Why are models so widely used in climate policy?

In the climate science-policy interface scenarios for pathways to a sustainable low-carbon future are often made using Integrated Assessment Models (IAMs). But today there is a whole range of ways to explore the future, such as visioning, gaming and speculative design. IAMs are uniquely capable of exploring complex interactions between societal and climatic processes, but also face limitations in representing socio-cultural change. Why have IAMs become such powerful tools? And how can they be better used in the future in combination with other imagination techniques?

PhD candidate Lisette van Beek, Prof. Dr. Maarten Hajer, Prof. Dr. Detlef van Vuuren and Dr. Peter Pelzer recently published a historical analysis of interactions between IAM and policy to answer this question. A key finding is that IAMs could successfully adjust to emerging knowledge demands from the policy community and adopt different roles. This success can be explained from the typical model structure of IAMs as well as the pro-active nature of the IAM community.

The role of IAMs in the science-policy interface

The 1.5°C and 2°C degree targets that were set in the Paris Agreement stress the need for tools and approaches to anticipate explore possible low-carbon futures. IAMs are currently the key tool used for this task: their scenarios are central in reports by the Intergovernmental Panel on Climate Change (IPCC). A key strength of IAMs is their capacity to represent complex interlinkages between the socio-economic and climate system. They also face challenges, such as a limited capacity to represent non-quantifiable socio-cultural changes that are necessary to transform to a low-carbon society. It is therefore not self-evident that IAMs have such a prominent position.

Different roles throughout history
This role can be explained from historic interactions between models and policy. The origins of IAMs can be traced back to the Limits to Growth study in 1972, which marked a paradigm change in environmental policy. Between the 1970s and 2015, IAMs were successful in evolving along shifts in knowledge demands from the policy community. Throughout the past decades, they became increasingly prominent and were able to fulfil multiple roles towards policy-making: from agenda-setting, to target-formulation and monitoring political ambition.

What explains the success of IAMs?
Apart from the more general ‘trust in numbers’ and advances in computing power, two key factors explain the success of IAMs: the model structure and the pro-active nature of the IAM community. IAMs are relatively flexible, allowing for integration of different disciplines, and are wide in scope: covering causes, impacts and responses. But their success would not be possible without the IAM modellers always being pro-active in gaining policy-relevance. Throughout the past decades, the community employed several strategies to become and maintain policy-relevant. 

The future role of IAMs
The historically embeddedness of IAMs in the science-policy interface indicates that the models will likely play an important role in the future. But the climate crisis is becoming more urgent and no longer an issue of the science-policy interface alone. This implies a consideration to seek alliances with other approaches to imagine possible futures and to engage a wider range of publics.

Publication
Lisette van Beek, Maarten Hajer, Peter Pelzer, Detlef van Vuuren, Christophe Cassen, Anticipating futures through models: the rise of Integrated Assessment Modelling in the climate science-policy interface since 1970, Global Environmental Change, https://doi.org/10.1016/j.gloenvcha.2020.102191