Abstract:  Political elites in the US are ideologically divided over climate change. We identify two perspectives: The intrinsic view on ideological climate polarisation views climate beliefs as entrenched parts of an actor’s identity and posits that ideological positions have factually shifted towards ever more extreme positions over time. The instrumental view, in contrast, emphasises that polarisation entrepreneurs mobilise their constituency to participate in the climate policy debate by amplifying ideological differences over climate-related focusing events when they arise, leading to fluctuations in visible polarisation, rather than a steady trend. This study examines which of the two perspectives holds in US Congressional and subnational media debates by analysing time trends of polarisation and phases of structural stability. We distinguish between endogenous events, which can be attributed to the political process, and exogenous focusing events, such as extreme events or those related to the international climate regime, and investigate which type of event tends to be associated with changes in polarisation. Applying two novel time series measures for discourse networks—structural polarisation and the detection of phases of structural stability—to the climate debate during the 112th to 114th Congress (2013–2017) and subnational print media in four swing states, we find that exogenous events are largely irrelevant while endogenous political dynamics increase the polarisation of the debate considerably. We find ups and downs of polarisation corresponding to distinct structural phases in which polarisation is linked to participation. This temporal fluctuation of polarisation around endogenous political events is consistent with the instrumental perspective.

Keywords:  climate; discourse networks; environment; issue attention cycle; polarisation

Published:   17 September 2025

Issue:   Vol 13 (2025): The Politics of Environmental Networks (In Progress)