Editing IPCC:AR6/WGIII/Chapter-2 (section)

=== 2.4.4 Rapid and Large-scale Urbanisation as a Driver of GHG Emissions ===

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Economic growth and urbanisation go hand in hand and are both influencing GHG emissions. However, the exact role of urban development in driving emissions is multi-faceted and heterogeneous, depending on development status and other regional factors ( ''medium evidence'' , ''high agreement'' ) ( [[#Jorgenson--2014|Jorgenson et al. 2014]] ; [[#Lamb--2014|Lamb et al. 2014]] ; [[#Liddle--2014|Liddle and Lung 2014]] ; [[#Creutzig--2015|Creutzig et al. 2015]] ; [[#Pincetl--2017|Pincetl 2017]] ; [[#Azizalrahman--2019|Azizalrahman and Hasyimi 2019]] ; [[#Muñoz--2020|Muñoz et al. 2020]] ). This calls for a differentiated assessment. This section assesses the process of rapid urban growth in developing countries and how emissions change over time when cities’ urban populations and infrastructure expand at fast speed and at a massive scale ( [[#Seto--2017|Seto et al. 2017]] ; [[#Elmqvist--2021|Elmqvist et al. 2021]] ). To distinguish, [[#2.6|Section 2.6]] includes the carbon footprint of urban lifestyles and the difference in emissions profiles between already urbanised and less urbanised areas. [[IPCC:Wg3:Chapter:Chapter-8|Chapter 8]] deals with urban strategies for climate change mitigation.

Urban development is most significant and rapid in developing and transition countries, accompanied by a substantial migration of rural populations to urban areas ( [[#Apergis--2016|Apergis and Li 2016]] ; [[#Azizalrahman--2019|Azizalrahman and Hasyimi 2019]] ; Z. [[#Wang--2019|]] [[#Wang--2019|]] [[#Wang--2019|Wang et al. 2019]] ) and associated impacts on land use ( [[#Richardson--2015|Richardson et al. 2015]] ). If the trend of developing countries following infrastructure stock patterns in industrialised nations continues until 2050, this could cause approximately 350 GtCO 2 from the production of materials ( [[#Müller--2013|Müller et al. 2013]] ). This would be equivalent to 70% of the 500 GtCO 2 estimated remaining carbon budget from the beginning of 2020 to limit global warming to 1.5°C with a likelihood of 50% ( [[#IPCC--2021b|IPCC 2021b]] ).

In many developing countries across the world, the process of urban expansion leads to higher per capita consumption-based GHG emissions ( ''medium evidence'' , ''high agreement'' ) ( [[#Jorgenson--2014|Jorgenson et al. 2014]] ; [[#Yao--2015|Yao et al. 2015]] ; [[#Zhang--2016|Zhang et al. 2016]] ; [[#Wood--2018|Wood et al. 2018]] a; [[#Muñoz--2020|Muñoz et al. 2020]] ). The high disparity between rural and urban personal carbon footprints in these countries ( [[#Wiedenhofer--2017|Wiedenhofer et al. 2017]] ) ( [[#2.6|Section 2.6]] ) means that migration to urban areas increases overall emissions as levels of income and expenditure rise, leading to further economic growth and infrastructure development in urban areas ( [[#Müller--2013|Müller et al. 2013]] ; [[#Li--2015|Li et al. 2015]] ; [[#Wang--2016|Wang and Yang 2016]] ; [[#Zhang--2016|Zhang et al. 2016]] ; [[#Wiedenhofer--2017|Wiedenhofer et al. 2017]] ; Cetin and Bakirtas 2019; [[#Fan--2019|Fan et al. 2019]] ; [[#Li--2019|Li and Zhou 2019]] ; [[#Xia--2019|Xia et al. 2019]] ; [[#Sarkodie--2020|Sarkodie et al. 2020]] ).

For total production-based emissions in general, urbanisation is thought to have a smaller effect than changes in population, GDP per capita, and energy and emissions intensities, which are all more influential ( [[#Lin--2017|Lin et al. 2017]] ). Another driver of urban emissions is rising ambient air temperature caused by urban land expansion, which will likely drive a substantive increase in air conditioning use and cold storage for food ( [[#Huang--2019|Huang et al. 2019]] ). Specific emission drivers, however, depend on city- and place-specific circumstances such as income, household size, density, or local climate ( [[#Baiocchi--2015|Baiocchi et al. 2015]] ; H. [[#Wang--2019|]] [[#Wang--2019|]] [[#Wang--2019|Wang et al. 2019]] ). Geographical factors, urban form, and transport/fuel costs are dependent on each other, and, together with economic activity, have been found to explain 37% of urban direct energy use and 88% of urban transport energy use in a global sample of 274 cities ( [[#Creutzig--2015|Creutzig et al. 2015]] ).

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