In the short term, aerosol effects may counter the effect of rising concentrations
of greenhouse gases in some areas. Results from transient experiments for around
the middle of the twenty-first century suggest that once aerosol effects are considered, precipitation over Southern Europe and Turkey may increase slightly
(Kattenberg et al. 1996). These changes are far from certain, as they depend on both
the aerosol scenario used and how aerosols are represented in the models. In any
case, the long prospect remains of hotter, drier conditions throughout the
Mediterranean region, as the relative influence of greenhouse gases increases over
time.
In addition to the tendency for reduced rainfall, a reduction in moisture availability is also predicted. Indeed, moisture availability is determined both by water
gains from precipitation and water losses through runoff and evapotranspiration.
The future global temperature increase will cause an increase in evapotranspiration,
and therefore loss of available water.
The projected seasonal precipitation variations are also likely to reduce water
availability during the plant growth season (Kattenberg et al. 1996; Wigley 1992),
due to water runoff in the winter. This implies that even when precipitation is
forecasted to increase, available water can decrease if the gains are surpassed by
losses. On the other hand, if rainfall peaking episodes increase, the likelihood is that
water will not be stored in the soil, but lost as runoff (Segal et al. 1994). The
evaluation of moisture availability by GCMs can be complex due to the difficulty in
assessing potential evapotranspiration and the hydrological cycle (Rind et al. 1990).
Anyway, the global influence of GHGs is likely to grow and the long-term prospect
is of a tendency for dryness throughout the Mediterranean region.
8.6.4 Changes in Extreme Events
The Mediterranean Basin as aforementioned, is a region particularly vulnerable to
global warming with specificities at the local level. In addition to changes in the
mean climate, more fluctuations in extreme events, which are a component of
natural climate change variability, were recorded both in terms of frequency and
intensity. Presently, about 75% of the daily hot extremes over land is mainly due to
climate change, and the frequency of very hot days, exceeding the 99th percentile of
the daily maximum temperature, has tripled during the twentieth century (e.g.,
Fischer and Knutti 2015).
Attention should also be paid by all stakeholders to changes in seasonal shifts
and the timing of climate change events. Based on phenology as well as climate
data, seasonal shifts have been reported in different regions, mainly in early spring
and shortened winters. Phenomena including extended warm periods over the years,
and shifting in hot weather profiles, have multidisciplinary impacts on distinct but
interconnected issues such as the environment, human health, agriculture, and
energy demand (Founda et al. 2019). For example, Fontana et al. (2015) showed
that heat stress in Italy had a strong impact on wheat yield.
8.6 A Brief Analysis of the Mediterranean …
297
of greenhouse gases in some areas. Results from transient experiments for around
the middle of the twenty-first century suggest that once aerosol effects are considered, precipitation over Southern Europe and Turkey may increase slightly
(Kattenberg et al. 1996). These changes are far from certain, as they depend on both
the aerosol scenario used and how aerosols are represented in the models. In any
case, the long prospect remains of hotter, drier conditions throughout the
Mediterranean region, as the relative influence of greenhouse gases increases over
time.
In addition to the tendency for reduced rainfall, a reduction in moisture availability is also predicted. Indeed, moisture availability is determined both by water
gains from precipitation and water losses through runoff and evapotranspiration.
The future global temperature increase will cause an increase in evapotranspiration,
and therefore loss of available water.
The projected seasonal precipitation variations are also likely to reduce water
availability during the plant growth season (Kattenberg et al. 1996; Wigley 1992),
due to water runoff in the winter. This implies that even when precipitation is
forecasted to increase, available water can decrease if the gains are surpassed by
losses. On the other hand, if rainfall peaking episodes increase, the likelihood is that
water will not be stored in the soil, but lost as runoff (Segal et al. 1994). The
evaluation of moisture availability by GCMs can be complex due to the difficulty in
assessing potential evapotranspiration and the hydrological cycle (Rind et al. 1990).
Anyway, the global influence of GHGs is likely to grow and the long-term prospect
is of a tendency for dryness throughout the Mediterranean region.
8.6.4 Changes in Extreme Events
The Mediterranean Basin as aforementioned, is a region particularly vulnerable to
global warming with specificities at the local level. In addition to changes in the
mean climate, more fluctuations in extreme events, which are a component of
natural climate change variability, were recorded both in terms of frequency and
intensity. Presently, about 75% of the daily hot extremes over land is mainly due to
climate change, and the frequency of very hot days, exceeding the 99th percentile of
the daily maximum temperature, has tripled during the twentieth century (e.g.,
Fischer and Knutti 2015).
Attention should also be paid by all stakeholders to changes in seasonal shifts
and the timing of climate change events. Based on phenology as well as climate
data, seasonal shifts have been reported in different regions, mainly in early spring
and shortened winters. Phenomena including extended warm periods over the years,
and shifting in hot weather profiles, have multidisciplinary impacts on distinct but
interconnected issues such as the environment, human health, agriculture, and
energy demand (Founda et al. 2019). For example, Fontana et al. (2015) showed
that heat stress in Italy had a strong impact on wheat yield.
8.6 A Brief Analysis of the Mediterranean …
297