Extended Data Fig. 3: Illustration of system configurations and of contributions of CDR technologies to achieve net zero CO₂ emissions.

Corresponding system configurations are shown for all cases shown in Fig. 3. The four levels of net negative CO₂ emissions to be achieved by the end of the century are for identification purposes only and are not visible on this figure as they will only be achieved after the point of reaching net zero CO₂ emissions. In the cases selected here, net zero CO₂ emissions are reached in 2050. Five illustrative system variations are shown per level (labelled A–E, defined in Extended Data Tables 3, 4). NA, scenarios did not solve under the imposed CDR and bioenergy constraints (Extended Data Table 4). Fossil fuel and industry CCS contributions (white hatched areas) represent CO₂ that is generated but not emitted to the atmosphere. Net negative CO₂ emissions are the sum of gross positive CO₂ emissions from energy and industrial sources and gross positive land-use CO₂ emissions, and are zero by design in this time step. Gross negative CO₂ emissions comprise gross negative land-use CO₂ emissions and CDR through BECCS. The combined size of all bars per scenario gives an indication of the overall size of the remaining CO₂ producing system by the end of the century. Because the timing of CDR upscaling and amount of CDR at the time of reaching global net zero CO₂ emissions was not explicitly varied in the set of illustrative scenarios developed for this study, it would be wrong to interpret the narrow degree of variation and general agreement across scenarios as a robust feature. Variations could be explored through additional dedicated studies (Extended Data Table 2).