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

Changes in the climate systemways. First of all, it has important effects onglobal sea level. Furthermore, it modifies oceantemperatures and circulation, vegetation andland-surface albedo.• Glaciers: Glaciers and ice caps influence sea level,river flow and freshwater supply, ecosystemsand many human activities.• Permafrost: Permafrost is ecologically importantin high mountains and in Arctic areas. Itinfluences the water content of soils, vegetation,ecosystems and landscapes. The thawingof permafrost causes structural change oflandscapes and potentially increases naturalhazards. In the Arctic, thawing permafrostcontributes to the release of GHGs, includingCH 4, from frozen organic material.• Arctic and Baltic Sea ice: Sea ice covers large areas.It reflects light more than open sea and impactson ocean circulation, which transports heatfrom the equator to the poles. The sea ice and itsvariation affects navigation and the exploitationof natural resources.• Lake and river ice: Seasonal lake ice is importantfor aquatic ecosystems and in some areas forwinter tourism. This indicator is presented inSection 3.3.6.Data quality and data needsData on the cryosphere vary significantly withregard to availability and quality. Snow and icecover have been monitored globally since satellitemeasurements started in the 1970s. Improvementsin technology allow for more detailed observationsand higher resolution. High quality long-term datais also available on glaciers throughout Europe.Direct historical area-wide data on the Greenland icesheet tracks about 20 years, but reconstructions givea 200 000 year perspective. Data on permafrost aregenerally restricted to the last 15–25 years.Continuous efforts are being made to improve onknowledge of the cryosphere. Intensive developmentwork is under way to develop projections, whichare essential for scenarios of climate change impactsand adaptation. Due to their economic importancespecial effort is also devoted to improving real-timemonitoring of, for example, snow cover and seaice. In general, glacier and sea ice extent are easilyobservable but ice mass information, for example, isdifficult to obtain.2.3.2 Snow coverRelevanceSnow influences the climate and climate‐relatedsystems because of its high reflectivity, insulatingproperties, effects on water resources andecosystems, and cooling of the atmosphere.A decrease in snow cover contributes to acceleratedclimate change (Flanner et al., 2011).In Europe about half of the 800 million peoplelive on areas that have snow cover in Januaryin an average winter. Changes in snow coveraffect human well-being through effects on wateravailability, hydropower, navigation, infrastructure,the livelihoods of indigenous Arctic people,environmental hazards, winter recreation andoutdoor light conditions. Variation in snow coveraffects winter road and rail maintenance, and theexploitation of natural resources in cold regions(ACIA, 2005; UNEP, 2007). Snow cover is mostsensitive to climate change at low elevations intemperate regions.Key messages: 2.3.2 Snow cover• Snow cover extent in the Northern Hemisphere has fallen by 7 % in March and 11 % in April during thepast 4 decades. In winter and autumn no significant changes have occurred.• Snow mass in Europe has decreased by 7 % in March from 1982 to 2009.• Model simulations project widespread reductions in the extent and duration of snow cover in Europeover the 21st century. However, there are large uncertainties in the projections.• Changes in snow cover affect the Earth's surface reflectivity, water resources, the flora and fauna andtheir ecology, agriculture, forestry, tourism, snow sports, transport and power generation.74 Climate change, impacts and vulnerability in Europe 2012