Comparing future patterns of energy system change in 2 degrees C scenarios to expert projections

Integrated assessment models (IAMs) are computer-based instruments used to assess the implications of human
activity on the human and earth system. They are simultaneously also used to explore possible response strategies
to climate change. As IAMs operate simplified representations of real-world processes within their model
structures, they have been frequently criticised to insufficiently represent the opportunities and challenges in
future energy systems over time. To test whether projections by IAMs diverge in systematic ways from projections
made by technology experts we elicited expert opinion on prospective change for two indicators and
compared these with the outcomes of IAM studies. We specifically focused on five (energy) technology families
(solar, wind, biomass, nuclear, and carbon capture and storage or CCS) and compared the considered implications
of the presence or absence of climate policy on the growth and diffusion of these technologies over the
short (2030) to medium (2050) term. IAMs and experts were found to be in relatively high agreement on system
change in a business-as-usual scenario, albeit with significant differences in the estimated magnitude of technology
deployment over time. Under stringent climate policy assumptions, such as the internationally agreed
upon objective to limit global mean temperature increase to no more than 2 °C, we found that the differences in
estimated magnitudes became smaller for some technologies and larger for others. Compared to experts, IAM
simulations projected a greater reliance on nuclear power and CCS to meet a 2 °C climate target. In contrast,
experts projected a stronger growth in renewable energy technologies, particularly solar power. We close by
discussing several factors that are considered influential to the alignment of the IAM and expert perspectives in
this study