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

=== 2.7.2 Estimates of Future CO 2 Emissions From Long-lived Infrastructures ===

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Table 2.6 summarises studies that apply an accounting approach based on plant-level data to quantify future CO 2 emissions from long-lived fossil fuel infrastructure ( [[#Davis--2010|Davis et al. 2010]] ; [[#Davis--2014|Davis and Socolow 2014]] ; [[#Rozenberg--2015|Rozenberg et al. 2015]] ; [[#Edenhofer--2018|Edenhofer et al. 2018]] ; [[#Pfeiffer--2018|Pfeiffer et al. 2018]] ; [[#Cui--2019|Cui et al. 2019]] ; [[#Smith--2019|Smith et al. 2019]] ; [[#Tong--2019|Tong et al. 2019]] ; [[#Pradhan--2021|Pradhan et al. 2021]] ). Differences between studies arise in the scope of the infrastructure covered (including resolution), the inclusion of new infrastructure proposals, the exact estimation methodology applied as well as their assessments of uncertainties. Other studies provide analysis with a sectoral focus ( [[#Bullock--2020|Bullock et al. 2020]] ; [[#Vogl--2021|Vogl et al. 2021]] ) or with a regional focus on the power sector ( [[#Shearer--2017|Shearer et al. 2017]] , 2020; [[#González-Mahecha--2019|González-Mahecha et al. 2019]] ; [[#Grubert--2020|Grubert 2020]] ; [[#Tao--2020|Tao et al. 2020]] ).

Assuming variations in historic patterns of use and decommissioning, comprehensive estimates of cumulative future CO 2 emissions from ''current'' fossil fuel infrastructures are 720 (550–910) GtCO 2 ( [[#Smith--2019|Smith et al. 2019]] ) and 660 (460–890) ( ''high confidence'' ) ( [[#Tong--2019|Tong et al. 2019]] ) (Table 2.6 and Figure 2.26). This is about the same size as the overall cumulative net CO 2 emissions until reaching net zero CO 2 of 510 (330–710) Gt in pathways that limit warming to 1.5°C with no or limited overshoot (Chapter 3). About 50% of cumulative future CO 2 emissions from ''current'' fossil fuel infrastructures come from the power sector and 70% of these (or about 40% of the total) are from coal plants only. Like global annual CO 2 emissions ( [[#Friedlingstein--2020|Friedlingstein et al. 2020]] ; [[#Peters--2020|Peters et al. 2020]] ), future CO 2 emissions from fossil fuel infrastructures have increased over time – that is, future CO 2 emissions from fossil fuel infrastructure additions in a given year still outgrow ‘savings’ from infrastructure retirements ( [[#Davis--2014|Davis and Socolow 2014]] ; [[#Tong--2019|Tong et al. 2019]] ). This could add further inertia to the system as it may require more and faster retirement of fossil-fuel based infrastructures later, and lead to higher costs for meeting climate goals (e.g., [[#Bertram--2015|Bertram et al. 2015]] ; [[#Johnson--2015|Johnson et al. 2015]] ).

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[[File:6a59e082f68aa72e46afe7da590c9fff IPCC_AR6_WGIII_Figure_2_26.png]]

'''Figure 2.26''' '''|''' '''Future CO''' 2 '''emissions from existing and currently planned fossil fuel infrastructure in the context of Paris carbon budgets in GtCO''' 2 '''based on historic patterns of infrastructure lifetimes and capacity utilisation.''' Future CO 2 emissions estimates of existing infrastructure for the electricity sector as well as all other sectors (industry, transport, buildings, other fossil fuel infrastructures) and of proposed infrastructures for coal power as well as gas and oil power. Grey bars on the right depict the range (5th–95th percentile) in overall cumulative net CO 2 emissions until reaching net zero CO 2 in pathways that limit warming to 1.5°C with no or limited overshoot (1.5°C scenarios), and in pathways that limit warming to 2°C (&lt;67%) (2°C scenarios). Source: based on [[#Edenhofer--2018|Edenhofer et al. (2018)]] and [[#Tong--2019|Tong et al. (2019)]] .

Estimates of total cumulative future CO 2 commitments from ''proposed infrastructure'' focus only on the power sector due to data availability (Table 2.6 and Figure 2.26). Infrastructure proposals can be at various stages of development involving very different probabilities of implementation. About one-third of the currently proposed projects are more probable as they are already under construction ( [[#Cui--2019|Cui et al. 2019]] ). [[#Pfeiffer--2018|Pfeiffer et al. (2018)]] and [[#Tong--2019|Tong et al. (2019)]] assess the cumulated CO 2 emissions from proposed infrastructure in the entire power sector at 270 GtCO 2 and 190 GtCO 2 respectively. Estimates of CO 2 emissions implications for new coal power infrastructure plans are more frequent ( [[#Edenhofer--2018|Edenhofer et al. 2018]] ; [[#Pfeiffer--2018|Pfeiffer et al. 2018]] ; [[#Cui--2019|Cui et al. 2019]] ; [[#Tong--2019|Tong et al. 2019]] ) ranging between 100 and 210 GtCO 2 . Differences across estimates of future CO 2 emissions from proposed power infrastructure mostly reflect substantial cancellations of coal infrastructure proposals in 2017 and 2018 ( [[#Tong--2019|Tong et al. 2019]] ).

The global estimate of future CO 2 emissions from ''current and planned'' fossil-fuel infrastructures is 850 (600–1100) GtCO 2 ( [[#Tong--2019|Tong et al. 2019]] ). This already exceeds total cumulative net CO 2 emissions in pathways that limit warming to 1.5°C with no or limited overshoot (see above). It is about the same size as the total cumulative net CO 2 emissions of 890 (640–1160) GtCO 2 from pathways that limit warming to 2°C (&lt;67%) (Chapter 3). Hence, cumulative net CO 2 emissions to limit warming to 2°C (&lt;67%) or lower could already be exhausted by current and planned fossil fuel infrastructure ( ''high confidence'' ) even though this estimate only covers a fraction of all infrastructure developments over the 21st century as present in mitigation pathways, does not cover all sectors (e.g., AFOLU) and does not include currently infrastructure development plans in transport, buildings, and industry due to a lack of data.

Hence, the Paris climate goals could move out of reach unless there are dedicated efforts for early decommissioning, and reduced utilisation of existing fossil fuel infrastructures, cancellation of plans for new fossil fuel infrastructures, or compensation efforts by removing some of the CO 2 emissions from the atmosphere ( [[#Cui--2019|Cui et al. 2019]] ; [[#Smith--2019|Smith et al. 2019]] ; [[#Tong--2019|Tong et al. 2019]] ; [[#Pradhan--2021|Pradhan et al. 2021]] ). For example, [[#Fofrich--2020|Fofrich et al. (2020)]] suggest in a multi-model study that coal and gas power infrastructure would need to be retired 30 (19–34) and 24 (21–26) years earlier than the historical averages of 39 and 36 years when following 1.5°C pathways and 23 (11–33) and 19 (11–16) years earlier when following 2°C pathways. [[#Cui--2019|Cui et al. (2019)]] arrive at more conservative estimates for coal power plants, but only consider the existing and currently proposed capacity. Premature retirement of power plants pledged by members of the Powering Past Coal Alliance would cut emissions by 1.6 GtCO 2 , which is 150 times less than future CO 2 emissions from existing coal power plants ( [[#Jewell--2019|Jewell et al. 2019]] ).

Few quantifications of carbon lock-in from urban infrastructure, in particular urban form, have been attempted, in part because they also relate to behaviours that are closely tied to routines and norms that co-evolve with ‘hard infrastructures’ and technologies, as well as ‘soft infrastructure‘ such as social networks and markets ( [[#Seto--2016|Seto et al. 2016]] ). There are some notable exceptions providing early attempts ( [[#Guivarch--2011|Guivarch and Hallegatte 2011]] ; [[#Driscoll--2014|Driscoll 2014]] ; Seto et al.2014; Lucon et al. 2014; [[#Erickson--2015|Erickson and Tempest 2015]] ; [[#Creutzig--2016|Creutzig et al. 2016]] ). [[#Creutzig--2016|Creutzig et al. (2016)]] attempt a synthesis of this literature and estimate the total cumulative future CO 2 emissions from existing urban infrastructure at 210 Gt, and from new infrastructures at 495 Gt for the period 2010–2030.

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