Extended Data Fig. 4: The 1.5 °C (RCP 1.9) pathways under a conventional ETS or a CRO-ETS.
a, b, A conventional ETS is used. c, d, A CRO-ETS is used. The underlying set of scenarios was filtered for those scenarios that achieve at least a 15% reduction in total carbon debt compared with their baselines (see Methods). a, c, Geometric median net emissions (solid line) and gross emissions from FFI, BECCS, LUC and DACS. Net emissions from a are also displayed in c (dashed line) and vice versa. The total carbon debt D is shown as a box-and-whiskers plot. Boxes indicate the 25–75% interquartile range around the median values (bold line), whiskers indicate minimum to maximum ranges, points mark the outliers. b, d, Annual mitigation costs as a percentage of GDP, including the share of average abatement costs attributed to emission reductions (ABM), to the compensation of residual emissions by CDR (RES) and to net-negative emissions (NNE) as well as expenditures for allowances (ETS) and interest costs (INT). Total mitigation costs (that is, ABM + RES + NNE + ETS + INT) from d are also displayed in b (dashed line) and vice versa. Box-and-whiskers plots show the total discounted abatement costs (that is, ABM + RES + NNE) as a percentage of GDP, the number above the chart indicates out-of-range outliers. Pie charts in d summarize the properties of the underlying set of scenarios (see Methods). The distribution of rd in CRO-ETS scenarios is depicted in c.