The scientific case for co-ordinated global governance of the climate system is firmly established, but how does this fit with a politician’s mandate as a democratically elected representative? What role do national politicians think they can and should play in climate governance? This paper tests these questions empirically, using data from interviews with 23 Members of the UK Parliament (MPs), and a focus group of civil society advocates, conducted between 2016 and 2018. A global goal to limit climate change has been agreed through the 2015 Paris Agreement. Yet while the Agreement sets a clear goal, the means to achieve it remain firmly at the level of the nation-state, with each country assuming responsibility for its own national plan. Thus national administrations, run by elected politicians, have a crucial role to play. This study shows that, while MPs have an understanding of the challenges posed by climate change and wider changes to earth systems, few have yet been able to operationalise this understanding into meaningful responses at the national level. The study highlights two, linked, reasons for this. First, politicians’ ability to act – their agency – is limited by the practicalities and procedures of everyday politics, and by the norms and cultures of their working life. Second, UK politicians feel little pressure from their electors to act on climate change, and have to work to justify why action on climate change carries democratic legitimacy. The paper concludes with a discussion of the implications of this research, in the light of the recent high-profile climate protests and declarations of a ‘climate emergency’. It argues that politicians, working with other stakeholders, need support in order to articulate the scale and significance of global climate governance, and craft responses which build democratic support for further action.