LTSM1 UKESM Extension

Lead Research Organisation: UK CENTRE FOR ECOLOGY & HYDROLOGY
Department Name: Hydro-climate Risks


Global climate change is one of the leading environmental threats facing mankind. To develop appropriate mitigation and adaptation strategies requires accurate projections of the future state of the Earth's climate. To address this, we develop Global Climate Models (GCMs) that describe the main physical processes in the coupled climate system. These models are integrated forwards in simulated time, from a pre-industrial period to present-day, forced by observed estimates of key greenhouse gases, aerosols and land-use. The models are then continued into the future forced by a range of greenhouse gas, aerosol and land-use scenarios. Each of the model future climates can then compared to the simulated present-day climates. This analysis results in an ensemble of climate change estimates that can be used to assess the socio-economic and ecological impacts of the simulated changes and aid in the development of mitigation and adaptation policies.

GCMs have been further developed into Earth system models (ESMs), as we did in the UKESM LTSM, where UKESM1 was developed from the physical model, HadGEM3-GC3.1. A key difference between ESMs and GCMs is the former include an interactive description of the global carbon cycle supporting analysis of both physical climate change and potential changes in the efficacy by which anthropogenic emitted CO2 is taken up by natural carbon reservoirs. A reduction in the uptake efficiency of Earth's natural carbon reservoirs may result in a larger fraction of emitted carbon dioxide remaining in the atmosphere to warm the planet. Accurate estimates of the future evolution of both the global climate system and the carbon cycle are therefore crucial for getting a clear picture of the future risks humanity faces, as well as for developing mitigation actions (that typically target modifying the efficacy of carbon uptake) to keep global warming to acceptable levels.

To address this need we developed the 1st UK Earth system model (UKESM1) and ran it for a large suite of experiments in the 6th Coupled Model Intercomparison Project (CMIP6). UKESM1 is the most advanced Earth system model in the world today and as well as a coupled physical climate model also includes interactive treatment of (i) the global carbon cycle and vegetation, (ii) atmospheric chemistry and aerosols and (iii) models for the Greenland and Antarctic ice sheets. We have run a large (19 member) ensemble of historical simulations with UKESM1 (1850 to 2015) and extended a number of these into the future (2015 to 2100) following 7 different future emission pathways from CMIP6 scenarioMIP. In this extension, we propose a detailed analysis of the UKESM1 historical ensemble and the suite of scenarioMIP projections. Our aims are (i) to better understand what drives observed historical Earth system change and ask how well UKESM1 represents these changes, (ii) with the knowledge from (i), analyse simulated Earth system change in the UKESM1 scenarioMIP ensemble, combining this with the CMIP6 multi-model ensemble, to document the range of simulated changes across the coupled Earth system over the coming century. Two primary emphases in this analysis will be; (a) to document and contrast regional changes at different levels of global mean warming (e.g. 2C or 3C) and (b) where possible, to constrain the various coupled feedbacks simulated by UKESM1 that drive the changes we see. In addition to these two science goals, we will also continue to provide support to the large UK UKESM user and model development community and plan to hold two consultation workshops with (i) UK climate policymakers and (ii) UK climate impacts researchers. In these workshops, we will present our findings on predicted future Earth system change and begin a two-way dialogue on how UK Earth system modelling can best serve the needs of these two groups, developing future collaborations based on mutual understanding of each groups needs and goals.


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Description The UK Centre for Ecology & Hydrology (UKCEH) is the project lead for land-related aspects of the UK Earth System Model. UKCEH provides staff to the UKESM core development team and also undertakes model development to add new science or processes. (1) Core: UKCEH staff developed and tested areas of the land-surface component of UKESM1. The CEH core team members contributed to the UKESM models runs undertaken for international modelling activities (CMIP6), created the CO2 emission driving data used in some of the CMIP6 runs and contributed to papers describing and assessing the model. The LTSM UKESM project (and the Met Office) delivered the UK contribution to CMIP6. The output from CMIP6 will inform the IPCC's sixth assessment report. (2) Development: CEH also contributes new science or processes for incorporation into future version of UKESM. This includes: (a) improved representations of plant physiological processes in JULES, including the Medlyn model of stomatal conductance, the Farquhar model of photosynthesis, and thermal acclimation of photosynthetic capacity; (b) the ECOSSE model of soil carbon and nitrogen biogeochemistry in JULES; and (c) an improved representation of atmospheric deposition processes and transfer of the deposition code base from the UKCA atmospheric chemistry module to JULES. The paper by Mercado et al. (2018) showed the importance of temperature adaptation and acclimation on current and future land-carbon storage. Further, allowing for acclimation reduces the spread in global climate model projections. The paper by Kelley et al. (2019) highlighted the added importance of understanding long-term changes in the controls on fire and the effect of fire trends on ecosystem function. Fires have received increased attention and is a current gap in UKESM1. A new, Bayesian-based optimization scheme that has been developed to help constrain fire processes in the UKESM is also showing promising results in other areas of the model, including vegetation dynamics and leaf reflectance parameters, as well as use in fire event attribution studies. UKCEH contributed to the UKESM model runs and papers published (Sellars et al., 2020), which were undertaken for inclusion in the sixth assessment report on Climate Change prepared by the Intergovernmental Panel on Climate Change. Further papers are in preparation.
Exploitation Route Outputs of the different model runs can be used for climate impacts studies
Sectors Environment,Government, Democracy and Justice

Description The UK Earth System model (UKESM1) participated in the 6th Coupled Model Intercomparison Project (CMIP6), delivering an ensemble of Earth system projections, for the coming century and beyond, for use by UK researchers and government. The future projections of climate and Earth system changes made using UKESM1 are providing data and knowledge to support planning around climate change impacts, adaptation and mitigation. Scientific papers based on UKESM1 simulations form an important contribution to the Intergovernmental Panel on Climate Change (IPCC) - 6th Assessment Report (AR6). The IPCC provides policymakers with regular scientific assessments on climate change, its implications and potential future risks, as well putting forward adaptation and mitigation options.
First Year Of Impact 2021
Sector Environment
Impact Types Policy & public services

Description UNEP Report "Spreading like Wildfire: The Rising Threat of Extraordinary Landscape Fires"
Geographic Reach Multiple continents/international 
Policy Influence Type Contribution to a national consultation/review
Description TerraFIRMA: Future Impacts, Risks and Mitigation Actions in a changing Earth system
Amount £9,400,000 (GBP)
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 03/2022 
End 03/2027
Description New Scientist Live 2022 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact The New Scientist Live exhibition "the world's greatest festival of ideas and discoveries", was held on 7-9 October 2022 at the ExCeL Centre in London. It is one of the biggest science festivals in the UK. Within the event there were 5 stages, 56 main stage talks and 80 exhibitors. The first day was dedicated to schools only and the following 2 days were open to the public.

The UK TerraFIRMA (and the preceding UKESM) project manned a stand at the exhibition "Predicting Climate Change", together with the European Union funded ESM2025 project. The two projects work on Earth System modelling using models to develop climate simulations to help design climate mitigation and adaptation strategies. Both of these projects have dedicated actions on public outreach as part of their deliverables.

The PufferSphere 360° display, loaned by the National Oceanography Centre, was used to explore how the oceans, ice, atmosphere and land are changing and could change in the future due to the impacts of climate change. A team of 21 project researchers and climate science communicators were on-hand to speak to the public during the 3-day exhibition. The researchers represented organisations including: Meteo-France, Office of Climate Education, Met Office, National Centre for Atmospheric Science (Reading and Leeds), National Oceanography Centre, National Centre for Earth Observation, UK Centre for Ecology and Hydrology and the University of Exeter.
Year(s) Of Engagement Activity 2022
Description UNCOP26 Events 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact UKESM participated in several COP26 related activities, including a presence in the Green Zone (public events in the Glasgow Science Centre) in Glasgow. See for more information
Year(s) Of Engagement Activity 2021
Description UNCOP27 Side Event: "Wildfire increase, a challenge for Earth system and societies" 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact Climate and land use changes affect frequency, distribution and intensity of wildfires, which impact ecosystems, societies, weather and climate. Wildfires also provide ecosystem services and nutrients to marine biota. A side event was held at the UNFCCC COP27 to discuss fire risk from a natural and social science view.

Speakers: CSU: P.Backlund, H.Mahmoud, C.Shultz ; SOLAS: D.Hamilton; iLEAPS: S.V.Shamsudheen; PAGES: B.Vannière, BRIDGES: S.Hartman, I.Oosterbeek, I.Camara; FireMIP: S.Hantson.

Available online:
Year(s) Of Engagement Activity 2022