The carbon budget implications of INDCs (2016 UNEP Emissions Gap Report)

To give an indication of the carbon budget implications of the INDC scenarios, Figure 3.2 (on the right) shows the cumulative CO2 emissions implied by the INDC scenarios until 2030. Figure 3.2 shows that under the INDC scenarios, the IPCC CO2 budget for limiting warming to below 2°C with at least 66 per cent probability will be close to depleted by 2030, and the IPCC CO2 budget in line with limiting warming to below 1.5°C with at least 50 per cent probability will already be well exceeded by 2030. The Figure also illustrates the limited CO2 budget implications of the INDC scenarios compared to the current policy scenario. If the CO2 budget is exceeded, negative emissions at a global scale are required to capture the excess CO2 . <snip> limitations or absence of negative emissions technologies would significantly limit the feasibility of keeping temperature rise to low levels in 2100. Steep emission reductions would be required over the coming 5 to 15 years to hedge against a strong reliance on negative emissions technologies later in this century. 

Figure 3.2 (on the right): Comparison of projected emissions by 2030 and alltime 1.5°C and 2°C carbon budgets. Cumulative global total carbon dioxide emissions for the conditional INDC case, the unconditional INDC case and the current policies scenario, and carbon budgets from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5) (IPCC, 2014a). The carbon budget ranges show the values based on the range of scenarios assessed by Working Group III (IPCC, 2014b). The solid horizontal line at 1,000 GtCO2 shows the estimate based on complex Earth-System Models, assessed by Working Group I (IPCC, 2014a).Historical emissions until 2015 are based on Le Quéré et al. (2015).