The Paris Agreement and NDCs: are the national mitigation targets sufficient to stay below the 1.5-2°C limit?

Short introduction on Mexico’s emissions

Although CO₂ is the driving force behind the temperature changes, other gases such as methane (CH₄) also contribute their share to global warming, for example through the exploitation of gas fields, and emissions by livestock. While methane is emitted much less than CO₂ on a global scale, it is a much stronger greenhouse gas (GHG). Scientists estimated the relative strength of the important Kyoto greenhouse gases so that we can convert all emissions to an equivalent of CO₂ emissions. For example, the emission of one ton of methane has approximately the warming effect of 25 tons of CO₂. The factor of 25 reflects the climate forcing on a 100-year time horizon, following the Global Warming Potential presented in the IPCC Fourth Assessment Report (AR4).

With greenhouse gas emissions of approximately the equivalent of 741.7 mega tonnes of CO₂ (Mt CO₂eq), Mexico contributed 1.55% to the global greenhouse gas emissions of 2017 (rank 12 - incl. EU27 on rank 3). All emissions estimates exclude emissions and absorption from land, which result from activities such as cutting down or planting of forests (Land Use, Land-Use Change and Forestry: LULUCF). Emissions from bunker fuels (international aviation and shipping) were also excluded, as they are not accounted for in national totals.

For 2030, Mexico’s global contribution to greenhouse gas emissions is projected to stay at a similar level of approximately 1.55% (872.0 mega tonnes of CO₂ equivalent / rank 11 - incl. EU27 on rank 4). The emissions projections for Mexico were derived by downscaling the Shared Socio-Economic Pathways’ (SSPs) “Middle-of-the-Road” baseline marker scenario SSP2. These pathways describe certain narratives of socio-economic developments and were, i.a., used to derive greenhouse gas emissions scenarios that correspond to these developments. SSP2 is a narrative with little shifts in socio-economic patterns compared to historical ones, and is connected to medium socio-economic challenges for both climate mitigation and adaptation. While different models were used for each storyline, per SSP (SSPs1-5) one model was chosen as representative “marker scenario”. As the emissions projections are not readily available on country-level, but national estimates are important, the pathways were downscaled in the aftermath. In 2017, Mexico represented 1.65% of the global population. Its Gross Domestic Product (GDP) in 2017 were 2.096% of the global GDP.

Looking at the highest contributing emissions sectors and gases separately, we find that in 2017 the highest contributing emissions sectors were Energy and Agriculture (71.1% and 13.9%). Amongst the greenhouse gases that are considered in the Kyoto Protocol, the strongest contributor with 72.7% was CO₂. This was followed by CH₄ emissions, with a significantly lower share of 19.3%. When not considering the sectors and gases independently, but the sector-gas combinations instead, Energy CO₂ and Agriculture CH₄ (66.4% and 8.7%) represented the largest emissions in 2017.

Greenhouse gas mitigation and Nationally Determined Contribution (NDC)

In 2015, the majority of countries agreed to the Paris Agreement (PA), with the goal of “Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change” (Article 2.1.a). Countries stated their pledges and targets towards achieving the PA’s goals in their Nationally Determined Contributions (NDCs). With Article 4.4 of the Paris Agreement, Parties decided that “Developed country Parties should continue taking the lead by undertaking economy-wide absolute emission reduction targets. Developing country Parties should continue enhancing their mitigation efforts, and are encouraged to move over time towards economy-wide emission reduction or limitation targets in the light of different national circumstances.”

In its updated 2020 NDC, Mexico communicates that “The mitigation component considers unconditional contributions, which will be implemented with the country’s own resources, and conditional contributions, which require the support of financial, technical and technological instruments, as well as capacity-building which will accelerate the implementation of mitigation actions across the country.” (NDC, p. 5). Its unconditional contributions consist of a “Reduction of 22% of greenhouse gas emissions (GHG) and 51% of black carbon emissions by 2030 as compared to the baseline business-asusual scenario (BAU).”, which could be enhanced to “A [conditional] reduction of up to 36% of GHG emissions and 70% of black carbon emissions by 2030 compared to the BAU scenario.” (NDC, p. 5).

Mexico further provides relevant quantitative information to ease the understanding of its mitigation contributions. “The projected BAU scenario to 2030, without any mitigation policy intervention, was quantified at 991 MtCO₂e [AR5].” (NDC, p. 22). Starting year of this BAU projection is 2013 (NDC, p. 22). The GWP is not provided in the NDC, but we assume the GWP from the previous submission to also apply to the updated NDC. In the NDC, the relative reductions are also given translated into absolute reductions compared to BAU emissions in 2030. “The reduction of unconditional emissions by 2030 translates into a reduction of approximately 210 MtCO₂e [AR5] that year, while compliance with conditional commitments would imply reductions of an additional 137 MtCO₂e [AR5].” (NDC, p. 22). This adds up to a conditional reduction of 347 MtCO₂eq AR5, while the absolute target emissions can be calculated to be 781 and 644 MtCO₂eq AR5 (subtracting the absolute reductions from BAU emissions). When checking the numbers that are provided in the NDC, a slight inconsistency arises, as 22% or 36% of 991 MtCO₂eq are 218 MtCO₂eq and 357 MtCO₂eq, respectively, which would reduce the targeted 2030 emissions. The projected BAU emissions in Mexico’s NDC include Land-Use Change and Forestry (LUCF) emissions, but exclude GHG absorptions by LUCF (NDC, p. 22). The availability of national estimates of emissions mitigation targets and pathways in line with countries’ NDCs is of great importance when, e.g., aggregating to global emissions to then derive, i.a., the resulting end-of-century warming levels.

In the country’s NDC, BAU emissions are provided per sector for several years, and projections for 2030 are -109 MtCO₂eq AR5 for LULUCF, 833 MtCO₂eq AR5 for the national emissions including LULUCF, and 942 MtCO₂eq AR5 when excluding LULUCF (NDC, p. 29). For an easier comparison with other contributions by other Parties, we recalculated the relative reductions compared to BAU and absolute target emissions to include both, emissions and absorptions from LUCF. For that purpose, we use the given absolute reductions and reference them to the BAU emissions including emissions and absorptions from LUCF that are additionally provided within Mexico’s NDC. This results in absolute target emissions of 623 MtCO₂eq AR5 or 486 MtCO₂eq AR5 (including LULUCF) in the unconditional and conditional case, corresponding to reductions by 25% or 40%. All main IPCC sectors are covered by Mexico’s mitigation contributions and stated explicitly in its NDC (Energy, IPPU, AFOLU, and Waste; NDC, p. 30). In terms of Kyoto GHGs, the NDC addresses CO₂, CH₄, N₂O, PFC, HFC, and SF₆ emissions (NDC, p. 30). The gas NF₃ is not mentioned as covered, but following PRIMAP-hist v2.1 HISTCR, no data are available for that gas, which has only been added to the Kyoto GHG basket for the second period of the Kyoto Protocol and is reported by few countries only. Therefore, the coverage of Mexico’s NDC is assessed as 100% of national emissions.

Regarding Article 6 of the PA (cooperation and markets), “Mexico expresses its interest in participating in international carbon markets under Article 6 of the Paris Agreement. It is expected that these transfers will support the country in increasing the target to 36% of emission reductions.” (NDC, p. 36).

The NDC-assessment is based on Mexico’s NDC submitted to the UNFCCC in December 2020.

The Figure below provides additional information, regarding both the baseline emissions used in our assessment and the quantified mitigated pathways for Mexico.

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Baseline emissions and mitigated emissions pathways based on the country’s Nationally Determined Contribution. In terms of national emissions, we look at the SSP2 baseline marker scenario, and the emissions of all IPCC sectors. Contributions from LULUCF are excluded (exclLU), and the emissions are based on GWPs from AR4. The left panel (a) shows the baseline emissions, indicating the contributions of the Kyoto Greenhouse Gases CO₂, CH₄, N₂O, and the basket of F-gases to the national emissions. If we could extract baseline data exclLU from the NDC, you can see their values as black squares (converted from GWP SAR to AR4 if needed). In the right panel (b), the quantified mitigated emissions pathways are shown, based on information from the country’s NDC and also on non-NDC emissions baselines, per target conditionality and range (marked un-/conditional best/worst). Even though not all countries have targets with different conditionalities or ranges, we need assumptions for all four cases to build one global pathway per conditionality plus range combination and to derive corresponding temperature estimates. Therefore, we indicate these four pathways here. Per combination, we performed several quantifications with differing assumptions and show the median and the minimal and maximal pathways here. Additionally, if we could quantify the targets based on data extracted purely from the NDC - or if the targets were directly given in absolute emissions, these targets are shown as squares (in the GWP originally given in the NDC).

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FIG 1

Data sources and further information

• Historical emissions: PRIMAP-hist v2.1 (Guetschow et al., 2016, 2019).
• Historical socio-economic data: PRIMAP-hist Socio-Eco v2.1 (Guetschow et al., 2019).
• Projected emissions and socio-economic data: downscaled SSPs (Guetschow et al., 2020, 2020).
• NDC quantifications: NDCmitiQ (Guenther et al., 2020, 2021).
• GDP is given in purchasing power parity (PPP).
• Main emissions sectors (Intergovernmental Panel on Climate Change, IPCC): Energy, Industrial Processes and Product Use (IPPU), Agriculture and LULUCF (Land Use, Land-Use Change and Forestry), also named AFOLU (Agriculture, Forestry and Other Land Use), and Waste.
• Kyoto GHG: basket of several GHGs, namely carbon dioxide (CO₂), Methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulphur hexafluoride (SF₆), and since the second Kyoto Protocol period (2013-20) additionally nitrogen fluoride (NF₃).
• Global Warming Potentials (GWPs): GHGs have very different warming potentials. To make them comparable and for aggregation purposes, GWPs are used (how much energy will 1 ton of a certain gas absorb over a defined period of time, relative to the same mass of CO₂?).