Understanding who influences climate policy and how expertise shapes decision-making is crucial in tackling climate change effectively. This perspective piece seeks to unravel the complexities of climate governance by reflecting on the role of experts in shaping climate policies. We suggest a new research agenda for studies on the representation and role of expertise in national climate institutions and in policymaking. With a shift towards national implementation, following the Paris Agreement, greater scholarly attention to the role of domestic institutions, including their scientific foundations, is crucial for our understanding of today's climate governance. Focusing on national climate councils, we debate the role of their expert composition and diversity of scientific expertise. We highlight the need for more research on the epistemic diversity and pay special attention to the role of social sciences, particularly the discipline's ability to address the political dimensions of climate action, such as equity, justice, and public acceptance.