134
1. Luterbacher and E. Xop1aki
1 Introduction
The Mediterranean region lies in an area of great climatic interest. It is influenced
by some of the most relevant mechanisms influencing the global climate system: it
marks a transitional zone between the deserts of North Africa, which are situated
within the arid zone of the subtropical high, and central and northern Europe, which
is influenced by the westerly flow during the whole year. In addition, the
Mediterranean climate is exposed to the South Asian Monsoon (SAM), the Siberian
High Pressure System, the Southern Oscillation (SO) and the North Atlantic
Oscillation (NAO). There is recent evidence that the teleconnection of ENSO has
extended its reach into parts of the Mediterranean in recent decades (Roda et al.
1997; Prize et al. 1998; Moron and Ward 1998; Kadioglu et al. 1999).
The main physical and physico-geographical factors controlling the spatial
distribution of the climatic conditions over the Mediterranean are the atmospheric
circulation, the latitude, the altitude and, generally, the orography, the Atlantic and
Mediterranean sea surface temperature (SST) distribution, the land-sea interactions
(distance from the sea) and smaller-scale processes (Xoplaki et al. 2000). The
Mediterranean area is a climate-sensitive region which is climatically stressed by
limited water resources and extremes of heat which help to create or exacerbate
existing socio-political tensions (Mann 200 I). Especially high-frequency (monthly,
seasonal, annual and interannual) as well as low-frequency (interdecadal) variations
of precipitation plays a crucial role in the management of regional agriculture,
ecosystems, environment and socio-economics and water resources (Xoplaki et al.
2000).
The current climate debate remains centered around questions related to the
reasons and the detection of spatial and temporal patterns of climate change over the
last few centuries. Better understanding of natural climate variability is of
importance to assist in the detection of any 'anthropogenic signal'. Reliable,
spatially and temporally highly resolved estimates of past natural climate variability
before the instrumental period are necessary to assess recent significant climate
trends. Over the last half millennium, Europe inclusive the whole Mediterranean
area experienced complex climatic change, which is believed to have been connected
with a marked change of the atmospheric circulation. Therefore, understanding of
natural climate variability is of much importance but it is difficult to diagnose from
the relatively short instrumental record.
For the western, central and eastern parts of the Mediterranean area there are
numerous studies dealing with the description of past climate variability and its
interactions with the tropical and extratropical modes of the global climate system,
climatic change or climate reconstructions (mainly temperature, precipitation and
atmospheric circulation over parts of the Mediterranean and for limited time
periods) prior to the instrumental period (Serre-Bachet and Guiot 1987; Guiot 1991;
Serre-Bachet et al. 1992; Camuffo and Enzi 1991, 1992, 1994, 1995; Grove and
Conterio 1994,1995; Martin-Vide and Barriendos 1995; Barriendos 1997; Glaser
et al. 1999; Camuffo et al. 2000; A1coforado et al. 2000; Felis et al. 2000; Xoplaki
1. Luterbacher and E. Xop1aki
1 Introduction
The Mediterranean region lies in an area of great climatic interest. It is influenced
by some of the most relevant mechanisms influencing the global climate system: it
marks a transitional zone between the deserts of North Africa, which are situated
within the arid zone of the subtropical high, and central and northern Europe, which
is influenced by the westerly flow during the whole year. In addition, the
Mediterranean climate is exposed to the South Asian Monsoon (SAM), the Siberian
High Pressure System, the Southern Oscillation (SO) and the North Atlantic
Oscillation (NAO). There is recent evidence that the teleconnection of ENSO has
extended its reach into parts of the Mediterranean in recent decades (Roda et al.
1997; Prize et al. 1998; Moron and Ward 1998; Kadioglu et al. 1999).
The main physical and physico-geographical factors controlling the spatial
distribution of the climatic conditions over the Mediterranean are the atmospheric
circulation, the latitude, the altitude and, generally, the orography, the Atlantic and
Mediterranean sea surface temperature (SST) distribution, the land-sea interactions
(distance from the sea) and smaller-scale processes (Xoplaki et al. 2000). The
Mediterranean area is a climate-sensitive region which is climatically stressed by
limited water resources and extremes of heat which help to create or exacerbate
existing socio-political tensions (Mann 200 I). Especially high-frequency (monthly,
seasonal, annual and interannual) as well as low-frequency (interdecadal) variations
of precipitation plays a crucial role in the management of regional agriculture,
ecosystems, environment and socio-economics and water resources (Xoplaki et al.
2000).
The current climate debate remains centered around questions related to the
reasons and the detection of spatial and temporal patterns of climate change over the
last few centuries. Better understanding of natural climate variability is of
importance to assist in the detection of any 'anthropogenic signal'. Reliable,
spatially and temporally highly resolved estimates of past natural climate variability
before the instrumental period are necessary to assess recent significant climate
trends. Over the last half millennium, Europe inclusive the whole Mediterranean
area experienced complex climatic change, which is believed to have been connected
with a marked change of the atmospheric circulation. Therefore, understanding of
natural climate variability is of much importance but it is difficult to diagnose from
the relatively short instrumental record.
For the western, central and eastern parts of the Mediterranean area there are
numerous studies dealing with the description of past climate variability and its
interactions with the tropical and extratropical modes of the global climate system,
climatic change or climate reconstructions (mainly temperature, precipitation and
atmospheric circulation over parts of the Mediterranean and for limited time
periods) prior to the instrumental period (Serre-Bachet and Guiot 1987; Guiot 1991;
Serre-Bachet et al. 1992; Camuffo and Enzi 1991, 1992, 1994, 1995; Grove and
Conterio 1994,1995; Martin-Vide and Barriendos 1995; Barriendos 1997; Glaser
et al. 1999; Camuffo et al. 2000; A1coforado et al. 2000; Felis et al. 2000; Xoplaki