The Intergovernmental Panel on Climate Change (IPCC) regularly publishes summaries for policymakers (SPMs) following the principle of policy-neutrality. As the urgency of climate change grows, there have been calls for IPCC assessments to be more solution-oriented, which means to assess policy instruments. Yet, there is a scholarly debate regarding whether and how it is possible to discuss policy instruments while staying policy-neutral. To inform this debate we conduct a content analysis of Working Group III SPMs on mitigation published in the last two decades. We find that the SPMs contain limited content on policy instruments with little change over time. This suggests that the SPMs have not yet become more solution-oriented while abiding by their policy-neutrality principle. On the other hand, we show that SPMs have shifted from emphasizing the cost-effectiveness of mitigation towards emphasizing projections of required emissions reductions. Thus, SPM content development is consistent with the evolution of ideas in global climate negotiations. Regardless of whether it chooses to amend its policy-neutrality principle, we recommend that the IPCC still strive to be more solution-oriented. For example, the IPCC could better support the growing ecosystem of national and local boundary organizations which can broker context-specific knowledge on policy instruments. ... Read more

Model-based scenarios are widely used to guide energy planning and climate policy decisions. While the mathematical and physical foundations of many techno-economic models assume universal truth and objectivity, their application to explore a yet unwritten future demands a more nuanced understanding of these concepts. Although modellers' beliefs about the certainty and universality of knowledge may influence how they present their findings to decision-makers, the matter has received little empirical attention to date. Here, we address this gap and investigate modellers' epistemic beliefs concerning energy modelling and scenarios, as well as their perspectives on the communication of model outputs and expert authority. To that end, we conducted a survey with over 160 experts from a broad range of geographical regions and disciplines. Our results show significant polarisation in the participants' beliefs, revealing the two stylised profiles of a Positivist and a Postpositivist Modeller. While there are few differences in the respondents' attitudes based on educational level and background or model usage, we find significant variation particularly based on geographic location. In an effort to overcome this polarisation, we consider our study a call for diversity in modelling teams and argue for fostering the discussion of epistemic beliefs within the broader modelling community. Finally, we recommend incorporating key topics beyond technical aspects into the training and education of future modellers. ... Read more