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

==== 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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