72
H.-J. Bolle
dioxide pool cannot be concluded from a few local flux measurements. Careful
integration over the ecosystems is necessary. Forest fires, forest or macchia
regrowth, industrial emissions, and the carbon exchange through the sea surface and
the fertilization of the sea with iron containing minerals have to be accounted for as
well. The carbon and water cycles are intimately coupled to each other as shown in
Fig. 18. A basin wide aggregation becomes urgent.
Whether the mostly man-made changes at the land surfaces with their impact on
the regional climates reach out also to the larger scale via atmospheric exchange -
are, so to say, "exported" to other regions - is difficult to decide. Some model studies
seem to indicate it but the changes introduced into these model calculations have
been very drastic and transient developments which have to include a manifold of
interrelated parameters so far have not been completed.
7.4 What Are the Future Perspectives?
The answer to this question can only be given by climate models and therefor is
related to the problem just referred to, that global climate models seem to be not very
reliable in the case of the Mediterranean. Small shifts of atmospheric activity belts
may cause large effects in the topographically highly structured landscape. At
present it looks like as if the variability - the frequency and the amplitude of extreme
events - is increasing, an observation which seems to be true for other regions of the
world as well. If one effect of global change is the intensification of the Westerlies
and of the hydrological cycle the hypothesis has much in favour that winters will
become wetter. If further the Hadley circulation does not get weaker or retreat and
the atmospheric aerosol content and cloudiness stay constant, summers may get
hotter due to a higher atmospheric thermal radiation caused by higher air
temperatures and increasing amounts of water vapour and carbon dioxide. This will
especially be the case in areas where vegetation is scarce and water for evaporative
cooling is rare. Thus the seasonal differences may increase.
Interannual to decadal climate variability and the tendency towards extended
drought periods as well as precipitation concentrating in heavy rainfall events falling
on dried-out hard soils or burned areas and causing flash floods are severe threads
for ecosystems, economy and human life in the Mediterranean area. Consequently
knowledge about the relationship between these threads and global warming is
mandatory to take measures for sustainable development of the region.
The most important clamp of all these problems is the water budget because the
sustainable development of the Mediterranean region is limited by the available
fresh water resources. The fundamental question therefore is, how these limited
water resources can efficiently be distributed to obtain an optimal result for living
conditions, productivity, ecology and economy in all Mediterranean countries.
In the global map that shows the modelled expectcd prccipitation changes under
the increasing greenhouse effect in the recently published IPCC 2001 assessment
report (Houghton et aI., 2001, McCarthy, 2001) there is only one red spot: The
Mediterranean. In the so-called scenario A2 - carbon dioxide increases by the year
H.-J. Bolle
dioxide pool cannot be concluded from a few local flux measurements. Careful
integration over the ecosystems is necessary. Forest fires, forest or macchia
regrowth, industrial emissions, and the carbon exchange through the sea surface and
the fertilization of the sea with iron containing minerals have to be accounted for as
well. The carbon and water cycles are intimately coupled to each other as shown in
Fig. 18. A basin wide aggregation becomes urgent.
Whether the mostly man-made changes at the land surfaces with their impact on
the regional climates reach out also to the larger scale via atmospheric exchange -
are, so to say, "exported" to other regions - is difficult to decide. Some model studies
seem to indicate it but the changes introduced into these model calculations have
been very drastic and transient developments which have to include a manifold of
interrelated parameters so far have not been completed.
7.4 What Are the Future Perspectives?
The answer to this question can only be given by climate models and therefor is
related to the problem just referred to, that global climate models seem to be not very
reliable in the case of the Mediterranean. Small shifts of atmospheric activity belts
may cause large effects in the topographically highly structured landscape. At
present it looks like as if the variability - the frequency and the amplitude of extreme
events - is increasing, an observation which seems to be true for other regions of the
world as well. If one effect of global change is the intensification of the Westerlies
and of the hydrological cycle the hypothesis has much in favour that winters will
become wetter. If further the Hadley circulation does not get weaker or retreat and
the atmospheric aerosol content and cloudiness stay constant, summers may get
hotter due to a higher atmospheric thermal radiation caused by higher air
temperatures and increasing amounts of water vapour and carbon dioxide. This will
especially be the case in areas where vegetation is scarce and water for evaporative
cooling is rare. Thus the seasonal differences may increase.
Interannual to decadal climate variability and the tendency towards extended
drought periods as well as precipitation concentrating in heavy rainfall events falling
on dried-out hard soils or burned areas and causing flash floods are severe threads
for ecosystems, economy and human life in the Mediterranean area. Consequently
knowledge about the relationship between these threads and global warming is
mandatory to take measures for sustainable development of the region.
The most important clamp of all these problems is the water budget because the
sustainable development of the Mediterranean region is limited by the available
fresh water resources. The fundamental question therefore is, how these limited
water resources can efficiently be distributed to obtain an optimal result for living
conditions, productivity, ecology and economy in all Mediterranean countries.
In the global map that shows the modelled expectcd prccipitation changes under
the increasing greenhouse effect in the recently published IPCC 2001 assessment
report (Houghton et aI., 2001, McCarthy, 2001) there is only one red spot: The
Mediterranean. In the so-called scenario A2 - carbon dioxide increases by the year