Why is the content of this map important?
Cold spells are unusually long-lasting cold periods when temperature drops much below normal conditions. They have strong negative impacts on many aspects of society including health, infrastructure and agriculture. It is thus beneficial to understand how cold spells may alter under future climate change.
Which sectors are affected by this result?
The health sector will be affected due to the fact that heart/respiratory diseases and strokes increase during cold spells. Additionally, the cold spells will affect the energy sector via consumer demand for electrical power rises. This can lead to overloads that can result in power cuts. Also the transport sector can be negatively affected due to potential collapse in infrastructure in the case of extremely strong and long cold spells. Finally, the agriculture sector will be affected by unusual cold conditions.
What is shown on the maps?
The 1971-2000 reference period shows that cold spell duration varies from 3 to 9 days across Europe, with a maximum of up to 10 days over Central and Eastern Europe. When the global mean temperature increases by 2°C, the duration of cold spells is strongly reduced. At this warming level, cold spells, which are typical for the reference period (1971-2000), almost completely disappear in Scandinavia and Iberian Peninsula. In Central and Eastern Europe, cold spell duration is halved from 6 to 8 days to 2 to 4 days.
Details and further information:
Cold spell duration is defined accordingly to recommendations from the Expert Team on Climate Change Detection and Indices (ETCCDI). They are estimated as the number of days with a minimum daily temperature below its climatological 10th percentile for at least 6 consecutive days. Under a +2°C global warming period, the 10th percentile for the 1971-2000 is used as a reference. Cold spell duration is calculated annually for each year. It has to be noted that after averaging over a 30-year periods, it can be less than 6 days. This simply means that cold spells occur only in some years but not in every year.
To investigate this, the ensemble mean of the five mandatory climate simulations is used. Hence, the ensemble consists of 5 simulations in total.
Cold Spell Duration Index (CSDI) is defined as the “annual count of days with at least 6 consecutive days when TN < 10th percentile”, where TN is the daily maximum temperature.
Grigory Nikulin
Sveriges Meteorologiska och Hydrologiska Institut (SMHI), Sweden