Climate uncertainty impacts on optimal mitigation pathways and social cost of carbon
File(s)
Published version
Author(s)
Smith, Christopher J
Al Khourdajie, Alaa
Yang, Pu
Folini, Doris
Type
Journal Article
Abstract
Emissions pathways used in climate policy analysis are often derived from integrated assessment models. However, such emissions pathways do not typically include climate feedbacks on socioeconomic systems and by extension do not consider climate uncertainty in their construction. We use a well-known cost-benefit integrated assessment model, the Dynamic Integrated Climate-Economy (DICE) model, with its climate component replaced by the Finite-amplitude Impulse Response (FaIR) model (v2.1). The climate uncertainty in FaIR is sampled with an ensemble that is consistent with historically observed climate and Intergovernmental Panel on Climate Change (IPCC) assessed ranges of key climate variables such as equilibrium climate sensitivity (ECS). By varying discounting assumptions, three scenarios are produced: a pathway similar to the ‘optimal welfare’ scenario of DICE that has similar warming outcomes to current policies, and pathways that limit warming to ‘well-below’ 2⁰C and 1.5⁰C with a short-term overshoot, aiming to meet Paris Agreement long-term temperature goals. Climate uncertainty alone is responsible for a factor of five variation (5%–95% range) in the social cost of carbon (SCC) in the 1.5⁰C overshoot scenario, with the spread in SCC increasing in relative terms with increasing stringency of climate target. CO2 emissions trajectories resulting from the optimal level of emissions abatement in all pathways are also sensitive to climate uncertainty, with 2050 emissions ranging from −12 to +14 GtCO2 yr−1 in the 1.5⁰C scenario. ECS and the strength of present-day aerosol effective radiative forcing are strong determinants of SCC and mid-century CO2 emissions. This shows that narrowing climate uncertainty leads to more refined estimates for the social cost of carbon and provides more certainty about the optimal rate of emissions abatement. Including climate and climate uncertainty in integrated assessment model derived emissions scenarios would address a key missing feedback in scenario construction.
Date Issued
2023-09-01
Date Acceptance
2023-08-07
Citation
Environmental Research Letters, 2023, 18 (9)
ISSN
1748-9326
Publisher
IOP Publishing
Journal / Book Title
Environmental Research Letters
Volume
18
Issue
9
Copyright Statement
© 2023 The Author(s). Published by IOP Publishing Ltd. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Subjects
climate
economics
EMISSIONS
ENERGY
Environmental Sciences
Environmental Sciences & Ecology
FRAMEWORK
IMPULSE-RESPONSE
Life Sciences & Biomedicine
Meteorology & Atmospheric Sciences
mitigation
MODEL
Physical Sciences
Science & Technology
TEMPERATURE
uncertainty
Publication Status
Published
Article Number
ARTN 094024
Date Publish Online
2023-08-18