The exchange of carbon between oceanic plates, the deep Earth, and the atmosphere plays a significant role in modulating global climate1,2. Icehouse-greenhouse climate fluctuations have been attributed to changes in palaeogeography and solid Earth degassing3, particularly along continental arcs2,4,5, to arc weathering5 and to the sequestration of carbon into oceanic carbonate-rich sediments6. However, the proportions of these contributions and their effect on modulating global climate are poorly constrained. Here we show that the changing balance between volcanic outgassing and carbon sequestration into oceanic lithosphere is the key driver for major climate shifts. Combined volcanic arc, mid-ocean ridge and continental rift emissions exceed carbon sequestration during greenhouse climates. In contrast, oceanic plate sequestration exceeds emissions during icehouse climates. Our results challenge the long-held view that carbon degassing along volcanic arcs is the main contributor to atmospheric carbon2,4,5, suggesting instead that mid-ocean ridge and rift degassing surpass arc emissions before 100 Ma.
Data availability: The datasets generated and analysed during the current study are available in the Zenodo repository, https://doi.org/10.5281/zenodo.15315706
