UK Earth System Modelling News

June 2021

The UK Earth system modelling project is a joint venture between the Met Office and the UKRI Natural Environment Research Council (NERC) to develop and apply a world-leading Earth System Model.

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Introducing UKESM1.1: a new configuration of the UKESM model with an improved historical temperature record

by Jane Mulcahy

We have developed a new configuration of UKESM, UKESM1.1, which includes the revised dry deposition of SO2 as its key science change. The new parameterization leads to a significant improvement (of the order of 50%) in the SO2 bias against ground-based observations in UKESM1 (Hardacre et al., 2021). Read more…

The Virtual Trees of UKESM – Improving Our Simulations

by Douglas Kelley, Nathan Betts, Chantelle Burton, Rebecca Oliver, Arthur Argles, Karina Williams, Chris Jones, Eleanor Blyth, Rahayu Adzhar, France Gerard, Li Guangqi, Lina Mercado, Doug Clark

trees during day from

In the last issue of the UKESM newsletter we explained why trees are essential in climate projections, how we simulate changes in vegetation cover of the land surface and how we evaluate tree cover to ensure we are getting a good performance of the model.  In this newsletter we look at how to improve our simulation of tree cover in UKESM  Read more…

Four Seasons In One Day: The Met Office, Weather, Climate and Engagement

by Jeremy Walton.

Besides building and supporting the UK Earth System Model and providing science-based guidance on future Earth system change, the activities of the UKESM project include outreach and engagement.  Our group has presented at events such as the Blue Dot Music and Science Festival and the Royal Society Summer Exhibition. The Met Office also provides speakers in response to external requests from groups, such as, u3a, Probus, Women’s Institute etc..  Read more…

Recent Events

UKESM General Assembly 8 & 9 June 2021

The UKESM General Assembly 2021 took place online enabling a good attendance of over 60 participants.

The meeting provided an update on progress for the UKESM project, a look forward for the final year of the extension of the project and a series of UKESM related science talks. Presentation slides and videos of the main talks are available on the UKESM web site at:  UKESM General Assembly 2021 

UKCA Virtual Meeting – March 2021

On 26 March this year the UKCA Science Management Group and the UKCA Chemistry Working Group held a virtual UKCA community workshop. The virtual meeting framework allowed participation from researchers in the UK, Australia and New Zealand. The aim of the meeting was to inform the community about the delivery schedule for UKESM2, to consider potential science configurations, to obtain an overview of currently ongoing UKCA science & development projects and to devise a strategy for the evaluation and assessment of the chemistry and aerosol components of UKESM2 drawing from previous experience.

The meeting featured overview presentations from Colin Jones and Jane Mulcahy on the UKESM2 timeline, and an overview of lodging code into the UM trunk from Luke Abraham. UKESM2 will be built on HadGEM3-GC5 (expected freeze Dec 2021) and is expected to become operational and ready for science by the end of 2024. Therefore all new science changes need to be ready (code lodged and UKESM science tests completed) by spring 2022. We therefore encourage people to target the Autumn 2021 deadline for UM code lodging. However, it must be noted that there is no guarantee for all new UKCA developments to be included in UKESM2 due to resource and time limitations. A recording of the meeting, together with slides from the various presentations, is available via the UKCA wiki at

The meeting gave a broad overview of developments in the UKCA community, including the coupling of the INFERNO interactive fire module to the atmosphere and the land surface (Burton, Teixeira, UKMO), new treatments of the effects of cloud pH (Turnock, UKMO) an entirely new nitrate aerosol scheme (Jones, UKMO), lightning NOx (Luhar, CSIRO) and dry deposition (Luhar, CSIRO; Hayman, CEH).  The meeting also heard of new chemistry schemes: extension to the default UKCA chemistry scheme to better treat urban air quality (Liu, Edinburgh), a version of the Common Representative Intermediates including biogenic VOCs (Archer-Nicholls and Weber, Cambridge) and an improved treatment of short-lived halogen species (Bednarz, Lancaster).  Important structural improvements were also described – future work on the impact of aerosols on photolysis (O’Connor, UKMO) – as well as improved coupling of Earth system components via the nitrogen cycle (Robertson, UKMO).

Figure 1: improvements to the lightning NOx parameterisation by Luhar et al., as discussed in Atmospheric Chemistry and Physics, 21, 7053–7082, 2021

The UKCA Science Management Group welcomes participation in the design and forward planning of UKCA.  There is a Google Group that you are welcome to join; search for “ukca-general”  within or contact Alex Archibald for more details.  The next UKCA CWG meeting will focus on model evaluation – please keep an eye out on the mailing list for meeting announcements.


UKESM in the research literature


UKESM2 – the next generation..

Looking forward.., UKESM2 will be built on HadGEM3-GC5 (available ~ spring 2022, and should be frozen by the end of 2022). The aim is for UKESM2 to be “operational” / science ready about the end of 2024/start of 2025. Some of the proposed developments include:

  • Workhorse will stay at N96L85 – ORCA1L75
  • Have an exploratory configuration at higher resolution (using hybrid approach)
  • An ability to run the model with emissions of CO2, CH4
  • Interactive Antarctic and Greenland ice sheets as standard
  • Wildfires interactive and coupled to carbon cycle and atmospheric composition
  • Thermal acclimation of plant photosynthesis
  • Improved representation of human land use
  • Nitrate aerosol
  • Improved stratospheric ozone

Scientists wishing to contribute new developments to UKESM2 should contact Jane Mulcahy ( to outline their plans. You can find more information on the process and timelines on the UKESM trac homepage.

Whilst we were finalising the report on the 5-year UK coordinated CRESCENDO project, we have also been engaged in the start-up of a new EU research project ESM2025 with our European partners. The project is led by Météo France (MF-CNRM) and aims to develop the next generation of Earth System Models (ESMs). This will take a step forward in providing relevant climate simulations for the development of ambitious and realistic mitigation and adaptation strategies in line with the Paris Agreement

The project started on 1st June 2021 and you can follow the developments on Twitter at @esm2025_eu and soon on the new website.

The UKESM Team is pleased to announce that the UKESM project has been extended by UKRI-NERC for a year (from April 2021 to March 2022). A follow-on programme to the first phase of UKESM is being drafted.

UKESM Catch-up Videos

Missed any of the exciting science talks at the UKESM General Assembly? Want to catch up with European ESM developments through CRESCENDO? We have recorded key science talks and put them on the UKESM Youtube channel for your perusal. UK Earth System Modelling – YouTube