This article addresses two great global challenges of the 2020s. On one hand, the accelerating climate crisis and, on the other, the deepening crisis of representation within liberal democracies. As temperatures and water levels rise, rates of popular confidence in existing democratic institutions decline. So, what is to be done? This article discusses whether sortition – the ancient Greek practice of selecting individuals for political office through lottery – could serve to mitigate both crises simultaneously. Since the 2000s, sortition has attracted growing interest among activists and academics. Recently it has been identified in countries like the UK and France as a mechanism for producing legitimate political answers to the climate challenge. However, few theoretical reflections on the potentials and perils of sortition-based climate governance have yet emerged. This article contributes to filling the gap. Based on a critique of the first successful case of sortition used to enhance national environmental policy – in Ireland in 2017–18 – we argue that sortition-based deliberation could indeed speed up meaningful climate action whilst improving the health of democratic systems. However, this positive outcome is not preordained. Success depends not only on green social movements getting behind climate sortition but also on developing flexible, context-specific designs that identify adequate solutions to a number of problems, including those of power (providing citizens’ assemblies with clear agenda-setting prerogatives beyond non-binding consultation); expertise (allowing assembly participants to influence which stakeholders and experts to solicit inputs from); and participation (engaging wider parts of the citizenry in the deliberative process).