Editing IPCC:AR6/WGI/Chapter-12 (section)

=== 12.4.5 Europe ===

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The regional European climate and main hazards have been previously assessed in SREX, AR5 WGII, SR1.5, SROCC and SRCCL and a summary of key findings can be found in the Europe section of Atlas.8.1. For the purpose of this assessment Europe is divided into four climatic regions: Northern Europe (NEU), Western and Central Europe (WCE), Eastern Europe (EEU) and Mediterranean (MED) (Figure Atlas.24).

Since AR5 and SR1.5, a large body of literature that uses the EURO-CORDEX and MED-CORDEX ensembles of high-resolution simulations ( [[#Jacob--2014|Jacob et al., 2014]] ; [[#Ruti--2016|Ruti et al., 2016]] ; [[#Kjellström--2018|Kjellström et al., 2018]] ; [[#Vautard--2020|Vautard et al., 2020]] ; [[#Coppola--2021a|Coppola et al., 2021a]] ) to assess signals of climate change in Europe has emerged. These scenario-based simulations have been the basis of a number of impact studies (e.g., [[#Jacob--2014|Jacob et al., 2014]] , 2018; [[#Somot--2018|Somot et al., 2018]] ; [[#Faggian--2019|Faggian and Decimi, 2019]] ) highlighting the use of the climatic impact-drivers. The development of the science of attribution of weather events ( [[#Stott--2016|Stott et al., 2016]] ) has provided evidence of links between climate change and hazard changes such as the 2017 Mediterranean heatwave ( [[#Kew--2019|Kew et al., 2019]] ) and many others (Chapter 11).

The ability of global and regional models to reproduce the observed changes in mean and extreme temperature and precipitation in Europe is assessed in the literature (Atlas.8.3). In summary, both GCMs and RCMs have their limitations but, in general, the increased resolution of RCMs is shown to clearly add value in terms of resolving spatial patterns and seasonal cycles of precipitation and precipitation extremes in many European regions, especially in regions of complex topography such as the Alps and for quantities such as snowmelt-driven runoff, regional winds and Mediterranean hurricanes (Medicanes).

Examples of projected climatic impact-driver thresholds are illustrated in Figures 12.4 and 12.9 based on the most recently updated EURO-CORDEX RCM projections, CMIP5 and CMIP6 GCMs for comparison. For a more comprehensive representation of other climatic impact-driver index trends assessed in this section the reader is referred to the interactive Atlas.

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==== 12.4.5.1 Heat and Cold ====

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'''Mean air temperature:''' Since AR5, studies have confirmed that the mean warming trend in Europe is increasing (Atlas.8.2). The observed warming trend patterns are largely consistent with those simulated by global and regional climate models and it is ''very likely'' that such trends are, in large part, due to human influence on climate ( [[IPCC:Wg1:Chapter:Chapter-3#3.3.1|Section 3.3.1]] ).

All temperature trends are ''very likely'' to continue for a global warming of 1.5°C or 2°C and 3°C (Atlas.8.4). Future warming leads to the exceedance of different temperature thresholds relevant for vector-borne diseases ( ''medium confidence'' ) ( [[#Caminade--2012|Caminade et al., 2012]] ; [[#Medlock--2013|Medlock et al., 2013]] ), invasive allergens ( ''medium confidence'' ) ( [[#Storkey--2014|Storkey et al., 2014]] ; [[#Hamaoui-Laguel--2015|Hamaoui-Laguel et al., 2015]] ), SST thresholds in the Mediterranean ( ''likely'' to exceed 20°C), or relevant for the ''Vibrio'' bacteria development ( [[#Vezzulli--2015|Vezzulli et al., 2015]] ). Future warming is also projected to lead to the exceedance of cooling degree day index (&gt;22°C) thresholds, characterizing a potential increase in energy demand for cooling in southern Europe with increases ''likely'' exceeding 40% in some areas ( [[#Spinoni--2015|Spinoni et al., 2015]] ) by 2050 under RCP8.5 ( ''high confidence'' ) ( [[#12.3|Section 12.3]] and Atlas.8; [[#Coppola--2021a|Coppola et al., 2021a]] ).

'''Extreme heat:''' The frequency of heatwaves observed in Europe has ''very likely'' increased in recent decades due to human-induced change in atmospheric composition ( [[IPCC:Wg1:Chapter:Chapter-11#11.3|Section 11.3]] ) and a detectable anthropogenic increase in a summer heat stress index over all regions of Europe has been identified based on WBGT index trends for 1973–2012 ( ''medium confidence'' , ''limited evidence'' ) ( [[#Knutson--2016|Knutson and Ploshay, 2016]] ).

It is ''very likely'' that the frequency of heatwaves will increase during the 21st century regardless of the emissions scenario in each European region, and for 1.5°C and 2°C GWLs ( [[IPCC:Wg1:Chapter:Chapter-11#11.3.5|Section 11.3.5]] ). Heat stress due to both high temperature and humidity, affecting morbidity, mortality and labour capacity ( [[#12.3|Section 12.3]] ) is projected to increase under all emissions scenarios and GWLs by the middle of the century (Figure 12.4a–f). Under RCP8.5, the expected number of days with WBGT higher than 31°C is about 25, 30 and 40 days per year, as projected by EURO-CORDEX, CMIP5 and CMIP6 respectively on average over the Mediterranean region, and around 30, 40 and 60 days per year in low coastal plain areas such as the Po Valley, the Italian, Greek and Spanish coasts, and the Mediterranean islands ( [[#Coppola--2021a|Coppola et al., 2021a]] ). An average increase of a few days per year of maximum daily temperature exceeding 35°C, a typical critical threshold for crop productivity, is expected by the mid-century in central Europe, and an increase of 10–20 days is expected for the Mediterranean areas (Figure 12.4b; [[#Coppola--2021a|Coppola et al., 2021a]] ). By contrast, under SSP1-2.6, the increase in this number of days remains limited to less than about 10 days, and confined to the Mediterranean regions. Mitigation is expected to have a strong effect, with the dangerous heat threshold of HI &gt; 41°C projected to be crossed 5–10 days more per year in the Mediterranean regions and a few days per year more in WCE and EEU under SSP5-8.5, while such increases would be virtually absent under SSP1-2.6 (Figure 12.4d–f).

'''Cold spell and frost:''' Temperature observations for winter cold spells in Europe show a long-term decreasing frequency ( [[#Brunner--2018|Brunner et al., 2018]] ), with their probability of occurrence projected to decrease in the future ( ''high confidence'' ) and virtually disappear by the end of the century ( [[IPCC:Wg1:Chapter:Chapter-11#11.3|Section 11.3]] ). The frequency of frost days will ''very likely'' decrease for all scenarios and all time horizons ( [[#Lindner--2014|Lindner et al., 2014]] ; [[#Coppola--2021a|Coppola et al., 2021a]] ) with consequences for agriculture and forests. A simple heating degree day index, characterizing heating demand, shows a large observed decreasing trend for winter heating energy demand in Europe ( [[#Spinoni--2015|Spinoni et al., 2015]] ). This trend is ''very likely'' to continue through the 21st century, with decreases in the range of 20–30% for Northern Europe, about 20% for central Europe and 35% for southern Europe, by mid-century under RCP8.5 ( [[#Spinoni--2018b|Spinoni et al., 2018b]] ; [[#Coppola--2021a|Coppola et al., 2021a]] ; Interactive Atlas).

'''In summary, irrespective of the scenario, it is''' virtually certain '''that warming will continue in Europe, and there is''' high confidence '''that the observed increase in heat extremes is due to human activities. It is''' very likely '''that the frequency of heat extremes will increase over the 21st century with an increasing gradient toward the southern regions. Extreme heat will exceed critical thresholds for health, agriculture and other sectors more frequently''' ( high confidence '''), with strong differences between mitigation scenarios. It is''' very likely '''that the frequency of cold spells and frost days will keep decreasing over the course of this century and it is''' likely '''that cold spells will virtually disappear towards the end of the century.'''

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==== 12.4.5.2 Wet and Dry ====

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'''Mean precipitation:''' Precipitation has generally increased in northern Europe and decreased in southern Europe, especially in winter ( [[#Fischer--2016|Fischer and Knutti, 2016]] ; [[#Knutson--2018|Knutson and Zeng, 2018]] ) but in the latter, precipitation trends are strongly dependent on the examined period (Atlas.8). These trends in precipitation increases in the north and decreases in the south are also represented by global and regional climate simulations ( [[#Jacob--2014|Jacob et al., 2014]] ; [[#Rajczak--2017|Rajczak and Schär, 2017]] ; [[#Lionello--2018|Lionello and Scarascia, 2018]] ; [[#Coppola--2021a|Coppola et al., 2021a]] ; Atlas.8.2) and have been attributed to climate change (Sections 3.3.2, 8.3.1).

Studies since AR5, together with EURO-CORDEX and MED-CORDEX experiments and the latest CMIP6 ensemble, have increased confidence in regional projections of mean and extreme precipitation ( [[#Prein--2016|Prein et al., 2016]] ) despite their wet bias, and show that it is ''very likely'' that precipitation will increase in Northern Europe in DJF and decrease in the Mediterranean in JJA under all climate scenarios except RCP2.6/SSP1-2.6 and for both mid- and end-century periods ( [[#Coppola--2021a|Coppola et al., 2021a]] ; Atlas.8.5).

'''River flood:''' There is ''high confidence'' of an observed increasing trend of river floods in Western and Central Europe (WCE) and ''medium confidence'' of a decrease in Northern (NEU) and southern Europe (MED).

The SR1.5 shows evidence of an increase in reported floods in the UK over the period 1884–2013, and increasing trends in annual maximum daily streamflow data over 1966–2005 in parts of Europe. Although high flow does not show uniform trends for the entire region ( [[#Hall--2014|Hall et al., 2014]] ; [[#Mediero--2015|Mediero et al., 2015]] ) or specific regions ( [[#Mudersbach--2017|Mudersbach et al., 2017]] ; [[#Vicente-Serrano--2017|Vicente-Serrano et al., 2017]] ; [[#Tramblay--2019|Tramblay et al., 2019]] ), regional patterns of significant flood trends do exist. Based on the most extended river flow database spanning the period 1960–2010, an increase in floods frequency in north-western Europe, decreasing in medium and large catchments in southern Europe and decreasing floods in Eastern Europe has been detected ( [[#Blöschl--2019|Blöschl et al., 2019]] ) in line with [[#Mediero--2014|Mediero et al. (2014)]] , [[#Arheimer--2015|Arheimer and Lindström (2015)]] , [[#Gudmundsson--2017|Gudmundsson et al. (2017)]] , [[#Krysanova--2017|Krysanova et al. (2017)]] , [[#Kundzewicz--2018|Kundzewicz et al. (2018)]] and [[#Mangini--2018|Mangini et al. (2018)]] .

There is ''high confidence'' of river floods increasing in Western and Central Europe (WCE) and ''medium confidence'' of a decrease in Northern (NEU), Eastern (EEU) and southern Europe (MED) for mid- and end-century under RCP8.5 and ''low confidence'' under RCP2.6. The projected increase in WCE is roughly 10% (18% by end of century) and the projected decrease in NEU is 5% (11% by end of century) for the peak flow with a return period of 100 years for mid-century, under RCP8.5 ( [[#Di%20Sante--2021|Di Sante et al., 2021]] ; Figure 12.9a for mid-century (Q100) projections of flood discharges per unit catchment area ( [[#Blöschl--2019|Blöschl et al., 2019]] ) based on EURO-CORDEX models).

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[[File:86f12b8af8261abcbf2a23eda4f3289c IPCC_AR6_WGI_Figure_12_9.png]]

'''Figure 12.9''' '''|''' '''Projected changes in selected climatic impact-driver indices for Europe. (a)''' Mean change in 1-in-100-year river discharge per unit catchment area (Q100, m <sup>3</sup> s <sup>–1</sup> km <sup>–2</sup> ), and '''(b)''' median change in the number of days with snow water equivalent (SWE) over 100 mm (from November to March), from EURO-CORDEX models for 2041–2060 relative to 1995–2014 and RCP8.5. Diagonal lines indicate where less than 80% of models agree on the sign (direction) of change. '''(c)''' Bar plots for Q100 (m <sup>3</sup> s <sup>–1</sup> km <sup>–2</sup> ) averaged over land areas for the AR6 WGI Reference Regions (defined in Chapter 1). The left-hand column within each panel (associated with the left-hand y-axis) shows the ‘recent past’ (1995–2014) Q100 absolute values in grey shades. The other columns (associated with the right-hand y-axis) show the Q100 changes relative to the recent past values for two time periods (‘mid’ 2041–2060 and ‘long’ 2081–2100) and for three global warming levels (defined relative to the pre-industrial period 1850–1900): 1.5°C (purple), 2°C (yellow) and 4°C (brown). The bars show the median (dots) and the 10–90th percentile range of model ensemble values across each model ensemble. CMIP6 is shown by the darkest colours, CMIP5 by medium, and CORDEX by light. SSP5-8.5/RCP8.5 is shown in red and SSP1-2.6/RCP2.6 in blue. '''(d)''' As for (c) but showing absolute values for number of days with SWE &gt; 100mm, masked to grid cells with at least 14 such days in the recent past. See Technical ( [[IPCC:Wg1:Chapter:Annex-vi|Annex VI]] for details of indices. Further details on data sources and processing are available in the chapter data table (Table 12.SM.1).

Using frequency analysis of extreme peak flow events above a 100-year return period as a threshold, which is the average protection level of the European river network ( [[#Rojas--2013|Rojas et al., 2013]] ), [[#Alfieri--2017|Alfieri et al. (2017)]] and [[#Alfieri--2015|Alfieri et al. (2015)]] show that Europe is one of the regions where the largest increases in flood risk may occur, with only few countries in Eastern Europe showing a decrease (Poland, Lithuania, Belarus) ( [[#Osuch--2017|Osuch et al., 2017]] ). They find a significant increase of events with peak discharge above 100-year return period (Q100) in most of Europe in line with [[#Rojas--2012|Rojas et al. (2012)]] , [[#Hirabayashi--2013|Hirabayashi et al. (2013)]] , [[#Dankers--2014|Dankers et al. (2014)]] , [[#Forzieri--2016|Forzieri et al. (2016)]] , [[#Roudier--2016|Roudier et al. (2016)]] , [[#Thober--2018|Thober et al. (2018)]] , and an increase in the magnitude of floods in southern Europe, although [[#Giuntoli--2015|Giuntoli et al. (2015)]] projects no change. A modest but significant decrease in the 100-year return period river flood is projected for southern (due to reduction of precipitation) and north-eastern European regions, the latter because of the strong reduction in snowmelt induced river floods ( [[#Thober--2018|Thober et al., 2018]] ; [[#Di%20Sante--2021|Di Sante et al., 2021]] ).

'''Heavy precipitation and pluvial flood:''' Heavy precipitation frequency trends have been detected in Europe with ''high confidence'' for the NEU and Alpine regions and with ''medium confidence'' in WCE, and also attributed to climate change with ''high'' ''confidence'' in NEU ( [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] ). [[#Guerreiro--2017|Guerreiro et al. (2017)]] , based on observations, showed that 20% of city areas in WCE and MED regions are affected by pluvial flooding and less than 10% of city areas in the northern and western coastal cities.

Projections based on multiple lines of evidence from global to convective permitting model scales show ''high confidence'' in extreme precipitation increase in the northern, central and eastern European regions (NEU, WCE, EEU) and in the Alpine area. Increases with ''medium confidence'' are projected for the Mediterranean basin (with a negative gradient towards the south) for mid- and end-century under RCP4.5, RCP8.5 and SSP5-8.5 and for 2°C GWL and higher ( [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] ; [[#MedECC--2020|MedECC, 2020]] ).

'''Landslide:''' Rainfall periods connected to landslides are projected to increase in central Europe by up to one more period per year in flat areas in low altitudes and by up to 14 more periods per year at higher altitudes by mid-century, becoming even more evident by the end of the century ( [[#Schlögl--2018|Schlögl and Matulla, 2018]] ). An increase of landslides by up to 45.7% and 21.2% is projected for southern Italy (Calabria region) by mid-century under both RCP4.5 and RCP8.5 ( [[#Gariano--2016|Gariano and Guzzetti, 2016]] ) and by up to 40% in central Italy (Umbria) during the winter season ( [[#Ciabatta--2016|Ciabatta et al., 2016]] ). A decrease of landslides is projected in the Peloritani mountains in southern Italy (RCP4.5 and 8.5) by mid-century ( [[#Peres--2018|Peres and Cancelliere, 2018]] ). A slight increase for a 10-year return period landslide is projected in the eastern Carpathians, the Moldavian Subcarpathians and the northern part of the Moldavian Tableland and a higher increase in the 100-year return period event is projected in the western hilly and plateau areas of Romania ( [[#Jurchescu--2017|Jurchescu et al., 2017]] ).

'''Aridity:''' The Mediterranean region shows evidence of large-scale decreasing precipitation trends over 1901–2010, which are at least partly attributable to anthropogenic forcing according to CMIP5 models ( [[#Knutson--2018|Knutson and Zeng, 2018]] ). Nevertheless, there is ''low agreement'' among studies on observed precipitation trend in the Mediterranean region ( [[IPCC:Wg1:Chapter:Chapter-11#11.9.4|Section 11.9.4]] and Atlas.8.2).

Precipitation is projected to decrease by mid- and end-century for the RCP8.5 and SSP5-8.5 with ''strong agreement'' among CMIP5, CMIP6 and CORDEX regional climate ensemble models on the direction of change. With both temperature increase and precipitation decrease there is ''high confidence'' on increased aridity in the MED region (Sections 8.4.1.6 and 11.9.4 and Atlas.8.2; [[#Coppola--2021a|Coppola et al., 2021a]] ). In NEU there is '''high confidence''' of decrease in aridity linked to mean precipitation increase ( [[IPCC:Wg1:Chapter:Chapter-8#8.4.1.6|Section 8.4.1.6]] , [[IPCC:Wg1:Chapter:Atlas|Atlas]] 8.2) and meteorological drought decrease based on indicators like Standardized Precipitation Index and consecutive dry days ( [[IPCC:Wg1:Chapter:Chapter-11#11.9.4|Section 11.9.4]] , Figure 12.4, Coppola et al,, 2021a).

'''Hydrological drought:''' There is ''high confidence'' that hydrological droughts have increased in the Mediterranean basin with ''medium confidence'' in anthropogenic attribution of the signal, and ''high confidence'' that they will continue to increase through the 21st century for 2°C GWL and higher and all scenarios except RCP2.6/SSP1-2.6. (Sections 8.3.1.6, 8,4.1.6, and 11.9.4). There is ''medium confidence'' in hydrological drought increase in WCE and ''low confidence'' in direction of change for EEU and NEU from mid-century onwards and for 2°C GWL and higher and all scenarios except RCP2.6/SSP1-2.6 ( [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] and Figure 12.4g–i).

Streamflow droughts are projected to become more severe and persistent in the Mediterranean and western Europe (current 100-year events could occur approximately every 2–5 years by 2080; [[#Forzieri--2016|Forzieri et al., 2016]] ).

The opposite tendency is projected in Northern, Eastern and central Europe where higher precipitation that outweighs the effects of increased evapotranspiration is expected to result in a decrease in streamflow drought frequency ( [[#Forzieri--2014|Forzieri et al., 2014]] ). For a 2°C GWL droughts will become more intense in the MED and in France and longer mainly due to less rainfall and higher evapotranspiration. A reduction of drought length and magnitude is projected for NEU and EEU ( [[#Roudier--2016|Roudier et al., 2016]] ). In the southern Alps, both winter and summer low flows are projected to be more severe, with a 25% decrease in the 2050s ( [[#Vidal--2016|Vidal et al., 2016]] ).

'''Agricultural and ecological drought:''' There is ''medium confidence'' that agricultural and ecological droughts have increased in Western and Central Europe and in the Mediterranean region, and ''medium confidence'' that anthropogenic drivers contributed to the Mediterranean increase (Sections 8.3.1.6 and 11.9).

( [[IPCC:Wg1:Chapter:Chapter-11|Chapter 11]] assesses that agricultural and ecological droughts will increase in the Mediterranean regions ( ''high confidence'' ) and Western and Central Europe ( ''medium confidence'' ) by mid-century and with ''high confidence'' by the end of the century for the MED for 2°C GWL and higher and all scenarios except RCP2.6/SSP1-2.6 ( [[IPCC:Wg1:Chapter:Chapter-11#11.9.4|Section 11.9.4]] ). ''Low confidence'' in direction of change is assessed for EEU and NEU under all scenarios and global warming levels (Figure 12.4k).

Recent local studies provide additional risk-relevant context to changes in European drought. Agricultural and ecological drought conditions are expected to intensify in southern Europe by end-of-century based on the 12-month rainfall Drought Severity Index (a soil moisture indicator), precipitation deficit SPI and SPEI indices. There will be regions in southern Europe where this type of drought could be up to 14 times worse than the worst drought in the historical period ( [[#Guerreiro--2018|Guerreiro et al., 2018]] ). One-in-10-year drought events are projected to happen every second year ( [[#Mora--2018|Mora et al., 2018]] ; [[#Ruosteenoja--2018|Ruosteenoja et al., 2018]] ). The Mediterranean region will have 100 additional stress years (years with three consecutive months of precipitation deficits greater than 25%; [[#Giorgi--2018|Giorgi et al., 2018]] ); an increase of both drought frequency (up to two events per decade) and severity ( [[#Spinoni--2014|Spinoni et al., 2014]] , 2020) and an increase of consecutive dry days in the southern part of the MED region ( [[#Lionello--2020|Lionello and Scarascia, 2020]] ). In contrast, droughts are expected to decrease in winter in Northern Europe ( [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] ; [[#Spinoni--2018a|Spinoni et al., 2018a]] ). These findings are confirmed by the EURO-CORDEX, CMIP5 and CMIP6 ensemble that show a change of frequency of drought events in the MED between 2–3 events per decade by mid-century for scenario RCP8.5 (Figure 12.SM.3; [[#Coppola--2021a|Coppola et al., 2021a]] ).

'''Fire weather:''' Fire weather conditions have been increasing since about 1980 over a few regions in Europe including Mediterranean areas ( ''low confidence'' ) ( [[#Venäläinen--2014|Venäläinen et al., 2014]] ; [[#Urbieta--2019|Urbieta et al., 2019]] ; [[#Barbero--2020|Barbero et al., 2020]] ; [[#Giannaros--2021|Giannaros et al., 2021]] ). However, beyond a few studies, evidence is largely missing on attribution of these trends to anthropogenic climate change ( [[#Forzieri--2016|Forzieri et al., 2016]] ). An increase in fire weather is projected for most of Europe, especially western, eastern and central regions, by 2080 (current 100-year events will occur every 5–50 years), with a progressive increase in confidence and model agreement along the 21st century ( ''medium confidence'' ) ( [[#Forzieri--2016|Forzieri et al., 2016]] ; [[#Abatzoglou--2019|Abatzoglou et al., 2019]] ). With increased drying and heat combined, in Mediterranean areas, an increase in fire weather indices is projected under RCP4.5 and RCP8.5, or SRES A1B, as early as by mid-century ( ''high confidence'' ) ( [[#Bedia--2014|Bedia et al., 2014]] ; [[#Abatzoglou--2019|Abatzoglou et al., 2019]] ; [[#Dupuy--2020|Dupuy et al., 2020]] ; [[#Fargeon--2020|Fargeon et al., 2020]] ; [[#Ruffault--2020|Ruffault et al., 2020]] ) and an increase in burned area of 40% and 100% for a 2°C and 3°C GWL, respectively ( [[#Turco--2018|Turco et al., 2018]] ).

'''In summary, there is''' high confidence '''that river floods will increase in central and Western Europe and''' medium confidence '''that they will decrease in Northern, Eastern and southern Europe, for mid- and end of century under RCP8.5 and with''' low confidence '''under RCP2.6. There is''' high confidence '''that aridity will increase by mid- and end-century under the RCP8.5 and SSP5-8.5, and''' high confidence '''that agricultural, ecological and hydrological droughts will increase in the Mediterranean region by mid- and far end of century under all RCPs except RCP2.6/SSP1-2.6 and''' '''also for 2°C and higher GWLs. There is''' high confidence '''in fire weather increase in the Mediterranean region.'''

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==== 12.4.5.3 Wind ====

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'''Mean wind speed:''' Mean surface wind speeds have decreased in Europe as in many other areas of the Northern Hemisphere over the past four decades ( ''medium confidence'' ) (AR5 WGI), with a reversal to an increasing trend in the last decade ( ''low confidence'' ) that is, however, not fully consistent across studies ( [[#Tian--2019|Tian et al., 2019]] ; [[#Zeng--2019|Zeng et al., 2019]] ; Z. [[#Zhang--2019|]] [[#Zhang--2019|]] [[#Zhang--2019|]] [[#Zhang--2019|Zhang et al., 2019]] ; [[#Deng--2021|Deng et al., 2021]] ; see [[IPCC:Wg1:Chapter:Chapter-2#2.3.1.4.4|Section 2.3.1.4.4]] ). Re-analyses also show declining winds in Europe ( [[#Deng--2021|Deng et al., 2021]] ) with large interdecadal variability ( [[#Laurila--2021|Laurila et al., 2021]] ). The declining trend has induced a corresponding decline in wind power potential indices across Europe ( ''low confidence'' ) ( [[#Tian--2019|Tian et al., 2019]] ). However, there is ''low agreement'' and ''limited evidence'' that climate model historical trends are consistent with observed trends ( [[#Tian--2019|Tian et al., 2019]] ; [[#Deng--2021|Deng et al., 2021]] ). Several factors have been attributed to these trends, including forest growth, urbanization, local changes in wind measurement exposure and aerosols ( [[#Bichet--2012|Bichet et al., 2012]] ), as well as natural variability ( [[#Zeng--2019|Zeng et al., 2019]] ).

Due to changes in mean surface wind speed patterns ( [[#Li--2018|]] [[#Li--2018|]] [[#Li--2018|]] [[#Li--2018|]] [[#Li--2018|C. Li et al., 2018]] ) and the poleward shift of the North Atlantic jet stream exit, mean surface wind speeds are projected to decrease in the Mediterranean areas under RCP4.5 and RCP8.5 by the middle of the century and beyond, or for GWLs of 2°C and higher ( ''high confidence'' ), with a subsequent decrease in wind power potential ( ''medium confidence'' ) ( [[#Hueging--2013|Hueging et al., 2013]] ; [[#Tobin--2015|Tobin et al., 2015]] , 2018; [[#Davy--2018|Davy et al., 2018]] ; [[#Karnauskas--2018a|Karnauskas et al., 2018a]] ; [[#Kjellström--2018|Kjellström et al., 2018]] ; [[#Moemken--2018|Moemken et al., 2018]] ; Figure 12.4). However, sub-regional patterns of change are shown in regional climate models, such as an increase in wind speeds in the Aegean Sea and in the northern Adriatic Sea, where a reduction of Bora events and an increase of Scirocco events are projected for mid-century and beyond under RCP4.5 and RCP8.5 ( ''medium confidence'' ) ( [[#Tobin--2016|Tobin et al., 2016]] ; [[#Davy--2018|Davy et al., 2018]] ; [[#Belušić%20Vozila--2019|Belušić Vozila et al., 2019]] ). Projections (as cited above) also indicate a decrease in mean wind speed in Northern Europe ( ''medium confidence'' , ''medium agreement'' ) ( [[#Karnauskas--2018a|Karnauskas et al., 2018a]] ; [[#Tobin--2018|Tobin et al., 2018]] ; [[#Jung--2019|Jung and Schindler, 2019]] ). Daily and interannual wind variability is projected to increase under RCP8.5 only in Northern Europe ( ''low confidence'' ) ( [[#Moemken--2018|Moemken et al., 2018]] ), which can influence electrical grid management and wind energy production ( ''low confidence'' ). Wind speeds are projected to shift towards more frequent occurrences below thresholds inhibiting wind power production ( [[#Weber--2018|Weber et al., 2018]] ). Wind stagnation events may become more frequent in future climate scenarios in some areas of Europe in the second half of the 21st century ( [[#Horton--2014|Horton et al., 2014]] ; [[#Vautard--2018|Vautard et al., 2018]] ), with potential consequences on air quality ( ''low confidence'' ).

'''Severe wind storm:''' There are large uncertainties in past evolutions of windstorms and extreme winds in Europe. Extreme near-surface winds have been decreasing in the past decades ( [[#Smits--2005|Smits et al., 2005]] ; [[#Tian--2019|Tian et al., 2019]] ; [[#Vautard--2019|Vautard et al., 2019]] ) according to near-surface observations. Significant negative trends of cyclone frequency in spring and positive trends in summer have been found in the Mediterranean basin for the period 1979–2008 ( [[#Lionello--2016|Lionello et al., 2016]] ). By contrast increasing trends have been found in Arctic Ocean areas ( [[#Wickström--2020|Wickström et al., 2020]] ). These trends are not associated with significant trends in extratropical cyclones (Sections 8.3.2.8 and 11.7.2).

There is ''medium confidence'' that serial clustering of storms, inducing cumulated economic losses, in future climate will increase in many areas in Europe under climate projections over Europe ( [[#Karremann--2014|Karremann et al., 2014]] ; [[#Economou--2015|Economou et al., 2015]] ). Strong winds and extratropical storms are projected to have a slightly increasing frequency and amplitude in the future in northern, western and Central Europe ( [[#Outten--2013|Outten and Esau, 2013]] ; [[#Feser--2015|Feser et al., 2015]] ; [[#Forzieri--2016|Forzieri et al., 2016]] ; [[#Mölter--2016|Mölter et al., 2016]] ; [[#Ruosteenoja--2019a|Ruosteenoja et al., 2019a]] ; [[#Vautard--2019|Vautard et al., 2019]] ) under RCP8.5 and SRES A1B by the end of the century ( ''medium confidence'' ), as well as off the European coasts ( [[#Martínez-Alvarado--2018|Martínez-Alvarado et al., 2018]] ) due to the increase of intensity of extratropical storms at a 2°C GWL or above ( [[#Zappa--2013|Zappa et al., 2013]] ) in these areas. The frequency of storms, including Medicanes, is projected to decrease in Mediterranean regions, and their intensities are projected to increase, by the middle of the century and beyond for SRES A1B, A2 and RCP8.5 ( ''medium confidence'' ) ( [[#Nissen--2014|Nissen et al., 2014]] ; [[#Feser--2015|Feser et al., 2015]] ; [[#Forzieri--2016|Forzieri et al., 2016]] ; [[#Mölter--2016|Mölter et al., 2016]] ; [[#Tous--2016|Tous et al., 2016]] ; [[#Romera--2017|Romera et al., 2017]] ; [[#González-Alemán--2019|González-Alemán et al., 2019]] ; [[#MedECC--2020|MedECC, 2020]] ; Chapter 11).

Projections of smaller-scale hazard phenomena such as tornadoes, wind gusts, hail storms and lightning are currently not directly available partly due to the inability of climate models to simulate such phenomena. Observational networks for such phenomena usually lack homogeneity over long periods, hindering clear trends to be detected. For instance, while no robust trends have been identified ( [[#Hermida--2015|Hermida et al., 2015]] ; [[#Mohr--2015a|Mohr et al., 2015a]] ; [[#Burcea--2016|Burcea et al., 2016]] ; [[#Ćurić--2016|Ćurić and Janc, 2016]] ), hail storm environments (favourable atmospheric configurations) have increased in frequency ( ''low confidence'' , ''limited evidence'' ) ( [[#Sanchez--2017|Sanchez et al., 2017]] ). In future climate periods it is ''more likely than not'' that severe convection environments will become more frequent by the end of the century under RCP8.5 ( [[#Mohr--2015b|Mohr et al., 2015b]] ; [[#Púčik--2017|Púčik et al., 2017]] ), and there is ''medium confidence'' that such environments will become more frequent by the 2050s in RCP4.5. There is no evidence for changes in tornado frequencies in Europe in the observations ( [[#Groenemeijer--2014|Groenemeijer and Kühne, 2014]] ) as well as in future climate projections. Insufficient observational record length for lightning numbers does not allow an assessment of trends.

'''There is''' high confidence '''that mean wind speeds will decrease in Mediterranean areas and''' medium confidence '''of such decreases in Northern Europe for global warming levels of 2°C or more and beyond the middle of the century. A slightly increased frequency and amplitude of extratropical cyclones, strong winds and extratropical storms is projected for northern, central and western Europe by the middle of the century and beyond and for global warming levels of 2°C or higher''' ( medium confidence '''). The frequency of Medicanes is projected to decrease''' ( medium confidence '''), but their intensity is projected to increase by mid century and beyond and for global warming levels of 2°C or more. Proxies of intense convection indicate that the large-scale conditions conducive to severe convection will tend to increase in the future climate''' ( low confidence ''').'''

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<span id="snow-and-ice-5"></span>
==== 12.4.5.4 Snow and Ice ====

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'''Snow:''' Widespread and accelerated declines in snow depth ( [[#Fontrodona%20Bach--2018|Fontrodona Bach et al., 2018]] ) and snow water equivalent ( [[#Marty--2017a|Marty et al., 2017a]] ; see Figure 12.9b) have been observed in Europe. In the Pyrenees a slow snow cover decline has been observed starting from the industrial period with a sharp increase since 1955 ( [[#López-Moreno--2020|López-Moreno et al., 2020]] ). Under the RCP2.6, RCP4.5 and RCP8.5 scenarios the reliability elevation for snowmaking will rise by 200–300 m in the Alps and 400–600 m in the Pyrenees by mid-century. End of century projections of natural snow conditions are highly dependent on the scenario, being stationary for the RCP2.6 and continuously decreasing under RCP8.5 to not have any more natural snow conditions at any of the locations in the French Alps and Pyrenees ( [[#Spandre--2019|Spandre et al., 2019]] ). Similarly Norway and Austria will also see a rising of the natural snow elevation with consequences for the ski season ( [[#Scott--2020|Scott et al., 2020]] ; [[#Steiger--2020|Steiger and Scott, 2020]] ). In the Alps, recent simulations project a reduction in snow water equivalent (SWE) at 1500 m above sea level of 80–90% by 2100 under the A1B scenario and a snow season that would start 2-4 weeks later and end 5-10 weeks earlier than the 1992–2012 average ( [[#Schmucki--2015|Schmucki et al., 2015]] ), which is equivalent to a shift in elevation of about 700 m ( [[#Marty--2017b|Marty et al., 2017b]] ). For elevations above 3000 m above sea level, a decline in SWE of at least 10% is expected by the end of the century even when assuming the largest projected precipitation increase. Similar trends are observed for the Pyrenees and Scandinavia ( [[#López-Moreno--2009|López-Moreno et al., 2009]] ; [[#Räisänen--2012|Räisänen and Eklund, 2012]] ). For the northern French Alps above 1500 m and the Ötztal locations in the Austrian alps SWE has a similar decreasing trend altitudinally dependent for RCP2.6, RCP4.5 and RCP8.5 until mid-century and with significant differentiation among them in the second half of the century up to snow-free conditions under RCP8.5 ( [[#Hanzer--2018|Hanzer et al., 2018]] ; [[#Verfaillie--2018|Verfaillie et al., 2018]] ).

'''Glacier:''' Observations and future projections of European glacier mass changes are assessed in [[IPCC:Wg1:Chapter:Chapter-9#9.5.1%20|Section 9.5.1]] grouped in two main regions: Scandinavia and central Europe regions. It is ''virtually certain'' that glaciers will shrink in the future and there is ''medium confidence'' in the timing and mass change rates ( [[IPCC:Wg1:Chapter:Chapter-9#9.5.1|Section 9.5.1]] ). Central Europe is one of the regions where glaciers are projected to lose substantial mass even under low-emissions scenarios ( [[IPCC:Wg1:Chapter:Chapter-9#9.5.1.3|Section 9.5.1.3]] ; [[#MedECC--2020|MedECC, 2020]] ). GlacierMIP projections indicate that glaciers in the central Europe region will lose 63 ± 31%, 80 ± 22% and 93 ± 13% of their 2015 mass by the end of the century under RCP2.6, RCP4.5 and RCP8.5 respectively ( [[#Marzeion--2020|Marzeion et al., 2020]] ). For the same scenarios, glaciers in Scandinavia are projected to lose 55 ± 33%, 66 ± 34% and 82 ± 24% of their 2015 mass. The ''virtually certain'' shrink in glaciers is bolstered by RCM simulations from the EURO-CORDEX ensemble, with the Global Glacier Evolution Model (GloGEM) indicating a substantial reduction of glacier ice volumes in the European Alps by 2050 (47–52% with respect to 2017 for RCP2.6, RCP4.5 and RCP8.5). Under RCP2.6, about two-thirds (63 ± 11%) of the present-day (2017) ice volume is projected to be lost by 2100. In contrast, under the strong warming of RCP8.5, glaciers in the European Alps are projected to largely disappear by 2100 (94 ± 4% volume loss compared to 2017; [[#Zekollari--2019|Zekollari et al., 2019]] ).

'''Permafrost:''' In Europe, permafrost is found in high mountains and in Scandinavia, as well as in Arctic Islands (e.g., Iceland, Novaya Zemlia or Svalbard). In recent decades permafrost has been lost ( [[IPCC:Wg1:Chapter:Chapter-9#9.5.2|Section 9.5.2]] ) and accelerated warming at high altitudes and latitudes has favoured an increase of permafrost temperatures of the order of 0.2 ± 0.1°C between 2007 and 2016 ( [[#Romanovsky--2018|Romanovsky et al., 2018]] ; [[#Noetzli--2019|Noetzli et al., 2019]] ). Over the 21st century, permafrost is ''very'' ''likely'' to undergo increasing thaw and degradation under all scenarios ( [[#Hock--2019|Hock et al., 2019]] ) and it is ''virtually certain'' that permafrost extent and volume will decrease with increase of global warming ( [[IPCC:Wg1:Chapter:Chapter-9#9.5.2|Section 9.5.2]] ).

Permafrost thawing is projected to affect the frequency and magnitude of high-mountain mass wasting processes ( [[#Stoffel--2012|Stoffel and Huggel, 2012]] ). The temporal frequency of periglacial debris flows in the Alps is ''unlikely'' to change significantly by the mid-21st century but is ''likely'' to decrease during the second part of the century under the A1B scenario, especially in summer ( [[#Stoffel--2011|Stoffel et al., 2011]] , 2014). There is ''medium confidence'' that most of the Northern Europe periglacial processes will disappear by the end of the century, even in the RCP2.6 scenario ( [[#Aalto--2017|Aalto et al., 2017]] ). The magnitude of debris flow events might increase ( [[#Lugon--2010|Lugon and Stoffel, 2010]] ) and the debris-flow season may last longer under the A1B scenario ( [[#Stoffel--2018|Stoffel and Corona, 2018]] ) ''.'' Quantitative data for the European Alps is highly site dependent ( [[#Haeberli--2013|Haeberli, 2013]] ).

'''Heavy snowfall, ice storms and hail:''' There is ''low confidence'' that climate change will affect ice and snow-related episodic hazards ( ''limited evidence'' ). The change in snowpack in the Alps is expected to lead to a possible reduction in overall avalanche activity by end of the century ( ''low confidence'' ), except possibly in winter and at high altitudes ( [[#Castebrunet--2014|Castebrunet et al., 2014]] ).

For ice storms, or freezing rainstorms, there is also ''limited evidence'' due to a limited number of studies. Heavy snowfalls have decreased in frequency in the past decades and this is expected to continue in the future climate ( ''low confidence'' ) ( [[#Beniston--2018|Beniston et al., 2018]] ). Freezing rain is projected to increase in western, central and southern Europe by the end of the century under RCP4.5 and RCP8.5 ( ''low confidence'' ) ( [[#Kämäräinen--2018|Kämäräinen et al., 2018]] ). Rain-on-snow events, are decreasing in northern regions ( [[#Pall--2019|Pall et al., 2019]] ) and by 48% on average in southern Scandinavia ( [[#Poschlod--2020|Poschlod et al., 2020]] ) due to decreases in snowfall.

'''In summary, future snow cover extent and seasonal duration will reduce''' ( high confidence ''') and it is''' virtually certain '''that glaciers will continue to shrink.''' '''A reduction of glacier ice volume is projected in the European Alps and Scandinavia''' ( high confidence '''). There is''' high confidence '''that permafrost will undergo increasing thaw and degradation over the 21st century.''' '''Most of the Northern Europe periglacial will disappear by the end of the century even for a lower emissions scenario''' ( medium confidence ''') and the debris-flow season may last longer in a warming climate''' ( medium confidence ''').'''

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<span id="coastal-and-oceanic-4"></span>
==== 12.4.5.5 Coastal and Oceanic ====

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'''Relative sea level:''' Around Europe, over 1900–2018, a new tide gauge-based reconstruction finds a regional mean RSL change of 1.08 [0.79 to 1.38] mm yr <sup>–1</sup> in the subpolar North Atlantic ( [[#Frederikse--2020|Frederikse et al., 2020]] ), compared to a GMSL change of around 1.7 mm yr <sup>–1</sup> [[IPCC:Wg1:Chapter:Chapter-2#2.3.3.3|Section 2.3.3.3]] and Table 9.5). For the period 1993–2018, the RSLR rates around Europe, based on satellite altimetry, increased to 2.17 [1.66 to 2.66] mm yr <sup>–1</sup> ( [[#Frederikse--2020|Frederikse et al., 2020]] ), compared to a GMSL change of 3.25 mm yr <sup>–1</sup> [[IPCC:Wg1:Chapter:Chapter-2#2.3.3.3|Section 2.3.3.3]] and Table 9.5).

Relative sea level rise is ''extremely likely'' to continue in the oceans around Europe. Regional mean RSLR projections for the oceans around Europe range from 0.4–0.5 m under SSP1-2.6 to 0.7–0.8 m under SSP5-8.5 for 2081–2100 relative to 1995–2014 (median values), which means that there are locally large deviations from the projected GMSL change ( [[IPCC:Wg1:Chapter:Chapter-9#9.6.3.3|Section 9.6.3.3]] ). These RSLR projections may however be underestimated due to potential partial representation of land subsidence in their assessment ( [[IPCC:Wg1:Chapter:Chapter-9#9.6.3.2|Section 9.6.3.2]] ). The signal is strongest for the North Sea and Atlantic coasts, followed by the Black Sea. The Baltic Sea, on the contrary, shows the lowest increase due to land uplift ( [[#Vousdoukas--2017|Vousdoukas et al., 2017]] ). The model agreement is higher for the Mediterranean and in line with previous findings by [[#Gualdi--2013|Gualdi et al. (2013)]] .

'''Coastal flood:''' The present-day 1-in-100-year ETWL is between 0.5 and 1.5 m in the MED basin and 2.5 and 5.0 m in the western Atlantic European coasts, around the UK and along the North Sea coast, and lower at 1.5–2.5 m along the Baltic Sea coast ( [[#Kirezci--2020|Kirezci et al., 2020]] ). Similar values are reported by [[#Vousdoukas--2018|Vousdoukas et al. (2018)]] .

There is ''high confidence'' that extreme total water level (ETWL) magnitude and occurrence frequency will increase throughout Europe (see Figure 12.4p–r), except in the northern Baltic Sea. Across the region, the 5–95th percentile range of the 1-in-100-year ETWL is projected to increase (relative to 1980–2014) by 4–40 cm and by 6–47 cm by 2050 under RCP4.5 and RCP8.5, respectively. By 2100, this range is projected to be 6–88 cm and 25–186 cm under RCP4.5 and RCP8.5, respectively (Figure 12.SM.6; [[#Vousdoukas--2018|Vousdoukas et al., 2018]] ; [[#Kirezci--2020|Kirezci et al., 2020]] ). Mass addition across the Gibraltar Strait may play a role, although the extent of this contribution is currently unclear ( [[#Lionello--2017|Lionello et al., 2017]] ). Furthermore, under RCP4.5, the present day 1-in-100-year ETWL is projected to have median return periods of between 1-in-5 and 1-in-20 years by 2050 and occur at least once per year by 2100 in the Mediterranean and Black Sea, while in the rest of Europe it is mostly projected to have median return periods of between 1-in-20-years and 1-in-50-years by 2050 and between 1-in-5-years and 1-in-20-years by 2100 ( [[#Vousdoukas--2018|Vousdoukas et al., 2018]] ). Under RCP8.5, occurrence of the present day 1-in-100-year ETWL is projected to increase further to median return periods of 1-in-1-year to 1-in-5-years by 2050 and occur more than once per year by 2100 in the Mediterranean and Black Sea, while in the rest of Europe it is mostly projected to have median return periods between 1-in-5-years and more than once per year by 2100.

'''Coastal erosion:''' Satellite-derived shoreline change estimates over 1984–2015 indicate shoreline retreat rates of around 0.5 m yr <sup>–1</sup> along the sandy coasts of WCE and MED, around 4 m yr <sup>–1</sup> in EEU (Caspian Sea region) and more or less stable shorelines in NEU ( [[#Luijendijk--2018|Luijendijk et al., 2018]] ; [[#Mentaschi--2018|Mentaschi et al., 2018]] ). [[#Mentaschi--2018|Mentaschi et al. (2018)]] report a coastal area loss of 270 km <sup>2</sup> over a 30-year period (1984–2015) along the Atlantic coastlines of Europe.

Projections indicate that sandy coasts throughout the continent (except those bordering the northern Baltic Sea) will experience shoreline retreat through the 21st century ( ''high confidence'' ). Median shoreline change projections (CMIP5) relative to 2010, show that, by mid-century, shorelines will retreat by between 25 m and 60 m along sandy coasts in WCE and MED under both RCP4.5 and RCP8.5 ( [[#Athanasiou--2020|Athanasiou et al., 2020]] ; [[#Vousdoukas--2020b|Vousdoukas et al., 2020b]] ). Mid-century median projections for NEU indicate virtually no shoreline retreat under RCP4.5, but a retreat of around 40 m under RCP8.5. By 2100, median shoreline retreats of around 50 m are projected in NEU and MED under RCP4.5, increasing to around 80 m under RCP8.5. End-century median projections for WCE are far higher at 100 m (RCP4.5) and 160 m (RCP8.5). The total length of sandy coasts in Europe that is projected to retreat by more than a median of 100 m by 2100 under RCP4.5 and RCP8.5 is about 12,000 km and 18,000 km respectively, an increase of approximately 54% ( [[#Vousdoukas--2020b|Vousdoukas et al., 2020b]] ).

Local assessments of both long term shoreline retreat and episodic coastal erosion are given by [[#Li--2014b|Li et al. (2014b)]] , [[#Toimil--2017|Toimil et al. (2017)]] , [[#Bon%20de%20Sousa--2018|Bon de Sousa et al. (2018)]] and [[#Le%20Cozannet--2019|Le Cozannet et al. (2019)]] . In terms of episodic coastal erosion, 31–88% of all Aegean beaches are projected to experience complete erosion, with a RCP4.5 sea level rise of 0.5 m and a surge of 0.6 m, but with substantial uncertainty ( [[#Monioudi--2017|Monioudi et al., 2017]] ).

'''Marine heatwave:''' The mean SST of the Atlantic Ocean and the Mediterranean has increased between 0.25°C and 1°C since 1982–1998. This mean ocean surface warming is correlated to longer and more frequent marine heatwaves in the region ( [[#Oliver--2018|Oliver et al., 2018]] ). Over the period 1982–2016, the coastlines of Europe experienced on average more than 2.0 MHW yr <sup>–1</sup> , with the eastern Mediterranean and Scandinavia experiencing 2.5–3 MHWs yr <sup>–1</sup> . The average duration was between 10 and 15 days. Changes over the 20th century, derived from MHW proxies, show an increase in frequency of between 1.0 and 2.0 MHWs per decade in Europe, although the trend is not statistically significant; with an increase in intensity per event in the North Atlantic and the Mediterranean, and a decrease in the Atlantic off the British Isles. The total number of MHW days per decade has increased in the Mediterranean ( [[#Oliver--2018|Oliver et al., 2018]] ).

Mean SST is projected to increase by 1°C–3°C around Europe by 2100, with a hotspot of around 4°C–5°C along the Arctic coastline of Europe under RCP4.5 and RCP8.5 scenarios (see Interactive Atlas), leading to a continued increase in MHW frequency, magnitude and duration ( [[#Oliver--2018|Oliver et al., 2018]] ; [[#MedECC--2020|MedECC, 2020]] ). Projections for SSP1-2.6 and SSP5-8.5 both show an increase in MHWs around Europe by 2081–2100, relative to 1985–2014 (Box 9.2, Figure 1). [[#Darmaraki--2019|Darmaraki et al. (2019)]] project that, by the end of the 21st century and under RCP8.5, there will be one MHW occurring every year in the northern Mediterranean sea, and that these MHWs would be three months longer, four times more intense, and 42 times more severe than present day MHWs in the region. [[#Frölicher--2018|Frölicher et al. (2018)]] show that, in Europe, the change in the probability for the number of days of MHWs exceeding the 99th percentile of the pre-industrial level is 4%, 15% and 30% for global warming levels of 1°C, 2°C and 3.5°C, respectively. MHW increase in the Mediterranean will impact on many species that live in shallow waters and have reduced motility, with consequences for related economic activities ( [[#Galli--2017|Galli et al., 2017]] ).

'''In general, there is''' high confidence '''that most coastal/ocean-related climatic impact-drivers in Europe will increase over the 21st century for all scenarios and time horizons. Relative sea level rise is''' extremely likely '''to continue around Europe (except in the northern Baltic Sea), contributing to increased coastal flooding in low-lying areas and shoreline retreat along most sandy coasts''' ( high confidence '''). Marine heatwaves are also expected to increase around the region over the 21st century''' ( high confidence ''').'''

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<span id="other"></span>
==== 12.4.5.6 Other ====

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'''Compound events:''' One typical compound event that is observed in the European area is compound flooding due to the combination of extreme sea level events and extreme precipitation events associated with high levels of runoff. In the present climate, the Mediterranean coasts are exposed to a higher probability of this type of compound flooding event ( [[#Bevacqua--2019|Bevacqua et al., 2019]] ). Under RCP8.5, the probability of these events is projected to increase along northern European coasts (west coast of UK, northern France, the east and south coast of the North Sea, and the eastern half of the Black Sea), with the percentage of coastline now experiencing such events at least once every 6 years increasing by between 3% and 11% by the end of the 21st century ( [[#Bevacqua--2019|Bevacqua et al., 2019]] ).

Under RCP8.5, regions in Russia, France and Germany are projected to experience an increase in the frequency and the length of wet and cold compound events, while Spain and Bulgaria are projected to stay longer in the hot and dry state by mid-century ( [[#Sedlmeier--2016|Sedlmeier et al., 2016]] ).

Compound events of dry and hot summers have increased in Europe. [[#Manning--2019|Manning et al. (2019)]] found that the probability of such compound events has increased across much of Europe between 1950–1979 and 1984–2013, notably in southern, eastern and western Europe. Compound hot and dry extremes are projected to increase in Europe by mid-century for the SRES A1B and RCP8.5 with a particularly strong signal projected in southern and eastern Germany and the Czech Republic ( [[#Sedlmeier--2016|Sedlmeier et al., 2016]] ).

The assessed direction of change in climatic impact-drivers for Europe and associated confidence levels are illustrated in Table 12.7, together with emergence time information ( [[#12.5.2|Section 12.5.2]] ). No assessable literature could be found for sand and dust storms, although these phenomena may be relevant in parts of the region.

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'''Table 12.7''' '''|''' '''Summary of confidence in direction of projected change in climatic impact-drivers in Europe, representing their aggregate characteristic changes for mid-century for scenarios RCP4.5, SSP2-4.5, SRES A1B, or above within each AR6 region (defined in Chapter 1), approximately corresponding (for CIDs that are independent of sea level rise) to global warming levels between 2°C and 2.4°C (see [[#12.4|Section 12.4]] for more details of the assessment method).''' The table also includes the assessment of observed or projected time-of-emergence of the CID change signal from the natural interannual variability if found with at least ''medium confidence'' in [[#12.5.2|Section 12.5.2]] .

[[File:fbc83e7f7056db2332db339e39a0ab01 IPCC_AR6_WGI_Chapter12_Table_12_7.jpg]]

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