• Energy Research

Abstract Decarbonization of energy-using sectors is essential for tackling climate change. We use an ensemble of global integrated assessment models to assess CO2 emissions reduction potentials in buildings and transport, accounting for system interactions. We focus on three intervention strategies with distinct emphases: reducing or changing activity, improving technological efficiency and electrifying energy end use. We find that these strategies can reduce emissions by 51–85% in buildings and 37–91% in transport by 2050 relative to a current policies scenario (ranges indicate model variability). Electrification has the largest potential for direct emissions reductions in both sectors. Interactions between the policies and measures that comprise the three strategies have a modest overall effect on mitigation potentials. However, combining different strategies is strongly beneficial from an energy system perspective as lower electricity demand reduces the need for costly supply-side investments and infrastructure.

Large emission reductions in buildings and transport are possible by integrating demand-side strategies to electrify energy use, improve technological efficiency, and reduce or shift patterns of activity. With enabling policies and infrastructures, final energy users can make significant contributions to climate goals, particularly through widespread deployment of heat pumps and electric vehicles.

Abstract Global Integrated Assessment Models (IAMs) used to characterise mitigation pathways have very limited or no formal representation of lifestyles and lifestyle change. We demonstrate a novel approach to endogenously simulating low-carbon lifestyle heterogeneity and lifestyle change through soft-coupling with our new empirically-based LIFE model. Coupling LIFE to global IAMs enables dynamic simulation of distinctive lifestyle change contributions to targeted mitigation strategies. We set out the empirical basis of the LIFE model, the methodological steps for soft-coupling to a global IAM, and show results from a test application to the residential sector using the MESSAGEix-Buildings model. A first key insight is that coupling with the LIFE model introduces heterogeneous behaviour between ‘engaged’ types, who experience faster and higher reductions in final energy demand compared to ‘disengaged’ types. When we further simulate a widespread shift in normative values, this gap is closed. A second key insight is that drivers of lifestyle change, act differently across ‘Improve’ and ‘Avoid’ dimensions. The ‘disengaged’ types, characterised by lower incomes, are more highly responsive to energy saving ‘Avoid’ behaviours. Our approach demonstrates how improved understanding of lifestyle change dynamics and more realistic, empirically-based quantitative simulations in climate mitigation pathways enriches scientific and policy analysis of how to achieve Paris Climate Agreement goals.

As they are gaining new users, climate change mitigation scenarios are playing an increasing role in transitions to Net Zero. One promising practice is the analysis of scenario ensembles. Here we argue that this practice has the potential to bring new and more robust insights compared to the use of single scenarios. Yet, several significant challenges have to be addressed. We identify key methodological challenges, and existing methods and applications that have been or can be used to address them within a three-step approach: (i) pre-processing the ensemble, (ii) either selecting a few scenarios or analyzing the full ensemble, and (iii) providing users with efficient access to the information.

Lifestyle changes are key factors of the climate mitigation challenge because they drive the demand for energy, goods and food. They have received growing attention in the development and assessment of mitigation pathways, one of the key approaches used to inform mitigation policies. This paper contributes to this emerging literature by examining the political and scientific implications of integrating lifestyle changes into mitigation pathways. We analyse a large sample of pathways, supplemented by interviews with practitioners, to provide a perspective relevant to both scenario production practices themselves and the science-policy process in which they are included. We use three illustrative pathways to describe what it means to explore lifestyle changes and how this exploration can be conducted (indicators, dimensions, precision). We summarize the observed benefits of the explorations of lifestyle changes in scenario production by considering three main contributions of scenarios to policy decision-making: explicit knowledge, mediation tools and framing power. We also discuss why the integration of lifestyle changes poses a potential challenge to the robustness and reliability of pathway production methodologies, which is a condition for their policy-relevance. We therefore argue that the implications of this integration need to be carefully characterized in order to maximize the policy relevance of the analysis without compromising the robustness of the scenario development and assessment process. The nature of lifestyles, which reflect values and preferences and require a multidisciplinary approach, raises significant policy neutrality challenges and scientific challenges. Overcoming these challenges can lead to more policy-relevant pathways: we describe existing approaches in the literature and analyse their contributions and limitations.

Abstract In recent years, the decarbonisation of international shipping has become an important policy goal. While Integrated Assessment Models (IAMs) are often used to explore climate mitigation strategies, they typically provide little information on international shipping, which accounts for around 0.75 GtCO2/yr. Here, we perform the first multi-IAM analysis of international shipping, drawing on the results of six global models. Results indicate the need for decreasing emissions in the next decades, with reductions up to 88% in 2050. This is primarily achieved through the deployment of low-carbon fuels. Models that represent several potential low-carbon alternatives tend to show a deeper decarbonisation of international shipping, with drop-in biofuels, renewable alcohols and green ammonia standing out as the main substitutes of conventional maritime fuels.