UKESM 1 Year Extension

Lead Research Organisation: British Geological Survey
Department Name: Earth Hazards & Observatories


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 and use 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 successfully did in the UKESM LTSM, where UKESM1 was developed from the coupled 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 the 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 the efficacy of carbon uptake) to keep global warming below dangerous 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, includes interactive treatment of (i) the global carbon cycle and dynamic 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 evaluate how well UKESM1 represents these changes, (ii) with the knowledge from (i), analyze 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 magnitude of future change. In addition, we will continue to provide support to the large UKESM user and model development community and will 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 modeling can best support the needs of these two groups, developing future collaborations based on mutual understanding of each group's needs and goals.


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Description This award (UKESM) has enabled the volcano science community and climate change modelling communities of the UK to come together to discuss models and resources needed to better understand the impact of volcanic eruptions on climate change. The final stages of the project will enable a tool that will be accessible to all to relate the amount of aerosol (particles) in the stratosphere to the temperature at the Earth's surface.
Exploitation Route The tool will be available to any researcher to explore surface temperature response to large magnitude eruptions. This can help with understanding and also potentially contribute evidence for planning and preparation (e.g. National Security Risk Assessment).
Sectors Environment,Government, Democracy and Justice,Security and Diplomacy,Transport

Description Collaboration with Leeds University 
Organisation University of Leeds
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaboration on the UKESM project actually began in 2016. It has been reinvigorated in 2021-2022 with development of a tool to study climate change impacts (surface temperature) of stratospheric aerosols.
Collaborator Contribution Leeds University Centre for Environmental Modelling And Computation (CEMAC) will provide a starting point for a framework that couples together two existing models (EVA-H to obtain stratospheric aerosol optical depth (SAOD); and FaIR to obtain the surface temperature response) and a scaling relationship between SAOD and forcing. CEMAC will make available the code for the new tool on GitHub (or a similar platform). CEMAC will liaise with BGS to make the tool accessible on a website hosted at BGS
Impact Outputs in progress
Start Year 2021
Title Volc2Clim 
Description Volc2Clim is a webtool to calculate aerosol optical properties, global-mean radiative forcing and changes in global-mean surface temperature in response to volcanic sulfur emitted by explosive volcanic eruptions. It combines three simple and peer-reviewed models: EVA_H, which predicts perturbations in aerosol optical properties, such as the stratospheric aerosol optical depth (SAOD) for a given mass of sulfur dioxide (SO2), injection altitude and injection latitude (Aubry et al., 2020; A scaling factor that reflects the relationship between the global-mean SAOD perturbation (at 550 nm) and the global-mean effective volcanic radiative forcing at the top of the atmosphere (Schmidt et al., 2018; Marshall et al., 2020) FaIR, a simple climate response model that calculates the global-mean surface temperature response based on the global-mean effective volcanic radiative forcing calculated in 2. (Smith et al., 2018; 
Type Of Technology Webtool/Application 
Year Produced 2023 
Impact Volc2clim enables the user to calculate volcanic radiative forcing and the global climate response to an explosive volcanic eruption. The tool has just been released (2023) and is already providing a means for scientists of different disciplines (earth and atmospheric science) to explore and better understand the impacts of explosive eruptions. The tool has been introduced and explained widely to different communities, through email lists (e.g. volcanolist), on social media, at international conferences (e.g. IAVCEI General Assembly 2023), at project meetings and through UKESM and UKESM2 online presentations.