Climate change, impacts and vulnerability in Europe ... - MemoFin.fr

Changes in the climate systemIn the lowlands of western Europe, snow is not apermanent winter phenomenon — it may come andgo several times during the cold months. Decreasingsnow cover trends have been observed in, forexample, Britain (Perry, 2006), Germany (Schwarzet al., 2007), Poland (Bednorz, 2011) and Nordiccountries (Wilson et al., 2010). In general, snowconditions in these areas correlate strongly withlarge-scale circulation patterns as indicated by theNAO (Bednorz, 2011; Brown and Robinson, 2011).The snow mass (i.e. the amount of water thatthe snow contains) is another important variabledescribing seasonal snow. In the NorthernHemisphere, a 7 % decrease has been observedbetween 1982 and 2009 for March (Takala et al.,2011). An extension of this data focusing on EEAmember countries, excluding mountain areas, alsodemonstrates this decline (Figure 2.11).ProjectionsThe seasonal snow cover is likely to continueshrinking (Stewart, 2009). Map 2.11 showsprojections of changes in annual snow fall daysbased on a multi-model ensemble. The multi‐modelmean shows decreases in days with snow fallexceeding 1 cm across Europe. Days with snowfall above 10 cm show increases in large partsof northern Europe and decreases in most otherregions. There is, however, considerable uncertaintyin these projections due to large differences betweenthe upper and lower limits of the model projections(not shown here). Because snow cover is sensitive tosnowfall as well as temperature, increased snowfallwill not necessarily translate into more snow on theground (Räisänen and Eklund, 2011). A study hasprojected a reduced number of snow cover days innorthern Europe (defined as 55–70 °N, 4.5–30 °E)Figure 2.11 Trend in March snow mass in Europe (excluding mountain areas) (1980–2011)Anomaly (%)50-30°-20°-10°0°10°20°30°40°50°60°70°403060°2050°10050°– 1040°– 2040°– 30– 400 500 0° 1000 150010°km20°30°40°– 501980 1985 1990 1995 2000 2005 2010Snow mass from GlobSnow SWE v1.230-year trend (– 8.9 % per decade)Snow coverSnow covered areasBare areasMountain areas (excluded)Outside coverageNote:Left: Anomalies for March snow mass and the 30-year linear trend in the EEA region (excluding mountain areas).Right: Snapshot of snow cover on 15 February 2009.Source: GlobSnow (http://www.globsnow.info) (Luojus et al., 2011).76 Climate change, impacts and vulnerability in Europe 2012