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

=== 9.3.1 Past and Future Emission Trends ===

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Total GHG emissions in the building sector reached 12 GtCO 2- eq in 2019, equivalent to 21% of global GHG emissions that year. 57% of GHG emissions from buildings were indirect CO 2 emissions from generation of electricity and heat off-site, 24% were direct CO 2 emissions produced on-site, and 18% were from the production of cement and steel used for construction and refurbishment of buildings (see Cross-Chapter Box 3 and Cross-Working Group Box 1 in Chapter 3, and Figure 9.3a). Halocarbon emissions were equivalent to 3% of global building GHG emissions in 2019. In the absence of the breakdown of halocarbon emissions per end-use sectors, they have been calculated for the purpose of this chapter, by considering that 60% of global halocarbon emissions occur in buildings ( [[#Hu--2020|Hu et al. 2020]] ). CH 4 and N 2 O emissions were negligible, representing 0.08% each out of the 2019 global building GHG emissions. Therefore, this chapter considers only CO 2 emissions from buildings. By limiting the scope of the assessment to CO 2 emissions, the share of emissions from buildings increases to 31% of global 2019 CO 2 emissions. Energy use in residential and non-residential buildings contributed 50% and 32% respectively, while embodied emissions contributed 18% to global building CO 2 emissions.

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'''Figure 9.3: Building GHG emissions: historical based on IEA data and future emissions based on two IEA scenarios (sustainable development, and net zero emissions), IMAGE Lifestyle-Renewable scenario and Resource Efficiency and Climate Change-Low Energy Demand scenario (RECC-LED).''' RECC-LED data include only space heating and cooling and water heating in residential buildings. The IEA current policies scenario is included as a baseline scenario (IEA current policies scenario).

Over the period 1990–2019, global CO 2 emissions from buildings increased by 50%. Global indirect CO 2 emissions increased by 92%, driven by the increase of fossil fuels-based electrification, while global direct emissions decreased by 1%. At regional level, emissions in residential buildings decreased in Developed Countries, except in Australia, Japan and New Zealand, while they increased in developing countries. The highest decrease was observed in Europe and Eurasia, with 13.6% decrease of direct emissions and 33% decrease of indirect emissions, while the highest increase of direct emissions occurred in Middle East, 198%, and the highest increase of indirect emissions occurred in Eastern Asia, 2258%. Indirect emissions from non-residential buildings increased in all regions. The highest increase occurred in Eastern Asia, 1202%, and the lowest increase occurred in Europe and Central Asia, 4%, where direct emissions from non-residential buildings decreased by 51%. Embodied emissions have also increased in all regions. The highest increase occurred in Southern Asia, 334%, while the lowest increase occurred in North America, 4% (Figure 9.3b).

Future emissions were assessed using four global scenarios and their respective baselines (Box 9.2). The selection of the scenarios was based on the features of each scenario, the geographic scope, and the data availability to analyse future building emissions based on the SER framework (Box 9.1).

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