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Indicator Assessment
Past trends
Satellite observations of monthly snow cover extent in the Northern Hemisphere are available from 1967 onwards [i]. A detailed analysis based on multiple sources shows there have been significant decreases in Northern Hemisphere snow cover extent during the spring melt season since about 1980 (March to June; Figure 1, left) [ii]; in other seasons, the snow cover extent has remained stable or even slightly increased. A separate analysis for Europe (EEA-39 region) shows even larger reductions of 13 % for March and April, and 76 % for June between 1980 and 2015 (Figure 1, right).
Decreases in snow cover extent are caused by an earlier onset of melting and a shorter duration of the snow season. Since 1972, the duration of the snow season averaged over the Northern Hemisphere declined by five days per decade, but with substantial regional variation. The duration of the snow season has decreased by up to 25 days in western, northern and eastern Europe due to earlier spring melt, whereas it has increased by up to 15 days in south-eastern Europe due to an earlier onset of the snow season [iii].
The snow mass (i.e. the amount of water that the snow contains) is an important variable, as it affects the role of snow in the hydrological cycle. For the whole of the Northern Hemisphere, a 7 % decrease in March snow mass was observed between 1982 and 2009 [iv]. An extension of this data focusing on EEA member countries demonstrates a stronger average decline of 30 % for the period 1980–2015, although the year-to-year variation is large (Figure 2). Winter increases in precipitation have also led to an increase in snow mass at higher altitudes in Norway.
Projections
Northern Hemisphere snow cover will continue to shrink and snow seasons shorten as temperatures rise [v], although in the coldest regions snowfall can also increase in the middle of winter [vi]. The multi-model mean from the CMIP5 modelling exercise projects changes in March/April snow cover extent in the Northern Hemisphere during the 21st century ranging from 7 % for a low emissions scenario (RCP2.6) to 25 % for a high emissions scenario (RCP8.5) (Figure 3). The projected snow mass generally follows the snow cover extent with an estimated range of reduction from about 10 % for RCP2.6 to about 30 % for RCP8.5; projected reductions in the duration of the snow season range from about 10 days for RCP2.6 to about 40 days for RCP8.5 [vii].
Specific regional studies suggest significant reductions in snow mass in, for example, the Alps in general [viii], Switzerland [ix], the alpine range of Italy [x], the Pyrenees [xi], Norway [xii], the Turkish mountains [xiii] and the Balkan mountains [xiv]. These changes can have dramatic downstream effects as melt water contributes up to 60–70 % to annual river flows. Despite the projected decrease in long-term mean snow mass in the Northern Hemisphere, model simulations indicate occasional winters of heavy snowfall, but these become increasingly uncommon towards the end of the 21st century.
[i] T. W. Estilow, A. H. Young, and D. A. Robinson, ‘A Long-Term Northern Hemisphere Snow Cover Extent Data Record for Climate Studies and Monitoring’,Earth System Science Data 7, no. 1 (18 June 2015): 137–42, doi:10.5194/essd-7-137-2015.
[ii] 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, no. 1 (16 March 2011): 219–29, doi:10.5194/tc-5-219-2011; D. G. Vaughan et al., ‘Observations: Cryosphere’, inClimate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, ed. T. F. Stocker et al. (Cambridge; New York: Cambridge University Press, 2013), 317–82, http://www.climatechange2013.org/images/report/WG1AR5_Chapter04_FINAL.pdf.
[iii] Gwangyong Choi, David A. Robinson, and Sinkyu Kang, ‘Changing Northern Hemisphere Snow Seasons’,Journal of Climate 23, no. 19 (October 2010): 5305–10, doi:10.1175/2010JCLI3644.1; J. R. Mioduszewski et al., ‘Controls on Spatial and Temporal Variability in Northern Hemisphere Terrestrial Snow Melt Timing, 1979–2012’,Journal of Climate 28, no. 6 (March 2015): 2136–53, doi:10.1175/JCLI-D-14-00558.1.
[iv] 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, no. 12 (December 2011): 3517–29, doi:10.1016/j.rse.2011.08.014.
[v] Vaughan et al., ‘Observations: Cryosphere’.
[vi] I. Hanssen-Bauer et al., eds.,Klima I Norge 2100.Kunnskapsgrunnlag for Klimatilpasning Oppdatert I 2015 (Climate in Norway 2100. Knowledge Basis for Climate Change Adaptation Updated in 2015) [in Norwegian], NCCS Report, 2/2015 (Norsk klimaservicesenter (NKSS), 2015), http://www.miljodirektoratet.no/20804; Jouni Räisänen, ‘Twenty-First Century Changes in Snowfall Climate in Northern Europe in ENSEMBLES Regional Climate Models’,Climate Dynamics, no. 46 (2016): 339–53, doi:10.1007/s00382-015-2587-0.
[vii] 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 7, no. 1 (21 January 2013): 67–80, doi:10.5194/tc-7-67-2013.
[viii] Christian Steger et al., ‘Alpine Snow Cover in a Changing Climate: A Regional Climate Model Perspective’,Climate Dynamics 41, no. 3–4 (August 2013): 735–54, doi:10.1007/s00382-012-1545-3; Edgar Schmucki et al., ‘Simulations of 21st Century Snow Response to Climate Change in Switzerland from a Set of RCMs: Snow Response to Climate Change in Switzerland’,International Journal of Climatology 35, no. 11 (September 2015): 3262–73, doi:10.1002/joc.4205.
[ix] BAFU,Auswirkungen Der Klimaänderung Auf Wasserressourcen Und Gewässer. Synthesebericht Zum Projekt ‘Klimaänderung Und Hydrologie in Der Schweiz’ (CCHydro), vol. 2012, Umwelt-Wissen 1217 (Bern: Bundesamt für Umwelt, 2012).
[x] A. Soncini and D. Bocchiola, ‘Assessment of Future Snowfall Regimes within the Italian Alps Using General Circulation Models’,Cold Regions Science and Technology 68, no. 3 (September 2011): 113–23, doi:10.1016/j.coldregions.2011.06.011.
[xi] 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, no. 3–4 (2009): 384–96, doi:10.1016/j.jhydrol.2009.06.049.
[xii] Hanssen-Bauer et al.,Klima I Norge 2100.Kunnskapsgrunnlag for Klimatilpasning Oppdatert I 2015 (Climate in Norway 2100. Knowledge Basis for Climate Change Adaptation Updated in 2015) [in Norwegian].
[xiii] M. Özdoğan, ‘Climate Change Impacts on Snow Water Availability in the Euphrates-Tigris Basin’,Hydrology and Earth System Sciences 15, no. 9 (2011): 2789–2803, doi:10.5194/hess-15-2789-2011.
[xiv] FAO, ‘Forests and Climate Change in Eastern Europe and Central Asia’, Forests and Climate Change Working Paper 8 (Rome: Food and Agriculture Organization (FAO), 2010), http://www.fao.org/docrep/014/k9589e/k9589e.pdf.
In April 2013, the European Commission (EC) presented the EU Adaptation Strategy Package. This package consists of the EU Strategy on adaptation to climate change (COM/2013/216 final) and a number of supporting documents. The overall aim of the EU Adaptation Strategy is to contribute to a more climate-resilient Europe.
One of the objectives of the EU Adaptation Strategy is Better informed decision-making, which will be achieved by bridging the knowledge gap and further developing the European climate adaptation platform (Climate-ADAPT) as the ‘one-stop shop’ for adaptation information in Europe. Climate-ADAPT has been developed jointly by the EC and the EEA to share knowledge on (1) observed and projected climate change and its impacts on environmental and social systems and on human health, (2) relevant research, (3) EU, transnational, national and subnational adaptation strategies and plans, and (4) adaptation case studies.
Further objectives include Promoting adaptation in key vulnerablesectors through climate-proofing EU sector policies and Promoting action by Member States. Most EU Member States have already adopted national adaptation strategies and many have also prepared action plans on climate change adaptation. The EC also supports adaptation in cities through the Covenant of Mayors for Climate and Energy initiative.
In September 2016, the EC presented an indicative roadmap for the evaluation of the EU Adaptation Strategy by 2018.
In November 2013, the European Parliament and the European Council adopted the 7th EU Environment Action Programme (7th EAP) to 2020, ‘Living well, within the limits of our planet’. The 7th EAP is intended to help guide EU action on environment and climate change up to and beyond 2020. It highlights that ‘Action to mitigate and adapt to climate change will increase the resilience of the Union’s economy and society, while stimulating innovation and protecting the Union’s natural resources.’ Consequently, several priority objectives of the 7th EAP refer to climate change adaptation.
No targets have been specified.
Satellite observations on the monthly snow cover extent in the Northern Hemisphere are available since November 1966 from the Rutgers University Global Snow Lab. Reconstructed historical estimates are used to extend the time series back to 1922. Trend lines have been added for the satellite area.
Data on snow mass in Europe (exculding mountain areas) are available since 1979 from the Globsnow project. Trend lines have been added.
Projcted changes in snow cover extent up to 2100 are available from the CMIP5 ensemble of climate models for different climate forcing scenarios (RCPs).
Not applicable
Not applicable
Data on the cryosphere vary significantly with regard to availability and quality. Snow and ice cover have been monitored globally since satellite measurements started in the 1970s. Improved technology allows for more detailed observations and observations of a higher resolution.
Continuous efforts are being made to improve knowledge of the cryosphere. Scenarios for the future development of key components of the cryosphere have recently become available from the CMIP5 project, which has provided climate change projections for the IPCC AR5. Owing to their economic importance, considerable efforts have also been devoted to improving real-time monitoring of snow cover and sea ice.
No uncertainty has been specified
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/snow-cover-3/assessment or scan the QR code.
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