UKESM1: description and evaluation of the U.K. Earth System Model

Sellar, Alistair A.; Jones, Colin G.; Mulcahy, Jane P.; Tang, Yongming; Yool, Andrew ORCID: https://orcid.org/0000-0002-9879-2776; Wiltshire, Andy; O'Connor, Fiona M.; Stringer, Marc; Hill, Richard; Palmieri, Julien ORCID: https://orcid.org/0000-0002-0226-5243; Woodward, Stephanie; de Mora, Lee; Kuhlbrodt, Till; Rumbold, Steven T.; Kelley, Douglas I.; Ellis, Rich; Johnson, Colin E.; Walton, Jeremy; Abraham, Nathan Luke; Andrews, Martin B.; Andrews, Timothy; Archibald, Alex T.; Berthou, Segolene; Burke, Eleanor; Blockley, Ed; Carslaw, Ken; Dalvi, Mohit; Edwards, John; Folberth, Gerd A.; Gedney, Nicola; Griffiths, Paul T.; Harper, Anna B.; Hendry, Maggie A.; Hewitt, Alan J.; Johnson, Ben; Jones, Andy; Jones, Chris D.; Keeble, James; Liddicoat, Spencer; Mordenstern, Olaf; Parker, Robert J.; Predoi, Valeriu; Robertson, Eddy; Siahaan, Antony; Smith, Robin S.; Swaminathan, Ranjini; Woodhouse, Matthew T.; Zeng, Guang; Zerroukat, Mohamed. 2019 UKESM1: description and evaluation of the U.K. Earth System Model. Journal of Advances in Modeling Earth Systems, 11 (12). 4513-4558. https://doi.org/10.1029/2019MS001739

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Official URL: https://agupubs.onlinelibrary.wiley.com/doi/10.102...

Abstract/Summary

We document the development of the first version of the United Kingdom Earth System Model UKESM1. The model represents a major advance on its predecessor HadGEM2‐ES, with enhancements to all component models and new feedback mechanisms. These include: a new core physical model with a well‐resolved stratosphere; terrestrial biogeochemistry with coupled carbon and nitrogen cycles and enhanced land management; tropospheric‐stratospheric chemistry allowing the holistic simulation of radiative forcing from ozone, methane and nitrous oxide; two‐moment, five‐species, modal aerosol; and ocean biogeochemistry with two‐way coupling to the carbon cycle and atmospheric aerosols. The complexity of coupling between the ocean, land and atmosphere physical climate and biogeochemical cycles in UKESM1 is unprecedented for an Earth system model. We describe in detail the process by which the coupled model was developed and tuned to achieve acceptable performance in key physical and Earth system quantities, and discuss the challenges involved in mitigating biases in a model with complex connections between its components. Overall the model performs well, with a stable pre‐industrial state, and good agreement with observations in the latter period of its historical simulations. However, global mean surface temperature exhibits stronger‐than‐observed cooling from 1950 to 1970, followed by rapid warming from 1980 to 2014. Metrics from idealised simulations show a high climate sensitivity relative to previous generations of models: equilibrium climate sensitivity (ECS) is 5.4 K, transient climate response (TCR) ranges from 2.68 K to 2.85 K, and transient climate response to cumulative emissions (TCRE) is 2.49 K/TtC to 2.66 K/TtC.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1029/2019MS001739
UKCEH and CEH Sections/Science Areas:	Hydro-climate Risks (Science Area 2017-)
ISSN:	1942-2466
NORA Subject Terms:	Ecology and Environment Meteorology and Climatology
Date made live:	01 Nov 2019 16:37 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/525748

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1029/2019MS001739

UKCEH and CEH Sections/Science Areas:

Hydro-climate Risks (Science Area 2017-)

ISSN:

1942-2466

NORA Subject Terms:

Ecology and Environment
Meteorology and Climatology

Date made live:

01 Nov 2019 16:37 +0 (UTC)