Designing Climate Change Modelling to Support Societal Decisions

The history of climate modelling is one of increasing complexity and increasing resolution, driven by and constrained by the available computational capacity. These models are widely used, directly and indirectly, to support policy and adaptation decisions across society. They are also used in academic studies across a range of disciplines to study the response of the climate system to future atmospheric greenhouse gas concentrations on multi-decadal timescales. These are extrapolatory endeavours in a non-stationary system without possibility of relevant verification.

There has been much research on individual and multi-model analyses in this context. Here I will instead discuss how the targets of our endeavours (particularly the support of societal decisions) demands a rethinking of our modelling activities. I will highlight the need to reflect on the minimum requirements for ensemble size and ensemble variety, and the role of a hierarchy of models in providing the best possible information to stakeholders across society.

These issues will be discussed in the light of a recent meeting on the foundations of climate change science attended by over 70 researchers across a variety of disciplines. The meeting was entitled “How to spend 15 billion dollars?: A workshop on how to make climate change modelling more robust and more useful to society.” It gathered expertise from disciplines as diverse as earth system modelling, integrated assessment modelling, philosophy, economics, maths, statistics and finance.

Here I will present the key messages coming out of this meeting alongside the themes presented in a recent essay on the subject, “A Model of Catastrophe”[1].

[1] Stainforth, D.A., “A Model of Catastrophe”, Aeon.co, 2025 (https://aeon.co/essays/todays-complex-climate-models-arent-equivalent-to-reality)