CDO

Hi there,

I'm trying to use `cdo ml2pl` to regrid some CMIP6 data to pressure levels, data attached.

The script I'm using is:

```
#!/bin/bash

1. environment with newest cdo version
   conda activate cdo_env

plevels="100,500,1000,2000,3000,5000,7000,10000,15000,20000,25000,30000,40000,50000,60000,62500,65000,67500,70000,72500,75000,77500,80000,82500,85000,87500,90000,92500,95000,97500,100000"

cdo ml2pl,$plevels -selname,mc MIROC6_example.nc MIROC6_example_cmip6_plevs.nc
```

However, I get this error:

```
cdo(1) selname: Process started
cdo ml2pl (Warning): No 3D variable with hybrid sigma pressure coordinate found!
Exception caught when trying to allocate 9555082875204796416 vector elements: vector::_M_default_append in field.cc:33
terminate called after throwing an instance of 'std::length_error'
what(): vector::_M_default_append
cdo_remap_cmip6_plev.sh: line 11: 44744 Aborted cdo ml2pl,$plevels -selname,mc MIROC6_example.nc MIROC6_example_cmip6_plevs.nc
```

I worry it's something to do with the lack of "bounds" for `a` and `b`, but I'm really not sure. Any help appreciated!
Cheers
Andrew