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Total precipitation year
Total precipitation represents the total amount of precipitation over a given period (e.g., whole year or a season).
Warmest three-day mean temperature
The warmest three-day mean temperature is the highest daily mean temperature in a year averaged over a three-day window. In variations of this index, the length of the time window over which the moving average of temperature is computed could vary depending on the specific application.
Europe’s changing climate hazards — about the report
Europe’s changing climate hazards report lets users explore the latest data on 32 climate hazard indices. It provides the big picture and also the detailed information needed for smarter decision-making to prevent the worst impacts of climate change from affecting communities and regions across Europe. Here, we show how information can help Europe tackle the hazards created by man-made climate change.
Extreme precipitation total
The extreme precipitation total index represents the total precipitation on all days with heavy precipitation, defined as exceeding the 99th percentile of daily precipitation over the reference period. Therefore, it accounts for both the frequency and magnitude of unusual precipitation events identified with respect to the baseline conditions. Other implementations of this index may use a different percentile (e.g., 95th) depending on the level of rarity of events to be considered.
Frequency of extreme precipitation
The frequency of extreme precipitation refers to the total number of days in a year with total precipitation exceeding the 99th percentile of the daily precipitation values during the reference period. Other implementations of this index may use a different percentile (e.g., 95th) depending on the level of rarity of events to be considered.
Frost days
The frost days index is defined as the number of days in a year with a daily minimum temperature below 0°C. Variations of this index limit the counting of frost occurrences to particular seasons (e.g., the growing season or the spring months). A closely related index is ‘ice days’, which uses daily maximum instead of minimum temperature.
Annual economic losses caused by weather - and climate - related extreme events in the EU Member States
In this indicator, events are grouped according to the available information in CATDAT. Meteorological events: storms (including lightning and hail) and mass movements. Hydrological events: floods. Climatological events: heatwaves, cold waves, droughts, forest fires. Total economic losses, in EUR billion (2022 prices), are based on recorded estimates from CATDAT provided by RiskLayer (dataset url is not available) and Eurostat structural indicators.
Cooling degree days
The cooling degree days index represents a proxy for the energy demand for cooling buildings. It is computed from the outdoor air temperature as cumulated daily deviation above a given base temperature threshold from April to September (see the ETC-CCA Technical Paper for details). The temperature threshold, period and formulation of this index can vary according to the local climate and applications. A base temperature of 22 °C is considered here as representative for assessing the energy demand at the pan-European scale and daily minimum, mean and maximum temperature values are used as input ECVs.
Days with fire danger exceeding a threshold
The index reports the total number of days per year with a critical level of fire danger. Fire danger is based on the Canadian Fire Weather Index (FWI) which is one of the most commonly used fire indices globally. It is based on a numerical rating of the potential frontal fire intensity and combines the rate of fire spread with the amount of fuel being consumed. The calculation of FWI requires several meteorological input variables (see the ETC-CCA Technical Paper for details). FWI values are classified into several fire danger classes. According to the classification of the European Forest Fire Information System (EFFIS; EC, 2020), FWI values in the range 11.2-21.3, 21.3-38 and 38-50 represent ‘moderate’, ‘high’ and ‘very high’ fire risk, respectively. However, different classifications are being used at national levels. The index presented here shows the annual number of days with high fire danger conditions (defined as daily FWI values above 30 in the underlying CDS dataset).
Growing degree days
The growing degree days index represents a measure of the accumulated heat available for vegetation growth. It is calculated as the accumulated sum over the year of the daily mean temperature exceedances of a base threshold (see the ETC-CCA Technical Paper for details). A base temperature of +5 °C is considered as representative for most European crops. Other definitions of the index are possible, including variations of the minimum temperature, the use of an upper temperature threshold, and restrictions to a given growing season.
Heating degree days
The heating degree days index represents a proxy for the use of energy required for heating buildings. It is computed from the outdoor air temperature as the cumulated daily deviation from a base temperature threshold from October to March (see the ETC-CCA Technical Paper for details). The temperature threshold, period and formulation can vary according to the local climate and applications. A base temperature of 15.5 °C is considered here as representative for the pan-European scale and daily minimum, mean and maximum temperature values are used as input variables.
Hot days
The hot days index represents the total number of days in a year registering maximum daily temperature above a fixed threshold. 30 °C is here considered as a suitable threshold at pan-European level, but higher thresholds can be considered depending on the regional climate conditions.
Key future hazards reported in 2023
Magnitude of meteorological droughts
The index magnitude of meteorological droughts combines information about the duration and severity of droughts. It is defined as the positive sum of the SPI for all the months within drought events in a given year, thereby giving more weight to months with severe droughts than those with less severe droughts (see the ETC-CCA Technical Paper for details). For consistency with ‘Duration of meteorological droughts’ above, this index is also based on SPI-3 and a threshold of -1 is used to identify drought occurrences. Alternative aggregation periods for SPI can be used depending on the type of drought considered and the specific applications.
Maximum consecutive five-day precipitation
The maximum consecutive five-day precipitation index accounts for the greatest precipitation total over five consecutive days in a year.
Mean temperature
Mean temperature is a base index representing the average air temperature over different timescales (e.g., seasonal or annual). This index is well covered by data for past, present and future periods from both observations and model simulations.
Mean wind speed
Mean wind speed is a base index accounting for the average values of wind speed at 10 m height over longer timescales (e.g., seasonal or annual).
Duration of meteorological droughts
The duration of meteorological droughts represents the average number of months in a year experiencing drought conditions as determined by anomalously low precipitation values. The index is based on the Standardized Precipitation Index aggregated over three months (SPI-3), which accounts for the deficit or surplus of precipitation with respect to a reference period. Alternative aggregation periods for SPI can be used depending on the type of drought considered and the specific applications. SPI values represent standard deviations of precipitation from the long-term mean. A drought event is considered to start when SPI values fall below -1 for at least two consecutive months and to end when the index returns to a positive number (see the ETC-CCA Technical Paper for details).