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

=== 8.6.3 Mitigation Opportunities for New and E merging Cities ===

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'''New and emerging cities have unparalleled potential to become low- or net-zero-emissions urban areas while achieving high quality of life by creating compact, co-located, and walkable urban areas with mixed land use and TOD, that also preserve existing green a''' '''nd blue assets.'''

The fundamental building blocks that make up the physical attributes of cities, such as the layout of streets, the size of the city blocks, the location of where people live versus where they work, can affect and lock in energy demand for long time periods ( [[#Seto--2016|Seto et al. 2016]] ) ( [[#8.4.1|Section 8.4.1]] ). A large share of urban infrastructures that will be in place by 2050 has yet to be constructed and their design and implementation will determine both future GHG emissions as well as the ability to meet mitigation goals ( [[#Creutzig--2016a|Creutzig et al. 2016a]] ) (Figure 8.10 and Table 8.1). Thus, there are tremendous opportunities for new and emerging cities to be designed and constructed to be low-emissions while providing high quality of life for their populations.

The UN International Resource Panel (IRP) estimates that building future cities under conventional practices will require a more than doubling of material consumption, from 40 billion tonnes annually in 2010 to about 90 billion tonnes annually by 2050 ( [[#Swilling--2018|Swilling et al. 2018]] ). Thus, the demand that new and emerging cities will place on natural resource use, materials, and emissions can be minimised and avoided only if urban settlements are planned and built much differently than today, including minimised impacts on land use based on compact urban form, lowered use of materials, and related cross-sector integration, including energy-driven urban design for sustainable urbanisation.

Minimising and avoiding raw material demands depends on alternative options while accommodating the urban population. In addition, operational emissions that can be committed by new urban infrastructure can range between 8.5 GtCO 2 and 14 GtCO 2 annually up to 2030 ( [[#Erickson--2015|Erickson and Tempest 2015]] ). Buildings and road networks are strongly influenced by urban layouts, densities, and specific uses. Cities that are planned and built much differently than today through light-weighting, material substitution, resource efficiency, renewable energy, and compact urban form, have the potential to support more sustainable urbanisation and provide co-benefits for inhabitants (Figures 8.17 and 8.22).

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'''Figure 8.22: Raw material demands and committed emissions from building urban areas.''' The horizontal bars represent the projected increase in raw material demands in the year 2050. The vertical bars represent the possible range of committed CO 2 emissions in 2030. The importance of alternative solutions to reduce raw material demands and committed emissions while increasing co-benefits is represented by the circular process on the right-hand side. Ranges for committed emissions from new urban infrastructure are based on [[#Erickson--2015|Erickson and Tempest (2015)]] SEI WP 11. Source: drawn using data from [[#Erickson--2015|Erickson and Tempest (2015)]] and [[#Swilling--2018|Swilling et al. (2018)]] .

In this context, illustrative mitigation strategies that can serve as a roadmap for emerging cities includes priorities for co-located and mixed land use, as well as TOD, within an integrated approach (Table 8.3 and Figure 8.19). This has cascading effects, including conserving existing green and blue assets (e.g., forests, grasslands, wetlands), many of which sequester and store carbon. Priorities for decarbonising electricity and energy carriers while electrifying mobility, heating, and cooling take place within the integrated approach ( [[#8.4.3|Section 8.4.3]] ). Increasing greenways and permeable surfaces, especially from the design of emerging urban areas onward, can be pursued, also for adaptation co-benefits and linkages with the SDGs ( [[#8.4.4|Section 8.4.4]] and Figure 8.18).

In low-energy-driven urban design, parameters are evaluated based on the energy performance of the urban area in the early design phase of future urban development ( [[#Shi--2017b|Shi et al. 2017b]] ). Energy-driven urban design generates and optimises urban form according to the energy performance outcome ( [[#Shi--2017b|Shi et al. 2017b]] ). Beyond the impact of urban form on building energy performance, the approach focuses on the interdependencies between urban form and energy infrastructure in urban energy systems. The process can provide opportunities for both passive options for energy-driven urban design, such as the use of solar gain for space heating, or of thermal mass to moderate indoor temperatures, as well as active options that involve the use of energy infrastructure and technologies while recognising interrelations of the system. Future urban settlements can also be planned and built with net-zero CO 2 or net-zero GHG emissions, as well as renewable energy targets, in mind. Energy master planning of urban areas that initially target net-zero operational GHG emissions can be supported with energy master planning from conceptual design to operation, including district-scale energy strategies ( [[#Charani%20Shandiz--2021|Charani Shandiz et al. 2021]] ).

Integrated scenarios across sectors at the local level can decouple resource usage from economic growth ( [[#Hu--2018|Hu et al. 2018]] ) and enable 100% renewable energy scenarios ( [[#Zhao--2017a|Zhao et al. 2017a]] ; [[#Bačeković--2018|Bačeković and Østergaard 2018]] ). Relative decoupling is obtained ( [[#Kalmykova--2015|Kalmykova et al. 2015]] ) with increasing evidence for turning points in per capita emissions, total emissions, or urban metabolism ( [[#Chen--2018b|Chen et al. 2018b]] ; [[#Shen--2018|Shen et al. 2018]] ). The importance of integrating energy and resource efficiency in sustainable and low-carbon city planning ( [[#Dienst--2015|Dienst et al. 2015]] ), structural changes, as well as forms of disruptive social innovation, such as the ‘sharing economy’ (see Glossary), is also evident based on analyses for multiple cities, including those that can be used to lower the carbon footprints of urban areas relative to sub-urban areas ( [[#Chen--2018a|Chen et al. 2018a]] ).

To minimise carbon footprints, new cities can utilise new intelligence functions as well as changes in energy sources and material processes. Core design strategies of a compact city can be facilitated by data-driven decision-making so that new urban intelligence functions are holistic and proactive rather than reactive ( [[#Bibri--2020|Bibri 2020]] ). In mainstream practices, for example, many cities use environmental impact reviews to identify potentially negative consequences of individual development projects on environmental conditions on a piecemeal project basis.

New cities can utilise: system-wide analyses of construction materials, or renewable power sources, that minimise ecosystem disruption and energy use, through the use of lifecycle assessments for building types permitted in the new city ( [[#Ingrao--2019|Ingrao et al. 2019]] ); urban-scale metabolic impact assessments for neighbourhoods in the city ( [[#Pinho--2019|Pinho and Fernandes 2019]] ); strategic environmental assessments (SEAs) that go beyond the individual project and assess plans for neighbourhoods ( [[#Noble--2017|Noble and Nwanekezie 2017]] ); or modelling of the type and location of building masses, tree canopies and parks, and temperature (surface conditions) and prevailing winds profiles to reduce the combined effects of climate change and UHI phenomena, thus minimising the need for air conditioning ( [[#Matsuo--2019|Matsuo and Tanaka 2019]] ).

Resource-efficient, compact, sustainable, and liveable urban areas can be enabled with an integrated approach across sectors, strategies, and innovations. From a geophysical perspective, the use of materials with lower lifecycle GHG impacts, including the use of timber in urban infrastructure and the selection of urban development plans with lower material and land demand can lower the emission impacts of existing and future cities ( [[#Müller--2013|Müller et al. 2013]] ; [[#Carpio--2016|Carpio et al. 2016]] ; [[#Liu--2016a|Liu et al. 2016a]] ; [[#Ramage--2017|Ramage et al. 2017]] ; [[#Shi--2017a|Shi et al. 2017a]] ; Stocchero et al. 2017; [[#Bai--2018|Bai et al. 2018]] ; [[#Zhan--2018b|Zhan et al. 2018b]] ; [[#Swilling--2018|Swilling et al. 2018]] ; [[#Xu--2018b|Xu et al. 2018b]] ; [[#UNEP%20IRP--2020|UNEP IRP 2020]] ) (Figure 8.17). The capacity to implement relevant policy instruments in an integrated and coordinated manner within a policy mix while leveraging multi-level support as relevant can increase the enabling conditions for urban system transformation ( [[#Agyepong--2017|Agyepong and Nhamo 2017]] ; [[#Roppongi--2017|Roppongi et al. 2017]] ).

The integration of urban land use and spatial planning, electrification of urban energy systems, renewable energy district heating and cooling networks, urban green and blue infrastructure, and circular economy can also have positive impacts on improving air and environmental quality with related co-benefits for health and well-being ( [[#Diallo--2016|Diallo et al. 2016]] ; [[#Nieuwenhuijsen--2016|Nieuwenhuijsen and Khreis 2016]] ; [[#Shakya--2016|Shakya 2016]] ; [[#Liu--2017|Liu et al. 2017]] ; [[#Ramaswami--2017a|Ramaswami et al. 2017a]] ; [[#Sun--2018b|Sun et al. 2018b]] ; [[#Tayarani--2018|Tayarani et al. 2018]] ; [[#Park--2019|Park and Sener 2019]] ; [[#González-García--2021|González-García et al. 2021]] ). Low-carbon development options can be implemented in ways that reduce impacts on water use, including water use efficiency, demand management, and water recycling, while increasing water quality ( [[#Koop--2015|Koop and van Leeuwen 2015]] ; [[#Topi--2016|Topi et al. 2016]] ; [[#Drangert--2017|Drangert and Sharatchandra 2017]] ; [[#Lam--2017|Lam et al. 2017]] , 2018; [[#Vanham--2017|Vanham et al. 2017]] ; [[#Kim--2018|Kim and Chen 2018]] ). The ability to enhance biodiversity while addressing climate change depends on improving urban metabolism and biophilic urbanism towards urban areas that are able to regenerate natural capital ( [[#Thomson--2018|Thomson and Newman 2018]] ; [[#IPBES--2019b|IPBES 2019b]] ).

There are readily available solutions for low-carbon urban development that can be further supported by new and emerging ones, such as tools for optimising the impact of urban form on energy infrastructure ( [[#Hu--2015|Hu et al. 2015]] ; [[#Shi--2017b|Shi et al. 2017b]] ; [[#Xue--2017|Xue et al. 2017]] ; [[#Dobler--2018|Dobler et al. 2018]] ; [[#Egusquiza--2018|Egusquiza et al. 2018]] ; [[#Pedro--2018|Pedro et al. 2018]] ; [[#Soilán--2018|Soilán et al. 2018]] ). The costs of low-carbon urban development are manageable, and enhanced with a portfolio approach for cost-effective, cost-neutral, and reinvestment options with evidence across different urban typologies ( [[#Colenbrander--2015|Colenbrander et al. 2015]] , 2017; [[#Gouldson--2015|Gouldson et al. 2015]] ; [[#Nieuwenhuijsen--2016|Nieuwenhuijsen and Khreis 2016]] ; [[#Saujot--2016|Saujot and Lefèvre 2016]] ; [[#Sudmant--2016|Sudmant et al. 2016]] ; [[#Brozynski--2018|Brozynski and Leibowicz 2018]] ).

Low-carbon urban development that triggers economic decoupling can have a positive impact on employment and local competitiveness ( [[#Kalmykova--2015|Kalmykova et al. 2015]] ; [[#Chen--2018b|Chen et al. 2018b]] ; [[#García-Gusano--2018|García-Gusano et al. 2018]] ; [[#Hu--2018|Hu et al. 2018]] ; [[#Shen--2018|Shen et al. 2018]] ). In addition, sustainable urban transformation can be supported with participatory approaches that provide a shared understanding of future opportunities and challenges where public acceptance increases with citizen engagement and citizen empowerment as well as an awareness of co-benefits ( [[#Blanchet--2015|Blanchet 2015]] ; [[#Bjørkelund--2016|Bjørkelund et al. 2016]] ; [[#Flacke--2017|Flacke and de Boer 2017]] ; [[#Gao--2017|Gao et al. 2017]] ; [[#Neuvonen--2017|Neuvonen and Ache 2017]] ; [[#Sharp--2017|Sharp and Salter 2017]] ; [[#Wiktorowicz--2018|Wiktorowicz et al. 2018]] ; [[#Fastenrath--2018|Fastenrath and Braun 2018]] ; [[#Gorissen--2018|Gorissen et al. 2018]] ; [[#Herrmann--2018|Herrmann et al. 2018]] ; [[#Moglia--2018|Moglia et al. 2018]] ). Sustainable and low-carbon urban development that integrates issues of equity, inclusivity, and affordability, while safeguarding urban livelihoods, providing access to basic services, lowering energy bills, addressing energy poverty, and improving public health can also improve the distributional effects of existing and future urbanisation ( [[#Friend--2016|Friend et al. 2016]] ; [[#Claude--2017|Claude et al. 2017]] ; [[#Colenbrander--2017|Colenbrander et al. 2017]] ; [[#Ma--2018|Ma et al. 2018]] ; [[#Mrówczyńska--2018|Mrówczyńska et al. 2018]] ; [[#Pukšec--2018|Pukšec et al. 2018]] ; [[#Wiktorowicz--2018|Wiktorowicz et al. 2018]] ) ( [[#8.2|Section 8.2]] ).

Information and communications technologies can play an important role for integrating mitigation options at the urban systems level for achieving zero-carbon cities. Planning for decarbonisation at the urban systems level involves integrated considerations of the interaction among sectors, including synergies and trade-offs among households, businesses, transport, land use, and lifestyles. The utilisation of big data, artificial intelligence and internet of things (IoT) technologies can be used to plan, evaluate and integrate rapidly progressing transport and building technologies, such as autonomous EVs, zero-energy buildings, and districts as an urban system, including energy-driven urban design ( [[#Creutzig--2020|Creutzig et al. 2020]] ; [[#Yamagata--2020|Yamagata et al. 2020]] ). Community-level energy sharing systems will contribute to realising the decarbonisation potential of urban systems at community scale, including in smart cities ( [[IPCC:Wg3:Chapter:Chapter-4#4.2.5.9|Section 4.2.5.9]] , Box 10.1, and Cross-Chapter Box 11 in Chapter 16).

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