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Wet and dry — fire weather

Page Last modified 25 Nov 2021
3 min read
Most wildfires in Europe are started by human activities but climatic conditions determine their intensity and impact. Soaring temperatures, tinder-dry forests and gusting winds are trademark fire weather conditions. Raging wildfires and choking smoke are a growing threat to human lives, property and energy infrastructure in Europe. They can also affect water quality, threaten biodiversity, release large amounts of greenhouse gases, cause soil erosion and spoil the landscape. Yet wildfires can also do some good, reducing insect populations and the amount of fuel available for future fires, which sometimes helps to restore balance to fragile forest ecosystems adapted to wildfires.

Key messages


  • Forest fires largely affect southern Europe and increasingly central and even northern Europe.
  • The number of days with high fire danger is projected to increase in Europe, in particular under a high-emissions scenarios. By far the highest absolute values and the largest increases are projected for southern Europe, but increases are also anticipated for central Europe.

Days with fire danger exceeding a threshold 

 

Definition

This 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 the FWI requires several meteorological input variables.

FWI values are classified into several fire danger classes. According to the classification of the European Forest Fire Information System (EFFIS), FWI values in the ranges 11.2-21.3, 21.3-38 and 38-50 represent ‘moderate’, ‘high’ and ‘very high’ fire risks, respectively. However, different classifications are 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 Copernicus Climate Change Service (CS3) Climate Data Store (CDS) data set).

Index factsheet (ETC/CCA Technical Paper): Days with fire danger exceeding a threshold

Relevance

The index is relevant for fire risk management related to forestry, infrastructure, human health, and urban and regional planning.

Past and projected changes

The annual number of days with high fire danger is projected to increase in Europe, whereby higher emissions scenarios are associated with larger increases. By far the highest absolute values and the largest increases are projected for southern Europe, but central Europe is also expected to experience increases. FWI values in northern Europe are projected to exceed the chosen threshold for high fire danger only rarely, even though large forest fires have recently occurred in this region. The uncertainty in future projections for this index is larger than for most other indices, which reflects the complex computation of this index involving the consideration of several essential climate variables.

Further information (European Climate Data Explorer): Fire weather index — Monthly mean, 1979-2020; Fire weather index — days with high fire danger, 2011-2099

Annual days with high fire danger (FWI value > 30) for the European land area and sub-regions

Notes:   Solid grey, blue, yellow and red lines represent the ensemble mean of projections for the historical period and under low-, medium- and high-emissions scenarios (RCP2.6, RCP4.5 and RCP8.5, respectively) (smoothed by a 20-year moving average) from 1971 to 2098. Shaded areas show the lower (minimum) and upper (maximum) bounds of the model ensembles. The dashed horizontal lines show the means for 1986-2005 computed from the model ensemble means of historical simulations. The size of the model ensemble used for each scenario is shown by the coloured numbers in the top-right corner.

Source:  C3S CDS data set — Fire danger indicators for Europe from 1970 to 2098 derived from climate projections.


Current situation and projected changes in days with high fire danger (FWI value > 30) in Europe 

Notes:   The top panel shows the 1986-2005 mean values based on the ensemble model mean of the historical simulations. The central row and bottom row show the projected values and projected changes, respectively, of the lower (minimum) and upper (maximum) bounds of model simulations for the for near and far future. The size of the model ensemble used for each scenario is reported in the time-series figure above. The spatial resolution is 0.11 ° × 0.11 °.

Source:  C3S CDS data set — Fire danger indicators for Europe from 1970 to 2098 derived from climate projections.

Chapters of the Europe's changing climate hazards report

  1. Heat and cold

  2. Wet and dry

  3. Wind

  4. Snow and ice

  5. Coastal

  6. Open ocean

                                                                               

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Filed under: forest fires
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