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Change in global GHG emissions in 2050 compared to 2010: 450 Delayed Action and 550 ppm scenarios

Figure 3.23. Change in global GHG emissions in 2050 compared to 2010: 450 Delayed Action and 550 ppm scenarios DOECD A1 ORussia & rest of A1 ORest of BRIICS ORest World IWORLD 450 Delayed Action 550 ppm Baseline -80% -60% -40% -20% 0% 20% 40% 60% 80% 100% 120% Source: OECD Environmental Outlook projections, output from ENV-Linkages.

Change in global GHG emissions in 2050 compared to 2010: 450 Delayed Action and 550 ppm scenarios

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Less stringent climate mitigation (550 ppm) scenarios Achieving the 450 ppm scenarios require global emission levels to peak before or around 2020. This is only possible if emissions can be reduced in... nearly all global regions and if action starts now. If not, as suggested by the 450 Delayed Action scenario, emissions in 2020 may be too high to achieve the 2 °C/450 ppm goal cost-effectively. If the 450 ppm target is to be reached, unprecedented rates of emission reductions will be required after 2020. The only way to do this will be to drastically transform the highcarbon energy system into which the world is becoming more tightly locked every year (IEA, 2011b). Given the uncertainties surrounding our ability to achieve this, less stringent long-run targets should also be investigated. Up until 2020, the 450 Delayed Action scenario is very close to a 550 Core scenario, which would require less mitigation in the rest of the century (see Figure 3.17 above). However, the 550 ppm Core scenario represents a much greater likelihood of a global average temperature rise above 2 °C. This implies that unless the required rapid transformation occurs after 2020, the Copenhagen pledges are more likely to lead to a 2.5 °CC to 3 °C increase in global average temperature than 2 °C. If the 550 Core pathway is followed this would imply a trade-off between lower short-term mitigation costs and higher long-term costs from more serious climate impacts and the need for higher levels of adaptation than the 450 Delayed Action scenario.45 Once the “low-hanging fruit” (cheap mitigation options) have been exhausted, the marginal abatement cost of mitigation actions rises significantly. The 550 Core scenario requires that emissions in 2050 are down to 2010 levels (Figure 3.23). It leads to a decline in global real income of 1.3% as shown in Figure 3.24. Achieving the additional 28 GtCO2e reduction necessary to reach the 450 Delayed Action pathway would lead to an additional real income decline of about 8 percentage-points, and global emissions would be 60% below 2010 levels.