The IPCC approved and accepted Special Report on the Ocean and Cryosphere in a Changing Climate at its 51st Session held on 20 – 23 September 2019. The approved Summary for Policymakers (SPM) was presented at a press conference on 25 September 2019.
The report contain several references to the Mediterranean region :
(analysis conducted by Lina Tode- Plan Bleu, UN Environment Regional Activity Center)
One single mention of the Mediterranean in the Summary for Policymakers:
- ” B3.5 Significant wave heights (the average height from trough to crest of the highest one-third of waves) are projected to increase across the Southern Ocean and tropical eastern Pacific (high confidence) and Baltic Sea (medium confidence) and decrease over the North Atlantic and Mediterranean Sea under RCP8.5 (high confidence).”
And 81 mentions of the Mediterranean (including in reference titles) in the full report, with the related content below:
- Vulnerable posidonia meadows with possible extinction by 2100: “The regional characteristics and habitat heterogeneity of many coastal seas support endemic fauna and flora (e.g., seagrass meadows in the Mediterranean), which makes them particularly vulnerable to climate change impacts with high risk of diversity loss and alterations in ecosystem structure and functioning (Rilov, 2016; Chefaoui et al., 2018).” And ” Nevertheless, severe habitat loss (70%) of endemic species such as Posidonia oceanica is projected by 2050 with the potential for functional extinction by 2100 under RCP8.5 climate scenario.“
- more largely on seagrass impacts: “Reduction in plant fitness due to temperature stress and reduction in underwater light levels due to turbidity and SLR. Mass mortality events due to heatweaves. Spread of invasive tropical species. Warming will lead to significant reduction of Cymodosea nodosa meadows (46 %) in the Mediterranean, and expansion into the Atlantic. Increased herbivory by tropical consumers on temperate seagrasses, ecosystem biodiversity loss. ”
- Increased salinity: “Increased surface salinity in the Atlantic subtropical gyres are pumped into the interior by the winds, leading to an increased salinity of the interior subtropical gyres, along with contributions from increasingly salty Mediterranean water (Jordà et al., 2017).”
- loss of nesting habitats for turtles due to sea level rise: ” In addition, a projected global mean SLR 35 of ~1.2 m under the upper likely range of RCP8.5 by 2100 implies a loss of 59% and 67% in the present 36 nesting area of the green turtle and the loggerhead respectively in the Mediterranean (Varela et al., 2019)”
- loss of carbon sequestration: ” Others have highlighted the declining value of 29 open ocean carbon sequestration in the eastern tropical Pacific (Martin et al., 2016b) and the Mediterranean 30 (Melaku Canu et al., 2015)”
- ph change of −0.044 between 2012-2015 at Gibraltar
- climate impacts on some cold water corals in the Med: some neutral effects, some negative effects on calcification and respiratory metabolism
- Decrease in cyclones: “Recent projection studies indicate that trends in regional extra-tropical cyclones (ETCs) vary from region to region, e.g., a projected […] decrease in the numbers of ETCs in the North Atlantic basin and the Mediterranean (Zappa et al., 2013; Michaelis et al., 2017). ”
- Marine heatwaves: “… simulations suggest that the Mediterranean Sea will experience at least one long lasting Marine heatwave (MHW) every year by the end of the 21st century under the RCP8.5 scenario (Darmaraki et al., 2019)”. And: “The Mediterranean Sea 2003 MHW lead to mass mortalities of macro-invertebrate species (Garrabou et al., 2009)”. And: ” Similarly, MHWs in the Mediterranean Sea may have amplified heatwaves (Feudale and Shukla, 2007; García-Herrera et al., 2010) and heavy precipitation events over central Europe (Messmer et al., 2017), as well as trigger intense extratropical cyclones over the Mediterranean Sea (González-Alemán et al., 2019) [note: the report also mentions that cyclones will decrease in numbers, see above]. Such physical changes induced by MHWs may then also affect ecosystems and human systems on land (Reimer et al., 2015). “
- Decreasing precipitation: ” Future projections of annual precipitation indicate increases of the order of 5 to 20% over the 21st century in many mountain regions, including the Hindu Kush and Himalaya, East Asia, East Africa, the European Alps and the Carpathian region, and decreases in the Mediterranean and the Southern Andes (medium confidence, Table SM2.5).”
- Simulated regional sea level changes 1900-2015 modelled in two Mediterranean cities: Venice and Alexandria
- Case study on Climate Change Adaptation in Nile Delta Regions of Egypt