A large gap exists between the ambition of countries’ emission reduction targets and the stringency of their mitigation policy instruments. This target-policy stringency gap will need to be closed to avoid dangerous levels of global warming. A central question, then, is what factors drive the upscaling of climate change mitigation policy instruments? Despite the need for countries to deliver step-changes in the stringency of their mitigation instruments, the anatomy of upscaling events remains under researched. This thesis will seek to address this gap by examining the small but growing set of upscaling events that have occurred in recent years in order to build an empirically-founded understanding of the drivers of climate policy stringency upscaling.

The thesis will be developed in two parts. Part I will be a case study of Australia’s 2023 upscaling of its core climate change policy instrument—the Safeguard Mechanism. Through this case study, theories will be developed to explain how an implement-then-upscale approach to policy adoption can weaken otherwise insurmountable barriers to stringency, and how mitigation instruments can be primed for future upscaling by balancing different design elements at the initial adoption stage. In Part II, a broader set of upscaling case studies, including upscaling events in Singapore, Ireland and New Zealand will be examined to test the theories developed in Part I. The practical implication of this research will be to provide an evidence base for decision makers to intentionally design mitigation instruments for future upscaling, allowing for greater levels of stringency than may have otherwise been feasible.