[x] Example added (in the documentation, to an existing notebook, or in a new notebook)
[x] Description in CHANGELOG.rst added (single line such as: (`#XX <https://github.com/openscm/openscm-twolayermodel/pull/XX>`_) Added feature which does something)
CHANGELOG.rst
added (single line such as:(`#XX <https://github.com/openscm/openscm-twolayermodel/pull/XX>`_) Added feature which does something
)