Navigating the political: An analysis of political calibration of integrated assessment modelling in light of the 1.5 °C goal

Beek, Lisette van; Oomen, Jeroen; Hajer, Maarten; Pelzer, Peter; Vuuren, Detlef van

doi:10.1016/j.envsci.2022.03.024

Cited by 61 publications

(52 citation statements)

References 43 publications

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“…Such a control is especially needed to prevent policy-oriented models from getting as complex as to cloak value-laden assumptions and output uncertainties ( 55 ). For instance, how many readers outside the circle of practitioners know that the 1.5 degree climate target is achieved in integrated assessment models thanks to the adoption of so-called negative emissions, a technology still to be fully developed ( 56 )? Or that global hydrological models assume that irrigation optimizes crop production and water use (a premise at odds with the practices of traditional irrigators) ( 40 )?…”

Section: Discussionmentioning

confidence: 99%

“…Since larger-scale models can command more epistemic authority ( 57 ), modelers may be tempted to add detail to reinforce their status as influential actors at the science-policy interface and gain recognition and reward ( 58 ). More complex models are also more ductile to political calibration, a sequential process of continuously refining the fit between modeling and policy requirements ( 56 ). In this situation, the model becomes a moving target as it is continuously rearranged to include new data and processes to match evolving policy needs, with no evidence as to how it works prospectively.…”

Section: Discussionmentioning

confidence: 99%

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Models with higher effective dimensions tend to produce more uncertain estimates

et al. 2022

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Mathematical models are getting increasingly detailed to better predict phenomena or gain more accurate insights into the dynamics of a system of interest, even when there are no validation or training data available. Here, we show through ANOVA and statistical theory that this practice promotes fuzzier estimates because it generally increases the model’s effective dimensions, i.e., the number of influential parameters and the weight of high-order interactions. By tracking the evolution of the effective dimensions and the output uncertainty at each model upgrade stage, modelers can better ponder whether the addition of detail truly matches the model’s purpose and the quality of the data fed into it.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Models with higher effective dimensions tend to produce more uncertain estimates

et al. 2022

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“…The most recent and most rigorous scenario assessment until AR6 was done in SR1.5. Insights from IAM-based assessment have influenced the global science-policy discourse (van Beek et al, 2020(van Beek et al, , 2022 and are even referred to in outcomes from informed ambitions in the Glasgow Climate Pact (UNFCCC, 2021). The results of SR1.5 have been influential in the academic literature, influenced public debate around the world, and legitimised as well as challenged climate policy (Hermansen et al, 2021;Livingston and Rummukainen, 2020).…”

Section: Changes In Methods Between Sr15 and Ar6 Wgiii And Their Impl...mentioning

confidence: 99%

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

Kikstra

Nicholls

Smith

et al. 2022

Preprint

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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.

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“…The remaining illustrative pathway (IMP-Ren) does not meet Criterion III (net zero greenhouse gas emissions). While the IMP-LD does not meet Criterion II, it misses this criteria by just about 1% points and we include it for illustrative purposes given the prominence of this scenario 39 .…”

Section: Methodsmentioning

confidence: 99%

An emission pathway classification reflecting the Paris Agreement climate objectives

Schleußner

Ganti

Rogelj

et al. 2022

Preprint

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The 2015 Paris Agreement sets the objectives of global climate ambition as expressed in its long-term temperature goal and mitigation goal. The scientific community has explored the characteristics of greenhouse gas emission reduction pathways in line with the Paris Agreement. However, when categorizing such pathways, the focus has been put on the temperature outcome and not on emission reduction objectives. Here we propose a pathway classification that aims to comprehensively reflect the climate criteria set out in the Paris Agreement. We show how such an approach allows for a fully consistent interpretation of the Agreement. For Paris Agreement compatible pathways, we report net zero CO 2 and greenhouse gas emissions around 2050 and 2065, respectively. We illustrate how pathway design criteria not rooted in the Paris Agreement, such as the 2100 temperature level, result in scenario outcomes wherein about 6 -24% higher deployment (interquartile range) of carbon dioxide removal is observed.

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Navigating the political: An analysis of political calibration of integrated assessment modelling in light of the 1.5 °C goal

Cited by 61 publications

References 43 publications

Models with higher effective dimensions tend to produce more uncertain estimates

Models with higher effective dimensions tend to produce more uncertain estimates

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

An emission pathway classification reflecting the Paris Agreement climate objectives

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