The use of accounting expertise to shape voluntary sustainability reporting has been interpreted as an implicit form of financialization' whereby technical debates that promote profit maximization are privileged over corporate accountability. Research has yet to assess empirically how accounting expertise is deployed as a public practice' to influence sustainability reporting. To address this gap, I explore the emergence of the Climate Disclosure Standards Board (CDSB), and the way it uses accounting expertise to shape climate change risk reporting. While it is clear that professional accountants are playing a more significant role in risk disclosure, the CDSB is a form of experimental governance' that exposes accounting expertise to uncertainty and contestation. Indeed, the CDSB reconstitutes a public space' within the field of accounting where the link between accounting standards and sustainability reporting is exposed to environmental politics rather than subverted into market-friendly debate.