Editing IPCC:AR6/WGIII/Chapter-9 (section)

=== 9.6.2 Assessment of the Potentials at Regional and Global Level ===

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This section presents an aggregation of bottom-up potential estimates for different countries into regional and then global figures for 2050, based on literature presented in [[#9.6.1|Section 9.6.1]] . First, national potential estimates reported as a share of baseline emissions in 2050 were aggregated into regional potential estimates. Second, the latter were multiplied with regional baseline emissions to calculate the regional potential in absolute numbers. Third, the global potential in absolute numbers was calculated as a sum of regional absolute potentials. When several bottom-up studies were identified for a region, either a rounded average or a rounded median figure was taken, giving the preference to the one that was closest to the potential estimates of countries with very large contribution to regional baseline emissions in 2050 (e.g., to China in Eastern Asia). Furthermore, we preferred studies, which assessed the whole or a large share of sector emissions and considered a comprehensive set of measures. The regional baseline emissions, refer to the World Energy Outlook (WEO) Current Policy Scenario (International Energy Agency 2019c). The sector mitigation potential reported in [[IPCC:Wg3:Chapter:Chapter-12|Chapter 12]] for the year 2030 was estimated in the same manner.

Figure 9.16 presents the mitigation potential in the building sector for the world and each region in 2050, estimated as a result of this aggregation exercise. The potentials presented in the figure are different from those reported in [[#9.3.3|Section 9.3.3]] , where they are estimated by IEA and IMAGE hybrid model. The figure provides two breakdowns of the potential, into the reduction of direct and indirect emissions as well as into the reduction of emissions from introducing sufficiency, energy efficiency, and renewable energy measures. The potential estimates rely on the incremental stepwise approach, assembling the measures according to the SER framework (Box 9.1) and correcting the amount of the potential at each step for the interaction of measures. The sequence of energy efficiency and renewable energy measures follow the conclusion of the IPCC Special Report on Global Warming of 1.5°C (SR1.5) ( [[#Rogelj--2018|Rogelj et al. 2018]] ) that lower energy demand allows more choice of low-carbon energy supply options, and therefore such sequencing is more beneficial and cost-effective.

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[[File:e778f2c6216f51a66c1a32857e688ccd IPCC_AR6_WGIII_Figure_9_16.png]]

'''Figure 9.16''' | Global and regional estimates of GHG emissions in the building sector in 2020 and 2050, and their potential reduction in 2050 broken down by measure (sufficiency/energy efficiency/renewable energy) and by emission source (direct/indirect). Note: the baseline refers to the WEO Current Policy Scenario (International Energy Agency 2019c). It may differ from other chapters.

Figure 9.16 argues that it is possible to mitigate 8.2 GtCO 2 or 61% of global building emissions in 2050, as compared to their baseline. At least 1.4 GtCO 2 or 10% of baseline emissions could be avoided introducing the sufficiency approaches. Further 5.6 GtCO 2 or 42% of baseline emissions could be mitigated with the help of energy efficiency technologies and practices. Finally, at least 1.1 GtCO 2 or 9% of baseline emissions could be reduced through the production and use of onsite renewable energy. Out of the total potential, the largest share of 5.4 GtCO 2 will be available in developing countries; these countries will be able to reduce 59% of their baseline emissions. Developed Countries will be able to mitigate 2.7 GtCO 2 or 65% of their baseline emissions. Only few potential studies, often with only few mitigation options assessed, were available for the countries of South-East Asia and Pacific, Africa, and Latin America and Caribbean; therefore, the potential estimates represent low estimates, and the real potentials are likely be higher.

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