Net zero emissions pathways, related
feasibility challenges and enabling
conditions
Keywan Riahi
International Institute for Applied Systems Analysis (IIASA)
riahi@iiasa.ac.at

ALPS Symposium 2022,
8 March 2022

Rapid and unprecedented effort required
to stay “well below 2C”
World GHG Emissions

CurrentAmbition

Investingnow
Delay &OvershootRiahi et al, Nature Climate Charge, 2021

• CO2 emissions need to reach net zero inparallel to rapid reductions of non-CO2
GHG emissions• Reductions across all sectors needed• A portfolio of technologies are available• Behavioral and lifestyle change important
to manage the challenge• Carbon dioxide removal required tocompensate for residual emissions• Investments need to be scaled up

What does carbon neutrality mean?
SECTORAL emissions sources and sinks

Different strategies across models

Illustrative zero emissions pathway

Timing of sectors for zero emissions(compared to the timing of the overall system)

Net zero CO2 emissions 2050-2070
Riahi et al, 2021

What does carbon neutrality mean?
REGIONAL emissions sources and sinks
Illustrative zero emissions pathway

Riahi et al, 2021

Timing of regions for zero emissions(compared to the timing of the overall system)

Innovation & Decarbonization in service
sectors needed
CO2 emissions in Industry in 2050:• 75-90% reductions compared to 2010 (1.5°C)
50-80% for 2°C

Share of low-carbon transport:• 35-65% in 2050 (1.5°C)
25-45% for 2°C
Keywan Riahi – LA, Chapter 5 – IPCC SR1.5

We are still early stage in developing
many CDR options

Nemet et al. (2018), Negative Emissions – Part 3: Innovation and upscaling, Environ Res Lett.

Policies to accelerate technology
diffusion needed

Minx and Nemet (2018), The inconvenient truth about carbon capture, Washington Post; Figure byWilliam Lamb (MCC)Conceptual Framework
Are the global
pathwaysfeasible?

Based on: Brutschin, E., Pianta, S., Tavoni, M., Riahi, K.,
Bosetti, V., Marangoni, G., & Ruijven, B. J. van. (2021).
A multidimensional feasibility evaluation of low-carbon
scenarios. Environmental Research Letters, 16(6),064069. https://doi.org/10.1088/1748-9326/abf0ce

How much can we accelerate technology
diffusion – empirical research

Brutschin et al, 2021

Solar and wind upscaling in scenarios

2C1.5C

1.5C (500Gt): global phase-out by 2030
2C (1000Gt): decline in global capacity by more than 50% by 2030

In preparation: Brutschin, Schenuit, et al.

Global Coal Phase Out for ambitious
mitigation goals

Ca. 70 % of global coal capacity in countries with
rapidly growing energy demand In preparation: Brutschin, Schenuit, et al.
Aging coal fleet and signs of coal substitution ordecline

NORTH

Young coal fleet and cases of premature (<30years) retirement only in ChinaSOUTH

Energy investment requirements• 1.5°C require rapid shift and scale-upof energy investments:•In the next decade, investments into
decarbonizing power are dominating,especially solar and wind, plus “system”
investments into transmission &distribution and storage•

Coal, and fossil power generation
investments are eliminated nearly
immediately, and gas and oil investments
strongly reduced•

13

Share of investments 1.5°C scenarios

Bertram et al, 2021

Investment needs small
compared to COVID-19
recovery packages

14

Andrijevic et al. (2020)

Limiting Demand critical for feasibility,
however, an own challenge➢ Change in consumer preferences(e.g. diets)➢ Genrational change in materilism(service orientation rather thanowenership)➢ New business models(sharing & circular economy)➢ Digitalization and ICT
convergence➢ Rapide innovation in granularer
technologies und integrated
digital services

Government effectiveness andmitigation capacity

Overall EPI indicates which countries are best
addressing the environmental challenges thatevery nation faces.
Source: https://epi.yale.edu/about-epi

Government Effectiveness(from the WB governanceindicators):
Government effectiveness captures
perceptions of the quality of publicservices, the quality of the civil service
and the degreeof its independence from politicalpressures, the quality of policy formulationand implementation, and the credibility ofthegovernment's commitment to suchpolicies.

Regional near-term institutional
feasibility risks

Preliminary scenarios with governancerepresentation very different fromcost-effective solution
Emissions reductions 2030-2040

Without governanceWith governanceIn preparation: Please do not cite or distribute – Brutschin et alDelays in mitigation do not resolve
governance issues – temporal trade-offs

High level insights from the ENGAGEprojectThank you.
Keywan Riahi
riahi@iiasa.ac.atNote PRELIMINARY results of ENGAGE – UNDER EMBARGO, please do not circulate outside the meeting
3/8/2022

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