What determines climate ambition? Analysing NDC enhancement with a mixed-method design

Global climate action under the Paris Agreement follows a procedural approach in which countries determine their own contributions through Nationally Determined Contributions (NDCs). The freedom to choose mitigation pathways has led to variation in commitments, and countries are required to increase ambition every five years. While many countries have not meaningfully improved targets, less is known about factors determining variation in enhancement between initial and updated/revised NDCs. This study addresses that gap by examining political, economic, and structural drivers and barriers of NDC enhancement, focusing on domestic factors due to the discretion afforded by the Paris Agreement. Building on literature highlighting transparent and inclusive processes, the study emphasizes the potential roles of democracy and stakeholder consultations—particularly engagement with civil society organizations (CSOs)—in shaping enhanced ambition. Given the absence of formal enforcement under Paris, the ratchet mechanism may hinge on domestic social pressures. The study employs a mixed-method approach: quantitative logistic regression analysis of enhancement in updated/revised NDCs (2019–2021) across 111 countries, and qualitative case studies of Brazil and South Africa.

Prior work has examined determinants of NDC ambition and cross-country variation in initial NDC targets, but comparisons between initial and updated/revised NDCs remain limited. Literature emphasizes that transparent, inclusive processes can legitimize international pledges, enable accountability, and influence ambition through domestic interest group participation. Studies point to the positive role of democratic institutions, civil liberties, and free civil society in advancing climate policy. Scholarship on domestic political economy highlights how business and labour interests can shape climate outcomes, with fossil fuel–aligned actors often resisting ambition increases and civil society typically supporting them. This study builds on these strands by explicitly testing the roles of electoral democracy and CSO-inclusive stakeholder consultations in explaining NDC enhancement, while considering economic development, climate finance, fossil-fuel rents, and climate hazard exposure.

Design: Mixed-method study combining large-N quantitative analysis with qualitative case studies. Quantitative component: - Outcome: Dichotomous indicator of NDC enhancement based on Climate Watch (WRI), capturing whether total GHG emissions estimated for 2030 were reduced in updated/revised NDCs submitted March 2016–December 2021 (coded 1 = enhanced, 0 = not enhanced). - Sample: 111 countries with updated/revised NDCs; EU Member States aggregated per year. Due to data limitations, the most expansive logistic regression model includes a reduced subset of countries (noted as a limitation). - Estimation: Bayesian logistic regression. To mitigate multicollinearity and small-sample risks, main models evaluate predictors in separate specifications with controls for GDP per capita (log) and year of updated NDC submission. Bivariate models also presented; coefficients as log-odds with 95% CIs. - Key predictors: • Political institutions: Electoral democracy (V-Dem Polyarchy index). Stakeholder engagement operationalized via a CSO consultation index combining Climate Watch’s NDC stakeholder consultation coding (1 = no mention; 2 = mentioned) with V-Dem’s CSO consultation indicator (rescaled 0–6). Index defined as CSO consultation index = V2csocnsult × M.PL2, centered between approximately −2 and +2 to reflect both the documented use of consultations in NDCs and the institutional capacity for meaningful CSO input. • Economic factors: GDP per capita (constant 2015 USD, log, t−1), climate finance received for mitigation (OECD Rio Markers; developing countries only). • Structural factors: Fossil fuel rents (coal+oil+gas as % of GDP; average between initial and updated NDC), climate hazard exposure (population affected by storms, floods, landslides, wildfires, extreme temperatures per EM-DAT; averaged between initial and updated NDC, population-normalized). • Time control: Submission year of updated/revised NDC (2019–2021), capturing evolving information and political dynamics. - Rationale for dichotomous outcome: Avoids subjective thresholds required for a continuous enhancement measure and better accommodates heterogeneous NDC target structures (e.g., target types, baselines, BAU updates, sectoral net-zero pledges). Qualitative component: - Case selection: Two illustrative cases (Brazil and South Africa) chosen for variation in government type, democratic institutions and consultation practices, fossil fuel production, climate finance, and climate hazards—both major economies/emitters and BRICS members with similar development levels. Aim is to illuminate mechanisms underpinning quantitative associations. - Data: Documentary analysis and expert interviews (referenced as interviewees #1–#11). Process tracing of NDC development, consultation processes, political dynamics, and sectoral contexts. - Focus: How stakeholder consultations and domestic political-economic shifts influenced enhancement outcomes in updated NDCs (Brazil 2020; South Africa 2021).

- Overall enhancement rate: 53% of the 111 updated/revised NDCs enhanced their 2030 emissions estimates. - Democracy effect: Higher electoral democracy (V-Dem) is positively and significantly associated (p < 0.05) with NDC enhancement, robust to controls for GDP per capita and submission year. Predicted probabilities indicate greater likelihood of enhancement in more democratic settings. - Stakeholder consultations: Countries scoring higher on the CSO consultation index are more likely to enhance. Illustratively, medium index countries (e.g., Paraguay, Jordan) have ~54% likelihood of enhancement; highest index scores (e.g., United States, Switzerland) correspond to ~71% likelihood. - Submission timing: Later submission years (2019–2021) are positively and significantly associated with enhancement, consistent with improved scientific information, social mobilization, and the Paris ratchet mechanism. - Economic and structural variables: Fossil fuel rents, climate finance receipts, and climate hazard exposure are not significant predictors of enhancement in the main specifications. - Case study—Brazil: The December 2020 updated NDC reaffirmed the initial unconditional 43% reduction by 2030 versus 2005, offered limited information on measures, and floated carbon neutrality by 2060 (and possibly 2050) without concrete pathways. Development occurred behind closed doors, with weakened or absent consultations via the Brazilian Forum on Climate Change, reflecting broader democratic backsliding under President Bolsonaro. Result: no enhancement. - Case study—South Africa: The September 2021 updated NDC increased ambition by ~28% relative to the 2016 target range, reducing the 2030 upper bound by 32% and lower bound by 12% (initial range 398–614 MtCO2e). Establishment of the Presidential Climate Commission (PCC) enabled broad consultations (government, business, labour, civil society, science), shifting the balance toward enhancement despite concerns from some ministries and unions. Falling renewable costs, Eskom reliability crises, and investment considerations supported stronger targets. Result: enhancement.

Findings indicate that domestic political institutions—especially democratic practices and inclusive stakeholder consultations—are key drivers of NDC enhancement. The quantitative analysis identifies electoral democracy and the timing of submissions as robust predictors, while economic and structural variables show limited explanatory power. The case studies corroborate these relationships: Brazil’s curtailed, opaque process under a climate-skeptical administration coincided with a non-enhanced update; South Africa’s institutionalized, transparent consultations through the PCC supported a substantially more ambitious target, aided by evolving energy economics (renewables cost declines, Eskom’s crisis) and investment incentives. Policy implications include: (1) strengthening open, transparent, and democratic stakeholder engagement processes—particularly meaningful CSO inclusion—to facilitate ambition increases; and (2) institutionalizing consultation mechanisms to build domestic buy-in, inform feasible targets, catalyze policy shifts, and potentially improve subsequent implementation. The results underscore the Paris Agreement’s ratchet mechanism operating partly through diffusion and learning as later submissions tended to be more ambitious.

This study advances understanding of why some countries enhanced their updated/revised NDCs by integrating cross-national statistical analysis with in-depth cases. It shows that democratic institutions and comprehensive stakeholder consultations—especially with civil society—are associated with higher likelihoods of enhancing 2030 GHG targets, while commonly cited economic and structural constraints were not significant in explaining changes between NDC rounds. The Brazil and South Africa cases illuminate mechanisms: closed, politically constrained processes hindered enhancement in Brazil, whereas institutionalized, transparent engagement under South Africa’s PCC supported stronger targets amid shifting energy economics. Future research should (a) assess how these dynamics operate in non-democratic regimes; (b) examine links between initial static ambition and subsequent enhancement; (c) extend metrics to compare ambition across future NDC timeframes beyond 2030; and (d) evaluate implementation to determine whether enhanced pledges translate into realized emission reductions.

- Outcome measurement: Dichotomous enhancement indicator does not capture baseline ambition levels or the magnitude of change; countries with different starting points may appear similar in enhancement coding. - Scope: Focus on domestic determinants; international influences beyond climate finance are not systematically analyzed. - Sample/data constraints: Missing data for many parties’ updates and limited availability for some predictors; the most expansive regression uses a reduced subset of countries. Potential multicollinearity led to separate models and parsimonious specifications. - Timing heterogeneity: Different submission years may reflect evolving global knowledge and politics, complicating causal attribution. - Implementation not assessed: The study does not evaluate whether enhanced NDCs are implemented or over/underachieved, limiting inferences about real-world emissions outcomes. - Future-cycle comparability: Metrics tailored to 2030 targets may be harder to apply to future NDCs with different target years (e.g., 2035).