Editing IPCC:AR6/WGIII/Chapter-6 (section)

=== Box 6.11 | Illustrative Low-carbon Energy System Transitions ===

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There are multiple possible strategies to transform the energy system to reach net-zero CO 2 emissions and to limit warming to 2°C (&gt;67%) or lower. All pathways rely on the strategies for net-zero CO 2 energy systems highlighted in [[#6.6.2|Section 6.6.2]] , but they vary in the emphasis that they put on different aspects of these strategies and the pace at which they approach net-zero emissions. The pathway that any country or region might follow will depend on a wide variety of factors ( [[#6.6.4|Section 6.6.4]] ), including, for example, resource endowments, trade and integration with other countries and regions, carbon sequestration potential, public acceptability of various technologies, climate, the nature of domestic industries, the degree of urbanisation, and the relationship with other societal priorities such as energy access, energy security, air pollution, and economic competitiveness. The Illustrative Mitigation Pathways presented in this box demonstrate four distinct strategies for energy system transformations and how each plays out for a different region, aligned with global strategies that would limit warming to 2.0°C (&gt;67%) or to 1.5°C (&gt;50%). Each pathway represents a very different vision of a net-zero energy system. Yet, all these pathways share the common characteristic of a dramatic system-wide transformation over the coming decades.

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'''Box 6.11, Figure 1 | Illustrative Mitigation Pathway 2.0-Neg: Latin America &amp; Caribbean (LAM) in a scenario that limits warming to 2°C (&gt;67%) (LAM net-zero economy 2040–2045, net-zero energy system 2045–2050).''' Supply-side focus with growing dependency on carbon dioxide removal and agriculture, forestry and other land-use (AFOLU), thus achieves net-zero CO 2 relatively early.

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'''Box 6.11, Figure 2 | Illustrative Mitigation Pathway 1.''' '''5-Renewables: Africa (AF) in a scenario that limts warming to 1.5°C (&gt;50%) (AF net-zero economy, 2055–2060, AF net-zero energy system 2055–2060).''' Rapid expansion of non-biomass renewables, high electrification, and a fossil fuel phase-out.

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'''Box 6.11, Figure 3 | Illustrative Mitigation Pathway 1.5-Low Demand: Developed Countries (DEV) in a scenario that limits warming to 1.5°C (&gt;50%) (DEV net-zero economy, 2055–2060, net-zero energy system 2075–2080).''' Major reduction of energy demand, high electrification, and gradual fossil fuel phase-out.

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'''Box 6.11, Figure 4 | Illustrative Mitigation Pathway 1.5-Shifting Pathways:''' Asia and Pacific '''(''' '''APC) in a scenario that limits warming to 1.5°C (&gt;50%) (APC net-zero economy, 2075–2080, net-zero energy system 2090–2095).''' Renewables, high electrification, fossil fuel phase-out and low agriculture, forestry and other land-use (AFOLU) emissions. Reaches net-zero CO 2 relatively late.

'''Box 6.11, Table 1 | Summary of selected Illustrative Mitigation Pathways energy system characteristics in 2050 for the chosen regions.'''

{| class="wikitable"
|-
|
| Energy sector CO 2 Reduction 2020–2050

| colspan="2"| Energy intensity

| colspan="2"| Variable renewable electricity generation

| colspan="2"| Low-carbon electricity capacity additions

| CO 2 removal BECCS, AFOLU, Total

| colspan="2"| GDP per capita

| colspan="3"| Year net-zero CO 2 emissions

|-
|
| %

| colspan="2"| MJ/PPP USD2010

| colspan="2"| EJ yr –1 (%)

| colspan="2"| GW yr –1

| GtCO 2 yr –1

| colspan="2"| PPP USD2010 per person

| rowspan="2"| Full economy

| rowspan="2"| Energy sector

| rowspan="2"| Electricity

|-
|
| Region

| 2050

| 2020

| 2050

| 2020

| 2050

| 2020

| 2050

| 2050

| 2020

| 2050

|-
| IMP-Neg

| LAM

| 124

| 3

| 2.1

| 0.5 (9)

| 7.7 (53)

| 15.4

| 21.5

| 1.1, 0.2, 1.9

| 12,952

| 24,860

| 2040–2045

| 2045–2050

| 2025– 2030

|-
| IMP-Ren

| AF

| 85

| 7.6

| 1.9

| 0.1 (5)

| 18 (84)

| 5

| 217

| 0.1, 0, 0.1

| 2965

| 8521

| 2055–2060

| 2055–2060

| 2025– 2030

|-
| IMP-LD

| DEV

| 92

| 3.1

| 0.9

| 4.6 (13)

| 37 (72)

| 52

| 188

| 0, 0.6, 0.6

| 42,945

| 61,291

| 2055–2060

| 2075–2080

| 2045– 2050

|-
| IMP-SP

| APC

| 76

| 3.8

| 1.1

| 3 (7)

| 91 (79)

| 123

| 603

| 0.1, 0.4, 0.4

| 10,514

| 37,180

| 2075–2080

| 2085–2090

| 2085– 2090

|}

'''Switching to low-carbon energy carriers.''' Switching to energy carriers produced from low-carbon sources will be an important strategy for energy sector decarbonisation. Accelerated electrification of end uses such as light duty transport, space heating, and cooking is a critical near-term mitigation strategy ( [[#Sugiyama--2012|Sugiyama 2012]] ; [[#Zou--2015|Zou et al. 2015]] ; [[#Rockström--2017|Rockström et al. 2017]] ; [[#IEA--2019f|IEA 2019f]] ; [[#Waisman--2019|Waisman et al. 2019]] ; B. [[#Tang--2021|]] [[#Tang--2021|Tang et al. 2021]] ). Electricity supplies 48–58% (interquartile range) of the global final energy demand by 2050 in scenarios limiting warming to 1.5°C (&gt;50%) with no or limited overshoot and 36–47% in scenarios limiting warming to 2°C (&gt;67%) (Figure 6.29). Globally, the current level of electrification is about 20%.

Indirect electrification encompasses the use of electricity to produce hydrogen and synthetic fuels (efuels or power fuels). The extent of indirect electrification of final energy will depend on resource endowments and other regionally specific circumstances. Although indirect electrification is less efficient compared to direct electrification, it allows low-carbon fuels to be imported from regions with abundant low-carbon electricity generation resources (Fasihi and Bogdanov 2016; [[#Lehtveer--2019|Lehtveer et al. 2019]] ; [[#Fasihi--2020|Fasihi and Breyer 2020]] ) (Box 6.10 on regional integration).

While electrifying end uses is a key decarbonisation strategy, some end uses such as long-distance transport (freight, aviation, and shipping) and energy-intensive industries will be harder to electrify. For these sectors, alternative fuels or energy carriers such as biofuels, hydrogen, ammonia or synthetic methane, may be needed ( [[#6.6|Section 6.6]] and Box 6.9). Most scenarios find that hydrogen consumption will grow gradually, becoming more valuable when the energy system has become predominantly low-carbon (Figure 6.31).

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'''Figure 6.31 | Shares of electricity and hydrogen in final energy in scenarios that limit/return''' '''warming to 1.''' '''5°C (&gt;50%) with no or limited/after a high, overshoot, and scenarios that limit warming to 2°C (&gt;67%), with action starting in 2020 or NDCs until 2030, during 2030–2050''' (Source: AR6 Scenarios Database). Boxes indicate 25th and 75th percentiles while whiskers indicate 5th and 95th percentiles.

'''Reducing energy demand.''' Energy service demand is expected to continue to increase with growth of the economy, but there is great uncertainty about how much it will increase ( [[#Bauer--2017|Bauer et al. 2017]] ; [[#Riahi--2017|Riahi et al. 2017]] ; [[#Yu--2018|Yu et al. 2018]] ). Given the need to produce low-carbon energy, the scale of energy demand is a critical determinant of the mitigation challenge ( [[#Riahi--2012|Riahi et al. 2012]] ). Higher energy demand calls for more low-carbon energy and increases the challenge; lower energy demand reduces the need for low-carbon sources and therefore can ease a low-carbon transition. Recent studies have shown that tempering the growth of energy demand, while ensuring services and needs are still satisfied, can materially affect the need for technological CDR ( [[#6.7.1.3|Section 6.7.1.3]] ) ( [[#Grubler--2018|Grubler et al. 2018]] ; [[#van%20Vuuren--2018|van Vuuren et al. 2018]] ). Two of the Illustrative Mitigation Pathways (IMP-SP, IMP-LD) feature substantially lower final energy demand across buildings, transport, and industry than most other pathways in the literature. In some cases, energy demand levels are lower in 2050 (and later) than in 2019. These lower demands result in less reliance on bioenergy and a more limited role for CDR (Figure 3.18).

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==== 6.7.1.3 Technology Options to Offset Residual Emissions ====

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CDR technologies can offset emissions from sectors that are difficult to decarbonise ( [[#6.6|Section 6.6]] ), altering the timeline and character of energy sector transitions. A number of studies suggest that CDR is no longer a choice, but rather a necessity to limit warming to 1.5°C ( [[#Rogelj--2015a|Rogelj et al. 2015a]] ; [[#Detz--2018|Detz et al. 2018]] ; [[#Luderer--2018|Luderer et al. 2018]] ; [[#Strefler--2018|Strefler et al. 2018]] ; [[#van%20Vuuren--2018|van Vuuren et al. 2018]] ). The reliance on CDR varies across scenarios and is tightly linked to future energy demand and the rate of emission reductions in the next two decades: deeper near-term emissions reductions will reduce the need to rely on CDR to constrain cumulative CO 2 emissions. Some studies have argued that only with a transition to lower energy demands will it be possible to largely eliminate the need for engineered CDR options ( [[#Grubler--2018|Grubler et al. 2018]] ; [[#van%20Vuuren--2018|van Vuuren et al. 2018]] ). Overall, the amount of CDR will depend on CO 2 capture costs, lifestyle changes, reduction in non-CO 2 GHGs, and utilisation of zero-emission end-use fuels (Muratori et al. 2017; [[#van%20Vuuren--2018|van Vuuren et al. 2018]] ).

There is substantial uncertainty about the amount of CDR that might ultimately be deployed. In most scenarios that limit warming to 1.5°C, CDR deployment is fairly limited through 2030 at less than 1 GtCO 2 yr –1 . The key projected increase in CDR deployment (BECCS and DAC only) occurs between 2030 and 2050, with annual CDR in 2050 projected at 2.5–7.5 GtCO 2 yr –1 in 2050 (interquartile range) in scenarios limiting warming to 1.5°C (&gt;50%) with limited or no overshoot, and 0.7–1.4 GtCO 2 yr –1 in 2050 in scenarios limiting warming to 2°C (&gt;67%) with action starting in 2020. This characteristic of scenarios largely reflects substantial capacity addition of BECCS power plants. BECCS is also deployed in multiple ways across sectors. For instance, the contribution (interquartile range) of BECCS to electricity is 1–5% in 2050 in scenarios limiting warming to 1.5°C (&gt;50%) with no or limited overshoot, and 0–5% in scenarios that limit warming to 2°C (&gt;67%) with action starting in 2020. The contribution (interquartile range) of BECCS to liquid fuels is 9–21% in 2050 in scenarios limiting warming to 1.5°C (&gt;50%) with no or limited overshoot and 2–11% in scenarios that limit warming to 2°C (&gt;67%) with action starting in 2020. Large-scale deployment of CDR allows flexibility in timing of emissions reduction in hard-to-decarbonise sectors.

CDR will influence the potential fossil-related stranded assets (Box 6.13). Availability of low-cost CDR can help reduce premature retirement for some fossil fuel infrastructure. CDR can allow countries to reach net-zero emissions without phasing out all fossil fuels. Specific infrastructure could also be extended if it is used to burn biomass or other non-emitting sources. For example, existing coal-fired power plants, particularly those with CCS, could be co-fired with biomass ( [[#Woolf--2016|Woolf et al. 2016]] ; [[#Lu--2019|Lu et al. 2019]] ; [[#Pradhan--2021|Pradhan et al. 2021]] ). In many scenarios, energy sector CDR is deployed to such an extent that energy sector CO 2 emissions become negative in the second half of the century (Chapter 3).

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