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Likewise, the frequency of extreme precipitation events and coastal high waters
are projected to increase in many regions across the globe (IPCC
2013
). Heavy
precipitation events are projected to increase particularly in higher latitudes, tropi-
cal regions, as well as in the Northern Hemispheric mid-latitudes during winter
(IPCC
2012a
). A recent study by Kunkel et al. (
2013a
) confi rms this projection.
They found that many regions of the Northern Hemisphere are expected to see a
20-30 % increase in the maximum precipitation by the end of this century if green-
house gas emissions continue to rise (Kunkel et al.
2013a
). They analyzed moisture
in the atmosphere, upward motion of air in the atmosphere, and horizontal winds,
all factors that contribute to extreme precipitation events. Following the Clausius-
Clapeyron equation, a warmer atmosphere as a result of increased greenhouse gas
concentration can hold more water. This increased moisture content dominates the
other factors (upward motion and horizontal winds) and hence fuels more intense
extreme precipitation events (Kunkel et al.
2013a
).
The confi dence remains medium or low regarding projections of droughts,
fl oods, and cyclones. However, the projected precipitation and temperature patterns
are most likely impacting natural hazards. Increasing extreme precipitation events,
for example, can infl uence the occurrence of fl oods and landslides (IPCC
2012a
).
Drought events, likewise, can be intensifi ed by reduced overall precipitation and
increased temperatures which affect evapotranspiration (IPCC
2012a
). Increased
drought events, for example, are projected with medium confi dence in southern
Europe and the Mediterranean region, central Europe, central North America,
Central America and Mexico, northeast Brazil, and southern Africa (IPCC
2012a
).
Sea-level rise is projected to continue to increase during the twenty-fi rst century. All
of the Representative Concentration Pathways scenarios predict an even higher rate
of increase than the rate observed during 1971-2000, which will be mainly caused
by increased thermal expansion of the oceans and melting of glaciers and ice sheets
(IPCC
2013
). Regarding cyclone projections, precipitation rates and average wind
speed are expected to increase in the coming century (IPCC
2012a
; Seneviratne
et al.
2012
) (see next section for more details).
2.2.4
Infl uence of Climate Change on Past
and Future Tropical Cyclones
Formal detection of past trends in measures of tropical cyclone activity is con-
strained by the length and quality of the historical data records and uncertain under-
standing of natural variability in these measures, particularly on decadal time-scales
(Knutson et al.
2010
; Lee et al.
2012
; Seneviratne et al.
2012
; Kunkel et al.
2013a
,
b
;
Zwiers et al.
2013
). When designing Early Warning Systems (EWS), it is useful to
consider past and projected trends on the spatial scale of a particular ocean basin,
but trends focused on more targeted regions such as those defi ned by islands or sec-
tions of coastline are most relevant. Unfortunately, this narrowing of the spatial
scales of interest introduces further uncertainty into both detection of past trends
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