Newsletter 16 – December 2022

NEWSLETTER December 2022

UKESM develops, applies and analyses UK Earth system models to deliver projections of future change

TerraFIRMA – Future impacts, risks and mitigation actions in a changing Earth system


TerraFIRMA Update on Progress

TerraFIRMA is making progress in a number of areas across the project including: warming overshoot scenarios, UKESM1 methane emissions capability and climate-air quality co-benefits, using UKESM1.0 to assess the mitigation potential from enhanced ocean alkalinity, investigating the risk of triggering abrupt change in ice sheets, oceans and forests, and developing a series of pilot studies on groundwater response to climate for Africa and South Asia. See the full update on TerraFIRMA progress.

New Scientist Live – Engaging the public

Two projects joined forces for a stand at the New Scientist Live Exhibition, “the world’s greatest festival of ideas and discoveries”, on 7-9 October at the ExCeL Centre in London. Our stand on ‘Predicting Climate Change’ provided an opportunity for schools and the public to visualise climate processes and how the climate may change in the future and for our team of scientists to hear first hand what the public are most interested in. We’ve captured our insights and what we could do better next time!

UKESM1 on the Catwalk

An international collaboration into the world of textile art and design continues UKESM1’s engagement with the arts, with some stunning designs based on the biogeochemical “Underworld”. Find out more about how “Zooplankton Resurrection” came to life.

The Global Stocktake: Progress at the COP27

One essential part of putting the Paris Agreement into action is the Global Stocktake (GST). Every five years, and currently for the first time, it assesses the world’s collective progress towards achieving the purpose of the Paris Agreement and its long-term goals. The GST process is designed to be comprehensive and inclusive, giving a wide array of stakeholders the opportunities to take part and influence the outcome of the GST process. Experts from the Earth system modelling community are directly involved in the Technical Dialogues, thus delivering a crucial impact to the results from ESM simulations. Read more about the Global Stocktake.


UKESM2.0 Update

UKESM2.0 will be the next generation UK Earth System Model that will be used in a future CMIP7 and beyond. It remains a collaborative activity involving the Met Office, NERC centres as well as academic and UM partners. Development of UKESM2 has started with regular meetings of the component development groups and a coupled UKESM2 steering group. UKESM2 will be built on the HadGEM3 Global Coupled 5.0 (GC5) configuration and will have the same resolution as UKESM1 in its standard configuration (N96ORCA1). While GC5 is largely frozen the N96ORCA1 configuration used in many climate applications, including UKESM, is not and tuning is on-going. We have however forged ahead with the technical work to build an ESM prototype on the latest GC5-climate configuration. This couples the interactive stratosphere-troposphere chemistry (UKCA), terrestrial and ocean (MEDUSA) biogeochemistry models with GC5-climate. A pre-industrial simulation of this configuration is now running. The Earth system components in this prototype currently reflect UKESM1.1 science. Implementation of the proposed UKESM2 science developments will commence once GC5-Climate is frozen. We aim to have a finalised UKESM2 configuration by mid-2025.

Developments for UKESM2.0 are largely driven by Earth system science questions around the feasibility of the Paris Agreement temperature target, climate mitigation options (and associated co-benefits) to achieve this and the societal and ecosystem risks if not achieved. UKESM2 will be used to investigate the risks and impacts of rapid and potentially irreversible change in key Earth system phenomena such as Antarctic ice sheet collapse, loss of tropical forests or abrupt changes in ocean circulation and marine ecosystems. Other key focus areas include understanding the role of land-use and near-term climate forcers in climate mitigation, in particular methane (CH4). These questions motivate key new science capabilities in UKESM2 including, running the model in emission driven mode for both CH4 (Folberth et al. 2022) and CO2; implementation of the interactive fire model, INFERNO, coupled to atmospheric composition and vegetation; implementation of interactive ice sheet models for both Greenland and Antarctica (Smith et al. 2021, Siahaan et al 2022). The inclusion of nitrate aerosol (Jones et al. 2021) is important for not only historical aerosol forcing, but essential for investigating air quality implications of climate change, particularly into the future where SO2 emissions decline. Nitrate aerosol has been extensively evaluated in UKESM1.1 (e.g. Figure 1) and impacts on aerosol effective radiative forcing have been assessed. In addition, we will look to couple atmospheric nitrogen to the land surface via wet and dry deposition. For UKESM2 we aim to replace the current CLASSIC binned dust scheme with a modal scheme, making the treatment of dust consistent with all other aerosol species. Evaluation of prototype 2-mode and 3-mode modal dust configurations are currently being evaluated against our current CLASSIC scheme. While the interactive fire capability is well advanced (Teixera et al. 2021, Burton et al. 2021), on-going work looking at the sensitivity of fire emissions to the driving climate processes will inform our tuning work in the coupled model. Progress has also been made on the technical work to enable the thermal acclimation of vegetation, improved permafrost physics (via deeper and more soil layers) and biogeochemistry in both the UM and JULES. While the standard resolution of UKESM2 will be N96ORCA1, a hybrid resolution configuration is also being developed, with a resolution for the physical atmosphere of N216 (~50km) and 0.25° for the physical ocean. Earth system process complexity is afforded by running the more costly processes (e.g. chemistry, aerosols and ocean biogeochemistry) interactively at a lower resolution (N96 ORCA1). In addition, the UKESM1.1-FAST configuration is now frozen, with a documentation paper planned in 2023. The resolution of FAST is N48 (~280km) in the atmosphere and targets large ensemble simulations. FAST is traceable to the full UKESM apart from running with prescribed chemical oxidants and a longer UM timestep. UKESM1.1-FAST in CO2 emission driven mode is currently being applied to idealised warming overshoot scenarios within TerraFIRMA.  

Figure 1 Annual mean near-surface concentrations of ammonium and nitrate aerosol from UKESM1.1-nitrate simulations compared with observations at EMEP and CASTNET ground-based sites. Fast and Slow simulations represent sensitivities to the uptake coefficient for the NH4NO3 system.


Burton, C., Kelley, D.I., Jones, C.D., Betts, R.A., Cardoso, M., & Anderson,, L. (2022) South American fires and their impacts on ecosystems increase with continued emissions. Climate Resilience and Sustainability, 1, e8.  

Folberth, G. A., Staniaszek, Z., Archibald, A. T., Gedney, N., Griffiths, P. T., Jones, C. D., et al. (2022). Description and evaluation of an emission-driven and fully coupled methane cycle in UKESM1Journal of Advances in Modeling Earth Systems, 14, e2021MS002982. 

Jones, A.C., Hill, A., Remy, S., Abraham, N. L., Dalvi, M., Hardacre, C., Hewitt, A. J., Johnson, B., Mulcahy, J. P., and Turnock, S. T.: Exploring the sensitivity of atmospheric nitrate concentrations to nitric acid uptake rate using the Met Office’s Unified Model. Atmos. Chem. Phys., 21, 15901–15927, 2021.

Siahaan, A., Smith, R. S., Holland, P. R., Jenkins, A., Gregory, J. M., Lee, V., Mathiot, P., Payne, A. J. ​., Ridley, J. K. ​., and Jones, C. G.: The Antarctic contribution to 21st-century sea-level rise predicted by the UK Earth System Model with an interactive ice sheet. The Cryosphere, 16, 4053–4086, 2022.

Smith, R. S., Mathiot, P., Siahaan, A., Lee, V., Cornford, S. L., Gregory, J. M., et al. (2021). Coupling the U.K. Earth System model to dynamic models of the Greenland and Antarctic ice sheetsJournal of Advances in Modeling Earth Systems, 13, e2021MS002520. 

Teixeira, J. C., Folberth, G. A., O’Connor, F. M., Unger, N., and Voulgarakis, A.: Coupling interactive fire with atmospheric composition and climate in the UK Earth System Model. Geosci. Model Dev., 14, 6515–6539, 2021

UKESM contributions to COP27

Science played an important part in the programme during COP27 in Egypt from 7 to 18th November. With science talks at the UN, EU and UK Pavilions as well as many other side-events, UKESM science had a small part to play…

Fiona O’Connor from the Met Office participated in the session “Co-benefits and trade-offs of climate action, uncovering new incentives for early climate action” at the UK pavilion in Egypt during COP27. Fiona’s talk focused on how the co-benefits of climate action on aspects such as air quality, health, energy and food security can be realised much sooner and add to the benefit of avoided climate impacts. This work is based on the new capability of running a fully emission-driven CH4 cycle in UKESM1 model and enables us to better evaluate co-benefits of climate action on #AirQuality. See our previous news article on methane.

Watch the recorded event at:

Co-benefits and trade-offs of climate action, uncovering new incentives for early climate action

A poster on ‘The Physical Climate at 2oC and 4oC as seen in the UK Earth System model (UKESM1)’ was presented at COP27. Based on the paper, the poster set out how the team investigated the likelihood of achieving a key goal of the 2015 Paris Climate agreement – keeping global mean temperature change under 2°C and if possible 1.5°C by the end of the century. Further details are at COP27 – UKESM and in our Twitter thread

UKESM Retreat

In September 2022, most of the UKESM team were able to get together in Bristol after a long time apart due to the pandemic. The team is made up of members from different UK Centres and the Met Office from across the UK, so we don’t often get a chance to meet each other face-to-face. Before the pandemic we’d try to meet as a group about every 6 weeks, however moving our group meetings online through Zoom has proved to work quite well and often saved us from tortuous rail travel!

We kicked off the short retreat with a team treasure hunt in Bristol, which enabled us to get to know Bristol a bit better and gave us some team bonding time! Jeremy Walton produced another entertaining music quiz for the group with the winners almost getting away with a tub of chocolates.

Steve George, Stephen Pring, Doug Kelley, Robin Smith, Kaitlin Naughten
Rob Parker, Richard Hill, Jeremy Walton, Marc Stringer, Jane Mulcahy
Phil Harris, Lee de Mora, Steven Rumbold, Catherine Hardacre, Valeriu Predoi

Nicely warmed up through our team activities, we spent the next morning discussing the nitty-gritty of Earth system modelling (model developments and the evaluation and constraint of models), exploring how the team is using machine learning and would like to engage with this vast subject going forwards and discussing tipping points and the role of models.


Steve George at NCAS, University of Reading, joined the UKESM team in June 2022. Steve models the decadal and longer impacts of Arctic and Antarctic sea ice on ocean and atmosphere circulation.

The core group has lost two members this year: Vicky Lee and Antony Siahaan. Both of them contributed primarily to ice sheet work in UKESM, Vicky from CPOM Bristol and Antony at BAS, and we wouldn’t be the first (and currently only!) CMIP6 ESM with interactive Greenland and Antarctic ice sheets without their work.


Attribution of Stratospheric and Tropospheric Ozone Changes Between 1850 and 2014 in CMIP6 Models

Bayesian retro- and prospective assessment of CMIP6 climatology in Pan Third Pole region

Comparison of particle number size distribution trends in ground measurements and climate models

Description and Evaluation of an Emission-Driven and Fully Coupled Methane Cycle in UKESM1

Evaluating Long-Term Variability of the Arctic Stratospheric Polar Vortex Simulated by CMIP6 Models

Evaluation of atmospheric circulations for dynamic downscaling in CMIP6 models over East Asia

Evaluation of Present-Day CMIP6 Model Simulations of Extreme Precipitation and Temperature over the Australian Continent

Improved representation of plant physiology in the JULES-vn5.6 land surface model: photosynthesis, stomatal conductance and thermal acclimation

Representation of the phosphorus cycle in the Joint UK Land Environment Simulator (vn5.5_JULES-CNP)

Source attribution of cloud condensation nuclei and their impact on stratocumulus clouds and radiation in the south-eastern Atlantic

The Future Climate and Air Quality Response From Different Near-Term Climate Forcer, Climate, and Land-Use Scenarios Using UKESM1

Understanding model spread in sea ice volume by attribution of model differences in seasonal ice growth and melt