Fig. 4: Consequences of fair targets for international mitigation finance.

a–l, Fair emissions allowances in 2030 compared with NDC (black, average between conditional and unconditional) and cost-optimal (brown) results and their consequences as a combination of increased domestic mitigation ambition (grey) and ensuring additional mitigation through international finance (paying in red, receiving in blue) for the USA (a), the European Union (b), Japan (c), Saudi Arabia (d), Russian Federation (e), Brazil (f), South Africa (g), Indonesia (h), Mexico (i), China (j), India (k) and Nigeria (l). Fair emissions allowances are shown for ECPC (proxying responsibility; purple), AP (proxying capability; yellow) and PCC (proxying equality; dark blue) under default settings (minima and maxima across all global and allocation rule variables in whiskers, apart from temperature (1.6 °C), climate sensitivity (50%) and convergence year (2050–2080)). The top panel shows an example; the rest are individual countries as depicted on the left. Default settings for a 1.6 °C, 50% pathway are used here. Globally cost-optimal results are obtained as averaged from the IPCC AR6 WGIII scenario database, C1 category (Methods) with 10–90 quantiles across scenarios that project these regions in whiskers. To the right, the gaps (default settings) between fair allocations, cost-optimal emissions and NDC projections are given in GHG emissions (GtCO₂e). In the text, we also provide a few estimates of how these emissions gaps could translate to financial flows.