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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	IPCC WGII Sixth Assessment Report. Cross-Chapter Paper 4: Mediterranean Region
Auteurs :	Ali Elham, Auteur ; Wolfgang Cramer, Auteur ; Jofre Carnicer, Auteur ; Elena Georgopoulou, Auteur ; Nathalie Hilmi, Auteur ; Gonéri Le Cozannet, Auteur ; Piero Lionello, Auteur
Type de document :	Chapitre
Editeur :	[S.l.] : IPCC, 2022
Format :	50
Mots-clés :	zone méditerranéenne ; Impact changement climatique ; Impact activités humaines ; Zone littorale
Résumé :	he Mediterranean Region hosts exceptional biological diversity and socio-cultural richness originating from three continents. The nature of the semi-enclosed Mediterranean Sea and the complex topography imply unique physiographic and ecological features. The region has undergone continuous change in human activities during several millennia, and it now hosts more than 500 million people with a high concentration of urban settlements and industrial infrast`ructure close to sea level. The region is the world’s leading tourist destination and one of its busiest shipping routes. Climate change strongly interacts with other environmental problems in the Mediterranean Basin, resulting from urbanisation, land use change, overfishing, pollution, biodiversity loss and degradation of land and marine ecosystems. {CCP4.1.1} Previous IPCC reports have never assessed the Mediterranean region as an entity – but they have nevertheless shown that virtually all parts of it are vulnerable and face significant risks due to climate change. Identified regional key risks include increased water scarcity (notably in the South and East) and droughts (in the North), coastal risks due to flooding, erosion and saltwater intrusions, wildfire, terrestrial and marine ecosystem losses, as well as risks to food production and security, human health, well-being and the cultural heritage. {CCP4.1.2} Surface temperature in the Mediterranean region is now 1.5°C above pre-industrial level, with a corresponding increase in high-temperature extreme events (high confidence1). Trends in precipitation are variable across the basin (low confidence). Droughts have become more frequent and intense, especially in the North Mediterranean (high confidence). The sea surface has warmed by 0.29-0.44°C per decade since the early 1980s with stronger trends in the Eastern Basin. Sea level has risen by 1.4±0.2 mm yr-1 during the 20th century (2.8±0.1 mm yr-1 over 1993-2018) (high confidence). Ocean acidity is increasing (medium confidence). {CCP4.1.3} A growing number of observed impacts across the entire basin are now being attributed to climate change, along with major roles of other forcings of environmental change (medium to high confidence). These impacts include multiple consequences of longer and/or more intensive heat waves, droughts, floods, ocean acidification and sea-level rise, such as cascading impacts on marine and terrestrial ecosystems as well as on land and sea use (agriculture, forestry, fisheries, tourism, recreation etc.) and human health. {CCP4.1.4} During the 21st century, climate change is projected to intensify throughout the region. Air and sea temperature and their extremes (notably heat waves) are likely2 to continue to increase more than the global average (high confidence). The projected annual mean warming on land at the end of the century is in the range from 0.9 to 5.6°C compared to the last two decades of the 20th century, depending on the emission scenario (high confidence). Precipitation will likely decrease in most areas by 4% to 22%, depending on the emission scenario (medium confidence). Rainfall extremes will likely increase in the northern part of the region (high confidence). Droughts will become more prevalent in many areas (high confidence). {CCP4.1.3} Mediterranean sea-level is projected to rise further during the coming decades and centuries (high confidence), likely reaching 0.15 to 0.33 m in 2050, and 0.3 to 0.6 m for SSP1-1.9 and 0.6 to 1.1 m for SSP5-8.5 in 2100 (relative to 1995-2014) (medium confidence). Higher values cannot be excluded (low confidence) and the process is irreversible at the scale of centuries to millennia (high confidence). Coastal flood risks will increase in low-lying areas along 37% of the Mediterranean coastline that currently host 42 million people. The number of people exposed to sea-level rise is projected to increase up to 2050, especially in the Southern and Eastern Mediterranean region, and may reach up to 130% compared to present in 2100 (medium confidence). Coastal settlements, world heritage sites and ecosystems are at longer-term risk from sustained sea-level rise over at least the coming three centuries (high confidence). {CCP4.1.3, CCP4.2, CCP4.3, SMCCP4.4} Due to its particular combination of multiple strong climate hazards and high vulnerability, the Mediterranean region is a hotspot for highly interconnected climate risks. The main economic sectors in the region (agriculture, fisheries, forestry, tourism) are highly vulnerable to climatic hazards, while socio- economic vulnerability is also considerable. The low-lying areas are the most vulnerable areas for coastal climate-related risks (e.g. sea level rise, floods, erosion) and other consequent risks (e.g. saltwater intrusion and agriculture damage) (high confidence). Climate change threatens water availability, reducing river low flows and annual runoff by 5-70%, reducing hydropower capacity (high confidence). Yields of rain-fed crops may decrease by 64% in some locations (high confidence). Ocean warming and acidification will impact marine ecosystems, with uncertain consequences on fisheries (low confidence). Desertification will affect additional areas, notably in the South and South-East (medium confidence). Burnt area of forests may increase by 96-187% under 3°C, depending on fire management (low confidence). Beyond 3°C, 13-30% of the Natura 2000 protected area and 15-23% of Natura 2000 sites could be lost due to climate-driven habitat change (medium confidence). {CCP4.2, CCP4.3} The adaptive capacity of ecosystems and human systems is expected to encounter hard limits due to the interacting, cumulative and cascading effects of droughts, heat waves, sea-level rise, ocean warming and acidification (high confidence). Coastal protection can reduce risks from sea-level rise in some regions, but the costs of such interventions and their consequences for coastal ecosystems are high (medium confidence) {CCP4.4.1}. There is low confidence in the feasibility of adaptation options to sea- level rise beyond 2100 or for large Antarctic ice melting. {CCP4.4.5} Progress towards achievement of the UN Sustainable Development Goals differs strongly between Mediterranean sub-regions, with north-western countries having stronger resilience than southern and eastern countries (high confidence). To equitably enhance regional adaptive capacity and sustainable development, while safeguarding the rights of the most vulnerable people, regional cooperation can be strengthened with a focus on the link between adaptation, costs and financial limitation and climate justice (high confidence). Cooperative policies across multiple various sectors, involving all user groups and considering all regional and sectorial differences may enhance sustainable resource use in the region (high confidence). {CCP4.4.6} Sharing and co-production of knowledge can support climate adaptation practices and enhance sustainability in the Mediterranean region (medium to high confidence). Currently incomplete knowledge of climate impacts and risks in the southern and eastern part of the basin hinders the implementation of adaptation measures, creating a need for implementable plans with enhanced and cooperative research and monitoring capacities between the north and south/east countries (high agreement). {CCP4.4}
contenu dans :	Climate Change 2022. Impacts, Adaptation and Vulnerability

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