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Quantifying greenhouse gas emissions from pledges of the Paris Agreement

19-01-2018

A new study analyzes national greenhouse gas emission reduction targets for the 2025-2030 horizon as measured by Nationally Determined Contributions (NDC). It estimates that NDCs project global emissions in the range of 56.8 to 66.5 GtCO2eq / yr, which is higher than previous estimates. The range of uncertainty is wider than most of those published so far, which is mainly explained by the fact that a set of GDP scenarios are envisaged rather than a single scenario for the countries that have expressed their goal as a reduction in the carbon intensity of their economy. This study, conducted by Hélène Benveniste and colleagues from Institut Pierre-Simon Laplace (IPSL), the International Center for Research on Environment and Development (CIRED) and the University Grenoble-Alpes is published in Environmental Research Letters.

The goal of the Paris Agreement on climate change is to keep global temperature rise to well below 2 °C above pre-industrial levels. The mitigation action in the Paris Agreement relies on the Nationally Determined Contributions (NDCs), which summarize domestic objectives for greenhouse gases (GHG) emissions reductions for the 2025-2030 time horizon.


A few studies have estimated global emissions levels that would result from NDCs in 2030. As summarized in the UNEP Gap Report 2017, they would be in the range of 49.5 – 56.2 Gt CO2eq/year. This range compares to 51.9 CO2eq/year today, and to the level that would be compatible with the 2°C target estimated around 42 CO2eq/year. This estimation led the authors of the report to conclude « the gap between the reductions needed and the national pledges made in Paris is alarmingly high. ».


A new study, published in Environmental Research Letters, shows that this warning may still be an understatement of the situation. The study, conducted by Hélène Benveniste and colleagues from the Institute Pierre-Simon Laplace, the Centre International de Recherche sur l'Environnement et le Développement and Université Grenoble-Alpes, performed an analysis of NDCs at a highly disaggregated level (103 countries are treated individually and all countries are considered). It provides an analysis of uncertainty sources and their impacts on 2030 global GHG emissions based on the sole and full achievement of the NDCs. This analysis estimates that NDCs project into a range of 56.8 to 66.5 Gt CO2eq/year emissions in 2030 (90% confidence interval), which is higher than previous estimates, and with a larger uncertainty range.


The uncertainty range is larger than most of those published so far, essentially because a range of GDP scenarios are considered rather than a single scenario for countries that have expressed their target partly as a reduction in the carbon intensity of their economy.


The estimate is also higher than previous estimates because, unlike previous studies, it does not consider the impact of current policies that are not (yet) reflected into a high-level NDC target. It interprets the absolute level of GHG emissions implied literally by the NDCs. It is conceivable that current economic trends and/or current policies result in smaller emissions than implied by the NDCs for some countries. Conversely, some other countries may experience higher emissions than predicted. The analysis thus informs on what would emissions be if NDCs targets are taken “at face value”, i.e. if they would be exactly met. Such information can be used to highlight the need for NDCs update, and to track how updates would reduce 2030 emissions and the associated uncertainty. For instance, China presented a rather conservative intensity target in its NDC, and some analysists consider it likely to be overachieved.


Despite these uncertainties, the study shows that NDCs robustly shift GHG emissions towards emerging and developing countries and reduce international inequalities in per capita GHG emissions.


To exploit the strengths of the methodology, namely its high country resolution, its flexibility, and its transparency, the projections and code are made available for other teams to reproduce, improve or update the analysis. By monitoring actual GHG emissions against the projections, it will be possible to assess which NDCs are over- or underachieved. The approach also allows updating the projected emissions when new data become available or when new NDCs are submitted as part of the stocktake and revision process of the Paris Agreement.


Figure présentant les trajectoires types d’émissions de gaz à effet de serre pour différents niveaux de réchauffement climatique et intervalle d’émissions résultant des engagements des pays exprimés dans les NDC. L’écart entre notre évaluation et celle de l’UNEP provient du fait que l’UNEP inclut des modélisations des changements en cours alors que nous ne considérons que les engagements en émissions explicités dans les NDC. GICN, UNEP



Estimate the GHG emissions in 2030

The NDC app: Estimating GHG emissions in 2030



Source

Impacts of nationally determined contributions on 2030 global greenhouse gas emissions: uncertainty analysis and distribution of emissions , Hélène Benveniste, Olivier Boucher, Céline Guivarch, Hervé Le Treut, and Patrick Criqui, Environ. Res. Lett., Vol. 13,  014022, 2018.



Contacts

Hélène Benveniste , IPSL et Woodrow Wilson School, Université de Princeton (USA)

Céline Guivarch , Centre International de Recherche sur l’Environnement et le Développement (CIRED)

Olivier Boucher , Institut Pierre-Simon Laplace (IPSL), Tél. : 01 44 27  47 63

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