This thesis explores how climate policy is developing at sub-national or “regional” scales of
decision-making. It considers local-global connections on both the science and the politics of
climate change by investigating four main research questions as they pertain to regional climate
action: What triggers regional policy action on global climate change? What arguments and lines
of evidence underlie the policy discourse? How do “winning” arguments gain salience? How does
regional action make a difference to broader scale climate policy? The research is conducted
through one in-depth case study in California. It shows that action on climate change mitigation in
California is enabled in part by past action in related policy arenas of air pollution control and
energy policy within a multilevel, social-practice environmental governance framework. More
recently the emergences of a comprehensive policy framework is triggered by a unique policy
window where a change in California’s leadership capitalised on the void of federal policy to reframe
arguments for state-level action on climate change. The case study identifies two dominant
policy frames leading to a third master frame or meta-narrative in the period 2004-6: i) climate
change as a problem of regional environment risk; ii) mitigation policy as a “win-win” for the
local economy and the environment; iii) climate change as a regional policy issue. This period
represents a paradigm shift from a previous dominant framing that characterised climate change
as predominantly a national rather than a state policy issue. The case study shows that today’s
dominant policy frames rely upon a process of co-construction that combine insights from expert
and local knowledge, thus intertwining “facts” and “ values in the policy process. “Winning
arguments” or policy frames gain salience through a relatively open policy process, which permits
an array of non-governmental actors -- including social movement organisations, business
organisations and experts -- to operate in the outer-periphery of the policy process and generate
ideas in a timely way to influence policy decisions. The research underscores the power of
localising problems of global environmental change and their solutions, of taking up climate
change as a regional policy issue where solutions can be tapered to reflect regional contexts and
norms. It shows that there is a relatively larger scope for experimentation and social and technical
innovation at regional scale, compared to broader scales of action, which can open the way for
cross-scale learning and influence to emerge