025.08.0/user-guide/combining.html#merge

[fmaussion]

Do you want to make the change @lilianschuster ?