Editing IPCC:AR6/WGIII/Chapter-8 (section)

=== 8.3.3 Trends in Urban Greenhouse Gas Emissions ===

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One major innovation presented in AR6 – particularly in this chapter – is the inclusion of trend data on urban GHG emissions. Using multiple datasets in conjunction with the SSP and RCP scenarios, this chapter provides an estimate of urban GHG emissions from 1990 through 2100, based on a consumption-based approach. This innovation provides, for the first time, a temporal dimension to urban footprints considering different climate scenarios with implications for urban mitigation. The new analysis presents a comparison of ways urban emissions can evolve given different scenario contexts ( [[#8.3.4.2|Section 8.3.4.2]] ). Additionally, new research has quantified trends in urban CO 2 emissions and their key drivers across 91 global cities from 2000 to 2018 ( [[#Luqman--2021|Luqman et al. 2021]] ).

Figures 8.8 and 8.9 present key urban emission metrics and trends for six regions (based on the AR6 WGIII regional breakdown) – the first for the year 2015, and the latter for both 2000 and 2015.

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[[File:1374f4832addd1c1b4d359522502fad2 IPCC_AR6_WGIII_Figure_8_8.png]]

'''Figure 8.8: 2015 average urban greenhouse gas emissions per capita, considering carbon dioxide (CO''' 2 ''') and methane (CH''' 4 ''') emissions from a consumption-based perspective, alongside urban population, for regions represented in the AR6 WGIII 6-region aggregation.''' The average urban per capita emissions are given by the height of the bars while the width represents the urban population for a given region, based on 2015 values for both axes. Provided within the bars are the percentage shares of the urban population by region as a share of the total urban population. Source: synthesised based on data from [[#UN%20DESA--2019|UN DESA (2019)]] and [[#Gurney--2022|Gurney et al. (2022)]] .

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[[File:47ec500df9aab4e5d177461ef2f3dfcc IPCC_AR6_WGIII_Figure_8_9.png]]

'''Figure 8.9''' : '''Changes in six metrics associated with urban and national-scale carbon dioxide (CO''' 2 ''') and methane (CH''' 4 ''') emissions represented in the AR6 WGIII 6-region aggregation, with (a) 2000 and (b) 2015.''' The trends in [[#Luqman--2021|Luqman et al. (2021)]] were combined with the work of [[#Moran--2018|Moran et al. (2018)]] to estimate the regional urban CO 2 -eq share of global urban emissions, the urban share of national CO 2 -eq emissions, and the urban per capita CO 2 -eq emissions by region. This estimate is derived from consumption-based accounting that includes both direct emissions from within urban areas and indirect emissions from outside urban areas related to the production of electricity, goods, and services consumed in cities. It incorporates all CO 2 and CH 4 emissions except aviation, shipping and biogenic sources (i.e., land-use change, forestry, and agriculture). The dashed grey line represents the global average urban per capita CO 2 -eq emissions. The regional urban population share, regional CO 2 -eq share in total emissions, and national per capita CO 2 -eq emissions by region are given for comparison. Source: adapted from [[#Gurney--2022|Gurney et al. (2022)]] . 5

The key trends are as follows. First, the urban share of global GHG emissions (including CO 2 and CH 4 ) is substantive and continues to increase (Figure 8.9). Total urban CO 2 -eq emissions based on consumption-based accounting were estimated to be 25 GtCO 2 -eq, or 62% of the global total in 2015, and increased to an estimated 29 GtCO 2 -eq in 2020, representing about 67–72% of global emissions. This estimate includes all CO 2 and CH 4 emissions except aviation, shipping, and biogenic sources (i.e., land-use change, forestry, and agriculture). About 100 of the highest-emitting urban areas account for approximately 18% of the global carbon footprint ( [[#Moran--2018|Moran et al. 2018]] ). Globally, the urban share of national CO 2 -eq emissions increased 6 percentage points, from 56% in 2000 to 62% in 2015.

Second, while urban CO 2 emissions were increasing in all urban areas, the dominant drivers were dependent upon development level. Emissions growth in urban areas other than in Developed Countries was driven by increases in area and per capita emissions. Across all cities, higher population densities are correlated with lower per capita GHG emissions ( [[#Luqman--2021|Luqman et al. 2021]] ).

Third, the urban share of regional GHG emissions increased between 2000 and 2015, with much inter-region variation in the magnitude of the increase ( ''high confidence'' ) (Figure 8.9) ''.'' Between 2000 and 2015, the urban emissions share across AR6 WGIII regions (6-region aggregation) increased from 28% to 38% in Africa, from 46% to 54% in Asia and Pacific, from 62% to 72% in Developed Countries, from 57% to 62% in Eastern Europe and West-Central Asia, from 55% to 66% in Latin America and Caribbean, and from 68% to 69% in the Middle East.

Between 2000 and 2015, urban population, urban CO 2 -eq emissions, and national CO 2 -eq emissions increased as a share of the global total in the Asia and Pacific region while the share declined for Developed Countries. The urban share of total regional CO 2 -eq emissions decreased in Developed Countries from 58.2% (2000) to 40.0% (2015). Urban per capita CO 2 -eq and national per capita CO 2 -eq also increased in all regions except for the urban per capita CO 2 -eq value in the Developed Countries region, which declined slightly.

Fourth, the global average per capita urban GHG emissions increased between 2000 and 2015, with cities in the Developed Countries region producing nearly seven times more per capita than the lowest emitting region ( ''medium confidence'' ) ''.'' From 2000 to 2015, the global urban GHG emissions per capita increased from 5.5 to 6.2 tCO 2 -eq per person (an increase of 11.8%), with increases across five of the six regions: Africa increased from 1.3 to 1.5 tCO 2 -eq per person (22.6%); Asia and Pacific increased from 3.0 to 5.1 tCO 2 -eq per person (71.7%); Eastern Europe and West-Central Asia increased from 6.9 to 9.8 tCO 2 -eq per person (40.9%); Latin America and Caribbean increased from 2.7 to 3.7 tCO 2 -eq per person (40.4%); and the Middle East increased from 7.4 to 9.6 tCO 2 -eq per person (30.1%). Albeit starting from the highest level, Developed Countries had a decline of 11.4 to 10.7 tCO 2 -eq per person (–6.5%).

In 2015, regional urban per capita consumption-based CO 2 -eq emissions were lower than regional consumption-based national per capita CO 2 -eq emissions in five of the six regions. These regions in order of the difference are: Developed Countries (lower by 1.0 tCO 2 -eq per capita); Latin America and Caribbean (lower by 0.8 tCO 2 -eq per capita); Eastern Europe and West-Central Asia (lower by 0.7 tCO 2 -eq per capita); Middle East (lower by 0.4 tCO 2 -eq per capita); and Africa (lower by 0.2 tCO 2 -eq per capita); while higher only in the Asia and Pacific region (higher by 0.9 tCO 2 -eq per capita). All regions show convergence of the urban and national per capita CO 2 -eq, as the urban share of national emissions increases and dominates the regional total.

'''[[#footnote-004|5]]'''

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