Evolution of the PRIME emissions-to-impacts modelling framework.

The PRIME emissions-to-impacts framework (Mathison et al. 2025) uses a chain of models, including the FaIR simple climate model and the JULEs land surface model, to simulate spatial resolved climate impacts and carbon cycle processes for policy relevant emissions scenarios. We present multiple updates to this framework, including a new methodology to sample large ensembles of the FaIR simple climate model, using an algorithm which maximises diversity across multiple dimensions (Sexton et al. 2021). The results are a sample with a more thorough representation of both atmospheric CO₂ concentration and Global Mean Temperature. We use this sample to simulate the response of the carbon cycle under a more representative range of CO₂ and temperature outcomes. In the latest version of PRIME we also include a more sophisticated representation of internal variability, and an updated daily climatology. A third methodological update is use of the PRIME framework with updated versions of JULES which include additional physical processes, such as permafrost physics and explicit representation of fire. This enables evaluation of processes not yet included in coupled Earth System Models. We use the PRIME framework in this configuration to model policy relevant overshoot scenarios, which gives us the opportunity to evaluate climate tipping points over a wide range of uncertainty. Finally, flexibility of the PRIME framework also allows us to provide driving data for other land surface models.