Climate of Europe

The climate of Europe shows large differences from west (Maritime) to east (Continental) and from north (Arctic) to south (Mediterranean) (Figure 1). The climatic effects of the distribution of land and ocean are further complicated by numerous high mountain ranges which act as physical barriers to atmospheric circulation and often introduce large precipitation gradients within small regions (Frei and Schar, 1998).

The studies carried out using the European long data records have shown some evident trends in European climate. Most of Europe has revealed increases in surface air temperature during the 20th century which, averaged across the continent, amounts to about 0.8 °C in annual temperature (ECSN 1995; EEA 1998; Beniston et al., 1998) (Figure 2). This warming has been largest over northwestern Russia and the Iberian Peninsula (Nicholls et al., 1996; Onate and Pou, 1996) and stronger in winter than in summer (Maugeri and Nanni, 1998; Brunetti et al., 2000). An exception is Fennoscandia, which has recorded cooling in both mean maximum and mean minimum temperature during (1910-1995) in winter but warming in summer (Tuomenvirta et al., 1998). The last decade in Europe (1990-1999) has been the warmest in the instrumental record, both annually and for winter. Increases in growing season length have also been observed in Europe, for example in western Russia (Jones and Briffa, 1995) and in Fennoscandia (Carter, 1998). The evidence for longer growing seasons in Europe is also supported by phenological data collected in central Europe (Menzel and Fabian, 1999). Trends in annual precipitation differ between northern Europe (wetting) and

Figure 1. Climate classification for Europe (adapted from Koeppe and de Jong, 1958) (Palutikof, 2000).

southern Europe (drying), reflecting a wider hemispheric pattern of contrasting zonal-mean precipitation trends between high and low latitudes (Dai et al., 1997; Hulmeetal., 1998). Precipitation over northern Europe has increased by between 10 and 40% in the 20th century, whereas some parts of southern Europe have dried by up to 20%.

Analyses of trends in extreme weather events in Europe have generally been limited to national studies, making it difficult to provide a Europe-wide overview. However, the studies made by Gruza et al. (1999) over Russia and that made by Osborn et al. (2000) over UK showed a diffuse increase in hot/cold day frequencies, precipitation intensities, etc.

1900 1920 1940 I960 1990

Figure 2. European mean temperatures anomalies over land, 1901-1997, with respect to 1961-1990 average. Annul (top), winter (middle) and summer (bottom) (data from IPCC DDC).

1900 1920 1940 I960 1990

Figure 2. European mean temperatures anomalies over land, 1901-1997, with respect to 1961-1990 average. Annul (top), winter (middle) and summer (bottom) (data from IPCC DDC).

Projection of future climate in impact studies are mainly obtained using climate scenarios based on General Circulation Model simulations. A recent work carried out within the ACACIA project and subsequently developed further for the IPCC (Hulme and Carter, 2000) has provided a complete set of future climate scenarios for Europe.

Annual temperatures over Europe warm at a rate of between 0.1 and 0.4 K per decade. This warming of future annual climate is greatest over southern Europe (Spain, Italy, Greece) and northeast Europe (Finland, western Russia), and least along the Atlantic coastline of the continent. Seasonal patterns indicated that in winter, the continental interior of eastern Europe and western Russia warm more rapidly than elsewhere. Whilst in summer, the pattern of warming displays a strong south-to-north gradient, with southern Europe warming at a lower rate than northern Europe.

The general pattern of future change in annual precipitation over Europe is for widespread increases in northern Europe (between +1 and +2% per decade), rather smaller decreases across southern Europe (maximum: -1% per decade), and small or ambiguous changes in central Europe (France, Germany, Hungary, Belarus).

There is a marked contrast between winter and summer patterns of precipitation change. Most of Europe gets wetter in the winter season (between +1 and +4% per decade), the exception being the Balkans and Turkey where winters become drier. In summer, there is a strong gradient of change between northern Europe (wetting of up to +2% per decade) and southern Europe (drying of up to -5% per decade).

The scenarios do not explicitly quantify changes in daily weather extremes. However, it is very likely that frequencies and intensities of summer heat-waves will increase throughout Europe, likely that intense precipitation events will increase in frequency, especially in winter, and that summer drought risk will increase in central and southern Europe (Hulme and Carter, 2000).

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