Analyse des sources d’émissions et des puits pour les trois principaux gaz à effet de serre par méthodes comparées montantes et descendantes : un outil incontournable pour l’évaluation du respect des engagements de l’Accord de Paris sur le Climat Le cas de l’Afrique

Depuis la deuxième moitié du XXème siècle, l’augmentation de la concentration des trois principaux gaz à effet de serre (GES) : le Dioxyde de Carbone (CO2), le Méthane (CH4) et le Protoxyde d’Azote (N2O) du fait des activités humaines a clairement été identifiée par la communauté scientifique comme la principale cause du récent forçage radiatif affectant l’équilibre des processus énergétiques du système terrestre. Ces perturbations anthropiques ont entre autres conséquences, une augmentation de la température annuelle moyenne globale à la surface de la Terre. Étant donné que les GES sont bien mélangés dans l’atmosphère, et du fait de la complexité des différents processus du transport atmosphérique, les conséquences du forçage radiatif anthropique induit par les principales zones émettrices de GES ne se produisent pas nécessairement directement sur ces territoires. Ainsi, l’Afrique est le continent qui est historiquement le moins responsable des émissions cumulées de GES. Pourtant, le dernier rapport du GIEC (AR6) a mis en évidence que cette région est l’une des zones qui est déjà les plus touchées au monde par les conséquences du changement climatique d’origine anthropique. Des articles pionniers sur les émissions anthropiques et le budget carbone de l’Afrique comme celui de Ciais et al. (2011) avaient aussi souligné que « l’Afrique augmentera probablement sa part d’émissions globales au cours des décennies à venir » (Canadell, 2009). Or ce continent est relativement peu étudié. C’est pourquoi, nous avons choisi de focaliser l’étude au centre de ce manuscrit sur le périmètre Africain, composé de 54 pays pour lesquels nous disposons de données. Notre objectif est d’effectuer une estimation des sources et des puits d’origine anthropique sur ce continent pour les trois principaux GES. Dans ce but, la méthodologie originale utilisée ici s’appuie d’une part, sur des données dites « montantes », c’est-à-dire des rapports nationaux officiels de pays, des inventaires statistiques et des modèles basés sur des processus chimiques et biogéochimiques. D’autre part, le deuxième volet de la méthode consiste en une comparaison de ces données « montantes », avec des inversions de la méthode dite « descendante », c’est-à-dire des données satellite. Nous conduisons cette analyse pour les trois dernières décennies (1990-2018) en vue de dégager des tendances. Le but de cette étude est aussi d’apporter des éléments de réponse à la problématique suivante : comment l’état actuel des outils scientifiques peut contribuer à évaluer le respect des engagements de l’Accord de Paris pour des pays ne faisant pas partie de l’Annexe I, et en particulier dans le cas des pays Africains ? Pour apporter des éléments de réponse à cette question importante du point de vue scientifique mais aussi sociétal, le chapitre 1 présente les principales caractéristiques du CO2, du CH4 et du N2O en ce qui concerne le forçage du budget radiatif de la planète Terre. Ce premier chapitre contextualise le monitoring des sources et des puits de GES d’origine anthropique dans le cadre du dispositif de Monitoring, Reporting et de Vérification de l’Accord de Paris. Le chapitre 2 est une analyse originale des tendances pour les sources et pour les puits de GES au cours des trente dernières années, centrée sur le cas Africain. Le chapitre 3 est une discussion élargie proposant des perspectives plus globales sur le rôle des outils scientifiques pour une évaluation indépendante des pays du respect des engagements de l’Accord de Paris.Since the second part of the 20th century, the role of three main greenhouse gases (GHG) : Carbon Dioxide (CO2), Methane (CH4) and Nitrous Oxide (N2O) has been clearly established by the scientific community as the main cause of the recent forcing of the Earth energetic processes from human-induced activities, resulting among other disturbances in an increase of the annual mean surface temperatures. As GHG are well-mixed in the atmosphere and due to the complexity of atmospheric transport processes, the main emitters do not necessarily face the consequences of the additional radiative forcing that they directly induce. In this study, we restrict the analysis to CO2, CH4 and N2O because they are the most important GHG in the atmosphere. For the following-up of GHG, the Paris Agreement has a device named the “Enhanced Transparency Framework “(ETF). Within the ETF, countries have to report annually or biannually their GHG emissions and removals starting in 2023 within the Global Stocktake (GST). The ETF is based on the Monitoring, Reporting and Verification (MRV) provisions of the PA, aiming at the measurement of GHG for the PA signatory countries, at the centralization of the regularly updated country-reports, and at the verification of the respect of the countries ex ante vs. ex post pledges. This GST will represent a challenge for many Non-Annex I countries, including Africa, where emissions and removals in national inventories have been irregular since the UNFCCC creation in 1992. The literature tends to be scarce about GHG emissions from African countries, usually thought to be small emitters by non-experts. However, the recent Sixth Assessment Report (AR6) of the IPCC (Intergovernmental Panel on Climate Change) underlines with high confidence that the speed of surface temperature increase in Africa has already been higher than elsewhere in the world due to anthropogenic emissions (IPCC Working Group I, 2021). Recent analyses also predict a fast increase of African emissions correlated with its demographic growth, which is the fastest in the world. Pioneering papers on anthropogenic emissions and the carbon balance in Africa like the one of Ciais et al. (2011), already underlined that “Africa is likely to increase its share of global emissions over the coming decades” (Canadell, 2009). That is the reason why we chose to strictly restrict to Africa the scope of our central analysis in the original study of the present manuscript. Our aim is to assess African CO2, CH4 and N2O anthropogenic emissions and removals using bottom-up datasets (inventories and process-based models) and to compare them with top-down inversions coming from satellites over three decades (1990-2018) in order to deliver trends’ analyses. The purpose of this analysis is also to discuss the following main question: how can the current state of science help for the evaluation of the Respect of the Paris Agreement (PA) in Non-Annex I countries, and most specifically in Africa? Chapter 1 presents CO2, CH4 and N2O main features and impacts with regards to the Earth Radiative Budget forcing, and contextualizes the scientific monitoring of GHG emissions and removals from anthropogenic origins in the climate policy context of the Monitoring, Reporting and Verification (MRV) provisions of the PA. Chapter 2 delivers an original analysis of GHG emissions and removals trends over the last three decades for the case of Africa. Chapter 3 discusses more broadly the conclusions of the African case analysis and proposes larger perspectives from both a scientific and from a climate policy view for future developments in the evaluation of the respect of the PA

Greenhouse gas emissions and their trends over the last 3 decades across Africa

International audienceA key goal of the Paris Agreement (PA) is to reach net-zero greenhouse gas (GHG) emissions by 2050 globally, which requires mitigation efforts from all countries. Africa's rapidly growing population and gross domestic product (GDP) make this continent important for GHG emission trends. In this paper, we study the emissions of carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2 O) in Africa over 3 decades (1990-2018). We compare bottom-up (BU) approaches, including United Nations Convention Framework on Climate Change (UNFCCC) national inventories, FAO, PRIMAP-hist, process-based ecosystem models for CO 2 fluxes in the land use, land use change and forestry (LULUCF) sector and global atmospheric inversions. For inversions, we applied different methods to separate anthropogenic CH 4 emissions. The BU inventories show that, over the decade 2010-2018, fewer than 10 countries represented more than 75 % of African fossil CO 2 emissions. With a mean of 1373 Mt CO 2 yr-1 , total African fossil CO 2 emissions over 2010-2018 represent only 4 % of global fossil emissions. However, these emissions grew by +34 % from 1990-1999 to 2000-2009 and by +31 % from 2000-2009 to 2010-2018, which represents more than a doubling in 30 years. This growth rate is more than 2 times faster than the global growth rate of fossil CO 2 emissions. The anthropogenic emissions of CH

e-courses for masters: online fundamental semester for master on climate – related sciencedisciplines

International audienceThe Climate Graduate School of the Institut Pierre-Simon Laplace (CGS-IPSL) iscurrently developing a series of seven courses online for Master students. On these sevencourses of 3 ECTS each, three have a strong focus on the ocean: Dynamics of the Ocean andAtmosphere; Contemporary Biogeochemical Cycles; Study of Paleo-climates. Each course is ledby a pair of university teachers specialists in their field accompanied by a pedagogical andgraphic team in order to design all resources specifically adapted to graduate students andonline education. Indeed, our first goal is to open these courses as self-paced learning underthe IPSL Learning Management System (Moodle) to students who will be joining CGS-IPSLmasters without having all the prerequisites so that they can update their academicbackground. These courses could also be open to second year CGS IPSL Master students whoaimed at acquiring credits on a secondary theme not necessarily developed in their master (e.g.on biogeochemistry for students registered in an ocean – climate master). Finally all the e-resources developed will be made available at least to the educational community of the CGS-IPSL that include several Universities in and around Paris (Sorbonne Universite, Paris Saclay,Universite Versailles Saint Quentin, Université Paris Est Créteil...) in order to reuse theseresources for higher education either on-line or face-to-face courses. The courses will beavailable in both French and English so that international students can have access to these e-resources

e-courses for masters: online fundamental semester for master on climate – related sciencedisciplines

International audienceThe Climate Graduate School of the Institut Pierre-Simon Laplace (CGS-IPSL) iscurrently developing a series of seven courses online for Master students. On these sevencourses of 3 ECTS each, three have a strong focus on the ocean: Dynamics of the Ocean andAtmosphere; Contemporary Biogeochemical Cycles; Study of Paleo-climates. Each course is ledby a pair of university teachers specialists in their field accompanied by a pedagogical andgraphic team in order to design all resources specifically adapted to graduate students andonline education. Indeed, our first goal is to open these courses as self-paced learning underthe IPSL Learning Management System (Moodle) to students who will be joining CGS-IPSLmasters without having all the prerequisites so that they can update their academicbackground. These courses could also be open to second year CGS IPSL Master students whoaimed at acquiring credits on a secondary theme not necessarily developed in their master (e.g.on biogeochemistry for students registered in an ocean – climate master). Finally all the e-resources developed will be made available at least to the educational community of the CGS-IPSL that include several Universities in and around Paris (Sorbonne Universite, Paris Saclay,Universite Versailles Saint Quentin, Université Paris Est Créteil...) in order to reuse theseresources for higher education either on-line or face-to-face courses. The courses will beavailable in both French and English so that international students can have access to these e-resources

e-courses for masters: online fundamental semester for master on climate – related sciencedisciplines

International audienceThe Climate Graduate School of the Institut Pierre-Simon Laplace (CGS-IPSL) iscurrently developing a series of seven courses online for Master students. On these sevencourses of 3 ECTS each, three have a strong focus on the ocean: Dynamics of the Ocean andAtmosphere; Contemporary Biogeochemical Cycles; Study of Paleo-climates. Each course is ledby a pair of university teachers specialists in their field accompanied by a pedagogical andgraphic team in order to design all resources specifically adapted to graduate students andonline education. Indeed, our first goal is to open these courses as self-paced learning underthe IPSL Learning Management System (Moodle) to students who will be joining CGS-IPSLmasters without having all the prerequisites so that they can update their academicbackground. These courses could also be open to second year CGS IPSL Master students whoaimed at acquiring credits on a secondary theme not necessarily developed in their master (e.g.on biogeochemistry for students registered in an ocean – climate master). Finally all the e-resources developed will be made available at least to the educational community of the CGS-IPSL that include several Universities in and around Paris (Sorbonne Universite, Paris Saclay,Universite Versailles Saint Quentin, Université Paris Est Créteil...) in order to reuse theseresources for higher education either on-line or face-to-face courses. The courses will beavailable in both French and English so that international students can have access to these e-resources

e-courses for masters: online fundamental semester for master on climate – related sciencedisciplines

International audienceThe Climate Graduate School of the Institut Pierre-Simon Laplace (CGS-IPSL) iscurrently developing a series of seven courses online for Master students. On these sevencourses of 3 ECTS each, three have a strong focus on the ocean: Dynamics of the Ocean andAtmosphere; Contemporary Biogeochemical Cycles; Study of Paleo-climates. Each course is ledby a pair of university teachers specialists in their field accompanied by a pedagogical andgraphic team in order to design all resources specifically adapted to graduate students andonline education. Indeed, our first goal is to open these courses as self-paced learning underthe IPSL Learning Management System (Moodle) to students who will be joining CGS-IPSLmasters without having all the prerequisites so that they can update their academicbackground. These courses could also be open to second year CGS IPSL Master students whoaimed at acquiring credits on a secondary theme not necessarily developed in their master (e.g.on biogeochemistry for students registered in an ocean – climate master). Finally all the e-resources developed will be made available at least to the educational community of the CGS-IPSL that include several Universities in and around Paris (Sorbonne Universite, Paris Saclay,Universite Versailles Saint Quentin, Université Paris Est Créteil...) in order to reuse theseresources for higher education either on-line or face-to-face courses. The courses will beavailable in both French and English so that international students can have access to these e-resources

e-courses for masters: online fundamental semester for master on climate – related sciencedisciplines

International audienceThe Climate Graduate School of the Institut Pierre-Simon Laplace (CGS-IPSL) iscurrently developing a series of seven courses online for Master students. On these sevencourses of 3 ECTS each, three have a strong focus on the ocean: Dynamics of the Ocean andAtmosphere; Contemporary Biogeochemical Cycles; Study of Paleo-climates. Each course is ledby a pair of university teachers specialists in their field accompanied by a pedagogical andgraphic team in order to design all resources specifically adapted to graduate students andonline education. Indeed, our first goal is to open these courses as self-paced learning underthe IPSL Learning Management System (Moodle) to students who will be joining CGS-IPSLmasters without having all the prerequisites so that they can update their academicbackground. These courses could also be open to second year CGS IPSL Master students whoaimed at acquiring credits on a secondary theme not necessarily developed in their master (e.g.on biogeochemistry for students registered in an ocean – climate master). Finally all the e-resources developed will be made available at least to the educational community of the CGS-IPSL that include several Universities in and around Paris (Sorbonne Universite, Paris Saclay,Universite Versailles Saint Quentin, Université Paris Est Créteil...) in order to reuse theseresources for higher education either on-line or face-to-face courses. The courses will beavailable in both French and English so that international students can have access to these e-resources