This post takes a quick look at global decarbonisation scenarios. For detailed explanations, links to the source articles (such as IPCC report chapters) are at the bottom.
Table of Contents
Decarbonisation
“Scenarios with very low or low GHG emissions (SSP1-1.9 and SSP1-2.6) lead within years to discernible effects on greenhouse gas and aerosol concentrations and air quality, relative to high and very high GHG emissions scenarios (SSP3-7.0 or SSP5-8.5). Under these contrasting scenarios, discernible differences in trends of global surface temperature would begin to emerge from natural variability within around 20 years, and over longer time periods for many other climatic impact-drivers (high confidence).”
Source: IPCC (2021) AR6 WGI Summary for Policymakers, D.2, pg. 30
Roles of carbon dioxide removal (CDR) in global or national mitigation strategies
Source: IPCC (2022) AR6 WGIII Chapter 12, Cross-Chapter Box 8, Figure 2
Shared Socio-Economic Pathways (SSPs)
Comparison of the range of fossil fuel and industrial CO2 emissions from scenarios used in previous assessments up to AR6
Source: IPCC (2021) AR6 WGI Chapter 1, Figure 1.28, pg. 237
Key Characteristics of the Five Shared Socio-Economic Pathways (SSPs)
Source: IPCC (2018) SR15, Table 2.3
Global mean surface air temperature (GSAT) illustrated as warming stripes from blue (cold) to red (warm) over three different time periods.
Source: IPCC (2021) WGI Chapter 1, Figure 1.25, pg. 228
Global CO2 emissions in the Low Energy Demand (LED) and SSP2 scenarios
Source: Grubler et al (2018) Supplementary Information – A low energy demand scenario for meeting the 1.5 °C target and sustainable development goals without negative emission technologies, Supplementary Figure 17
Illustrative Mitigation Pathways (IMPs)
An overview of the Illustrative Pathways selected for use in IPCC AR6 WGIII
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.5
Illustrative Mitigation Pathways used in AR6
Source: IPCC (2022) AR6 WGIII Chapter 1, Table 1.1, pg.175
Storylines for the two reference pathways and five Illustrative Mitigation Pathways (IMPs) limiting warming to 1.5°C–2°C
Source: IPCC (2022) AR6 WGIII Annex III, Table 9
The residual fossil fuel and industry emissions, carbon dioxide removal (CDR) {LUC, DACCS, BECCS}, and non-CO2 emissions (using AR6 GWP-100) for each of the seven illustrative pathways (IPs)
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.7
Evolution and breakdown of (a) global land-based GHG emissions and removals and (b) global land-use dynamics under four Illustrative Mitigation Pathways, which illustrate the differences in timing and magnitude of land-based mitigation approaches including afforestation and BECCS
Source: IPCC (2022) AR6 WGIII Chapter 7, Figure 7.17, pg. 811
Four mitigation pathways with different assumptions
Riahi et al (2021) Cost and attainability of meeting stringent climate targets without overshoot
Illustrative Mitigation Pathways (IMPs) and net zero CO2 and GHG emissions strategies
Source: IPCC AR6 (2022) WGIII SPM, Figure SPM.5
Global emissions scenarios to 2100
Source: IPCC (2022) WGIII Chapter 3, Figure 3.10, pg. 315
CO2 concentrations for SSPs
Source: Meinshausen et al. (2020) Figure 11 (modified to show CO2 only)
Global warming scenarios to 2100
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.11, pg. 317
Simulated temperature change up to 2300 under the extended SSP scenarios
Source: IPCC (2021) AR6 WGI Chapter 4, Figure 4.40, pg. 632
Key characteristics of the modelled global emissions pathways
Source: IPCC (2023) AR6 SYR Table 3.1, pg. 84
Characteristics of scenarios as a function of the remaining carbon budget (mean decarbonisation rate is shown as the average reduction in the period 2010–2050 divided by 2010 emissions)
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.15, pg. 333
Decade in which sectoral CO2 emissions first reach net negative values
Source: IPCC AR6 (2022) WGIII Chapter 3, Figure 3.19, pg. 339
“In most modelled pathways that likely limit warming to 2°C (>67%) above pre-industrial levels and below in the most cost-effective way, the agriculture, forestry and other land-use (AFOLU) and energy supply sectors reach net zero CO2 emissions several decades earlier than other sectors; however, many pathways show much reduced, but still positive, net GHG emissions in the AFOLU sector in 2100.”
Source: IPCC (2022) AR6 WGIII Chapter 3, FAQ 3.2, pg. 385
“Not all regions and sectors must reach net zero CO2 or GHG emissions individually to achieve global net zero CO2 or GHG emissions, respectively; instead, positive emissions in one sector or region can be compensated by net negative emissions from another sector or region. The time each sector or region reaches net zero CO2 or GHG emissions depends on the mitigation options available, the cost of those options, and the policies implemented (including any consideration of equity or fairness).”
Source: IPCC (2022) AR6 WGIII Chapter 3, FAQ 3.2, pg. 385
Source: IPCC (2023) AR6 Synthesis Report, Figure 4.1
Greenhouse gas (GHG) emissions, including CO2 emissions by sector and total non-CO2 GHGs in 2050 (top left), 2100 (top middle), year of global net zero CO2 (top right), cumulative CO2 emissions from 2020–2100 (bottom left), and cumulative CO2 emissions from 2020 until the year of net zero CO2 for scenarios that limit warming to below 2°C
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.20
Buildings final energy (a), CO2 emissions (b), carbon intensity (c), energy intensity (d), share of final energy from electricity (e), and share of final energy from gases (f)
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.24
Transport final energy (a), CO2 emissions (b), carbon intensity (c), and share of final energy from electricity (d), hydrogen (e), and biofuels (f)
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.25 (with label corrected for ‘(c)’)
Industrial final energy, including feedstocks (a), CO2 emissions (b), carbon intensity (c), energy intensity (d), share of final energy from electricity (e), and share of final energy from gases (f)
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.26
Reduction in AFOLU GHG emissions from 2019
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.27
Change in land cover from 2019 in million hectares
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.28
Marginal abatement cost of carbon in 2030, 2050 and 2100 for mitigation pathways with immediate global mitigation action (a), and ratio in 2050 between pathways that correspond to NDCs announced prior to COP26 in 2030 and strengthen action after 2030 and pathways with immediate global mitigation action, for C3 and C4 temperature categories (b)
Source: IPCC AR6 (2022) WGIII Chapter 3, Figure 3.32, pg. 360
Marginal abatement cost of carbon with respect to CO2 emissions for mitigation pathways with immediate global mitigation action, in 2030 (a) and 2050 (b)
Source: IPCC AR6 (2022) WGIII Chapter 3, Figure 3.33, pg. 360
Energy supply
World total primary energy supply (TPES) (EJ) and total final energy consumption (TFC) 2000–2019
Source: IPCC (2022) AR6 WGIII Chapter 6, Figure 6.5, pg. 622
“Reducing GHG emissions across the full energy sector requires major transitions, including a substantial reduction in overall fossil fuel use, the deployment of low emission energy sources, switching to alternative energy carriers, and energy efficiency and conservation. The continued installation of unabated fossil fuel infrastructure will ‘lock-in’ GHG emissions. (high confidence)”
Source: IPCC (2022) AR6 WGIII Summary for Policymakers, C.4, pg. 28
“Net-zero CO2 energy systems entail: a substantial reduction in overall fossil fuel use, minimal use of unabated fossil fuels, and use of CCS in the remaining fossil fuel system; electricity systems that emit no net CO2; widespread electrification of the energy system including end uses; energy carriers such as sustainable biofuels, low-emissions hydrogen, and derivatives in applications less amenable to electrification; energy conservation and efficiency; and greater physical, institutional, and operational integration across the energy system. CDR will be needed to counterbalance residual emissions in the energy sector. The most appropriate strategies depend on national and regional circumstances, including enabling conditions and technology availability. (high confidence)”
Source: IPCC (2022) AR6 WGIII Summary for Policymakers, C.4.1, pg. 28
Global energy use, 2019
Global energy use, 2060, Scenario IMP-REN-2.0
Global energy use, 2070, Scenario IMP-NEG-2.0
Source: IPCC (2022) AR6 WGIII Chapter 6, Figure 6.1
The energy system in each of the illustrative pathways (IPs)
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.8
IMP characteristics: primary energy
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.16a
Primary energy consumption across scenarios: total primary energy (a), fossil fuels (b), coal without CCS (c), non-biomass renewables (d), and biomass (e)
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.22
Electricity (top left), share of low-carbon electricity (top right), and hydrogen (bottom left) production across all scenarios
Source: IPCC (2022) AR6 WGIII Chapter 3, Figure 3.23
Characteristics of global net-zero energy systems when global energy and industrial CO2 emissions reach net-zero
Source: IPCC (2022) AR6 WGIII Chapter 6, Figure 6.22, pg. 673
Characteristics of regional energy systems and emissions when global energy and industrial CO2 emissions reach net-zero
Source: IPCC (2022) AR6 WGIII Chapter 6, Figure 6.25, pg. 683
Projected energy sector GHG emissions for the 1.5°C scenarios (without and with overshoot), and likely below 2°C scenarios (without and with delayed policy action) during 2020–2050
Source: IPCC (2022) AR6 WGIII Chapter 6, Figure 6.26, pg. 685
The timing of net-zero emissions for full economy greenhouse gases (GHGs), energy sector CO2, and electricity sector CO2
Source: IPCC (2022) AR6 WGIII Chapter 6, Figure 6.28, pg. 686
Reductions in CO2 emissions relative to 2020 levels for scenarios that limit/return warming to 1.5°C (>50%) with no or limited/after a high, overshoot, and scenarios that limit warming to 2°C (>67%), with action starting in 2020 or NDCs until 2030, during 2030–2050
Source: IPCC (2022) AR6 WGIII Chapter 6, Figure 6.29, pg. 687
Shares of low-carbon energy (all sources except unabated fossil fuels) and bioenergy (including both traditional and commercial biomass) in total primary energy, and solar+wind, CCS and nuclear in electricity for scenarios that limit/return warming to 1.5°C (>50%) with no or limited/after a high, overshoot, and scenarios that limit warming to 2°C (>67%), with action starting in 2020 or NDCs until 2030, during 2030–2050
Source: IPCC (2022) AR6 WGIII Chapter 6, Figure 6.30, pg. 688
Shares of electricity and hydrogen in final energy in scenarios that limit/return warming to 1.5°C (>50%) with no or limited/after a high, overshoot, and scenarios that limit warming to 2°C (>67%), with action starting in 2020 or NDCs until 2030, during 2030–2050
Source: IPCC (2022) AR6 WGIII Chapter 6, Figure, 6.31, pg. 692
Global average annual investments from 2023 to 2052 (undiscounted, in USD billion yr –1) for electricity supply sub-sectors and for extraction of fossil fuels in scenarios that limit warming to 2°C (>67%) or lower (C1-C3) (Source: AR6 Scenarios Database and Chapter 3)
Source: IPCC (2022) AR6 WGIII Chapter 6, Figure 6.32, pg. 694
Global average yearly investments from 2023–2052 for nine electricity supply subcomponents and for extraction of fossil fuels (in billion USD2015), in pathways by temperature categories
Source: IPCC (2022) WGIII Chapter 3, Figure 3.36, pg. 363
Global fossil fuel pathways for scenarios that limit/return warming to 1.5°C (>50%) with no or limited/after a high, overshoot, and scenarios that limit warming to 2°C (>67%), with action starting in 2020 or NDCs until 2030, during 2030–2050
Source: IPCC (2022) AR6 WGIII Chapter 6, Figure 6.35, pg. 699
IPCC (2018) Special Report: Global Warming of 1.5 ºC
Cumulative CO2 emissions for the four 1.5°C-consistent pathway archetypes
Source: IPCC (2018) SR15 Chapter 2, Figure 2.10, pg.123
Evolution and break down of global anthropogenic CO2 emissions until 2100
Source: IPCC (2018) SR15 Chapter 2, Figure 2.5, pg.133
Breakdown of contributions to global net CO2 emissions in four illustrative model pathways
Source: IPCC (2018) SR15 SPM, Figure SPM.3b
Potential synergies and trade-offs between the sectoral portfolio of climate change mitigation options and the Sustainable Development Goals (SDGs)
Source: IPCC (2018) SR15 SPM Figure SPM.4, pg. 20
Cumulative CDR deployment in 1.5°C-consistent pathways in the literature until 2050 and 2100
Source: IPCC (2018) SR15 Chapter 2, Figure 2.9, pg. 122
Primary energy supply for the four illustrative pathway archetypes plus the IEA’s Faster Transition Scenario (OECD/IEA and IRENA, 2017) (panel a), and their relative location in the ranges for pathways limiting warming to 1.5°C with no or limited overshoot (panel b)
Source: IPCC (2018) SR15 Chapter 2, Figure 2.15, pg.131
Electricity generation for the four illustrative pathway archetypes plus the IEA’s Faster Transition Scenario (IEA, 2017d) (panel a), and their relative location in the ranges for pathways limiting warming to 1.5°C with no or limited overshoot (panel b)
Source: IPCC (2018) SR15 Chapter 2, Figure 2.16, pg. 135
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 CO2 stored via CCS (in GtCO2 stored)
Source: IPCC (2018) SR15 Chapter 2, Figure 2.17, pg.136
Global price of carbon emissions consistent with mitigation pathways
Source: IPCC (2018) SR15 Chapter 2, Figure 2.26, pg. 153
Historical and projected global energy investments
Source: IPCC (2018) SR15 Chapter 2, Figure 2.27, pg. 155
Overview of land-use change transitions in 2030 and 2050, relative to 2010 based on pathways based on the Shared Socio-Economic Pathways (SSPs)
Source: IPCC (2018) SR15 Chapter 2, Figure 2.24, pg. 145
Land-use changes in 2050 and 2100 in the illustrative 1.5°C-consistent pathway archetypes
Source: IPCC (2018) SR15 Chapter 2, Figure 2.11, pg.126
Sources for this post:
- Grubler et al (2018) Supplementary Information – A low energy demand scenario for meeting the 1.5 °C target and sustainable development goals without negative emission technologies [Figure 17]
- IPCC (2018) Special Report: Global Warming of 1.5 ºC, Summary for Policymakers
- IPCC (2018) Special Report: Global Warming of 1.5 ºC, Chapter 2, Mitigation Pathways Compatible with 1.5°C in the Context of Sustainable Development
- IPCC (2021) AR6 WGI, Summary for Policymakers
- IPCC (2021) AR6 WGI, Chapter 1, Framing, Context and Methods
- IPCC (2021) AR6 WGI, Chapter 4, Future Global Climate: Scenario-based Projections and Near-term Information
- IPCC (2022) AR6 WGIII, Summary for Policymakers
- IPCC (2022) AR6 WGIII, Chapter 1, Introduction and Framing
- IPCC (2022) AR6 WGIII, Chapter 3, Mitigation pathways compatible with long-term goals
- IPCC (2022) AR6 WGIII, Chapter 6, Energy systems
- IPCC (2022) AR6 WGIII, Chapter 7, Agriculture, Forestry, and Other Land Uses (AFOLU)
- IPCC (2022) AR6 WGIII, Chapter 12, Cross sectoral perspectives
- IPCC (2022) AR6 WGIII Annex III, Scenarios and Modelling Methods
- IPCC (2023) AR6 SYR Section 3, Long-Term Climate and Development Futures
- IPCC (2023) AR6 SYR Section 4, Near-Term Responses in a Changing Climate
- Meinshausen et al (2020) The shared socio-economic pathway (SSP) greenhouse gas concentrations and their extensions to 2500
Featured image: from a presentation by Arnulf Grubler on a Low Energy Demand scenario
The link for the presentation is no longer active, but in 2019 it was downloaded from: “http://www.iiasa.ac.at/web/home/research/researchPrograms/TransitionstoNewTechnologies/LED_Greenpeace_Gruebler.pdf”
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Key ideas Our collective greenhouse gas (GHG) emissions are disrupting the Earth’s energy balance. This enhanced greenhouse effect is driving up global […]
“All global modelled pathways that limit warming to 1.5°C (>50%) with no or limited overshoot, and those that limit warming to 2°C (>67%), involve rapid and deep and in most cases immediate GHG emission reductions in all sectors. Modelled mitigation strategies to achieve these reductions include transitioning from fossil fuels without CCS to very low- or zero-carbon energy sources, such as renewables or fossil fuels with CCS, demand side measures and improving efficiency, reducing non-CO2 emissions, and deploying carbon dioxide removal (CDR) methods to counterbalance residual GHG emissions.” [IPCC (2022) AR6 WGIII, Summary for Policymakers, C.3, pg. 24]
“Cumulative net CO2 emissions over the last decade (2010–2019) are about the same size as the remaining carbon budget to limit warming to 1.5°C (>67%) (medium confidence). 62% of total cumulative CO2 emissions from 1850 to 2019 occurred since 1970 (1500 ± 140 GtCO2), about 43% since 1990 (1000 ± 90 GtCO2), and about 17% since 2010 (410 ± 30 GtCO2). For comparison, the remaining carbon budget for keeping warming to 1.5°C with a 67% (50%) probability is about 400 (500) ± 220 GtCO2” [IPCC (2022) AR6 WGIII Technical Summary, pg. 61]
Carbon dioxide removal (CDR) is defined as “Anthropogenic activities removing carbon dioxide (CO2) from the atmosphere and durably storing it in geological, terrestrial, or ocean reservoirs, or in products.” [IPCC (2021) AR6 WGI Annex VII, Glossary, pg. 2221]
Solar radiation modification (SRM) “contrasts with climate change mitigation activities, such as emissions reductions and CDR, as it introduces a ‘mask’ to the climate change problem by altering Earth’s radiation budget, rather than attempting to address the root cause of the problem, which is the increase in GHGs in the atmosphere. By masking only the climate effects of GHG emissions, SRM does not address other issues related to atmospheric CO2 increase, such as ocean acidification.” [IPCC (2021) AR6 WGI, Technical Summary, Box TS.8, pg. 105]