Climate change impacts and vulnerability in Europe 2016

Climate change impacts on environmental systems
local groundwater extraction or to other processes,
including tectonic activity.
In Europe, the potential impacts of sea level
rise include flooding, coastal erosion and the
submergence of flat regions along continental
coastlines and on islands. Rising sea levels can also
cause saltwater intrusion into low-lying aquifers, thus
threatening water supplies and endangering coastal
ecosystems and wetlands. Higher flood levels increase
the risk to life and property, including to sea dikes
and other infrastructure, with potential impacts on
tourism, recreation and transportation functions.
Low-lying coastlines with high population densities
and small tidal ranges are most vulnerable to sea level
rise, in particular where adaptation is hindered by a
lack of economic resources or by other constraints.
Damage associated with sea level rise is mostly
caused by extreme events, such as storm surges. Of
most concern are events when the surge coincides
with high tidal levels and increases the risk of coastal
flooding owing to extreme water levels. Changes
in the climatology of extreme water levels (i.e. the
frequency and height of maximum water levels) may
be caused by changes in local mean sea level (i.e. the
local sea level relative to land averaged over a year or
so), changes in tidal range, changes in the local wave
climate or changes in storm surge characteristics. One
multi-model study concluded that climate change can
both increase and decrease average wave height along
the European coastline, depending on the location and
season. Wave height is projected to change by less
than 5 % during the 21st century (Hemer et al., 2013).
Changes in storm surge characteristics are closely
linked to changes in the characteristics of atmospheric
storms, including the frequency, track and intensity of
the storms (see Section 3.2.6). The intensity of storm
surges can also be strongly affected by regional and
local-scale geographical features, such as the shape
of the coastline. Typically, the highest water levels are
found on the rising limb of the tide. The most intense
surge events typically occur during the winter months
in Europe.
The most obvious impact of extreme sea level is
flooding. The best known coastal flooding event in
Europe in living memory occurred in 1953 when
a combination of a severe storm surge and a high
spring tide caused in excess of 2 000 deaths in the
Netherlands, Belgium and the United Kingdom, and
damaged or destroyed more than 40 000 buildings
(Baxter, 2005; Gerritsen, 2005). Currently, around
200 million people live in the coastal zone in Europe,
as defined by Eurostat (Collet and Engelbert, 2013).
Coastal storms and storm surges can also have
considerable ecological impacts, such as seabird
wrecks, disruption to seal mating and pupping, and
increases in large mammal and turtle strandings.
Past trends: global mean sea level
Sea level changes can be measured using tide
gauges and remotely from space using satellite
altimeters. Many tide gauge measurements have long
multi‐decade time series, with some exceeding more
than 100 years. However, the results can be distorted
by various local effects. Satellite altimeters enable sea
level to be measured from space and give much better
spatial coverage (except at high latitudes). However,
the length of the altimeter record is limited to only
about two decades.
The IPCC AR5 estimated that GMSL rose by 19.5 cm in
the period between 1901 and 2015, which corresponds
to an average rate of around 1.7 mm/year (Figure 4.7,
updated from IPCC AR5). This rate is somewhat higher
than the sum of the known contributions to sea level
rise over this period (Church et al., 2013). This value
has been confirmed by more recent studies (Jevrejeva,
Moore et al., 2014; Wenzel and Schröter, 2014).
One reanalysis suggests that GMSL during the 20th
century rose at a lower rate of 1.2 ± 0.2 mm/year (Hay
et al., 2015), but this reanalysis has been criticised
for its non-representative selection of tide gauges
(Hamlington and Thompson, 2015). Evidence from
formal detection and attribution studies showing that
most of the observed increase in GMSL since the 1950s
can be attributed to anthropogenic climate change has
increased since the publication of the IPCC AR5 (Jordà,
2014; Slangen, Church et al., 2014; Clark et al., 2015).
All estimates for the rate of GMSL rise during the period
since 1993, for which satellite-based measurements are
available, are considerably higher than the 20th century
trend, at 2.6–3.2 mm/year (Church and White, 2011;
Masters et al., 2012; Church et al., 2013; Rhein et al.,
2013; Jevrejeva, Moore, et al., 2014; Clark et al.,
2015; Hay et al., 2015; Watson et al., 2015). Different
statistical methods for assessing sea level trends and
changes therein can come to somewhat different
conclusions (Visser et al., 2015). However, available
assessments agree that an acceleration in the rate of
GMSL rise since the early 1990s is detectable, despite
significant decadal variation. Global mean sea level in
2015 was the highest yearly average over the record
and ~ 70 mm higher than in 1993 (Blunden and Arndt,
2016).
The causes of GMSL rise over recent decades are now
reasonably well understood. Thermal expansion and
melting of glaciers account for around 75 % of the
measured sea level rise since 1971. The contribution
Climate change, impacts and vulnerability in Europe 2016 | An indicator-based report
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