Perceived feasibility and potential barriers of a net-zero system transition among Japanese experts

The study addresses whether national net-zero greenhouse gas targets are feasible and desirable, recognizing that feasibility is often framed as binary in public discourse but is treated probabilistically in academic research. Following accelerated net-zero pledges post-IPCC SR15, the literature provides option-level feasibility assessments and global scenario-based analyses, but often underrepresents socio-political, institutional, and cultural contexts, and exhibits limitations of IAMs in capturing complex sociotechnical dynamics. The authors propose a new framework grounded in political feasibility and futures-cone thinking to incorporate broader perspectives into feasibility assessment and apply it to Japan—a country with relatively slow energy transition after the 2011 Fukushima accident—to answer: (1) How do experts perceive feasibility and desirability of Japan’s net-zero transition, and how does this vary across expert communities? (2) What barriers to achieving national net-zero exist, and how do experts assess their risks?

The paper synthesizes several strands: (a) IPCC-led feasibility assessments of mitigation/adaptation options (SR15; AR6 WGII and WGIII), and methods to identify barriers/enablers at the option level; (b) scenario-based global feasibility assessments using IAMs that compare model outputs against historical analogues and reveal technoeconomic constraints; (c) debates on feasibility of sectoral transitions (renewables expansion, coal phase-out, green hydrogen); and (d) critiques of IAMs for underestimating innovation in solar, wind, and batteries and for limited representation of sociopolitical factors. The authors note that prior system-level feasibility studies largely emphasize technoeconomics, often reducing institutional and sociocultural dimensions to proxies. They argue for integrating broader disciplinary perspectives and for moving beyond a global focus to national/sectoral contexts, in line with the hybrid architecture of the Paris Agreement. The conceptual framework builds on political feasibility theory, futures cones distinguishing feasible (possible) from desirable (preferable) futures, and treats feasibility as a subjective/Bayesian probability shaped by soft constraints (economic, sociocultural, institutional) as well as hard constraints.

Conceptual framework: Feasibility is defined as the extent to which a socially important goal (e.g., net-zero by 2050) is achievable in a specific context, conditional on actors’ efforts, and expressible as a probability distribution (cumulative distribution function) over outcomes. Hard constraints (e.g., geophysical limits) act binarily; soft constraints (economic, sociocultural, institutional, technological) reduce likelihoods and are malleable over time. Perceived feasibility denotes individuals’ subjective probabilities, which may correlate with desirability due to psychological biases. The framework posits four propositions: (1) feasibility is probabilistic; (2) barriers shift feasibility distributions; (3) perceived feasibility and desirability are distinct but interact; (4) broader expert perspectives should inform assessments. Application and survey: The authors operationalized the framework for Japan’s 2050 goals, tailoring barrier items to national conditions (e.g., limited VRE potentials, nuclear opposition, lack of emissions trading, coal lock-in, renewable costs). Instrument development involved literature review and ~1-hour interviews with 10 experts to elicit soft constraints, mapped to IPCC’s six feasibility dimensions (geophysical, environmental-ecological, technological, economic, sociocultural, institutional). Survey content: Experts assessed desirability and feasibility for 2050 emissions reduction targets (80%, 90%, 100%, 110%). They evaluated 22 potential barriers via Likert scales for probability and negative impact, and risk was computed as probability × impact. Probability responses used IPCC-recommended likelihood language and were quantified on a scale (five levels corresponding to very likely to very unlikely; mapped to numerical values consistent with ranges such as ≥90%, ≥66%, 33–66%, ≤33%, ≤10%). Impact was rated from 1 (extremely small) to 5 (extremely large). Barriers were also categorized as easier-to-model or harder-to-model based on IAM literature limitations. Sampling and administration: Experts were identified via three sources to ensure breadth across disciplines: (1) IPCC WGIII-related authors; (2) Web of Science authors with multiple mitigation publications (2011–2021) in Japan (query TS: ("climat* change*" OR "global warming") AND (mitigat*)) AND CU=japan); (3) JSPS Kakenhi funding database for mitigation-related projects (2011–2021). A combined list (with duplicates removed and one-round snowballing) yielded 171 experts. The survey was conducted via online interviews (Zoom) from October 2021 to March 2022. Response rate was 63.7% (109/171). One respondent skipped desirability (yielding n=107 for desirability analyses; n=108 for other results); a few completed without interview or audio only. Demographics collected included affiliation (academia, government, industry, civil society), discipline (natural science, social science, humanities), and experience (2–5, 5–10, 10–15, 15–20, 20+ years). After completion, a summary was shared for possible response revision. System boundary followed UNFCCC/Paris Agreement conventions, including international transfers. Data and code were shared via Zenodo for reproducibility within privacy constraints.

- Desirability: Over half of respondents deemed a 100% emissions reduction by 2050 desirable; 80% and 110% targets also garnered notable support. No statistically significant difference in desirability between IPCC/IAM-affiliated respondents and others (Chi-square p=0.7037). More than 20% of the IPCC/IAM group considered 110% reduction desirable, aligning with equity-driven carbon dioxide removal considerations. Affiliation had some effect (non-academic experts more often chose 80% as desirable); experience and discipline effects were minor. - Feasibility: As targets became more ambitious (80% to 110%), perceived feasibility distributions shifted toward lower probabilities. For net-zero (100%), the modal response was 33–66%, with an overall pessimistic skew. The IPCC/IAM group reported higher feasibility for the 80% target than others and showed a broader distribution for net-zero, whereas others clustered at 33–66%. For 110%, the largest share across groups chose ≤10% feasibility, reflecting broad recognition of difficulty. Academics most often selected 33–66% feasibility for net-zero; non-academics most often selected ≤10%. - Feasibility–desirability relationship: A weak positive correlation existed between desirability and perceived feasibility; Spearman’s rho values were 0.40 (80%), 0.44 (90%), 0.38 (100%), and 0.29 (110%). Respondents preferring targets below 100% tended to be more pessimistic about ambitious goals; those preferring >100% often assigned higher feasibility to 100% and 110% outcomes. - Barriers: From 22 identified barriers, mean probability and impact across items were 0.5112 (SD 0.2683; 52% of mean) and 3.3721 (SD 1.0689; 31% of mean), respectively. Experts generally agreed that all barriers could have non-negligible impacts; probabilities varied substantially. No strong clustering by barrier type or actor emerged; responses were broadly similar across disciplines. High-impact barriers reflected Japan’s context: ensuring adequate clean energy supply (given high population density, mountainous terrain, local conflicts over renewable siting, higher costs) and limitations of a coherent national strategy. High-probability barriers included public concerns about nuclear energy and lack of local capacities. Top risk (probability × impact) barriers by median included: nuclear concerns, sufficiency of national strategy, local capacities, green recovery, clean energy supply technologies, carbon dioxide removal technologies, carbon tax resistance, social movement, hard-to-abate sectors, and power imbalance, among others. Many of these are harder-to-model in IAMs and often treated exogenously. - Group differences highlight both within-group disagreement among IAM/IPCC experts and differences from other experts, particularly in feasibility distributions.

The findings show that while Japanese experts broadly desire net-zero by 2050, they assign only moderate probabilities (33–66%) to achieving it, indicating perceived gaps between aspiration and likely realization under current conditions. This directly answers the first research question and underscores the need to examine sociopolitical and institutional soft constraints alongside technoeconomics. Differences in feasibility perceptions between IAM/IPCC-affiliated experts and others suggest epistemic heterogeneity and the value of pluralistic perspectives for robust feasibility assessment. Addressing the second research question, the highest-risk barriers—public concerns about nuclear energy, insufficiency of national strategy, and local capacity constraints—are strongly context-dependent and less amenable to inclusion in standard IAMs, highlighting areas where policy, governance reform, local capacity building, and public engagement are likely pivotal. The framework’s strength lies in its inclusivity and ability to surface national nuances, complementing global scenario analyses. Repeated surveys over time could track shifts due to events (e.g., COP outcomes, energy price shocks, geopolitical crises), inform adaptive policy mixes, and move public debate beyond binary feasibility framing. Integrating qualitative insights with quantitative modeling could better capture interactions among barriers and improve the realism of feasibility appraisals.

The study demonstrates a practicable framework to elicit perceived feasibility and assess barriers for net-zero transitions using expert surveys. Experts widely support the desirability of Japan’s net-zero goal but assign only moderate feasibility, emphasizing the need for accelerated action on high-risk barriers, notably nuclear energy concerns, national strategy sufficiency, local capacities, green recovery implementation, and clean energy supply. Differences in feasibility perceptions between IAM/IPCC experts and others point to opportunities for deeper cross-community dialogue and joint research to strengthen feasibility and barrier assessment within technoeconomic traditions. The framework’s light data requirements and contextual focus make it suitable for national and sectoral applications, including in data-scarce regions, and it can be extended to non-experts and combined with participatory methods (e.g., workshops) for broader stakeholder engagement. Future research should repeat elicitations over time, explore interactions among barriers, and more tightly integrate qualitative assessments with quantitative models.

Key limitations include potential cognitive and motivational biases in expert elicitation (e.g., availability, anchoring, overconfidence, desirability bias), possible influence of contemporaneous events during the survey period (COVID-19, COP26 Glasgow, Russia’s invasion of Ukraine, energy price spikes), and the difficulty of capturing interactions among numerous barriers. Stakeholders may view feasibility binarily and exhibit stronger motivated reasoning, which is why the initial application focused on experts. Some aspects (particularly technoeconomic ones) require grounding in system modeling; formally combining these with qualitative judgments was beyond the study’s scope. Additionally, expert identification via databases may introduce disciplinary coverage biases despite multi-source sampling.