A Momentum for Change? Systemic effects and catalytic impacts of transnational climate action

Non-state and subnational climate actors increasingly commit to act across borders to reduce greenhouse gas emissions, to help communities adapt to climate change, and to push governments into more ambitious climate policies. The effectiveness of such transnational climate initiatives, however, is still largely unknown. Current studies often only seek to estimate the mitigation potential of such initiatives or to study the design elements that may be more or less conducive to their effectiveness. Little is known about the impacts of such initiatives on broader social and environmental goals and about their "catalytic" impacts, that is, whether such transnational initiatives can grow and possibly replicate. Here we develop an approach inspired by political systems theory to reach a fuller understanding of the effectiveness of transnational initiatives. We operationalize a generalized framework through a combination of methodologies, using a new dataset of climate actions under the Momentum for Change program of the United Nations Framework Convention on Climate Change, which we combine with surveys, database analysis, and contextualizing interviews. We conclude with a reflection on the applicability of the framework and a discussion on opportunities for the Momentum for Change program to strengthen its efforts.