Climate, Climate Variability and Impacts in the Mediterranean Area: An Overview
7
which have not much to offer to mitigate the effect of strong rains. In addition
agriculture, industrialization, urbanization and tourism draw on the water resources
which causes sinking ground water levels in these areas to an extent that in some
areas rivers draw water out of the surrounding landscapes rather then fed them with
water CEFEDA 1992).
The Mediterranean basin is unique in the world because of its geographical
position which brings it under the descending branch of the Hadley circulation in
summer while the Westerlies prevail during the winter season. The alternation
between these two regimes and the strong int1uence of the Mediterranean Sea, which
constitute a more conservative but, as recent investigations have shown, nevertheless
changing element, makes the region vulnerable to large scale climate changes. The
problems arising in this area therefor differ considerably from those faced in other
areas of the world at which the World Climate Research Programme CWCRP) and
the International Geosphere-Biosphere Programme (IGBP) so far focussed their
research activities. The Mediterranean constitutes a counterpart of the Baltic Sea
which, as the Mediterranean, is surrounded by land masses but is dominated by the
Westerlies and the surrounding landscapes are mostly wet. This makes a comparison
of the hydrological cycles and the role of the different types of vegetation in both
areas highly desirable.
The complex structure of the land masses surrounding the Mediterranean Sea
makes it difficult to generalize the climatic variability, to assess the impact of
vegetation on the hydrological cycle, and to model the Mediterranean climate. It
requires high resolution models to resolve at least to a certain degree the coastal
features and the variety of ecosystems which is necessary to include the boundary
layer effects of both the int1uence ofthe sea and ofthe topography. At the same time
the topping of the basin by the large scale circulation pattern has to be accounted for.
This complexity makes it difficult to predict how the Mediterranean climate may
respond to global climate changes and explains the weakness of global climate
models in this region.
In this chapter some aspects of the climate variability and related issues in the
Mediterranean basin are discussed from which research needs result to better
understand (i) the role of the Mediterranean area in the global climate system, (ii)
the dependency of the Mediterranean climate and its vegetation on the large scale
circulation systems of both the ocean and the atmosphere, (iii) the internal processes
which couple the Mediterranean Sea through the sea-land circulation systems with
the inland hydrology and vegetation, and, finally, (iv) the possible responses of the
Mediterranean biosphere and water resources to climate variability and the future
development of global climate.
In the following sections firstly the present climatic situation in the
Mediterranean area is sketched. This prompts the question how the present situation
is related to past climatic developments and whether an inspection of past cycles
may give us a hint about what succeeding generations may have to expect. The
expectation is large that climate models may provide us with more reliable scenarios
about future developments. This requires a better resolution of the Mediterranean
7
which have not much to offer to mitigate the effect of strong rains. In addition
agriculture, industrialization, urbanization and tourism draw on the water resources
which causes sinking ground water levels in these areas to an extent that in some
areas rivers draw water out of the surrounding landscapes rather then fed them with
water CEFEDA 1992).
The Mediterranean basin is unique in the world because of its geographical
position which brings it under the descending branch of the Hadley circulation in
summer while the Westerlies prevail during the winter season. The alternation
between these two regimes and the strong int1uence of the Mediterranean Sea, which
constitute a more conservative but, as recent investigations have shown, nevertheless
changing element, makes the region vulnerable to large scale climate changes. The
problems arising in this area therefor differ considerably from those faced in other
areas of the world at which the World Climate Research Programme CWCRP) and
the International Geosphere-Biosphere Programme (IGBP) so far focussed their
research activities. The Mediterranean constitutes a counterpart of the Baltic Sea
which, as the Mediterranean, is surrounded by land masses but is dominated by the
Westerlies and the surrounding landscapes are mostly wet. This makes a comparison
of the hydrological cycles and the role of the different types of vegetation in both
areas highly desirable.
The complex structure of the land masses surrounding the Mediterranean Sea
makes it difficult to generalize the climatic variability, to assess the impact of
vegetation on the hydrological cycle, and to model the Mediterranean climate. It
requires high resolution models to resolve at least to a certain degree the coastal
features and the variety of ecosystems which is necessary to include the boundary
layer effects of both the int1uence ofthe sea and ofthe topography. At the same time
the topping of the basin by the large scale circulation pattern has to be accounted for.
This complexity makes it difficult to predict how the Mediterranean climate may
respond to global climate changes and explains the weakness of global climate
models in this region.
In this chapter some aspects of the climate variability and related issues in the
Mediterranean basin are discussed from which research needs result to better
understand (i) the role of the Mediterranean area in the global climate system, (ii)
the dependency of the Mediterranean climate and its vegetation on the large scale
circulation systems of both the ocean and the atmosphere, (iii) the internal processes
which couple the Mediterranean Sea through the sea-land circulation systems with
the inland hydrology and vegetation, and, finally, (iv) the possible responses of the
Mediterranean biosphere and water resources to climate variability and the future
development of global climate.
In the following sections firstly the present climatic situation in the
Mediterranean area is sketched. This prompts the question how the present situation
is related to past climatic developments and whether an inspection of past cycles
may give us a hint about what succeeding generations may have to expect. The
expectation is large that climate models may provide us with more reliable scenarios
about future developments. This requires a better resolution of the Mediterranean