Update variable mapping

[znicholls]

Pull request

Please confirm that this pull request has done the following:

• Tests added
• Documentation added (where applicable) (N/A)
• Example added (either to an existing notebook or as a new notebook, where applicable) (N/A)
• Description in CHANGELOG.rst added

Adding to CHANGELOG.rst

Please add a single line in the changelog notes similar to one of the following:

- (`#XX <http://link-to-pr.com>`_) Added feature which does something
- (`#XX <http://link-to-pr.com>`_) Fixed bug identified in (`#XX <http://link-to-issue.com>`_)

[lewisjared]

Does it handle DAT_SURFACE_TEMP_SUBANNUAL or *_GWPEMIS?

[znicholls]

Does it handle DAT_SURFACE_TEMP_SUBANNUAL or *_GWPEMIS?

DAT_SURFACE_TEMP_SUBANNUAL nope but will add. I'd rather not support *_GWPEMIS, I think this sort of conversion should be done in post-processing rather than relying on the values hard-coded in MAGICC to be right...