Climate change impacts and vulnerability in Europe 2016

Changes in the climate system
3.2.6 Wind storms
Key messages
• Storm location, frequency and intensity have shown considerable decadal variability across Europe over the past century,
such that no significant long-term trends are apparent.
• Recent studies on changes in winter storm tracks generally project an extension eastwards of the North Atlantic storm
track towards central Europe and the British Isles.
• Climate change simulations show diverging projections on changes in the number of winter storms across Europe.
However, most studies agree that the risk of severe winter storms, and possibly of severe autumn storms, will increase
for the North Atlantic and northern, north-western and central Europe over the 21st century.
Relevance
Wind storms are atmospheric disturbances that are
defined by strong sustained wind. They can range
from relatively small and localised events to large
features covering a substantial part of the continent.
Large storms in Europe are extra-tropical cyclones;
they develop from low-pressure weather systems that
capture their energy from the temperature contrast
between the sub-tropical and polar air masses
that meet in the Atlantic Ocean. In northern and
north‐western Europe, severe cyclones can occur all
year. In central Europe, severe cyclones occur mainly
between November and February, but weaker cyclones
can also occur in other seasons.
Wind storms can lead to structural damage, flooding
and storm surges (see Sections 4.2, 4.3 and 5.1), which
may be caused either by the wind itself, in particular
short gusts, or by accompanying heavy precipitation.
These events can have large impacts on human health
and on vulnerable systems, such as forests, as well
as transport and energy infrastructures. According
to Munich RE's natural catastrophe loss database
(NatCatSERVICE) (Munich RE, 2015), storms were the
costliest natural hazard (in terms of insured losses) in
Europe between 1980 and 2013; they ranked fourth
in terms of the number of human casualties (see
Section 5.1). The European regions most strongly
affected were north-western, western and northern
Europe, in particular regions close to the coast (Outten
and Esau, 2013; Osinski et al., 2015).
Studies of storm activity have increased in recent years
as a result of improved observational datasets, the
development of algorithms for the identification and
quantification of these phenomena, and improved
understanding of the causation of extreme weather
events. In addition, high-resolution GCM simulations for
both present-day climate and climate change scenarios
are increasingly becoming available. Nevertheless,
there are still considerable uncertainties in the
historical records and in our understanding of the
processes influencing current storm activity and how
these may be affected by climate change (Ulbrich et al.,
2009; Nikulin et al., 2011; Krueger et al., 2013; Outten
and Esau, 2013; Feser et al., 2014; Pfahl, 2014; Osinski
et al., 2015).
Past trends
Studies of past changes in extra-tropical storms
have used a variety of methods, making it difficult to
compare the results of different studies or to assess
if there is any underlying trend in climate change.
Storm location and intensity in Europe has shown
considerable variation over the past century, but
northern hemisphere storm tracks and intensity have
likely shifted northwards since at least 1970 (Ulbrich
et al., 2009; Hov et al., 2013).
Wind data at the local or regional levels can show a
series of decreases and increases continuing over
several decades. Long records of wind speed for
various regions across Europe indicate that storm
intensity (i.e. storminess) has not significantly
changed over the past 200 years. Available studies
of storminess in north-western Europe indicate
relatively high levels during the 1880s, followed by
below-average conditions between the 1930s and
1960s, a pronounced increase in storminess until the
mid-1990s, and average or below-average activity
afterwards. Somewhat similar patterns were observed
in other parts of Europe (Matulla et al., 2007; Feser
et al., 2014).
There is low confidence in the robustness of reanalysis
results for extreme wind speeds before the middle
of the 20th century (Hartmann et al., 2013; Feser
et al., 2014). A single reanalysis study for the period
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