Snow cover (CLIM 008) - Assessment published Nov 2012
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Climate change (Primary topic)
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
- CLIM 008
Key policy question: What is the trend in snow cover and snow fall across Europe?
- Snow cover extent in the Northern Hemisphere has fallen by 7 % in March and 11 % in April during the past 4 decades. In winter and autumn no significant changes have occurred.
- Snow mass in the Northern hemisphere has decreased by 7 % in March from 1982 to 2009; snow mass in Europe has decreased even more, but with large inter-annual variation.
- Model simulations project widespread reductions in the extent and duration of snow cover in Europe over 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 and their ecology, agriculture, forestry, tourism, snow sports, transport and power generation.
Trend in autumn, winter and spring snow cover extent over the Northern Hemisphere
Note: The figure shows the mean autumn (September, October, November), winter (December, January, February) and spring (March, April, May) snow cover extent over the Northern Hemisphere in 1967–2011 with linear trends.
- Fall, Winter, And Spring Northern Hemisphere Snow Cover Extent provided by Rutgers University Global Snow Lab
Trend in March snow mass in Europe
Note: The figure (left) shows anomalies for March snow mass in the EEA region (excluding mountain areas) and the 30-year linear trend. The map (right) shows a snapshot of snow cover on 15 February 2009.
- Final Report. GlobSnow Deliverable 3.5. GlobSnow. provided by Finnish Meteorological Institute (FMI)
Projected changes in annual snowfall days
Note: The figure shows the multi-model mean of changes in annual snowfall days from 1971-2000 to 2041-2070 exceeding (left) 1 cm and (right) 10 cm based on six RCM simulations and the emission scenario A1B
- Probabilities of Adverse Weather Affecting Transport in Europe: Climatology and Scenarios up to the 2050s provided by Finnish Meteorological Institute (FMI)
Satellite observations on the monthly snow cover extent in the Northern Hemisphere are available since November 1966 [i]. Figure 1 shows that snow covered on average 45 % of the land area of the Northern Hemisphere in winter (December to February), varying from less than 41 % in 1980–1981 to over 48 % in 1977–1978 [ii]. Satellite data shows that there are no trends from 1967 to 2010 in snow cover in fall (September-November) and winter (December-February), but snow cover in spring has decreased significantly. According to a detailed statistical analysis of the snow cover in the Northern hemisphere the rate of decrease in March and April in the period 1970–2010 was around 0.8 million km2 per decade, corresponding to a 7 % decrease in March and an 11 % decrease in April from the pre-1970 values [iii]. Trends in snow cover vary in different parts of Europe. In some mountain regions, such as the Alps and the Norwegian mountains, snow depth has decreased at low elevations where the temperature increased over the freezing point whereas it has increased at high elevations where both precipitation and temperature have increased but the temperature has remained below the freezing point for extended periods [iv]. In other mountain regions such as the Carpathians, Tatra, Pyrenees, and Caucasus, there have been either decreasing or variable trends [v] [vi]. In the lowlands of western Europe, snow is not a permanent winter phenomenon — it may come and go several times during the cold months. Decreasing snow cover trends have been observed in, for example, Britain[vii], Germany[viii], Poland [ix] and Nordic countries[x]. In general, snow conditions in these areas correlate strongly with large-scale circulation patterns as indicated by the NAO [xi] [xii]. The snow mass (i.e. the amount of water that the snow contains) is another important variable describing seasonal snow. In the Northern Hemisphere, a 7 % decrease has been observed between 1982 and 2009 for March[xiii]. An extension of this data focusing on EEA member countries, excluding mountain areas, also demonstrates this decline (Figure 2).
The seasonal snow cover is likely to continue shrinking [xiv]. Figure 3 shows projections of changes in annual snow fall days based on a multi-model ensemble. The multi-model mean shows decreases in days with snow fall exceeding 1 cm across Europe. Days with snow fall above 10 cm show increases in large parts of northern Europe and decreases in most other regions. There is, however, considerable uncertainty in these projections due to large differences between the upper and lower limits of the model projections. Because snow cover is sensitive to snowfall as well as temperature, increased snowfall will not necessarily translate into more snow on the ground [xv]. A study has projected a reduced number of snow cover days in northern Europe (defined as 55–70 °N, 4.5–30 °E) of up to 40–70 days in 2071–2100 compared to the baseline period 1961–1990. The study used a RCM driven by an ensemble of 7 GCMS for 4 SRES emission scenarios[xvi]. The projections depend on the emission scenario and the underlying GCM simulation. Model projections of 21st century change in snow water equivalent (SWE) in the Northern Hemisphere under the SRES A1B emissions scenario suggest that SWE increases in the coldest parts of the Northern Hemisphere continents, but decreases elsewhere [xvii]. The multi-model mean from the CMIP5 modelling exercise projects changes in March/April snow cover in the Northern Hemisphere during the 21st century of about 7 % and 27 % in a low emission scenario (RCP 2.6) and a high emission scenario (RCP 8.5), respectively [xviii]. Despite the projected decrease in long-term mean SWE in the Northern Hemisphere, model simulations indicate occasional winters of heavy snowfall, but these become increasingly uncommon towards the end of the 21st century. Significant reductions in snow mass in Europe are likely to occur in Switzerland[xix], the alpine range of Italy[xx], the Pyrenees[xxi], the Turkish mountains[xxii] and Balkan mountains [xxiii]. In these areas the change can have dramatic effects as melt water contributes up to 60–70 % of annual river flows.
[i] RUGSL, „Fall, Winter, and Spring Northern Hemisphere Snow Cover Extent from the Rutgers University Global Snow Lab“, Climate Science: Roger Pielke Sr., 2011, http://pielkeclimatesci.wordpress.com/2011/05/30/fall-winter-and-spring-northern-hemisphere-snow-cover-extent-from-the-rutgers-university-global-snow-lab/.
[ii] RUGSL, „Fall, Winter, and Spring Northern Hemisphere Snow Cover Extent from the Rutgers University Global Snow Lab“.
[iii] R. D. Brown and D.A. Robinson, „Northern Hemisphere spring snow cover variability and change over 1922–2010 including an assessment of uncertainty“, The Cryosphere 5 (2011): 219–229, doi:10.5194/tc-5-219-2011.
[iv] Daniele Bocchiola and Guglielmina Diolaiuti, „Evidence of climate change within the Adamello Glacier of Italy“, Theoretical and Applied Climatology 100, Nr. 3–4 (August 14, 2009): 351–369, doi:10.1007/s00704-009-0186-x; Iris T Stewart, „Changes in Snowpack and Snowmelt Runoff for Key Mountain Regions“, Hydrological Processes 23, Nr. 1 (Januar 1, 2009): 78–94, doi:10.1002/hyp.7128; A. V. Dyrral, Analysis of past snow conditions in Norway met.no report (Oslo: Norwegian Meteorological Institute, 2010), http://met.no/Forskning/Publikasjoner/filestore/ClimateReport_10_2010.pdf.
[v] Henry F. Diaz et al., „Variability of Freezing Levels, Melting Season Indicators, and Snow Cover for Selected High-Elevation and Continental Regions in the Last 50 Years“, Climatic Change 59, Nr. 1–2 (2003): 33–52, doi:10.1023/A:1024460010140.
[vi] M Lapin, P Faško, and J Pecho, „Snow Cover Variability and Trends in the Tatra Mountains in 1921–2006“, ed. V Ducrocq, Proceedings of the 29th International Conference on Alpine Meteorology, Chambery, France (Météo France, 2007), http://www.cnrm.meteo.fr/icam2007/ICAM2007/extended/manuscript_174.pdf.
[vii] Matthew Perry, A spatial analysis of trends in the UK climate since 1914 using gridded data sets, Bd. 2006, Climate Memorandum 21 (Devon: Met Office, 2006).
[viii] Rixa Schwarz, Sven Harmeling, and Christoph Bals, Auswirkungen des Klimawandels auf Deutschland (Berlin: Germanwatch, 2007), http://www.germanwatch.org/klima/klideu07.pdf.
[ix] Ewa Bednorz, „Synoptic Conditions of the Occurrence of Snow Cover in Central European Lowlands“, International Journal of Climatology 31, Nr. 8 (Juni 30, 2011): 1108–1118, doi:10.1002/joc.2130.
[x] Donna Wilson, Hege Hisdal, and Deborah Lawrence, „Has streamflow changed in the Nordic countries? – Recent trends and comparisons to hydrological projections“, Journal of Hydrology 394, Nr. 3–4 (November 26, 2010): 334–346, doi:10.1016/j.jhydrol.2010.09.010.
[xi] Bednorz, „Synoptic Conditions of the Occurrence of Snow Cover in Central European Lowlands“.
[xii] Brown and Robinson, „Northern Hemisphere spring snow cover variability and change over 1922–2010 including an assessment of uncertainty“.
[xiii] Matias Takala et al., „Estimating northern hemisphere snow water equivalent for climate research through assimilation of space-borne radiometer data and ground-based measurements“, Remote Sensing of Environment 115, Nr. 12 (Dezember 2011): 3517–3529, doi:10.1016/j.rse.2011.08.014.
[xiv] Stewart, „Changes in Snowpack and Snowmelt Runoff for Key Mountain Regions“.
[xv] Jouni Räisänen and Joonas Eklund, „21st Century changes in snow climate in Northern Europe: a high-resolution view from ENSEMBLES regional climate models“, Climate Dynamics (April 23, 2011), doi:10.1007/s00382-011-1076-3.
[xvi] Erik Kjellström et al., „21st Century Changes in the European Climate: Uncertainties Derived from an Ensemble of Regional Climate Model Simulations“, Tellus A 63, Nr. 1 (2011): 24–40, doi:10.1111/j.1600-0870.2010.00475.x.
[xvii] Jouni Räisänen, „Warmer climate: less or more snow?“, Climate Dynamics 30, Nr. 2–3 (Juli 12, 2007): 307–319, doi:10.1007/s00382-007-0289-y.
[xviii] C. Brutel-Vuilmet, M. Ménégoz, and G. Krinner, „An analysis of present and future seasonal Northern Hemisphere land snow cover simulated by CMIP5 coupled climate models“, The Cryosphere Discussions 6, Nr. 4 (August 8, 2012): 3317–3348, doi:10.5194/tcd-6-3317-2012.
[xix] BAFU, Auswirkungen der Klimaänderung auf Wasserressourcen und Gewässer. Synthesebericht zum Projekt «Klimaänderung und Hydrologie in der Schweiz» (CCHydro)., Bd. 2012, Umwelt-Wissen 1217 (Bern: Bundesamt für Umwelt, Bern., 2012).
[xx] A. Soncini and D. Bocchiola, „Assessment of future snowfall regimes within the Italian Alps using general circulation models“, Cold Regions Science and Technology 68, Nr. 3 (September 2011): 113–123, doi:10.1016/j.coldregions.2011.06.011.
[xxi] J.I. López-Moreno, S. Goyette, and M. Beniston, „Impact of climate change on snowpack in the Pyrenees: Horizontal spatial variability and vertical gradients“, Journal of Hydrology 374, Nr. 3–4 (elokuu 2009): 384–396, doi:10.1016/j.jhydrol.2009.06.049.
[xxii] M. Özdoğan, „Climate change impacts on snow water availability in the Euphrates-Tigris basin“, Hydrology and Earth System Sciences 15, Nr. 9 (2011): 2789–2803, doi:10.5194/hess-15-2789-2011.
[xxiii] FAO, Forests and climate change in Eastern Europe and Central Asia. Forests and Climate Change Working Paper 8 (Rome: Food and Agriculture Organization of the United Nations, 2010), http://www.fao.org/docrep/014/k9589e/k9589e.pdf.
Fall, Winter, And Spring Northern Hemisphere Snow Cover Extent
provided by Rutgers University Global Snow Lab
Projected changes in annual snowfall days
provided by Finnish Meteorological Institute (FMI)
Final Report. GlobSnow Deliverable 3.5. GlobSnow.
provided by Finnish Meteorological Institute (FMI)
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