.. _recipes_tcr:

Transient Climate Response
==========================

Overview
--------


The transient climate response (TCR) is defined as the global and annual mean
surface air temperature anomaly in the *1pctCO2* scenario (1% CO\ :sub:`2`
increase per year) for a 20 year period centered at the time of CO\ :sub:`2`
doubling, i.e. using the years 61 to 80 after the start of the simulation. We
calculate the temperature anomaly by subtracting a linear fit of the
*piControl* run for all 140 years of the *1pctCO2* experiment prior to the TCR
calculation (see `Gregory and Forster, 2008`_).

.. _`Gregory and Forster, 2008`: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2008JD010405


Available recipes and diagnostics
---------------------------------

Recipes are stored in recipes/

   * recipe_tcr.yml


Diagnostics are stored in diag_scripts/

   * climate_metrics/tcr.py
   * climate_metrics/create_barplot.py
   * climate_metrics/create_scatterplot.py


User settings in recipe
-----------------------

* Preprocessor

   * ``area_statistics`` (*operation: mean*): Calculate global mean.

.. _tcr.py:

* Script climate_metrics/tcr.py

   * ``calculate_mmm``, *bool*, optional (default: ``True``): Calculate
     multi-model mean TCR.
   * ``plot``, *bool*, optional (default: ``True``): Plot temperature vs. time.
   * ``read_external_file``, *str*, optional: Read TCR from external file. The
     path can be given relative to this diagnostic script or as absolute path.
   * ``savefig_kwargs``, *dict*, optional: Keyword arguments for
     :func:`matplotlib.pyplot.savefig`.
   * ``seaborn_settings``, *dict*, optional: Options for
     :func:`seaborn.set_theme` (affects all plots).

* Script climate_metrics/create_barplot.py

   See :ref:`here<create_barplot.py>`.

* Script climate_metrics/create_scatterplot.py

   See :ref:`here<create_scatterplot.py>`.


Variables
---------

* *tas* (atmos, monthly, longitude, latitude, time)


Observations and reformat scripts
---------------------------------

*None*


References
----------

* Gregory, J. M., and P. M. Forster. "Transient climate response estimated from
  radiative forcing and observed temperature change." Journal of Geophysical
  Research: Atmospheres 113.D23 (2008).


Example plots
-------------

.. _fig_tcr_1:
.. figure:: /recipes/figures/tcr/CanESM2.png
   :align: center
   :width: 50%

   Time series of the global mean surface air temperature anomaly (relative to
   the linear fit of the pre-industrial control run) of CanESM2 (CMIP5) for the
   1% CO\ :sub:`2` increase per year experiment. The horizontal dashed line
   indicates the transient climate response (TCR) defined as the 20 year
   average temperature anomaly centered at the time of CO\ :sub:`2` doubling
   (vertical dashed lines).