Climate, Climate Variability and Impacts in the Mediterranean Area: An Overview
23
recently was re-run with the present distribution of vegetation exchanged against the
land cover as suggested by Reale and Dirmeyer with the vegetation for the end ofthe
Roman classical period (Reale and Shukla, 2000). Many of the properties of
summertime precipitation suggested by both the historical and archeological
evidence are recreated in the simulations. For example, North Africa from the Nile
valley to the Atlas mountains are simulated as significantly wetter with the
vegetation at the time of the Roman classical period. Much of the southern Europe
(e.g. Greece and the Iberian Peninsula) are also wetter, with reduced rainfall over
the Mediterranean Sea itself. The model results also underline the interaction
between the Mediterranean area and the Hadley circulation. There is a stronger
northward propagation of the Inter-Tropical Convergence Zone and its associated
rains into the Sahel during boreal summer in the Roman classical period case by
which also rainfall over sub-Saharan Africa is affected. In these computations all
other parameters except the vegetation cover remained unchanged. In view of the
complex interactions between the surface and the atmosphere this may not be a fully
adequate procedure to really proof that climate is changed by changes of land-use,
but it gives a hint for future research needs.
Font Tullot (1988) reports about strong cold spells over the Iberian Peninsula
around the years 570 and in the winter of 763/4 when large snow masses were
recorded and a "Siberian" cold 859/60. During this period with variable climate
large floods of the rivers Guadiana (620 and 686), Tajo (849) and Guadalquivir (974
and 1011) are reported and also very dry years such as 675 and between 650 and
1000 the climate in Galicia in principle was dry and relatively warm. Again around
10 I 0 cold spells occurred.
The years 500 - 700 A.D. were marked as "dark age" because of the bubonic
plague which again reduced population but brought resilience to the "natural"
ecosystems. Rural estates were abandoned and hydraulic constructions destroyed.
After 700 A.D. until about 1500 A.D. agriculture expanded with improved irrigation
systems and terracing. New crops were introduced which were brought primarily
into the Iberian Peninsula by the Arabic. Wheat, barley, olives, legumes, almonds,
fruit trees were grown in semi-arid conditions, which must have been similar as
today, and the ecosystem is believed to have been in equilibrium at that time.
Again, around 1350 A.D., a severe depopulation of at least 30% took place due
to the Black Death. 1500 A.D. the Arabs were expelled from Spain, irrigation
systems were abandoned and badlands formed. Mulberry were replaced by olive
trees. From 1700 A.D. on there has been a steady increase of popUlation and an
intensification of agriculture. Forest clearing accompanied with soil erosion went on.
The "little ice age" did not leave traces in the Mediterranean area. The more recent
variability and trends are discussed in sections 2 and 6 and are the topic of the
chapters 4 and 5.
23
recently was re-run with the present distribution of vegetation exchanged against the
land cover as suggested by Reale and Dirmeyer with the vegetation for the end ofthe
Roman classical period (Reale and Shukla, 2000). Many of the properties of
summertime precipitation suggested by both the historical and archeological
evidence are recreated in the simulations. For example, North Africa from the Nile
valley to the Atlas mountains are simulated as significantly wetter with the
vegetation at the time of the Roman classical period. Much of the southern Europe
(e.g. Greece and the Iberian Peninsula) are also wetter, with reduced rainfall over
the Mediterranean Sea itself. The model results also underline the interaction
between the Mediterranean area and the Hadley circulation. There is a stronger
northward propagation of the Inter-Tropical Convergence Zone and its associated
rains into the Sahel during boreal summer in the Roman classical period case by
which also rainfall over sub-Saharan Africa is affected. In these computations all
other parameters except the vegetation cover remained unchanged. In view of the
complex interactions between the surface and the atmosphere this may not be a fully
adequate procedure to really proof that climate is changed by changes of land-use,
but it gives a hint for future research needs.
Font Tullot (1988) reports about strong cold spells over the Iberian Peninsula
around the years 570 and in the winter of 763/4 when large snow masses were
recorded and a "Siberian" cold 859/60. During this period with variable climate
large floods of the rivers Guadiana (620 and 686), Tajo (849) and Guadalquivir (974
and 1011) are reported and also very dry years such as 675 and between 650 and
1000 the climate in Galicia in principle was dry and relatively warm. Again around
10 I 0 cold spells occurred.
The years 500 - 700 A.D. were marked as "dark age" because of the bubonic
plague which again reduced population but brought resilience to the "natural"
ecosystems. Rural estates were abandoned and hydraulic constructions destroyed.
After 700 A.D. until about 1500 A.D. agriculture expanded with improved irrigation
systems and terracing. New crops were introduced which were brought primarily
into the Iberian Peninsula by the Arabic. Wheat, barley, olives, legumes, almonds,
fruit trees were grown in semi-arid conditions, which must have been similar as
today, and the ecosystem is believed to have been in equilibrium at that time.
Again, around 1350 A.D., a severe depopulation of at least 30% took place due
to the Black Death. 1500 A.D. the Arabs were expelled from Spain, irrigation
systems were abandoned and badlands formed. Mulberry were replaced by olive
trees. From 1700 A.D. on there has been a steady increase of popUlation and an
intensification of agriculture. Forest clearing accompanied with soil erosion went on.
The "little ice age" did not leave traces in the Mediterranean area. The more recent
variability and trends are discussed in sections 2 and 6 and are the topic of the
chapters 4 and 5.