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Der erste, vom 2015 gegründeten unabhängigen Netzwerk von Mittelmeer-Experten für Klima- und Umweltveränderungen (MedECC) erstellte Bewertungsbericht für den Mittelmeerraum (MAR1), wurde im November 2020 veröffentlicht. MAR1 bewertet die besten wissenschaftlichen Erkenntnisse über Klima- und Umweltveränderungen und die damit verbundenen Risiken im Mittelmeerraum, um sie politischen Entscheidungsträgern, Stakeholdern und Bürgern zugänglich zu machen. Der Bericht enthält eine Zusammenfassung für politische Entscheidungsträger (Summary for Policymakers, SPM), die die Kernaussagen des MAR1 zusammenfasst, der ursprünglich in englischer Sprache und hier in der deutschen Fassung veröffentlicht wurde. 190 Wissenschaftler aus 25 Ländern haben den Bericht verfasst, alle haben ihren Beitrag in ihrer Eigenschaft als Einzelpersonen und ohne finanzielle Vergütung geleistet. Das UNEP/MAP - Sekretariat des Übereinkommens von Barcelona arbeitet über sein Regionales Aktivitätszentrum Plan Bleu und das Sekretariat der Union für das Mittelmeer partnerschaftlich zusammen, um MedECC zu unterstützen und zur Schaffung eines soliden und transparenten wissenschaftlichen Bewertungsprozesses beizutragen., Preferred citation: Zitierweise für dieses Dokument: MedECC – Zusammenfassung für politische Entscheidungsträger 2020 In: Klima- und Umweltveränderungen im Mittelmeerbecken – Aktuelle Situation und Risiken für die Zukunft (Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future). Erster Sachstandsbericht für den Mittelmeerraum [Cramer W., Guiot J., Marini K. (Hrsg.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, Frankreich, S. 11-40, doi: 10.5281/zenodo.7081907

Il primo Rapporto di Valutazione del Mediterraneo (MAR1), preparato dalla rete indipendente di esperti mediterranei sui cambiamenti climatici e ambientali (MedECC) è stato pubblicato nel novembre 2020. MAR1 valuta le migliori conoscenze scientifiche sui cambiamenti climatici e ambientali e sui rischi associati nella regione del Mediterraneo, al fine di renderle disponibili ai responsabili politici, agli stakeholder e ai cittadini. Il rapporto comprende una Sintesi per i decisori politici (SPM) che coglie i messaggi chiave del MAR1, originariamente pubblicato in inglese e qui nella sua versione italiana. Il rapporto è stato redatto da 190 scienziati di 25 Paesi, che hanno contribuito individualmente e senza alcun compenso finanziario. L'UNEP/MAP - Segretariato della Convenzione di Barcellona, attraverso il suo Centro di attività regionale Plan Bleu, e il Segretariato dell'Unione per il Mediterraneo, lavoranno in partenariato per sostenere MedECC e contribuire alla creazione di un processo di valutazione scientifica solido e trasparente., Preferred Citation: Sintesi per i Decisori Politici come: Sintesi per i Decisori Politici. MedECC 2020 Summary for Policymakers. In: Climate and Environmental Change in the Mediterranean Basin - Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (ed.)] Unione per il Mediterraneo, Plan Bleu, UNEP/MAP, Marsiglia, Francia, pp 11-40, doi: 10.5281/zenodo.7515876.

Tree-ring widths represent the most commonly used proxy to reconstruct the climate of the last millennium at high resolution, thanks to their large-scale availability. The approach often relies on a relationship between tree-ring width series and climate estimated on the basis of a linear regression. The underlying linearity and stationarity assumptions may be inadequate. Dendroclimatic process-based models, such as MAIDEN (Modeling and Analysis In DENdroecology), may be able to overcome some of the limitations of the statistical approach. MAIDEN is a mechanistic ecophysiological model that simulates tree-ring growth starting from surface air temperature, precipitation and CO2 concentration daily inputs. In this study, we successfully include the MAIDEN model into a data assimilation procedure as a proxy system model to robustly compare the outputs of an Earth system model with tree-ring width observations and provide a spatially-gridded reconstruction of continental temperature, precipitation and winds in the mid to high latitudes of the Southern Hemisphere over the past centuries. More specifically, we evaluate the benefits of using process-based tree-growth models such as MAIDEN for reconstructing past climate with data assimilation compared to the commonly used linear regression. The comparison of the reconstructions with instrumental data indicates an equivalent skill of both the regression- and process-based proxy system models in the data assimilation framework. Nevertheless, the MAIDEN model still brings important advantages that could result in more robust reconstructions beyond the instrumental era. Moreover, improvements continuously made in such models or in their calibration procedure also offer encouraging perspectives. Important steps have thus been made to demonstrate that using a process-based model like MAIDEN as a proxy system model is a promising way to improve the large-scale climate reconstructions with data assimilation.

The First Mediterranean Assessment Report (MAR1) prepared by the independent network of Mediterranean Experts on Climate and environmental Change (MedECC) is now published.MAR1 assesses the best available scientific knowledge on climate and environmental change and associated risks in the Mediterranean Basin in order to render it accessible to policymakers, stakeholders and citizens.The report includes a Summary for Policymakers (SPM), which comprises the key messages of the MAR1. The text of the SPM has been approved during a Plenary Session of MedECC Stakeholders on September 22, 2020. The report has been written by 190 scientists from 25 countries, all contributing in individual capacity and without financial compensation.The UNEP/MAP – Barcelona Convention Secretariat, through its Plan Bleu Regional Activity Center, and the Secretariat of the Union for the Mediterranean work in partnership to support MedECC, and to contribute to establish a sound and transparent scientific assessment process.

International audience; Aix-Marseille Provence, a large metropolis located on the shores of the Mediterranean, reveals multiple social and environmental issues. This book aims to question the challenges of sustainable development in such a coastal metropolisMediterranean in the face of the challenge of climate change.Based on the scientific knowledge gathered within the research collective of the OT-Med Laboratory of Excellence,this work presents, from an interdisciplinary perspective, an inventory of environmental issuesof this metropolis in order to best answer the questions of managers and public decision-makers. We offer the readeran interdisciplinary synthesis of "local science" made available to all: urban space, soils,biodiversity, sea and coast, atmosphere and climatology, risks, protected areas, etc. Academic referencebut also a gateway to society, the economy and the management of environments, this book was designed to communicate dataenvironmental issues that concern Marseille to the greatest number and in an accessible language. It allows betterknow the current challenges posed by climate change, the actions already carried out or in progress, and the solutions stillto invent.; Aix-Marseille Provence, grande métropole située sur les bords de la Méditerranée, révèle de multiples questions sociales et environnementales. Cet ouvrage vise à questionner les enjeux du développement durable d’une telle métropole littoraleméditerranéenne face au défi du changement climatique.Sur la base des connaissances scientifiques rassemblées au sein du collectif de recherche du Laboratoire d’Excellence OT-Med,cet ouvrage présente, dans une perspective interdisciplinaire, un état des lieux sur la problématique environnementalede cette métropole afin de répondre au mieux aux interrogations des gestionnaires et décideurs publics. On offre au lecteurune synthèse interdisciplinaire de « science locale » mise à la portée de tous : sont examinés l’espace urbain, les sols, labiodiversité, la mer et le littoral, l’atmosphère et la climatologie, les risques, les espaces protégés, etc. Référence académiquemais aussi passerelle vers la société, l’économie et la gestion des milieux, ce livre a été conçu pour communiquer les donnéesenvironnementales actuelles qui concernent Marseille au plus grand nombre et dans un langage accessible. Il permet de mieuxconnaître les défis actuels posés par le changement climatique, les actions déjà réalisées ou en cours, et les solutions encoreà inventer.

International audience; Virtually all sub-regions of the Mediterranean Basin, on land and in the sea, are impacted by recent anthropogenic changes in the environment. The main drivers of change include climate (temperature, precipitation, atmospheric circulation, extreme events, sea-level rise, sea water temperature, salinity and acidification), population increase, pollution, unsustainable land and sea use practices and non-indigenous species. In most areas, both natural ecosystems and human livelihoods are affected. Due to global and regional trends in the drivers, impacts will be exacerbated in the coming decades, especially if global warming exceeds 1.5 to 2°C above the pre-industrial level. Significantly enhanced efforts are needed in order to adapt to inevitable changes, mitigate change drivers and increase resilience.

The 4.2 ka BP event is defined as a phase of environmental stress characterized by severe and prolonged drought of global extent. The event is recorded from the North Atlantic through Europe to Asia, leading scientists to evoke a 300-yr global mega-drought. Focusing on the Mediterranean and the Near East, this abrupt climate episode radically altered precipitation, with an estimated 30–50 % drop in precipitation in the eastern basin. While many studies reveal similar trends in the northern Mediterranean (from Spain to Turkey and the northern Levant), data from northern Africa and central/southern Levant are more nuanced, suggesting a weaker imprint of this climate shift on the environment and/or different climate patterns. Here, we provide a synthesis of environmental reconstructions for the Levant and show that, while the 4.2 ka BP event also corresponds to a drier period, a different climate pattern emerges in the central/southern Levant, with two dry phases framing a wetter period, suggesting a W-shaped event, particularly well defined by records from the Dead Sea area.

International audience; The United Nations Framework Convention on Climate Change Paris Agreement of December 2015 aims to maintain the global average warming well below 2°C above the preindustrial level. In the Mediterranean basin, recent pollen-based reconstructions of climate and ecosystem variability over the past 10,000 years provide insights regarding the implications of warming thresholds for biodiversity and land-use potential. We compare scenarios of climate-driven future change in land ecosystems with reconstructed ecosystem dynamics during the past 10,000 years. Only a 1.5°C warming scenario permits ecosystems to remain within the Holocene variability. At or above 2°C of warming, climatic change will generate Mediterranean land ecosystem changes that are unmatched in the Holocene, a period characterized by recurring precipitation deficits rather than temperature anomalies.

International audience

International audience; Initiated by the French community, the HyMeX international project aims to improve our understanding of water cycle in the Mediterranean, its variability from meteorological event to seasonal and interannual scales, and its characteristics over a decade in a context of global change. The project is motivated by the role of mesoscale processes, coupled between the atmosphere, land and sea, on the climate systemand the onset of extreme hydro-meteorological events (precipitation and flash-flooding, strong winds and ocean convection, heat waves and droughts). The project also aims to assess the consequences of these extreme events on the social and economic vulnerability of this region and adaptability.; D'initiative française, le projet international HyMeX a pour objectif d'améliorer la compréhension du cycle de l'eau en Méditerranée, de sa variabilité, de l'échelle de l'événement météorologique aux échelles saisonnières et interannuelles, et de ses caractéristiques sur une décennie, dans un contexte de changement global. Le projet est motivé par le rôle déterminant des processus de mésoéchelle, couplés entre l'atmosphère, la mer et la terre, sur la variabilité du système climatique et sur le déclenchement d'événements hydrométéorologiques extrêmes (précipitations et inondations, vents forts et convection océanique, canicules et sécheresses). Le projet vise enfin à évaluer les conséquences de ces événements extrêmes sur la vulnérabilité sociale et économique de cette région et sa capacité d'adaptation.

A data base of 236 reference sites throughout the North Atlantic and adjacent subpolar basins has been established to define the relations between the assemblages of organic-walled dinoflagellate cysts and sea-surface conditions, and to develop transfer functions for quantitative reconstructions of past temperature, salinity and seasonal sea-ice cover extent. Transfer functions using the best analogue method were tested by reconstructing modern sea-surface conditions on the basis of the reference dinoflagellate cyst assemblages. The correlation between instrumental averages and reconstructed values ranges from 0.899 (August temperature) to 0.977 (annual duration of sea-ice cover). Most of the reconstructed temperature and salinity values (>90%) are within the range (1σ) of interannual variability and all estimates of the sea-ice cover extent are within the range of observations. These transfer functions appear, therefore, accurate for the reconstruction of sea-surface conditions in marginal marine environments of high latitude basins.

Oxygen isotopes in tree-rings (δ18OTR) are widely used to reconstruct past climates. However, the complexity of climatic and biological processes controlling isotopic fractionation is not yet fully understood. Here, we use the MAIDENiso model to decipher the variability of δ18OTR of two temperature-sensitive species of relevant paleoclimatological interest (Picea mariana and Nothofagus pumilio) and growing at cold high-latitudes in North and South America. In this first modelling study on δ18OTR values in both northeastern Canada (53.86° N) and western Argentina (41.10° S), we specifically aim at: (1) evaluating the predictive skill of MAIDENiso to simulate δ18OTR values, (2) identifying the physical processes controlling δ18OTR by mechanistic modelling and, (3) defining the origin of the temperature signal recorded in the two species. Although the linear regression models used here to predict daily δ18O of precipitation (δ18OP) may need to be improved in the future, the resulting daily δ18OP values adequately reproduce observed (from weather stations) and simulated (by global circulation model) δ18OP series. The δ18OTR values of the two species are correctly simulated using the δ18OP estimation as MAIDENiso input, although some offset in mean δ18OTR levels is observed for the South American site. For both species, the variability of δ18OTR series is more likely linked to the effect of temperature on isotopic enrichment of the leaf water rather than on the isotopic composition of the source water. We show that MAIDENiso is a powerful tool for investigating isotopic fractionation processes but that the lack of a denser isotope-enabled monitoring network recording oxygen fractionation in the soil-vegetation-atmosphere compartments limits our capacity to decipher the processes at play. This study proves that the eco-physiological modelling of δ18OTR values is necessary to interpret the recorded climate signal more reliably.

Η Πρώτη Μεσογειακή Έκθεση Αξιολόγησης (MAR1) που εκπονήθηκε από το ανεξάρτητο δίκτυο Εμπειρογνωμόνων της Μεσογείου για το Κλίμα και την Περιβαλλοντική Αλλαγή (MedECC), το οποίο ιδρύθηκε το 2015, έχει τώρα δημοσιευθεί. Η MAR1 αξιολογεί τη βέλτιστη διαθέσιμη επιστημονική γνώση σχετικά με την κλιματική και περιβαλλοντική αλλαγή και τους συναφείς κινδύνους στη λεκάνη της Μεσογείου, προκειμένου να την καταστήσει προσιτή στους υπεύθυνους χάραξης πολιτικής, τους ενδιαφερόμενους φορείς και τους πολίτες. Η έκθεση περιλαμβάνει τη Σύνοψη για τους Υπεύθυνους Χάραξης Πολιτικής (SPM), η οποία περιλαμβάνει τα βασικά μηνύματα της MAR1. Η έκθεση συντάχθηκε από 190 επιστήμονες από 25 χώρες, οι οποίοι συνέβαλαν με την ατομική τους ιδιότητα και χωρίς οικονομική αποζημίωση. Η Γραμματεία της Σύμβασης UNEP/MAP - Barcelona, μέσω του Περιφερειακού Κέντρου Δραστηριοτήτων Plan Bleu, και η Γραμματεία της Ένωσης για τη Μεσόγειο (UfM) συνεργάζονται για να υποστηρίξουν το MedECC και να συμβάλουν στην καθιέρωση μιας ορθής και διαφανούς επιστημονικής διαδικασίας αξιολόγησης.

2015 yılında kurulan Akdeniz İklim Değişikliği ve Çevre Değişiklik Uzmanları (MedECC)’nın bağımsız ağı tarafından hazırlanan Birinci Akdeniz Değerlendirme Raporu (MAR1) yayınlandı. Politika yapıcılar, paydaşlar ve vatandaşlar tarafından erişilebilirliğini sağlamak için, MAR1, Akdeniz Havzası’nda iklim ve çevre değişikliği ve ilgili riskler hakkında mevcut en iyi bilimsel bilgiyi belirler. Rapor, MAR1'ın anahtar mesajlarını kapsayan Politika Yapıcılar için Özet (PYÖ)’i içermektedir. Bu rapor, 25 ülkeden 190 bilim insanı tarafından kaleme alındı, hepsi bireysel olarak ve herhangi bir maddi karşılık ödenmeden katkıda bulundu. MedECC'i desteklemek ve sağlıklı ve şeffaf bir bilimsel değerlendirme sürecinin oluşturulmasına katkıda bulunmak için, UNEP/MAP – Barselona Sözleşmesi Sekreterliği, Plan Bleu Bölgesel Faaliyet Merkezi aracılığıyla, ve Akdeniz Birliği Sekreterliği (UfM) ortaklaşa çalışır.

International audience

International audience

MedECC published the First Mediterranean Assessment Report (MAR1) on the current state and expected risks of climate and environmental change in the Mediterranean Basin in November 2020. The report has been written by 190 scientists from 25 countries, all contributing in individual capacity and without financial compensation. The report includes a Summary for Policymakers (SPM), which comprises the key messages of the MAR1 as approved during Plenary Session of MedECC Stakeholders on September 22, 2020. The UNEP/MAP – Barcelona Convention Secretariat, through its Plan Bleu Regional Activity Center, and the Secretariat of the Union for the Mediterranean work in partnership to support MedECC, and to contribute to establish a sound and transparent scientific assessment process., Preferred citation: MedECC (2020) Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer, W., Guiot, J., Marini, K. (eds.)]. Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, 632 pp., ISBN: 978-2-9577416-0-1, doi:10.5281/zenodo.4768833.

MedECC has published the First Mediterranean Assessment Report (MAR1) on the current state and expected risks of climate and environmental change in the Mediterranean Basin. The Chapter 2 "Drivers of change" describes characteristics and evolution of human-induced and natural factors that cause changes in the Mediterranean Basin ecosystems and human systems. In order to cover most major risks for people and biodiversity, four broad domains of change drivers are considered: climate change and variability, pollution, land and sea use changes and non-indigenous species., Preferred citation: Cherif S, Doblas-Miranda E, Lionello P, Borrego C, Giorgi F, Iglesias A, Jebari S, Mahmoudi E, Moriondo M, Pringault O, Rilov G, Somot S, Tsikliras A, Vila M, Zittis G 2020 Drivers of change. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, pp. 59-180, https://doi.org/10.5281/zenodo.7100601.

Chapter 5.2: Society – Development of the First Mediterranean Assessment Report (MAR1) published by MedECC in November 2020. Climate and environmental change cause a wide range of impacts on human health in Mediterranean countries. The vulnerability of people to the impacts of climate and environmental change is strongly influenced by population density, level of economic development, food availability, income level and distribution, local environmental conditions, pre-existing health status, and the quality and availability of public health care. Poorer countries, particularly in North Africa and the Levant, are at highest risk., This chapter should be cited as: Linares C, Paz S, Díaz J, Negev M, Sánchez Martínez G 2020 Health. In: Climate and Environmental Change in the Mediterranean Basin - Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, pp. 493-514, doi:10.5281/zenodo.7101115.

MedECC has prepared the First Mediterranean Assessment Report (MAR1) on the current state and expected risks of climate and environmental change in the Mediterranean Basin. The Chapter 4 is dedicated to the Marine ecosystems, Coastal ecosystems,Terrestrial and freshwater ecosystems.

Chapter 3.1: Resources – Water of the First Mediterranean Assessment Report (MAR1) published by MedECC in November 2020. Water resources in the Mediterranean are scarce. They are limited, unevenly distributed and often mismatching human and environmental needs. Three quarters of the resource are located in the northern Mediterranean while three quarters of the needs are in the south and east. As a consequence, approx. 180 million people in the southern and eastern Mediterranean countries suffer from water scarcity (, Preferred citation: Fader M, Giupponi C, Burak S, Dakhlaoui H, Koutroulis A, Lange MA, Llasat MC, Pulido-Velazquez D, Sanz-Cobeña A 2020 Water. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, pp. 181-236, doi:10.5281/zenodo.7101074.

MedECC has prepared the First Mediterranean Assessment Report (MAR1) on the current state and expected risks of climate and environmental change in the Mediterranean Basin (November 2020). This is the Chapter 6 on future risks management and socio-ecological resilience. The Mediterranean Basin is experiencing major changes in environmental conditions, which can introduce new challenges to the resilience of its natural and human systems. This situation is combined with rapid and spatially diverse socio-economic development in the region, mainly in terms of demographic trends and settlement patterns, thus leading to higher exposure to environmental hazards. Furthermore, new risks are expected to emerge from interactions between drivers and impacts across sectors, thus increasing the vulnerability of natural systems and human populations., This chapter should be cited as: Vafeidis AT, Abdulla AA, Bondeau A, Brotons L, Ludwig R, Portman M, Reimann L, Vousdoukas M, Xoplaki E 2020: Managing future risks and building socio-ecological resilience in the Mediterranean. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, pp. 539-588, doi:10.5281/zenodo.7101119.

Chapter 5.3 "Society: Human Security" of the First Mediterranean Assessment Report (MAR1) published by MedECC in November 2020. The impact of climate change on human security depends not only on climate events but also on country’s contextual factors, such as geographical, social, cultural, economic, and political conditions, resulting in a substantial heterogeneous effect among Mediterranean countries., Koubi V, Behnassi M, Elia A, Grillakis M, Turhan E 2020 Human security. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, pp. 515-538, doi:10.5281/zenodo.7216161.

The Chapter 1: Introduction of the First Mediterranean Assessment Report (MAR1) published by MedECC in November 2020 sets up the scope and objectives of the Assessment Report from What do we know about the Mediterranean Basin and what do we need to know? to the Principles and processes of work in MedECC., Preferred Citation: Lange MA, Llasat MC, Snoussi M, Graves A, Le Tellier J, Queralt A, Vagliasindi GM 2020 Introduction. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, pp. 41-58, doi:10.5281/zenodo.7100592.

Chapter 3.2: Resources – Food of the First Mediterranean Assessment Report (MAR1) published by MedECC in November 2020., Preferred citation: Mrabet R, Savé R, Toreti A, Caiola N, Chentouf M, Llasat MC, Mohamed AAA, Santeramo FG, Sanz-Cobena A, Tsikliras A 2020: Food. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, pp. 237-264, doi:10.5281/zenodo.7101080.

Chapter 5.1: Society – Development of the First Mediterranean Assessment Report (MAR1) published by MedECC in November 2020. Sustainable development seeks to address the needs of current and future generations with the objective of increasing well-being by balancing economic, social and environmental dimensions. Current unsustainable development patterns, such as poverty, increasing population pressure, agricultural intensification, land degradation, and air, land, rivers and ocean pollution, will be further exacerbated by climate change impacts. Environmental and climate change impacts are likely to have an effect on all economic sectors in the Mediterranean Basin, increasing production challenges and costs, affecting low-income cohorts increasingly disproportionally, and generally delaying the achievement of the Sustainable Development Goals (SDGs)., Preferred citation: Dos Santos M, Moncada S, Elia A, Grillakis M, Hilmi N 2020: Development. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, pp. 469-492, doi:10.5281/zenodo.7101111

International audience

First Mediterranean Assessment Report; International audience

Pollen preserved in lacustrine sediments form a crucial archive for reconstructing past climate and terrestrial vegetation change. Currently, climate reconstructions are based on statistical models describing the link between climate and pollen. These models raise methodological problems because they are all based on the hypothesis that climate-pollen relationships are constant over times; implying that non-climatic parameters driving the relation have weak influence. This is not in agreement with recent developments in ecology and ecophysiology. That is why, in this work, we develop an approach integrating a dynamical vegetation model and major processes linking vegetation and pollen trapped in lakes. The Bayesian framework provides us with a theoretical basis and tools for the inference of model parameters and past climate. We use these new models for reconstructing Holocene climate in various European sites. This approach, which may allow spatio-temporal reconstructions still requires developments around statistical inference for semi-mechanistic models., Le pollen conservé dans les sédiments lacustres constitue un indicateur essentiel pour reconstruire l'évolution de la végétation et du climat passés sur les continents. Actuellement, les reconstructions climatiques se basent sur des modèles statistiques décrivant le lien climat-pollen. Ces modèles posent des problèmes méthodologiques car ils sont tous basés sur l'hypothèse que la relation pollen-climat est constante au cours du temps, impliquant que les paramètres non climatiques déterminant cette relation aient une influence faible. Cela est contredit par les développements récents en écologie et en écophysiologie. C'est pourquoi, dans ce travail, nous développons une approche intégrant un modèle dynamique de végétation et les processus majeurs liant la végétation au pollen capté par les lacs. Le cadre bayésien fournit une base théorique ainsi que les outils pour inférer les paramètres des modèles et le climat passé. Nous utilisons ces nouveaux modèles pour reconstruire le climat de l'Holocène en différents sites européens. Cette approche qui permettra des reconstructions spatio-temporelles requiert encore des développements autour de l'inférence de modèles semi-mécanistes.