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Concentration pathways for the four Outlook scenarios including all climate forcers, 2010-2100

Figure 3.17. Concentration pathways for the four Outlook scenarios including all climate forcers, 2010-2100 550 525 500 475 450 425 400 375 Baseline - - 450 Core 450 Delayed Action 450 Accelerated Action 11 550 core 350 2010 2020 2030 2040 2050 2060 2070 2080 2000 2100 Source: OECD Environmental Outiook projections; output from IMAGE. CO, equivalent concentrations in ppmv)

Concentration pathways for the four Outlook scenarios including all climate forcers, 2010-2100

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Figure 3.17 illustrates the projected concentration pathways of the various scenarios, including all climate forcers.38 Figure 3.17. Concentration pathways for the four Outlook scenarios including all... climate forcers, 2010-2100 It shows that the pathway of the 450 Delayed Action scenario reflects a larger degree of overshoot than the other two 450 ppm scenarios. The catch-up in mitigation efforts in the middle of the century implies that concentration levels gradually fall back to the pathway of the 450 Core scenario and are nearly identical from 2080 onwards. In contrast, the 450 Accelerated Action scenario prevents some of the overshoot and has concentration levels peaking at less than 470 ppm. In all three 450 scenarios concentration levels decline after 2050 to ensure that temperature increases do not overshoot. Finally, note that the lower mitigation efforts in the coming decade under the 450 Delayed Action and 550 ppm scenarios lead to higher emission levels of aerosols, especially sulphur. This is because energy use is generally reduced less. The cooling effect of these gases would reduce temperatures in the short run compared to the 450 Core scenario, which explains the very similar concentration levels until 2030. Compared with the “no new policies” Baseline projection, all three 450 ppm scenarios would have significantly lower climate impacts, and offer at least a medium chance of limiting global average temperature increase in 2100 to 2 °C.39 The implications of achieving the 450 Core scenario Precipitation patterns would also change less in the 450 scenarios than in the Baseline (see Figure 3.10 and 3.11). However, the mitigation efforts undertaken in the 450 ppm scenarios will not avoid all climate impacts. Thus, adaptation to remaining impacts will still be required.