Revisiting the stabilisation wedges: a framework for exploring the impact of technology and behaviour on global greenhouse gas emissions
File(s)
Author(s)
Johnson, Nathan
Type
Thesis
Abstract
Energy and land use systems must transform rapidly to reduce global greenhouse gas emissions and limit climate change. Yet many individuals show little inclination or desire to engage with climate change mitigation. Models play a critical role in communicating the actions that the world must take to mitigate climate change; however, the models most widely used to produce mitigation pathways are complex, opaque, and dismiss the perspectives of individuals. This thesis builds on the exceedingly popular Stabilisation Wedge framework to help channel communications to a broader audience, who are interested in climate change but do not possess the technical knowledge needed to engage with mainstream mitigation pathways. The framework simplifies the discourse by translating mitigation strategies into the common unit of wedges, allowing diverse strategies to be compared objectively to each other and to targets for decarbonising the economy. Firstly, the thesis applies the wedge framework to quantify how historical deployment of key mitigation strategies has contributed towards meeting global targets for decarbonisation. It finds that substantial progress has been made by strategies that are not widely recognised (improving vehicle efficiency and declining vehicle use); yet this is tempered by negligible or even negative progress in many others (particularly tropical deforestation). Overall, progress has been insufficient to stabilise, let alone, reduce global emissions – historical mitigation efforts must be amplified by an order of magnitude if we are achieve net-zero emissions by mid-century. Secondly, the thesis revises the wedge framework and addresses critical limitations. It finds that 33 wedges must be achieved between now and 2050 to limit warming to 1.5°C, and that current policies contribute just 12 of these wedges. It then evaluates how widely 37 different strategies must be deployed to achieve a single wedge and reviews the advantages and disadvantages of deploying each strategy, providing a simple means for its user to explore their preferred pathway for decarbonising. The final analytical chapter applies two novel approaches to assess how different strategies contribute to achieving wedges in future emissions scenarios. It finds that there is vast disagreement over which measures contribute the greatest emissions savings across ‘cost-optimal’ scenarios with similar objectives. It also shows that strategies targeting human behaviour, which are absent from most mainstream mitigation pathways, can contribute large emissions reductions. Moving forward, the modelling community must broaden their scope to include more behavioural options and shift focus away from scenarios that deliver emissions reductions at the lowest cost (for which there is no definitive consensus) and towards those that are most likely to be supported by individuals.
Version
Open Access
Date Issued
2023-04
Date Awarded
2023-10
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Staffell, Iain
Gross, Robert
Sponsor
Engineering and Physical Sciences Research Council
Grant Number
EP/N509486/1
Publisher Department
Centre for Environmental Policy
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)
Rights Embargo Date
2025-03-31