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Indicator Assessment
Observed trends in maximum annual five-day consecutive precipitation in winter and summer
Note: The figure shows the observed trend in maximum annual five day precipitation over Europe between 1960 and 2018 for Winter (December-January-February) and Summer (June-July-August). The change is expressed in mm/decade. Grid boxes outlined in solid black contain at least three stations and so are likely to be more representative of the grid box. Significant (at the 5% level) long-term trend is shown by a black dot.
Projected changes in heavy precipitation in winter and summer
Note: Projected changes in heavy precipitation (in %) in winter and summer from 1971-2000 to 2071–2100 for the RCP8.5 scenario based on the ensemble mean of different regional climate models (RCMs) nested in different general circulation models (GCMs).
Past trends
The majority of observation-based studies that investigate trends in extreme rainfall intensity are based on data recorded at the daily time scale. An index for the maximum annual precipitation over five consecutive days (Rx5d) shows significant increases up to 5 mm per decade over northern and north-western Europe in winters (Figure 1 left). In summers, significant increases up to 5mm per decade are shown for eastern and parts of southern Europe (Figure 1 right). The same index shows decreases of more than 4 mm per decade in southern Europe, particularly the south west in winter (Figure 1 left) and more than 3 mm in summer in south-western Europe and parts of central Europe (Figure 1 right). The increase in northern and north-eastern Europe is a consequence of the observed shift towards the pole of the North Atlantic storm track and the weakening of Mediterranean storms [i].
A wider literature review suggests that heavy precipitation events have become more intense and more frequent in Europe on average, but there are important differences across regions, seasons, time periods, heavy precipitation indices and underlying datasets. A recent study has shown that the number of days with very heavy precipitation over Europe has increased on average by about 45 % (for the period1981-2013 compared with 1951-1980)[ii]. Studies generally agree that heavy precipitation has become more intense in northern and north-eastern Europe since the 1950s, even though not all changes are statistically significant. Different studies and indices show diverging trends for south-western and southern Europe.
Records of daily mean precipitation are often insufficient to study trends and changes in heavy precipitation. The damage associated with heavy precipitation often originates from sub-daily localised heavy precipitation events, which can lead to costly flash floods. Owing to a lack of available data, only a limited number of studies have focused on large regional scale assessments of sub-daily precipitation [iii]. A recent review concluded that extreme sub-daily precipitation events have generally increased in Europe, even in regions with decreases in mean rainfall, but there is large variability across regions, seasons and event durations [iv].
Projections
Global warming is projected to lead to a higher intensity of precipitation and longer dry periods in Europe [v]. Projections show an increase in heavy daily precipitation in most parts of Europe in winter, by up to 35 % during the 21st century. Heavy precipitation in winter is projected to increase over most of Europe, with increases of up to 30 % in north-eastern Europe (Figure 2 left) due to increases in the frequency of extreme extratropical cyclones [xiii]. In summer, an increase is also projected in most parts of Europe but decreases are projected for some regions in southern and south-western Europe, partly due to a projected decrease in cyclone frequency in the Mediterranean (Figure 2 right) [vi]. Similar patterns were found for other heavy precipitation indices [vii].
The continued increase in the spatial and temporal resolution of global and regional climate models has generally improved the representation of extreme precipitation and increased confidence in model-based projections [viii]. However, regional climate models with spatial resolutions of between 10 and 30 km typically used in climate change studies are still too coarse to explicitly represent sub-daily localised heavy precipitation events [ix]. Evidence from high-resolution climate models suggests that the intensity of sub-daily extreme rainfall is likely to increase in the future, whereby an increase of (theoretically estimated) ~7 % per °C appears most likely in many regions [x]. Findings in a recent study have suggested that future increases in intense precipitation events will be more pronounced at the sub-daily time scale over Spain and the western European seaboard. This could mean that changes in short-duration precipitation extremes in winter will exceed expectations, based on the estimated ~7 % per °C increase in these areas [xi]. A very high-resolution model (typically 1-5 km) used in explicit weather forecasts of convection was recently employed in a climate change experiment in a region of the United Kingdom. The results of the study project an intensification of short-duration heavy rain in the summer, with significantly more events exceeding the high thresholds indicative of serious flash flooding [xii].
[i] Øystein Hov et al., Extreme Weather Events in Europe: Preparing for Climate Change Adaptation (Oslo: Norwegian Meteorological Institute, 2013), http://www.dnva.no/binfil/download.php?tid=58783.
[ii] E.M Fischer and R. Knutti, Observed heavy precipitation increase confirms theory and early models, in nature climate change 6 (November 2016): doi:10.1038/nclimate3110
[iii] D. L. Hartmann et al., Observations: Atmosphere and Surface, in Climate 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), Chapter 2, http://www.climatechange2013.org/report/full-report/.
[iv] S. Westra et al., Future Changes to the Intensity and Frequency of Short-Duration Extreme Rainfall, in Reviews of Geophysics 52, no. 3 (September 1, 2014): 2014RG000464, doi:10.1002/2014RG000464.
[v] IPCC, Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. Special Report of the Intergovernmental Panel on Climate Change (Cambridge: Cambridge University Press, 2012), http://ipcc-wg2.gov/SREX/report/; Hov et al., Extreme Weather Events in Europe: Preparing for Climate Change Adaptation.
[vi] Daniela Jacob et al., EURO-CORDEX: New High-Resolution Climate Change Projections for European Impact Research, Regional Environmental Change 14, no. 2 (2014): 563–78, doi:10.1007/s10113-013-0499-2. M. Hawcroft et al., Significantly increased extreme precipitation expected in Europe and North America from extratropical cyclones, Environmental Research Letters 13, no 12 (2018), doi: 10.1088/1748-9326/aaed59
[vii] J. Rajczak, P. Pall, and C. Schär, Projections of Extreme Precipitation Events in Regional Climate Simulations for Europe and the Alpine Region, Journal of Geophysical Research: Atmospheres 118, no. 9 (2013): 3610–26, doi:10.1002/jgrd.50297; J. Sillmann et al., Climate Extremes Indices in the CMIP5 Multimodel Ensemble. Part 2: Future Climate Projections, Journal of Geophysical Research: Atmospheres 118, no. 6 (March 27, 2013): 2473–93, doi:10.1002/jgrd.50188; 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 (October 2014): 2014JD022238, doi:10.1002/2014JD022238; J. Rajczak and C. Schär, Projects of Future Precipitation Extremes Over Europe: A Multimodel Assessment of Climate Simulations, Journal of Geophysical Research: Atmospheres 122, no. 20 (2017): 10773-800, doi: 10.1002/2017JD027176.
[viii] Pushkar Kopparla et al., Improved Simulation of Extreme Precipitation in a High-Resolution Atmosphere Model, Geophysical Research Letters 40, no. 21 (November 16, 2013): 5803–8, doi:10.1002/2013GL057866; Filippo Giorgi et al., Changes in Extremes and Hydroclimatic Regimes in the CREMA Ensemble Projections, Climatic Change 125, no. 1 (April 12, 2014): 39–51, doi:10.1007/s10584-014-1117-0; Myriam Montesarchio et al., Performance Evaluation of High-Resolution Regional Climate Simulations in the Alpine Space and Analysis of Extreme Events, Journal of Geophysical Research: Atmospheres 119, no. 6 (March 27, 2014): 2013JD021105, doi:10.1002/2013JD021105.
[ix] Steven C. Chan et al., The Value of High-Resolution Met Office Regional Climate Models in the Simulation of Multihourly Precipitation Extremes, Journal of Climate 27, no. 16 (March 21, 2014): 6155–74, doi:10.1175/JCLI-D-13-00723.1; Nikolina Ban, Juerg Schmidli, and Christoph Schär, Heavy Precipitation in a Changing Climate: Does Short-Term Summer Precipitation Increase Faster?, Geophysical Research Letters 42, no. 4 (February 28, 2015): 2014GL062588, doi:10.1002/2014GL062588.
[x] Westra et al., Future Changes to the Intensity and Frequency of Short-Duration Extreme Rainfall.
[xi] E. Scoccimarro et al., Projected Changes in Intense Precipitation over Europe at the Daily and Subdaily Time Scales, Journal of Climate published online July 2015, doi: 10.1175/JCLI-D-14-00779.1
[xii] Elizabeth J. Kendon et al., “Heavier Summer Downpours with Climate Change Revealed by Weather Forecast Resolution Model, Nature Climate Change 4, no. 7 (June 1, 2014): 570–76, doi:10.1038/nclimate2258; Ban, Schmidli, and Schär, Heavy Precipitation in a Changing Climate; Jascha Lehmann, Dim Coumou, and Katja Frieler, Increased Record-Breaking Precipitation Events under Global Warming, Climatic Change 132, no. 4 (July 7, 2015): 501–15, doi:10.1007/s10584-015-1434-y.
[xiii] Hawcroft, M., et al., 2018, Significantly increased extreme precipitation expected in Europe and North America from extratropical cyclones, Environmental Research Letters13(12), p. 124006 (DOI: 10.1088/1748-9326/aaed59).
Heavy precipitation is defined as the maximum annual 5-day consecutive precipitation. Trends are calculated for the period between 1960 and 2015.
Projected changes in heavy precipitation are defined as changes in the 95th percentile of daily precipitation (only days with precipitation >1 mm/day are considered). Changes between the 1971-2000 and 2071-2100 are calculated using a multi-model ensemble forced by RCP8.5.
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'. This shall be achieved by bridging the knowledge gap and further developing the European climate adaptation platform (Climate-ADAPT) as the ‘first-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 sub-national adaptation strategies and plans; and (4) adaptation case studies. It was relaunched in early 2019 with a new design and updated content. Further objectives include 'Promoting adaptation in key vulnerable sectors 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 November 2018, the Commission published its evaluation of the 2013 EU Adaptation Strategy. The evaluation package includes a Report from the Commission, a Commission Staff Working Document, the Adaptation preparedness scoreboard country fiches, and the reports from the JRC PESETA III project. This evaluation includes recommendations for the further development and implementation of adaptation policies at all levels.
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.
Observed heavy precipitation is defined as maximum precipitation over five consecutive days (Rx5d). The ensemble of RCMs driven by different GCMs all using the RCP8.5 scenario has been used to calculate changes in heavy precipitation and dry spells.
Projected heavy precipitation is defined as the 95th percentile of daily precipitation (only days with precipitation >1 mm/day are considered).
Trends are calculated using a median of pairwise slopes algorithm. Black dots represent high confidence in the sign of the long-term trend in the box (if the 5th to 95th percentile slopes are of the same sign). Boxes which have a thick outline contain at least three stations.
To accurately assess trends in heavy precipitation at local scales, high-resolution datasets are required. These climatological datasets are compiled from the observation networks from countries and additional data from regional observations networks. As some countries do not share all of their datasets, the spatial and temporal coverage of the European dataset, and consequently the accuracy of past trends, varies across Europe.
However, even where sufficient data are available, several problems can limit their use for analysis. These problems are mainly connected with 1) limitations of distributing data in high spatial and temporal resolution by many countries, 2) unavailability of data in easy-to-use digital format, and lack of data homogeneity.
See under 'Methodology.
The risks posed by precipitation-related hazards, such as flooding events (including flash floods) and landslides, are also influenced by non-climatic factors, such as population density, floodplain development and land-use change. Hence, estimates of future changes in such risks need to consider changes in both climatic and non-climatic factors. Estimates of trends in heavy or extreme precipitation are more uncertain than trends in mean precipitation because, by their very nature, extreme precipitation events have a low frequency of occurrence. This leads to greater uncertainties when assessing the statistical significance of observed changes.
No uncertainty has been specified
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/precipitation-extremes-in-europe-3/assessment-1 or scan the QR code.
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