Taking stock of national climate policies to evaluate implementation of the Paris Agreement

The Paris Agreement aims to limit global warming to well below 2 °C and pursue efforts toward 1.5 °C. Success depends on national policy implementation framed through NDCs, updated every five years but not legally binding. Prior analyses indicate that current NDCs and national policies fall short of Paris-aligned ambition. Policymakers require clear, country-specific insights into the effects of implemented national policies for the upcoming 2023 global stocktake. This study addresses a gap in peer-reviewed literature by assessing global and country-level impacts of national climate policies based on a comprehensive policy inventory translated into inputs for multiple integrated assessment models (IAMs). It quantifies the implementation gap (policies vs NDCs) and ambition gap (NDCs vs Paris-consistent pathways), presenting results for seven large economies and the world, and decomposes drivers using the Kaya identity.

Previous IAM studies have predominantly explored cost-optimal strategies to meet temperature goals, often simplifying national policies as uniform emissions targets or carbon prices. While some assessments included more explicit policy formulations or focused on NDCs, these were typically single-model studies or lacked comprehensive policy detail. The post-Paris policy landscape necessitates analysis of specific policy contributions. The current work builds on and extends literature by employing a multi-model approach with explicit national policy representation, comparing national policy outcomes to NDCs and 1.5–2 °C pathways, and benchmarking global IAM outputs against national models.

The analysis was conducted within the CD-LINKS project using nine global IAMs and ten national models for seven major G20 economies (Brazil, China, EU, India, Japan, Russian Federation, United States). A detailed, open-access inventory of implemented national climate and energy policies (cut-off 31 December 2016) was compiled with national experts, from which approximately ten high-impact policies per G20 country were selected based on expected emissions impact, formal adoption, and implementability. These policies were translated into model inputs (e.g., carbon prices, standards, targets), represented as explicitly as feasible; in some cases, aspirational targets backed by instruments (e.g., feed-in tariffs, renewable auctions) were used. When instruments ended before target years, continuation was assumed to the target year. Where countries were aggregated in model regions, policy indicators were applied to countries with policies, business-as-usual to others. Some models with less sector detail used indicators calibrated from detailed models or literature. Four core scenarios were run starting from SSP2: (1) No new policies (no post-2010 climate policies), (2) National policies (implemented domestic policies), (3) NDCs (full implementation of conditional NDCs), and (4) cost-optimal 2 °C and 1.5 °C pathways (policies until 2020 then least-cost measures to meet global carbon budgets of 1000 and 400 GtCO2 for 2011–2100, respectively, achieving >66% probability of staying below temperature limits). Policy impacts were decomposed using indicators derived from the Kaya identity (low-carbon share of final energy, final energy intensity, and carbon intensity), alongside total GHG emissions and mitigation costs per GDP. Global IAM outputs were compared to analogous national model runs for coherence. Results are reported as medians with 10th–90th percentile ranges across models, with scenario differences computed per model before aggregating percentiles. Adjustments were applied for missing sectors or gases in specific models using averages from others (e.g., AFOLU for DNE21+, F-gases for COPPE-COFFEE) to ensure comparability.

• Under No new policies, global GHG emissions rise to 63.9 GtCO2eq by 2030 (61.0–69.1). Implemented national policies reduce 2030 emissions to 59.3 GtCO2eq (58.4–63.7), a 5.3% (3.8–7.9%) reduction relative to No new policies, covering 15.4% (10.8–19.0%) of the 2 °C gap and 11% (7.6–15.9%) of the 1.5 °C gap. • The median global emissions gap between National policies and cost-optimal pathways in 2030 is 22.4 GtCO2eq (13.6–29.6) for 2 °C (36% reduction needed) and 28.2 GtCO2eq (19.8–42.2) for 1.5 °C (45% reduction needed). • Full implementation of conditional NDCs decreases 2030 emissions to 51.9 GtCO2eq (50.4–57.4), leaving a global implementation gap (National policies → NDCs) of 7.7 GtCO2eq (5.3–9.7). Implementing NDCs reduces the 2 °C ambition gap by roughly one third (remaining median gaps: 16.5 GtCO2eq for 2 °C; 21.2 GtCO2eq for 1.5 °C). • To close the 2030 implementation gap (to NDCs), the low-carbon share of final energy must increase by 2.8 percentage points (pp) (1.5–4.7) and energy intensity must improve by 12.7% (9.1–16.1) versus National policies. To reach 2 °C from National policies, the non-fossil share must rise by 6.9 pp (4.0–12.3) and energy intensity improve by 9.6% (4.8–24.7); for 1.5 °C, 13.0 pp (7.2–24.0) and 17.5% (12.5–26.8). • Sectoral effects: Most reductions under National policies target CO2 from energy supply and transport; AFOLU contributes notably in Brazil. About 45% (30–70%) of reductions occur in OECD countries. • Country-level policy impacts relative to No new policies (median): United States 6% (absolute 0.4 GtCO2eq), EU 9% (0.5 Gt), China 5% (0.7 Gt), India 3% (0.1 Gt), Japan 7% (0.1 Gt), Brazil 3% (0.0–0.2 Gt), Russian Federation ~0%. Implementation gaps to NDCs vary: small for China, India, Japan, Russia; larger for EU, United States, Brazil (e.g., US 31% reduction needed from National policies to NDCs; 2.1 GtCO2eq). • Emissions gaps by country (National policies → 2 °C; median absolute): China 5.9 Gt (41%), US 2.3 Gt (37%), EU 1.6 Gt (31%), India 2.1 Gt (33%), Japan 0.4 Gt (25%), Brazil 0.7 Gt (40%), Russia 0.9 Gt (34%). For 1.5 °C, gaps are larger (e.g., China 7.2 Gt, 53%). • Costs: Global mitigation costs per GDP by 2030 are small under National policies, rising to 0.9% (0.3–2.2) for 2 °C and 1.3% (1.0–4.0) for 1.5 °C. Additional median costs per GDP to close national gaps to 2 °C range from ~0.5% (EU) to 2.8% (Russia); for 1.5 °C, 0.6–3.4%. • Mid-century indicator (2011–2050 cumulative emissions relative to 2010 annual emissions) shows substantial gaps to 2 °C/1.5 °C trajectories in most G20 economies; EU, US, Brazil NDC-consistent projections to 2050 are relatively closer to 2 °C than others, but large efforts remain necessary.

The analysis demonstrates that all assessed countries face either an implementation gap (policies insufficient to meet NDCs) or an ambition gap (NDCs insufficient for well-below 2 °C). Without enhanced ambition, current national policies fall short of both Paris objectives and even the collective NDCs. Insufficient near-term action risks higher long-term transformation rates, stranded assets, lock-in, and greater mitigation costs. While the 2 °C/1.5 °C scenarios assume cost-optimal global allocation, equity-based effort-sharing would imply more stringent allowances for high-income regions (EU, Japan, Russia, US) and more lenient ones for low-income regions (e.g., India), potentially altering the perceived national gaps. Policy redesign should strengthen coherence and coverage across sectors (notably industry and freight), combining economy-wide instruments (e.g., pricing) with targeted technology policies to accelerate renewable deployment and efficiency gains. International cooperation via carbon markets or climate finance can reconcile cost-effectiveness with equity. The Kaya-based indicators offer practical guidance for closing gaps: scale up non-fossil energy shares and improve final energy intensity, with emphasis on efficiency in emerging and fossil-fuel-dependent economies.

This study provides a comprehensive, multi-model assessment of implemented national climate policies against NDCs and Paris-consistent pathways using a detailed policy inventory. It quantifies substantial global and national implementation and ambition gaps and identifies the scale of changes in energy mix and efficiency needed by 2030. Key contributions include translating concrete national policies into IAM scenarios, benchmarking against national models, and offering indicator-based guidance to inform the 2023 global stocktake and NDC enhancement. Future research should deepen model representation of specific policy instruments, expand country and sectoral coverage (including actors and institutions), analyze individual policy impacts and cost-effectiveness, and integrate equity-based allocation with financing mechanisms to support realistic, politically feasible pathways.

The assessment is limited to G20 economies due to model aggregation, covering about 75% of 2010 global GHG emissions, with other high-impact policy countries (~5% of 2010 emissions) excluded. The policy inventory includes implemented and planned policies up to 31 December 2016; subsequent policy updates (e.g., EU climate actions, US vehicle standards revision) are not captured. IAMs vary in sectoral and regional detail; some policies could not be fully represented (implementation rates of high-impact policies across models ranged from 42% to 94%), and certain sectors/gases were supplemented using averages from other models (e.g., AFOLU, F-gases). Models often assume representative agents and may not capture detailed socio-political dynamics, behavioral heterogeneity, or phenomena like the green paradox. Uncertainty in results is driven largely by socioeconomic assumptions (GDP, population), historical emissions calibration, policy representation differences, and structural model heterogeneity; AFOLU emissions are particularly uncertain. National model comparisons reveal coherence in trends but differences in absolute levels.