Using large ensembles of climate change mitigation scenarios for robust insights

Guivarch, Céline; Gallic, Thomas Le; Bauer, Nico; Fragkos, Panagiotis; Huppmann, Daniel; Jaxa-Rozen, Marc; Keppo, Ilkka; Kriegler, Elmar; Krisztin, Tamás; Marangoni, Giacomo; Pye, Steve; Riahi, Keywan; Schaeffer, Roberto; Tavoni, Massimo; Trutnevyte, Evelina; Vuuren, Detlef van; Wagner, Fabian

doi:10.1038/s41558-022-01349-x

Cited by 46 publications

(32 citation statements)

References 93 publications

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“…Some gases that are represented in climate emulators are not modelled for any long-term global scenario IAM considered in AR6, though these particular emissions have a relatively small projected impact on climate change. To maximise the richness and diversity of scenarios available in a given assessment (Guivarch et al, 2022), a process of infilling scenarios with missing emissions data is performed. There is, however, no unique way of infilling scenarios with missing data.…”

Section: The Inclusion Of Multiple Climate Emulatorsmentioning

confidence: 99%

“…Describing larger scenario categories comes with further limitations, because summary statistics can conceal the underlying distribution or overemphasise outliers. Further efforts could be made to describe key scenario characteristics by developing methods that correct for potential biases in the underlying scenario database, such as overrepresentation of scenarios from one specific modelling framework or weightings based on feasibility, historical compatibility, or scenario similarity (Guivarch et al, 2022). Other topics that might be relevant for a more multidimensional categorisation could be a separation of scenarios by their temperature decline after their peak or the associated reliance on net-negative emissions to achieve this.…”

Section: Scenario Classification Approachesmentioning

confidence: 99%

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

et al. 2022

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Abstract. While the Intergovernmental Panel on Climate Change (IPCC) physical science reports usually assess a handful of future scenarios, the Working Group III contribution on climate mitigation to the IPCC's Sixth Assessment Report (AR6 WGIII) assesses hundreds to thousands of future emissions scenarios. A key task in WGIII is to assess the global mean temperature outcomes of these scenarios in a consistent manner, given the challenge that the emissions scenarios from different integrated assessment models (IAMs) 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 1202 mitigation scenarios in AR6 WGIII. We evaluate the global mean temperature projections and effective radiative forcing (ERF) characteristics of climate emulators FaIRv1.6.2 and MAGICCv7.5.3 and use the CICERO simple climate model (CICERO-SCM) for sensitivity analysis. We discuss the implied overshoot severity of the mitigation pathways using overshoot degree years and look at emissions and temperature characteristics of scenarios compatible with one possible interpretation of the Paris Agreement. We find that the lowest class of emissions scenarios that limit global warming to “1.5 ∘C (with a probability of greater than 50 %) with no or limited overshoot” includes 97 scenarios for MAGICCv7.5.3 and 203 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 in this category that comply with three criteria for being “Paris-compatible”, including net-zero or net-negative greenhouse gas (GHG) emissions, 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 their implications. This article also introduces a “climate-assessment” Python package which allows for fully reproducing the IPCC AR6 WGIII temperature assessment. This work provides a community tool for assessing the temperature outcomes of emissions pathways and provides a basis for further work such as extending the workflow to include downscaling of climate characteristics to a regional level and calculating impacts.

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Section: The Inclusion Of Multiple Climate Emulatorsmentioning

confidence: 99%

Section: Scenario Classification Approachesmentioning

confidence: 99%

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

et al. 2022

Self Cite

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“…These heterogeneous strengths and weaknesses of each model highlight the importance of diverse model ensembles, like the one employed here, in shedding light on various effects of policy and providing a robust assessment within a spectrum of uncertainty inherent in model theory and dynamics. 55…”

Section: Llmentioning

confidence: 99%

COVID-19 recovery packages can benefit climate targets and clean energy jobs, but scale of impacts and optimal investment portfolios differ among major economies

Ven

Νίκας²,

Koasidis³

et al. 2022

One Earth

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“…In this work, we have used an ethically, and methodologically transparent approach to construct emission scenarios with heterogenous regional objectives. However, as is true for any work that relies on an unstructured ensemble of opportunity, we cannot draw conclusions on whether the regional bounds assessed here are the actual lowest possible regional emissions (Guivarch et al, 2022). The scenarios (per modelling framework) constructed here should be understood to represent a potential scenario that could have been constructed by that modelling framework if: (i) regionally differentiated carbon prices were applied to match a predefined regional carbon budget, (ii) regional carbon budgets are applied.…”

Section: Limitations and Outlook For Further Workmentioning

confidence: 91%

Uncompensated claims to fair emission space risk putting Paris Agreement goals out of reach

Ganti

Gidden

Smith

et al. 2022

Preprint

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Addressing questions of equitable contributions to emission reductions is important to facilitate ambitious global action on climate change within the ambit of the Paris Agreement. Several large developing regions with low historical contributions to global warming have a strong moral claim to a large proportion of the remaining carbon budget. However, this claim needs to be assessed in a context where the remaining carbon budget consistent with the Long-Term Temperature Goal (LTTG) of the Paris Agreement is rapidly diminishing. Here we assess the potential tension between the moral claim to the remaining carbon space by large developing regions with low per capita emissions, and the collective obligation to achieve the goals of the Paris Agreement. Based on scenarios underlying the IPCC's 6th Assessment Report, we construct a suite of scenarios that combine the following elements: (i) two quantifications of a moral claim to the remaining carbon space by South Asia, and Africa, (ii) a "highest possible emission reduction" effort by developed regions, and (iii) a corresponding range for other developing regions.We find that even the best effort by developed regions cannot compensate for a unilateral claim to the remaining carbon space by South Asia and Africa. This would put the LTTG firmly out of reach unless other developing regions cede their moral claim to emissions space and, like developed regions, pursue highest possible emission reductions. Furthermore, regions such as Latin America would need to provide large-scale negative emissions with potential risks and negative side effects. Our findings raise important questions of perspectives on equity in the context of the Paris Agreement including on the critical importance of climate finance. A failure to provide adequate levels of financial support to compensate large developing regions to emit less than their moral claim will put the Paris Agreement at risk.

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Using large ensembles of climate change mitigation scenarios for robust insights

Cited by 46 publications

References 93 publications

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

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

COVID-19 recovery packages can benefit climate targets and clean energy jobs, but scale of impacts and optimal investment portfolios differ among major economies

Uncompensated claims to fair emission space risk putting Paris Agreement goals out of reach

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