Open AccessUKESM1: Description and Evaluation of the U.K. Earth System Model
Author(s) -
Sellar Alistair A.,
Jones Colin G.,
Mulcahy Jane P.,
Tang Yongming,
Yool Andrew,
Wiltshire Andy,
O'Connor Fiona M.,
Stringer Marc,
Hill Richard,
Palmieri Julien,
Woodward Stephanie,
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 Ségolène,
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,
Morgenstern Olaf,
Parker Robert J.,
Predoi Valeriu,
Robertson Eddy,
Siahaan Antony,
Smith Robin S.,
Swaminathan Ranjini,
Woodhouse Matthew T.,
Zeng Guang,
Zerroukat Mohamed
Publication year - 2019
Publication title -
journal of advances in modeling earth systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.03
H-Index - 58
ISSN - 1942-2466
DOI - 10.1029/2019ms001739
Subject(s) - radiative forcing , biogeochemistry , earth system science , environmental science , climate sensitivity , climate model , stratosphere , atmospheric sciences , forcing (mathematics) , biogeochemical cycle , climatology , ozone layer , atmosphere (unit) , carbon cycle , troposphere , atmospheric model , greenhouse gas , aerosol , climate change , meteorology , geology , chemistry , physics , oceanography , ecology , ecosystem , environmental chemistry , biology
We document the development of the first version of the U.K. 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 idealized simulations show a high climate sensitivity relative to previous generations of models: Equilibrium climate sensitivity is 5.4 K, transient climate response ranges from 2.68 to 2.85 K, and transient climate response to cumulative emissions is 2.49 to 2.66 K TtC −1 .