Preprints
https://doi.org/10.5194/egusphere-2022-471
https://doi.org/10.5194/egusphere-2022-471
28 Jun 2022
 | 28 Jun 2022

The IPCC Sixth Assessment Report WGIII climate assessment of mitigation pathways: from emissions to global temperatures

Jarmo S. Kikstra, Zebedee R. J. Nicholls, Christopher J. Smith, Jared Lewis, Robin D. Lamboll, Edward Byers, Marit Sandstad, Malte Meinshausen, Matthew J. Gidden, Joeri Rogelj, Elmar Kriegler, Glen P. Peters, Jan S. Fuglestvedt, Ragnhild B. Skeie, Bjørn H. Samset, Laura Wienpahl, Detlef P. van Vuuren, Kaj-Ivar van der Wijst, Alaa Al Khourdajie, Piers M. Forster, Andy Reisinger, Roberto Schaeffer, and Keywan Riahi

Abstract. While the IPCC’s physical science report usually assesses a handful of future scenarios, the IPCC Sixth Assessment Working Group III report (AR6 WGIII) on climate mitigation assesses hundreds to thousands of future emissions scenarios. A key task is to assess the global-mean temperature outcomes of these scenarios in a consistent manner, given the challenge that the emission scenarios from different integrated assessment models come with different sectoral and gas-to-gas coverage and cannot all be assessed consistently by complex Earth System Models. In this work, we describe the “climate assessment” workflow and its methods, including infilling of missing emissions and emissions harmonisation as applied to 1,202 mitigation scenarios in AR6 WGIII. We evaluate the global-mean temperature projections and effective radiative forcing characteristics (ERF) of climate emulators FaIRv1.6.2, MAGICCv7.5.3, and CICERO-SCM, discuss overshoot severity of the mitigation pathways using overshoot degree years, and look at an interpretation of compatibility with the Paris Agreement. We find that the lowest class of emission scenarios that limit global warming to “1.5 °C (with a probability of greater than 50 %) with no or limited overshoot” includes 90 scenarios for MAGICCv7.5.3, and 196 for FaIRv1.6.2. For the MAGICCv7.5.3 results, “limited overshoot” typically implies exceedance of median temperature projections of up to about 0.1 °C for up to a few decades, before returning to below 1.5 °C by or before the year 2100. For more than half of the scenarios of this category that comply with three criteria for being “Paris-compatible”, including net-zero or net-negative greenhouse gas (GHG) emissions, are projected to see median temperatures decline by about 0.3–0.4 °C after peaking at 1.5–1.6 °C in 2035–2055. We compare the methods applied in AR6 with the methods used for SR1.5 and discuss the implications. This article also introduces a ‘climate-assessment’ Python package which allows for fully reproducing the IPCC AR6 WGIII temperature assessment. This work can be the start of a community tool for assessing the temperature outcomes related to emissions pathways, and potential further work extending the workflow from emissions to global climate by downscaling climate characteristics to a regional level and calculating impacts.

Journal article(s) based on this preprint

20 Dec 2022
| Highlight paper
The IPCC Sixth Assessment Report WGIII climate assessment of mitigation pathways: from emissions to global temperatures
Jarmo S. Kikstra, Zebedee R. J. Nicholls, Christopher J. Smith, Jared Lewis, Robin D. Lamboll, Edward Byers, Marit Sandstad, Malte Meinshausen, Matthew J. Gidden, Joeri Rogelj, Elmar Kriegler, Glen P. Peters, Jan S. Fuglestvedt, Ragnhild B. Skeie, Bjørn H. Samset, Laura Wienpahl, Detlef P. van Vuuren, Kaj-Ivar van der Wijst, Alaa Al Khourdajie, Piers M. Forster, Andy Reisinger, Roberto Schaeffer, and Keywan Riahi
Geosci. Model Dev., 15, 9075–9109, https://doi.org/10.5194/gmd-15-9075-2022,https://doi.org/10.5194/gmd-15-9075-2022, 2022
Short summary Executive editor

Jarmo S. Kikstra et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2022-471', Richard Rosen, 09 Jul 2022
    • AC1: 'Reply on CC1', Jarmo Kikstra, 21 Sep 2022
  • RC1: 'Comment on egusphere-2022-471', Anonymous Referee #1, 20 Jul 2022
  • RC2: 'Comment on egusphere-2022-471', Anonymous Referee #2, 03 Aug 2022
  • AC2: 'Final author comment (AC) on behalf of all co-authors, responding to RC1 and RC2', Jarmo Kikstra, 21 Sep 2022

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2022-471', Richard Rosen, 09 Jul 2022
    • AC1: 'Reply on CC1', Jarmo Kikstra, 21 Sep 2022
  • RC1: 'Comment on egusphere-2022-471', Anonymous Referee #1, 20 Jul 2022
  • RC2: 'Comment on egusphere-2022-471', Anonymous Referee #2, 03 Aug 2022
  • AC2: 'Final author comment (AC) on behalf of all co-authors, responding to RC1 and RC2', Jarmo Kikstra, 21 Sep 2022

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Jarmo Kikstra on behalf of the Authors (10 Nov 2022)  Author's response   Author's tracked changes   Manuscript 
ED: Publish subject to minor revisions (review by editor) (11 Nov 2022) by Sam Rabin
AR by Jarmo Kikstra on behalf of the Authors (15 Nov 2022)  Author's response   Manuscript 
EF by Polina Shvedko (16 Nov 2022)  Author's tracked changes 
ED: Publish subject to technical corrections (16 Nov 2022) by Sam Rabin
AR by Jarmo Kikstra on behalf of the Authors (26 Nov 2022)  Manuscript 

Journal article(s) based on this preprint

20 Dec 2022
| Highlight paper
The IPCC Sixth Assessment Report WGIII climate assessment of mitigation pathways: from emissions to global temperatures
Jarmo S. Kikstra, Zebedee R. J. Nicholls, Christopher J. Smith, Jared Lewis, Robin D. Lamboll, Edward Byers, Marit Sandstad, Malte Meinshausen, Matthew J. Gidden, Joeri Rogelj, Elmar Kriegler, Glen P. Peters, Jan S. Fuglestvedt, Ragnhild B. Skeie, Bjørn H. Samset, Laura Wienpahl, Detlef P. van Vuuren, Kaj-Ivar van der Wijst, Alaa Al Khourdajie, Piers M. Forster, Andy Reisinger, Roberto Schaeffer, and Keywan Riahi
Geosci. Model Dev., 15, 9075–9109, https://doi.org/10.5194/gmd-15-9075-2022,https://doi.org/10.5194/gmd-15-9075-2022, 2022
Short summary Executive editor

Jarmo S. Kikstra et al.

Model code and software

Climate assessment of long-term emissions pathways: IPCC AR6 WGIII version Jarmo S. Kikstra, Zebedee R.J. Nicholls, Jared Lewis, Christopher J. Smith, Robin D. Lamboll, Edward Byers, Marit Sandstad, Laura Wienpahl, Philip Hackstock https://doi.org/10.5281/zenodo.6624519

Jarmo S. Kikstra et al.

Viewed

Total article views: 2,042 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
1,408 605 29 2,042 76 19 16
  • HTML: 1,408
  • PDF: 605
  • XML: 29
  • Total: 2,042
  • Supplement: 76
  • BibTeX: 19
  • EndNote: 16
Views and downloads (calculated since 28 Jun 2022)
Cumulative views and downloads (calculated since 28 Jun 2022)

Viewed (geographical distribution)

Total article views: 1,737 (including HTML, PDF, and XML) Thereof 1,737 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 

Cited

Latest update: 12 Dec 2023
Download

The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

This paper provides key insight into the methodology of Working Group III of the IPCC Sixth Assessment Report on climate mitigation. The paper will be essential reading for anyone wishing to understand the assessment of climate outcomes of mitigation pathways in the context of the Paris Agreement.
Short summary
Assessing hundreds or thousands of emission scenarios in terms of their global-mean temperature implications requires standardised procedures of infilling, harmonisation and probabilistic temperature assessments. We here present the ‘climate-assessment’ workflow that provides the methodology used in the IPCC Working Group III report.