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Indicator Assessment
Observed trends in frequency and severity of meteorological droughts
Note: Trends in frequency (upper) and severity (lower) of meteorological droughts between 1950 and 2012. Trends are based on a combination of three different drought indices - SPI, SPEI and RDI accumulated over 12-month periods. Dots: trends significant at ≥ 95%.
Model-based estimate of past change in summer low flows
Note: This map shows the ensemble mean trend in summer low flow from 1963 to 2000. ‘x’ denotes grid cells where less than three- quarters of the hydrological models agree on the direction of the trend.
Projected change in the frequency of meteorological droughts
Note: The maps show changes in the frequency of meteorological droughts for two future periods (2041-2070, left and 2071-2100, right) and for two emissions scenarios (RCP4.5, top and RCP8.5, bottom). Drought frequency is defined as the number of months in a 30 year period with the Standardised Precipitation Index accumulated over a 6 month period (SPI-6) having a value below -2.
Projected change in 20 year return level minimum flow and deficit volumes due to climate change and changes in water use
Note: Differences between the end of the 21st century (SRES A1B scenario) and the control period (1961-1990) for minimum discharges (left) and change in occurrence of deficits (right) for climate change only (top row) and a combination of climate change and water use (bottom row).
Past trends
Drought has been a recurrent feature of the European climate. From 2006–2010, on average 15 % of the EU territory and 17 % of the EU population have been affected by meteorological droughts each year. In the 1990s and 2000s the drought hotspots were the Mediterranean area and the Carpathian Region [i].
The frequency of meteorological droughts in Europe has increased since 1950 in parts of southern Europe and central Europe (Austria and Hungary), but droughts have become less frequent in northern Europe and parts of eastern Europe (Figure 1, left). Trends in drought severity (based on a combination of Standardised Precipitation Index (SPI), Standardised Precipitation Evapotranspiration Index (SPEI) and Reconnaissance Drought Index (RDI)) also show significant increases in the Mediterranean region (in particular the Iberian Peninsula, France, Italy and Albania) and parts of central and south-eastern Europe, and decreases in northern and parts of eastern Europe (Figure 1, right) [ii].
Most stream gauges in Europe show a decrease in summer low flows over the second half of the 20th century (Figure 2). However, current data availability is insufficient for attributing this trend to global climate change [iii].
Projections
An assessment of European meteorological droughts based on different drought indices and an ensemble of RCMs has projected drier conditions for southern Europe for the mid-21st century, with increases in the length, magnitude and area of drought events [iv]. In contrast, drought occurrence was projected to decrease in northern Europe [v]. Similar results were obtained in later studies based on different indices and climate projections [vi].
A model ensemble from the EURO-CORDEX community projects that the frequency and duration of extreme meteorological droughts (defined as having a value below –2 of the SPI-6) will significantly increase in the future [vii]. These projections showed the largest increases in frequency for extreme droughts in parts of the Iberian Peninsula, southern Italy and the eastern Mediterranean, especially at the end of the century with respect to the baseline period 1971–2000 (Figure 3). The changes are most pronounced for the RCP8.5 high emissions scenario and slightly less extreme for the moderate (RCP4.5) scenario.
Drought projections that also consider potential evapotranspiration (e.g. based on the SPEI, the Standardized Runoff Index (SRI) or the Supply–Demand Drought Index (SDDI)) showed substantially greater increases in the areas affected by drought than those based on the precipitation-based SPI alone. For example, the fraction of the Mediterranean region under drought was projected to increase by 10 % by the end of the 21st century based on RCP8.5 using the SPI, whereas an increase of 60 % was projected using the SPEI [viii].
The projected increases in droughts in large parts of southern Europe would increase competition between different water users, such as agriculture, industry, tourism and households.
The top row of Figure 4 depicts the projected impact of climate change on the 20-year return level minimum river flow (also known as minimum discharge; left) and deficit volumes (right), which are two measures for water availability and drought intensity. An increasing severity of river flow droughts is projected for most European regions, except for northern and north-eastern Europe. The greatest increase in drought risk is projected for southern Europe, but mean increases are also projected for large parts of central and north-western Europe. However, these increases show large seasonal variations and also depend on how the models represent evapotranspiration and soil moisture [ix].
The bottom row of Figure 4 shows the combined impact of climate change and changes in water consumption (based on the ‘Economy First’ water use scenario) on the same drought indices. In most regions, projected increases in water consumption further aggravate river flow droughts [x]. Water use and abstraction will exacerbate minimum low-flows in many parts of the Mediterranean region, leading to increased probabilities of water deficits when maximum water demand overlaps with minimum or low availability [xi].
[i] G. Sepulcre-Canto et al., ‘Development of a Combined Drought Indicator to Detect Agricultural Drought in Europe’,Natural Hazards and Earth System Sciences 12, no. 11 (29 November 2012): 3519–31, doi:10.5194/nhess-12-3519-2012; Jonathan Spinoni et al.,Meteorological Droughts in Europe: Events and Impacts, Past Trends and Future Projections, JRC100394, EUR 27748 EN (Luxembourg: Publications Office, 2016), http://bookshop.europa.eu/uri?target=EUB:NOTICE:LBNA27748:EN:HTML.
[ii] L. Gudmundsson and S. I. Seneviratne, ‘A Comprehensive Drought Climatology for Europe (1950-2013)’, inDrought: Research and Science-Policy Interfacing, ed. J. Andreu Alvarez et al. (London: CRC Press, 2015), 31–37, http://www.crcnetbase.com/doi/abs/10.1201/b18077-7; Jonathan Spinoni et al., ‘European Drought Climatologies and Trends Based on a Multi-Indicator Approach’,Global and Planetary Change 127 (April 2015): 50–57, doi:10.1016/j.gloplacha.2015.01.012; Spinoni et al.,Meteorological Droughts in Europe.
[iii] K. Stahl et al., ‘Streamflow Trends in Europe: Evidence from a Dataset of near-Natural Catchments’,Hydrology and Earth System Sciences 14, no. 12 (1 December 2010): 2367–82, doi:10.5194/hess-14-2367-2010; K. Stahl et al., ‘Filling the White Space on Maps of European Runoff Trends: Estimates from a Multi-Model Ensemble’,Hydrology and Earth System Sciences 16, no. 7 (11 July 2012): 2035–47, doi:10.5194/hess-16-2035-2012.
[iv] van der Linden and Mitchell, ‘ENSEMBLES: Climate Change and Its Impacts: Summary of Research and Results from the ENSEMBLES Project’.
[v] G. Henrich and A. Gobiet, ‘The Future of Dry and Wet Spells in Europe: A Comprehensive Study Based on the ENSEMBLES Regional Climate Model’,International Journal of Climatology 1 (2011): 101–23, doi:10.1002/joc.2421.
[vi] e.g. B. Orlowsky and S. I. Seneviratne, ‘Elusive Drought: Uncertainty in Observed Trends and Short- and Long-Term CMIP5 Projections’,Hydrology and Earth System Sciences 17, no. 5 (7 May 2013): 1765–81, doi:10.5194/hess-17-1765-2013; F. Giorgi, E. Coppola, and F. Raffaele, ‘A Consistent Picture of the Hydroclimatic Response to Global Warming from Multiple Indices: Models and Observations’,Journal of Geophysical Research: Atmospheres 119, no. 20 (27 October 2014): 11695–11708, doi:10.1002/2014JD022238; Jonathan Spinoni, Gustavo Naumann, and Jürgen V. Vogt, ‘Spatial Patterns of European Droughts under a Moderate Emission Scenario’,Advances in Science and Research 12 (2015), doi:10.5194/asr-12-179-2015; Danielle Touma et al., ‘A Multi-Model and Multi-Index Evaluation of Drought Characteristics in the 21st Century’,Journal of Hydrology, Drought processes, modeling, and mitigation, 526 (July 2015): 196–207, doi:10.1016/j.jhydrol.2014.12.011.
[vii] James H. Stagge et al., ‘Future Meteorological Drought: Projections of Regional Climate Models for Europe’, Drought R&SPI (Oslo, 2015), http://www.eu-drought.org/media/default.aspx/emma/org/10859960/DROUGHT+RSPI+Technical+Report+No.+25+-+Future+Meteorological+Drought+Projections+of+Regional+Climate.pdf.
[viii] Touma et al., ‘A Multi-Model and Multi-Index Evaluation of Drought Characteristics in the 21st Century’.
[ix] Wai Kwok Wong et al., ‘Climate Change Effects on Spatiotemporal Patterns of Hydroclimatological Summer Droughts in Norway’,Journal of Hydrometeorology 12, no. 6 (12 May 2011): 1205–20, doi:10.1175/2011JHM1357.1.
[x] G. Forzieri et al., ‘Ensemble Projections of Future Streamflow Droughts in Europe’,Hydrology and Earth System Sciences 18, no. 1 (9 January 2014): 85–108, doi:10.5194/hess-18-85-2014; Giovanni Forzieri et al., ‘Multi-Hazard Assessment in Europe under Climate Change’,Climatic Change 137 (2016): 105–19, doi:10.1007/s10584-016-1661-x.
[xi] EEA, ‘Water Resources in Europe in the Context of Vulnerability: EEA 2012 State of Water Assessment’, EEA Report (European Environment Agency, 2012), http://www.eea.europa.eu/publications/water-resources-and-vulnerability.
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.
Past trends in meteorological drought severity are based on a combination of Standardised Precipitation Index (SPI), Standardised Precipitation Evapotranspiration Index (SPEI) and Reconnaissance Drought Index (RDI). The indices are based on the precipitation and temperature data from the E-OBS gridded dataset. Hydrological drought is calculated as the decrease in summer low flows.
Future frequency and duration of extreme meteorological droughts is defined as having a value below –2 of the SPI-6 based on a model ensemble from the EURO-CORDEX project. Hydrological drought projections have been estimated as the 20-year return level minimum river flow (also known as minimum discharge and deficit volumes, which are two measures for water availability and drought intensity. Additionally, changes in water consumption (based on the ‘Economy First’ water use scenario) on the same drought indices have been considered.
Not applicable
Not applicable
The data required for the indicators in this sector are time series of precipitation (for meteorological droughts) and extreme low flows (for hydrological droughts, respectively). These time series can be observed or simulated for historical time periods and can be projected for future time windows, taking into account climate change and potentially also other drivers of change, such as land-use changes.
River flow and water level data are influenced by rainfall run-off and by hydromorphological changes of the river bed, e.g. through river engineering. Furthermore, homogeneous time series are generally shorter than those for meteorological data. Therefore, substantially more time may be required before statistically significant changes in hydrological variables can be observed, especially with respect to extreme and exceptional events (floods and droughts). Notwithstanding recent improvements of climate models to simulate large-scale patterns of precipitation and extreme events, projections of changes in precipitation remain uncertain, especially at catchment and local scales. Projections of river floods are plagued by the highest levels of uncertainty, as they often depend on changes in single extreme events, whereas changes in average and low-flow conditions depend on changes in precipitation on longer time scales (i.e. monthly to seasonal), which are more robust.
The main data sources for Europe-wide studies of the impacts of extreme hydrological events and their changes are global databases for natural disasters. Also at the European level, guidance for recording and sharing disaster damage and loss data is under development for Europe, coherent with the Sendai Framework for Disaster Risk Reduction.
Reliable information on the extent and impacts of water scarcity and droughts is indispensable for decision-making at all levels. An overview of water availability, water abstraction and water scarcity in Europe and more specifically for the Alpine region is discussed in several EEA reports). The water exploitation index is currently being revised to be calculated on the level of river basins instead of the administrative boundaries of countries. The Joint Research Centre (JRC) of the European Commission has developed a European Drought Observatory (EDO) for drought forecasting, assessment and monitoring. However, despite several activities, there is no systematic, comprehensive record of water scarcity and drought events in Europe, describing their duration, impact and severity, other than meteorological time series for precipitation.
No uncertainty has been specified
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/river-flow-drought-2/assessment or scan the QR code.
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