Editing IPCC:AR6/SR15/Chapter-2 (section)

=== 2.4.2 Energy Supply ===

<div id="section-2-4-2-block-1"></div>

Several energy supply characteristics are evident in 1.5°C pathways assessed in this section: (i) growth in the share of energy derived from low-carbon-emitting sources (including renewables, nuclear and fossil fuel with CCS) and a decline in the overall share of fossil fuels without CCS (Section 2.4.2.1), (ii) rapid decline in the carbon intensity of electricity generation simultaneous with further electrification of energy end-use (Section 2.4.2.2), and (iii) the growth in the use of CCS applied to fossil and biomass carbon in most 1.5°C pathways (Section 2.4.2.3).

<div id="section-2-4-2-1"></div>

<span id="evolution-of-primary-energy-contributions-over-time"></span>
==== 2.4.2.1 Evolution of primary energy contributions over time ====

<div id="section-2-4-2-1-block-1"></div>

By mid-century, the majority of primary energy comes from non-fossil-fuels (i.e., renewables and nuclear energy) in most 1.5°C pathways (Table 2.6). Figure 2.15 shows the evolution of primary energy supply over this century across 1.5°C pathways, and in detail for the four illustrative pathway archetypes highlighted in this chapter. Note that this section reports primary energy using the direct equivalent method on the basis of lower heating values (Bruckner et al., 2014) <sup>[[#fn:r363|363]]</sup> .

The share of energy from renewable sources (including biomass, hydro, solar, wind and geothermal) increases in all 1.5°C pathways with no or limited overshoot, with the renewable energy share of primary energy reaching 38–88% in 2050 (Table 2.6), with an interquartile range of 52–67%. The magnitude and split between bioenergy, wind, solar, and hydro differ between pathways, as can be seen in the illustrative pathway archetypes in Figure 2.15. Bioenergy is a major supplier of primary energy, contributing to both electricity and other forms of final energy such as liquid fuels for transportation (Bauer et al., 2018) <sup>[[#fn:r364|364]]</sup> . In 1.5°C pathways, there is a significant growth in bioenergy used in combination with CCS for pathways where it is included (Figure 2.15).

Nuclear power increases its share in most 1.5°C pathways with no or limited overshoot by 2050, but in some pathways both the absolute capacity and share of power from nuclear generators decrease (Table 2.15). There are large differences in nuclear power between models and across pathways (Kim et al., 2014; Rogelj et al., 2018) <sup>[[#fn:r365|365]]</sup> . One of the reasons for this variation is that the future deployment of nuclear can be constrained by societal preferences assumed in narratives underlying the pathways (O’Neill et al., 2017; van Vuuren et al., 2017b) <sup>[[#fn:r366|366]]</sup> . Some 1.5°C pathways with no or limited overshoot no longer see a role for nuclear fission by the end of the century, while others project about 95 EJ yr <sup>−1</sup> of nuclear power in 2100 (Figure 2.15).

The share of primary energy provided by total fossil fuels decreases from 2020 to 2050 in all 1.5°C pathways, but trends for oil, gas and coal differ (Table 2.6). By 2050, the share of primary energy from coal decreases to 0–11% across 1.5°C pathways with no or limited overshoot, with an interquartile range of 1–7%. From 2020 to 2050 the primary energy supplied by oil changes by −93 to −9% (interquartile range −77 to −39%); natural gas changes by −88 to +85% (interquartile range −62 to −13%), with varying levels of CCS. Pathways with higher use of coal and gas tend to deploy CCS to control their carbon emissions (see Section 2.4.2.3). As the energy transition is accelerated by several decades in 1.5°C pathways compared to 2°C pathways, residual fossil-fuel use (i.e., fossil fuels not used for electricity generation) without CCS is generally lower in 2050 than in 2°C pathways, while combined hydro, solar, and wind power deployment is generally higher than in 2°C pathways (Figure 2.15).

In addition to the 1.5°C pathways included in the scenario database (Supplementary Material 2.SM.1.3), there are other analyses in the literature including, for example, sector-based analyses of energy demand and supply options. Even though they were not necessarily developed in the context of the 1.5°C target, they explore in greater detail some options for deep reductions in GHG emissions. For example, there are analyses of transitions to up to 100% renewable energy by 2050 (Creutzig et al., 2017; Jacobson et al., 2017) <sup>[[#fn:r367|367]]</sup> , which describe what is entailed for a renewable energy share largely from solar and wind (and electrification) that is above the range of 1.5°C pathways available in the database, although there have been challenges to the assumptions used in high-renewable analyses (e.g., Clack et al., 2017) <sup>[[#fn:r368|368]]</sup> . There are also analyses that result in a large role for nuclear energy in mitigation of GHGs (Hong et al., 2015; Berger et al., 2017a, b; Xiao and Jiang, 2018) <sup>[[#fn:r369|369]]</sup> . BECCS could also contribute a larger share, but faces challenges related to its land use and impact on food supply (Burns and Nicholson, 2017) <sup>[[#fn:r370|370]]</sup> (assessed in greater detail in Sections 2.3.4.2, 4.3.7 and 5.4). These analyses could, provided their assumptions prove plausible, expand the range of 1.5°C pathways.

In summary, the share of primary energy from renewables increases while that from coal decreases across 1.5°C pathways ( ''high confidence'' ). This statement is true for all 1.5°C pathways in the scenario database and associated literature (Supplementary Material 2.SM.1.3), and is consistent with the additional studies mentioned above, an increase in energy supply from lower-carbon-intensity energy supply, and a decrease in energy supply from higher-carbon-intensity energy supply.

<div id="section-2-4-2-1-block-2"></div>

<span id="figure-2.15"></span>
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<!-- IMG TITLE -->
'''Figure 2.15'''

<span id="primary-energy-supply-for-the-four-illustrative-pathway-archetypes-plus-the-ieas-faster-transition-scenario-oecdiea-and-irena-2017-371-panel-a-and-their-relative-location-in-the-ranges-for-pathways-limiting-warming-to-1.5c-with-no-or-limited-overshoot-panel-b."></span>
<!-- IMG CAPTION -->
'''Primary energy supply for the four illustrative pathway archetypes plus the IEA’s Faster Transition Scenario (OECD/IEA and IRENA, 2017) <sup>[[#fn:r371|371]]</sup> (panel a), and their relative location in the ranges for pathways limiting warming to 1.5°C with no or limited overshoot (panel b).'''
<!-- IMG FILE -->
[[File:5166e16ac63ca47f503bb1215474fab2 Figure-2.15-1024x608.jpg]]

The category ‘Other renewables’ includes primary energy sources not covered by the other categories, for example, hydro and geothermal energy. The number of pathways that have higher primary energy than the scale in the bottom panel are indicated by the numbers above the whiskers. Black horizontal dashed lines indicates the level of primary energy supply in 2015 (IEA, 2017e) <sup>[[#fn:r372|372]]</sup> . Box plots in the lower panel show the minimum–maximum range (whiskers), interquartile range (box), and median (vertical thin black line). Symbols in the lower panel show the four pathway archetypes S1 (white square), S2 (yellow square), S5 (black square), LED (white disc), as well as the IEA–(red disc). Pathways with no or limited overshoot included the Below-1.5°C and 1.5°C-low-OS classes.

Original Creation for this Report using IAMC 1.5°C Scenario Data hosted by IIASA

<!-- END IMG -->
<div id="section-2-4-2-1-block-3"></div>

<span id="table-2.6"></span>
<!-- START TABLE -->
'''Table 2.6'''

<span id="global-primary-energy-supply-of-1.5c-pathways-from-the-scenario-database-supplementary-material-2.sm.1.3.-values-given-for-the-median-maximum-minimum-across-the-full-range-of-85-available-1.5c-pathways.-growth-factor-primary-energy-supply-in-2050primary-energy-supply-in-2020-1"></span>
'''Global primary energy supply of 1.5°C pathways from the scenario database (Supplementary Material 2.SM.1.3). Values given for the median (maximum, minimum) across the full range of 85 available 1.5°C pathways. Growth Factor = [(primary energy supply in 2050)/(primary energy supply in 2020) − 1]'''

Values given for the median (maximum, minimum) across the full range of 85 available 1.5°C pathways. Growth Factor = [(primary energy supply in 2050)/(primary energy supply in 2020) − 1]
<!-- TABLE -->
{| class="wikitable"
|-
! rowspan="2"|
! rowspan="2"| Median (max, min)
! rowspan="2"| Count
! colspan="3"| Primary Energy Supply (EJ)
! colspan="3"| Share in Primary Energy (%)
! rowspan="2"| Growth (factor)<br />
2020-2050
|-
! 2020
! 2030
! 2050
! 2020
! 2030
! 2050
|-
| rowspan="10"| Below-1.5°C and 1.5°C-<br />
low-OS pathways
| total primary
| 50
| 565.33
(619.70, 483.22)

| 464.50
(619.87, 237.37)

| 553.23
(725.40, 289.02)

| NA
| –0.05
(0.48, –0.51)

|-
| renewables
| 50
| 87.14
(101.60, 60.16)

| 146.96
(203.90, 87.75)

| 291.33
(584.78, 176.77)

| 14.90
(20.39, 10.60)

| 29.08
(62.15, 18.24)

| 60.24
(87.89, 38.03)

| 2.37
(6.71, 0.91)

|-
| biomass
| 50
| 60.41
(70.03, 40.54)

| 77.07
(113.02, 44.42)

| 152.30
(311.72, 40.36)

| 10.17
(13.66, 7.14)

| 17.22
(35.61, 9.08)

| 27.29
(54.10, 10.29)

| 1.71
(5.56, –0.42)

|-
| non-biomass
| 50
| 26.35
(36.57, 17.78)

| 62.58
(114.41, 25.79)

| 146.23
(409.94, 53.79)

| 4.37
(7.19, 3.01)

| 13.67
(26.54, 5.78)

| 27.98
(61.61, 12.04)

| 4.28
(13.46, 1.45)

|-
| wind &amp; solar
| 44
| 10.93
(20.16, 2.61)

| 40.14
(82.66, 7.05)

| 121.82
(342.77, 27.95)

| 1.81
(3.66, 0.45)

| 9.73
(19.56, 1.54)

| 21.13
(51.52, 4.48)

| 10.00
(53.70, 3.71)

|-
| nuclear
| 50
| 10.91
(18.55, 8.52)

| 16.26
(36.80, 6.80)

| 24.51
(66.30, 3.09)

| 2.10
(3.37, 1.45)

| 3.52
(9.61, 1.32)

| 4.49
(12.84, 0.44)

| 1.24
(5.01, –0.64)

|-
| fossil
| 50
| 462.95
(520.41, 376.30)

| 310.36
(479.13, 70.14)

| 183.79
(394.71, 54.86)

| 82.53
(86.65, 77.73)

| 66.58
(77.30, 29.55)

| 32.79
(60.84, 8.58)

| –0.59
(–0.21, –0.89)

|-
| coal
| 50
| 136.89
(191.02, 83.23)

| 44.03
(127.98, 5.97)

| 24.15
(71.12, 0.92)

| 25.63
(30.82, 17.19)

| 9.62
(20.65, 1.31)

| 5.08
(11.43, 0.15)

| –0.83
(–0.57, –0.99)

|-
| gas
| 50
| 132.95
(152.80, 105.01)

| 112.51
(173.56, 17.30)

| 76.03
(199.18, 14.92)

| 23.10
(28.39, 18.09)

| 22.52
(35.05, 7.08)

| 13.23
(34.83, 3.68)

| –0.40
(0.85, –0.88)

|-
| oil
| 50
| 197.26
(245.15, 151.02)

| 156.16
(202.57, 38.94)

| 69.94
(167.52, 15.07)

| 34.81
(42.24, 29.00)

| 31.24
(39.84, 16.41)

| 12.89
(27.04, 2.89)

| –0.66
(–0.09, –0.93)

|-
| rowspan="10"| 1.5°C-<br />
high-OS
| total primary
| 35
| 594.96
(636.98, 510.55)

| 559.04
(749.05, 419.28)

| 651.46
(1012.50, 415.31)

| NA
| 0.13
(0.59, –0.27)

|-
| renewables
| 35
| 89.84
(98.60, 66.57)

| 135.12
(159.84, 87.93)

| 323.21
(522.82, 177.66)

| 15.08
(18.58, 11.04)

| 23.65
(29.32, 13.78)

| 62.16
(86.26, 28.47)

| 2.68
(4.81, 1.17)

|-
| biomass
| 35
| 62.59
(73.03, 48.42)

| 69.05
(98.27, 56.54)

| 160.16
(310.10, 71.17)

| 10.30
(14.23, 8.03)

| 13.64
(16.37, 9.03)

| 23.79
(45.79, 10.64)

| 1.71
(3.71, 0.19)

|-
| non-biomass
| 35
| 28.46
(36.58, 17.60)

| 59.81
(92.12, 27.39)

| 164.91
(329.69, 55.72)

| 4.78
(6.64, 2.84)

| 10.23
(16.59, 4.49)

| 31.17
(45.86, 9.87)

| 6.10
(10.63, 1.38)

|-
| wind &amp; solar
| 26
| 11.32
(20.17, 1.91)

| 40.31
(65.50, 8.14)

| 139.20
(275.47, 30.92)

| 1.95
(3.66, 0.32)

| 7.31
(11.61, 1.83)

| 26.01
(38.79, 6.33)

| 16.06
(63.34, 3.13)

|-
| nuclear
| 35
| 10.94
(14.27, 8.52)

| 16.12
(41.73, 6.80)

| 22.98
(115.80, 3.09)

| 1.86
(2.37, 1.45)

| 2.99
(5.57, 1.20)

| 4.17
(13.60, 0.43)

| 1.49
(7.22, –0.64)

|-
| fossil
| 35
| 497.30
(543.29, 407.49)

| 397.76
(568.91, 300.63)

| 209.80
(608.39, 43.87)

| 83.17
(86.59, 79.39)

| 73.87
(82.94, 68.00)

| 33.58
(60.09, 7.70)

| –0.56
(0.12, –0.91)

|-
| coal
| 35
| 155.65
(193.55, 118.40)

| 70.99
(176.99, 19.15)

| 18.95
(134.69, 0.36)

| 25.94
(30.82, 19.10)

| 14.53
(26.35, 3.64)

| 4.14
(13.30, 0.05)

| –0.87
(–0.30, –1.00)

|-
| gas
| 35
| 138.01
(169.50, 107.07)

| 147.43
(208.55, 76.45)

| 97.71
(265.66, 15.96)

| 23.61
(27.35, 19.26)

| 25.79
(32.73, 14.69)

| 15.67
(33.80, 2.80)

| –0.31
(0.99, –0.88)

|-
| oil
| 35
| 195.02
(236.40, 154.66)

| 198.50
(319.80, 102.10)

| 126.20
(208.04, 24.68)

| 32.21
(38.87, 28.07)

| 33.27
(50.12, 24.35)

| 18.61
(27.30, 4.51)

| –0.34
(0.06, –0.87)

|-
| rowspan="10"| Two above classes combined
| total primary
| 85
| 582.12
(636.98, 483.22)

| 502.81
(749.05, 237.37)

| 580.78
(1012.50, 289.02)

| –
| 0.03
(0.59, –0.51)

|-
| renewables
| 85
| 87.70
(101.60, 60.16)

| 139.48
(203.90, 87.75)

| 293.80
(584.78, 176.77)

| 15.03
(20.39, 10.60)

| 27.90
(62.15, 13.78)

| 60.80
(87.89, 28.47)

| 2.62
(6.71, 0.91)

|-
| biomass
| 85
| 61.35
(73.03, 40.54)

| 75.28
(113.02, 44.42)

| 154.13
(311.72, 40.36)

| 10.27
(14.23, 7.14)

| 14.38
(35.61, 9.03)

| 26.38
(54.10, 10.29)

| 1.71
(5.56, –0.42)

|-
| non-biomass
| 85
| 26.35
(36.58, 17.60)

| 61.60
(114.41, 25.79)

| 157.37
(409.94, 53.79)

| 4.40
(7.19, 2.84)

| 11.87
(26.54, 4.49)

| 28.60
(61.61, 9.87)

| 4.63
(13.46, 1.38)

|-
| wind &amp; solar
| 70
| 10.93
(20.17, 1.91)

| 40.17
(82.66, 7.05)

| 125.31
(342.77, 27.95)

| 1.81
(3.66, 0.32)

| 8.24
(19.56, 1.54)

| 22.10
(51.52, 4.48)

| 11.64
(63.34, 3.13)

|-
| nuclear
| 85
| 10.93
(18.55, 8.52)

| 16.22
(41.73, 6.80)

| 24.48
(115.80, 3.09)

| 1.97
(3.37, 1.45)

| 3.27
(9.61, 1.20)

| 4.22
(13.60, 0.43)

| 1.34
(7.22, –0.64)

|-
| fossil
| 85
| 489.52
(543.29, 376.30)

| 343.48
(568.91, 70.14)

| 198.58
(608.39, 43.87)

| 83.05
(86.65, 77.73)

| 69.19
(82.94, 29.55)

| 33.06
(60.84, 7.70)

| –0.58
(0.12, –0.91)

|-
| coal
| 85
| 147.09
(193.55, 83.23)

| 49.46
(176.99, 5.97)

| 23.84
(134.69, 0.36)

| 25.72
(30.82, 17.19)

| 10.76
(26.35, 1.31)

| 4.99
(13.30, 0.05)

| –0.85
(–0.30, –1.00)

|-
| gas
| 85
| 135.58
(169.50, 105.01)

| 127.99
(208.55, 17.30)

| 88.97
(265.66, 14.92)

| 23.28
(28.39, 18.09)

| 24.02
(35.05, 7.08)

| 13.46
(34.83, 2.80)

| –0.37
(0.99, –0.88)

|-
| oil
| 85
| 195.02
(245.15, 151.02)

| 175.69
(319.80, 38.94)

| 93.48
(208.04, 15.07)

| 33.79
(42.24, 28.07)

| 32.01
(50.12, 16.41)

| 16.22
(27.30, 2.89)

| –0.54
(0.06, –0.93)

|}
<!-- END TABLE -->

<div id="section-2-4-2-1-block-4"></div>

<span id="table-2.7"></span>
<!-- START TABLE -->
'''Table 2.7'''

<span id="global-electricity-generation-of-1.5c-pathways-from-the-scenarios-database"></span>
'''Global electricity generation of 1.5°C pathways from the scenarios database'''

(Supplementary Material 2.SM.1.3). Values given for the median (maximum, minimum) values across the full range across 89 available 1.5°C pathways. Growth Factor = [(primary energy supply in 2050)/(primary energy supply in 2020) – 1].
<!-- TABLE -->
{| class="wikitable"
|-
! rowspan="2"|
! rowspan="2"| Median (max, min)
! rowspan="2"| Count
! colspan="3"| Electricity Generation (EJ)
! colspan="3"| Share in Electricity Generation (%)
! rowspan="2"| Growth (factor)<br />
2020–2050
|-
! 2020
! 2030
! 2050
! 2020
! 2030
! 2050
|-
| rowspan="10"| TBelow<br />
-1.5°C and 1.5°C-<br />
low-OS pathways
| total generation
| 50
| 98.45
(113.98, 83.53)

| 115.82
(152.40, 81.28)

| 215.58
(354.48, 126.96)

| NA
| 1.15
(2.55, 0.28)

|-
| renewables
| 50
| 26.28
(41.80, 18.50)

| 63.30
(111.70, 32.41)

| 145.50
(324.26, 90.66)

| 26.32
(41.84, 18.99)

| 53.68
(79.67, 37.30)

| 77.12
(96.65, 58.89)

| 4.48
(10.88, 2.65)

|-
| biomass
| 50
| 2.02
(7.00, 0.76)

| 4.29
(11.96, 0.79)

| 20.35
(39.28, 0.24)

| 1.97
(6.87, 0.82)

| 3.69
(13.29, 0.73)

| 8.77
(30.28, 0.10)

| 6.42
(38.14, –0.93)

|-
| non-biomass
| 50
| 24.21
(35.72, 17.70)

| 57.12
(101.90, 25.79)

| 135.04
(323.91, 53.79)

| 24.38
(40.43, 17.75)

| 49.88
(78.27, 29.30)

| 64.68
(96.46, 41.78)

| 4.64
(10.64, 1.45)

|-
| wind &amp; solar
| 50
| 1.66
(6.60, 0.38)

| 8.91
(48.04, 0.60)

| 39.04
(208.97, 2.68)

| 1.62
(7.90, 0.38)

| 8.36
(41.72, 0.53)

| 19.10
(60.11, 1.65)

| 26.31
(169.66, 5.23)

|-
| nuclear
| 50
| 10.84
(18.55, 8.52)

| 15.46
(36.80, 6.80)

| 21.97
(64.72, 3.09)

| 12.09
(18.34, 8.62)

| 14.33
(31.63, 5.24)

| 8.10
(27.53, 1.02)

| 0.71
(4.97, –0.64)

|-
| fossil
| 50
| 59.43
(68.75, 39.48)

| 36.51
(66.07, 2.25)

| 14.81
(57.76, 0.00)

| 61.32
(67.40, 47.26)

| 30.04
(52.86, 1.95)

| 8.61
(25.18, 0.00)

| –0.74
(0.01, –1.00)

|-
| coal
| 50
| 31.02
(42.00, 14.40)

| 8.83
(34.11, 0.00)

| 1.38
(17.39, 0.00)

| 32.32
(40.38, 17.23)

| 7.28
(27.29, 0.00)

| 0.82
(7.53, 0.00)

| –0.96
(–0.56, –1.00)

|-
| gas
| 50
| 24.70
(32.46, 13.44)

| 22.59
(42.08, 2.01)

| 12.79
(53.17, 0.00)

| 24.39
(35.08, 11.80)

| 20.18
(37.23, 1.75)

| 6.93
(24.87, 0.00)

| –0.47
(1.27, –1.00)

|-
| oil
| 50
| 2.48
(13.36, 1.12)

| 1.89
(7.56, 0.24)

| 0.10
(8.78, 0.00)

| 2.82
(11.73, 1.01)

| 1.95
(5.67, 0.21)

| 0.05
(3.80, 0.00)

| –0.92
(0.36, –1.00)

|-
| rowspan="4"| 1.5°C-<br />
high-OS
| total generation
| 35
| 101.44
(113.96, 88.55)

| 125.26
(177.51, 89.60)

| 251.50
(363.10, 140.65)

| NA
| 1.38
(2.19, 0.39)

|-
| renewables
| 35
| 26.38
(31.83, 18.26)

| 53.32
(86.85, 30.06)

| 173.29
(273.92, 84.69)

| 28.37
(32.96, 17.38)

| 42.73
(65.73, 25.11)

| 82.39
(94.66, 35.58)

| 5.97
(8.68, 2.37)

|-
| biomass
| 35
| 1.23
(6.47, 0.66)

| 2.14
(7.23, 0.86)

| 10.49
(40.32, 0.21)

| 1.22
(7.30, 0.63)

| 1.59
(6.73, 0.72)

| 3.75
(28.09, 0.08)

| 7.93
(33.32, –0.81)

|-
| non-biomass
| 35
| 24.56
(30.70, 17.60)

| 47.96
(85.83, 27.39)

| 144.13
(271.17, 55.72)

| 26.77
(31.79, 16.75)

| 40.07
(64.96, 23.10)

| 69.72
(94.58, 27.51)

| 5.78
(8.70, 1.38)

|-
| rowspan="6"| 1.5°C-<br />
high-OS
| wind &amp; solar
| 35
| 2.24
(5.07, 0.42)

| 8.95
(36.52, 1.18)

| 65.08
(183.38, 13.79)

| 2.21
(5.25, 0.41)

| 7.48
(27.90, 0.99)

| 25.88
(61.24, 8.71)

| 30.70
(106.95, 4.87)

|-
| nuclear
| 35
| 10.84
(14.08, 8.52)

| 16.12
(41.73, 6.80)

| 22.91
(115.80, 3.09)

| 10.91
(13.67, 8.62)

| 14.65
(23.51, 5.14)

| 11.19
(39.61, 1.12)

| 1.49
(7.22, –0.64)

|-
| fossil
| 35
| 62.49
(76.76, 49.09)

| 48.08
(87.54, 30.99)

| 11.84
(118.12, 0.78)

| 61.58
(71.03, 54.01)

| 42.02
(59.48, 24.27)

| 6.33
(33.19, 0.27)

| –0.80
(0.54, –0.99)

|-
| coal
| 35
| 32.37
(46.20, 26.00)

| 16.22
(43.12, 1.32)

| 1.18
(46.72, 0.01)

| 32.39
(40.88, 24.41)

| 14.23
(29.93, 1.19)

| 0.55
(12.87, 0.00)

| –0.96
(0.01, –1.00)

|-
| gas
| 35
| 26.20
(41.20, 20.11)

| 26.45
(51.99, 16.45)

| 10.66
(67.94, 0.76)

| 26.97
(39.20, 19.58)

| 22.29
(43.43, 14.03)

| 5.29
(32.59, 0.26)

| –0.57
(1.63, –0.97)

|-
| oil
| 35
| 1.51
(6.28, 1.12)

| 0.61
(7.54, 0.36)

| 0.04
(7.47, 0.00)

| 1.51
(6.27, 1.01)

| 0.55
(6.20, 0.26)

| 0.02
(3.31, 0.00)

| –0.99
(0.98, –1.00)

|-
| rowspan="10"| Two above classes combined
| total generation
| 85
| 100.09
(113.98, 83.53)

| 120.01
(177.51, 81.28)

| 224.78
(363.10, 126.96)

| NA
| 1.31
(2.55, 0.28)

|-
| renewables
| 85
| 26.38
(41.80, 18.26)

| 59.50
(111.70, 30.06)

| 153.72
(324.26, 84.69)

| 27.95
(41.84, 17.38)

| 51.51
(79.67, 25.11)

| 77.52
(96.65, 35.58)

| 5.08
(10.88, 2.37)

|-
| biomass
| 85
| 1.52
(7.00, 0.66)

| 3.55
(11.96, 0.79)

| 16.32
(40.32, 0.21)

| 1.55
(7.30, 0.63)

| 2.77
(13.29, 0.72)

| 8.02
(30.28, 0.08)

| 6.53
(38.14, –0.93)

|-
| non-biomass
| 85
| 24.48
(35.72, 17.60)

| 55.68
(101.90, 25.79)

| 136.40
(323.91, 53.79)

| 25.00
(40.43, 16.75)

| 47.16
(78.27, 23.10)

| 66.75
(96.46, 27.51)

| 4.75
(10.64, 1.38)

|-
| wind &amp; solar
| 85
| 1.66
(6.60, 0.38)

| 8.95
(48.04, 0.60)

| 43.20
(208.97, 2.68)

| 1.67
(7.90, 0.38)

| 8.15
(41.72, 0.53)

| 19.70
(61.24, 1.65)

| 28.02
(169.66, 4.87)

|-
| nuclear
| 85
| 10.84
(18.55, 8.52)

| 15.49
(41.73, 6.80)

| 22.64
(115.80, 3.09)

| 10.91
(18.34, 8.62)

| 14.34
(31.63, 5.14)

| 8.87
(39.61, 1.02)

| 1.21
(7.22, –0.64)

|-
| fossil
| 85
| 61.35
(76.76, 39.48)

| 38.41
(87.54, 2.25)

| 14.10
(118.12, 0.00)

| 61.55
(71.03, 47.26)

| 33.96
(59.48, 1.95)

| 8.05
(33.19, 0.00)

| –0.76
(0.54, –1.00)

|-
| coal
| 85
| 32.37
(46.20, 14.40)

| 10.41
(43.12, 0.00)

| 1.29
(46.72, 0.00)

| 32.39
(40.88, 17.23)

| 8.95
(29.93, 0.00)

| 0.59
(12.87, 0.00)

| –0.96
(0.01, –1.00)

|-
| gas
| 85
| 24.70
(41.20, 13.44)

| 25.00
(51.99, 2.01)

| 11.92
(67.94, 0.00)

| 24.71
(39.20, 11.80)

| 21.03
(43.43, 1.75)

| 6.78
(32.59, 0.00)

| –0.52
(1.63, –1.00)

|-
| oil
| 85
| 1.82
(13.36, 1.12)

| 0.92
(7.56, 0.24)

| 0.08
(8.78, 0.00)

| 2.04
(11.73, 1.01)

| 0.71
(6.20, 0.21)

| 0.04
(3.80, 0.00)

| –0.97
(0.98, –1.00)

|}
<!-- END TABLE -->

<div id="section-2-4-2-2"></div>

<span id="evolution-of-electricity-supply-over-time"></span>
==== 2.4.2.2 Evolution of electricity supply over time ====

<div id="section-2-4-2-2-block-1"></div>

Electricity supplies an increasing share of final energy, reaching 34–71% in 2050, across 1.5°C pathways with no or limited overshoot (Figure 2.14), extending the historical increases in electricity share seen over the past decades (Bruckner et al., 2014) <sup>[[#fn:r373|373]]</sup> . From 2020 to 2050, the quantity of electricity supplied in most 1.5°C pathways with no or limited overshoot more than doubles (Table 2.7). By 2050, the carbon intensity of electricity has fallen rapidly to −92 to +11 gCO <sub>2</sub> MJ <sup>−1</sup> electricity across 1.5°C pathways with no or limited overshoot from a value of around 140 gCO <sub>2</sub> MJ <sup>−1</sup> (range: 88–181 gCO <sub>2</sub> MJ <sup>−1</sup> ) in 2020 (Figure 2.14). A negative contribution to carbon intensity is provided by BECCS in most pathways (Figure 2.16).

By 2050, the share of electricity supplied by renewables increases from 23% in 2015 (IEA, 2017b) <sup>[[#fn:r374|374]]</sup> to 59–97% across 1.5°C pathways with no or limited overshoot. Wind, solar, and biomass together make a major contribution in 2050, although the share for each spans a wide range across 1.5°C pathways (Figure 2.16). Fossil fuels on the other hand have a decreasing role in electricity supply, with their share falling to 0–25% by 2050 (Table 2.7).

In summary, 1.5°C pathways include a rapid decline in the carbon intensity of electricity and an increase in electrification of energy end-use ( ''high confidence'' ). This is the case across all 1.5°C pathways and their associated literature (Supplementary Material 2.SM.1.3), with pathway trends that extend those seen in past decades, and results that are consistent with additional analyses (see Section 2.4.2.2).

<div id="section-2-4-2-2-block-2"></div>

<span id="figure-2.16"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure 2.16'''

<span id="electricity-generation-for-the-four-illustrative-pathway-archetypes-plus-the-ieas-faster-transition-scenario-oecdiea-and-irena-2017-375-panel-a-and-their-relative-location-in-the-ranges-for-pathways-limiting-warming-to-1.5c-with-no-or-limited-overshoot-panel-b."></span>
<!-- IMG CAPTION -->
'''Electricity generation for the four illustrative pathway archetypes plus the IEA’s Faster Transition Scenario (OECD/IEA and IRENA, 2017) <sup>[[#fn:r375|375]]</sup> (panel a), and their relative location in the ranges for pathways limiting warming to 1.5°C with no or limited overshoot (panel b).'''
<!-- IMG FILE -->
[[File:c8454f2802a6e2b045d8be6ea97976af Figure-2.16-1024x610.jpg]]

The category ‘Other renewables’ includes electricity generation not covered by the other categories, for example, hydro and geothermal. The number of pathways that have higher primary energy than the scale in the bottom panel are indicated by the numbers above the whiskers. Black horizontal dashed lines indicate the level of primary energy supply in 2015 (IEA, 2017e) <sup>[[#fn:r376|376]]</sup> . Box plots in the lower panel show the minimum–maximum range (whiskers), interquartile range (box), and median (vertical thin black line). Symbols in the lower panel show the four pathway archetypes – S1 (white square), S2 (yellow square), S5 (black square), LED (white disc) – as well as the IEA’s Faster Transition Scenario (red disc). Pathways with no or limited overshoot included the Below-1.5°C and 1.5°C-low-OS classes.

Original Creation for this Report using IAMC 1.5°C Scenario Data hosted by IIASA

<!-- END IMG -->
<div id="section-2-4-2-3"></div>

<span id="deployment-of-carbon-capture-and-storage"></span>
==== 2.4.2.3 Deployment of carbon capture and storage ====

<div id="section-2-4-2-3-block-1"></div>

Studies have shown the importance of CCS for deep mitigation pathways (Krey et al., 2014a; Kriegler et al., 2014b) <sup>[[#fn:r377|377]]</sup> , based on its multiple roles to limit fossil-fuel emissions in electricity generation, liquids production, and industry applications along with the projected ability to remove CO <sub>2</sub> from the atmosphere when combined with bioenergy. This remains a valid finding for those 1.5°C and 2°C pathways that do not radically reduce energy demand or do not offer carbon-neutral alternatives to liquids and gases that do not rely on bioenergy.

There is a wide range of CCS that is deployed across 1.5°C pathways (Figure 2.17). A few 1.5°C pathways with very low energy demand do not include CCS at all (Grubler et al., 2018) <sup>[[#fn:r378|378]]</sup> . For example, the ''LED'' pathway has no CCS, whereas other pathways, such as the S5 pathway, rely on a large amount of BECCS to get to net-zero carbon emissions. The cumulative fossil and biomass CO <sub>2</sub> stored through 2050 ranges from zero to 300 GtCO <sub>2</sub> across 1.5°C pathways with no or limited overshoot, with zero up to 140 GtCO <sub>2</sub> from biomass captured and stored. Some pathways have very low fossil-fuel use overall, and consequently little CCS applied to fossil fuels. In 1.5°C pathways where the 2050 coal use remains above 20 EJ yr <sup>−1</sup> in 2050, 33–100% is combined with CCS. While deployment of CCS for natural gas and coal vary widely across pathways, there is greater natural gas primary energy connected to CCS than coal primary energy connected to CCS in many pathways (Figure 2.17).

CCS combined with fossil-fuel use remains limited in some 1.5°C pathways (Rogelj et al., 2018) <sup>[[#fn:r379|379]]</sup> , as the limited 1.5°C carbon budget penalizes CCS if it is assumed to have incomplete capture rates or if fossil fuels are assumed to continue to have significant lifecycle GHG emissions (Pehl et al., 2017) <sup>[[#fn:r380|380]]</sup> . However, high capture rates are technically achievable now at higher cost, although efforts to date have focussed on reducing the costs of capture (IEAGHG, 2006; NETL, 2013) <sup>[[#fn:r381|381]]</sup> .

The quantity of CO <sub>2</sub> stored via CCS over this century in 1.5°C pathways with no or limited overshoot ranges from zero to more than 1,200 GtCO <sub>2</sub> , (Figure 2.17). The IPCC Special Report on Carbon Dioxide Capture and Storage (IPCC, 2005) <sup>[[#fn:r382|382]]</sup> found that that, worldwide, it is ''likely'' that there is a technical potential of at least about 2,000 GtCO <sub>2</sub> of storage capacity in geological formations. Furthermore, the IPCC (2005) <sup>[[#fn:r383|383]]</sup> recognized that there could be a much larger potential for geological storage in saline formations, but the upper limit estimates are uncertain due to lack of information and an agreed methodology. Since IPCC (2005) <sup>[[#fn:r384|384]]</sup> , understanding has improved and there have been detailed regional surveys of storage capacity (Vangkilde-Pedersen et al., 2009; Ogawa et al., 2011; Wei et al., 2013; Bentham et al., 2014; Riis and Halland, 2014; Warwick et al., 2014; NETL, 2015) <sup>[[#fn:r385|385]]</sup> and improvement and standardization of methodologies (e.g., Bachu et al. 2007a, b) <sup>[[#fn:r386|386]]</sup> . Dooley (2013) <sup>[[#fn:r387|387]]</sup> synthesized published literature on both the global geological storage resource as well as the potential demand for geologic storage in mitigation pathways, and found that the cumulative demand for CO <sub>2</sub> storage was small compared to a practical storage capacity estimate (as defined by Bachu et al., 2007a) <sup>[[#fn:r388|388]]</sup> of 3,900 GtCO <sub>2</sub> worldwide. Differences remain, however, in estimates of storage capacity due to, for example, the potential storage limitations of subsurface pressure build-up (Szulczewski et al., 2014) <sup>[[#fn:r389|389]]</sup> and assumptions on practices that could manage such issues (Bachu, 2015) <sup>[[#fn:r390|390]]</sup> . Kearns et al. (2017) <sup>[[#fn:r391|391]]</sup> constructed estimates of global storage capacity of 8,000 to 55,000 GtCO <sub>2</sub> (accounting for differences in detailed regional and local estimates), which is sufficient at a global level for this century, but found that at a regional level, robust demand for CO <sub>2</sub> storage exceeds their lower estimate of regional storage available for some regions. However, storage capacity is not solely determined by the geological setting, and Bachu (2015) <sup>[[#fn:r392|392]]</sup> describes storage engineering practices that could further extend storage capacity estimates. In summary, the storage capacity of all of these global estimates is larger than the cumulative CO <sub>2</sub> stored via CCS in 1.5°C pathways over this century.

There is uncertainty in the future deployment of CCS given the limited pace of current deployment, the evolution of CCS technology that would be associated with deployment, and the current lack of incentives for large-scale implementation of CCS (Bruckner et al., 2014; Clarke et al., 2014; Riahi et al., 2017) <sup>[[#fn:r393|393]]</sup> . Given the importance of CCS in most mitigation pathways and its current slow pace of improvement, the large-scale deployment of CCS as an option depends on the further development of the technology in the near term. Chapter 4 discusses how progress on CCS might be accelerated.

<div id="section-2-4-2-3-block-2"></div>

<span id="figure-2.17"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure 2.17'''

<span id="section-10"></span>
<!-- IMG CAPTION -->
CCS deployment in 1.5°C and 2°C pathways for (a) biomass, (b) coal and (c) natural gas (EJ of primary energy) and (d) the cumulative quantity of fossil (including from, e.g., cement production) and biomass  CO <sub>2</sub>  stored via CCS (in GtCO <sub>2</sub>  stored).
<!-- IMG FILE -->
[[File:cb4d3c78abee4a1910e8f532033e509f Figure-2.17-1024x674.jpg]]

TBox plots show median, interquartile range and full range of pathways in each temperature class. Pathway temperature classes (Table 2.1), illustrative pathway archetypes, and the IEA’s Faster Transition Scenario (IEA WEM) (OECD/IEA and IRENA, 2017) are indicated in the legend.

Original Creation for this Report using IAMC 1.5°C Scenario Data hosted by IIASA

<!-- END IMG -->
<span id="energy-end-use-sectors"></span>