Carbon plays a special role in the Earth system, as a dominant contributor to the planet’s greenhouse gas budget and radiative emissivity, and as a key biological component. Our understanding of past and future climate depends substantially on our understanding the biogeochemical cycling of carbon across a wide range of reservoirs and timescales, from those relevant to air-sea gas-exchange and biological turnover (seasonal-decadal), to those associated with ocean circulation, mean ocean chemistry change (centennial to multi-millennial), and weathering of the solid Earth (multi-millennial to tectonic). Radio- and stable carbon isotopes have a central role to play in advancing our understanding of the biogeochemical cycling of carbon in the Earth system. This session invites contributions that seek to apply or develop the use of radiocarbon and stable carbon isotopes for the study of past Earth system change, using observations, proxy data, or numerical models. Proxy and model studies that bear on the evolving radio- and stable carbon isotope budgets of the Earth’s main surface reservoirs, and on transports within and between these reservoirs, are particularly welcome. The session aims to gather contributors from a wide range of disciplines who share a common interest in understanding past Earth system- and carbon cycle change through the lens of carbon isotopes.