Abstract
Changes in the frequency and intensity of heat waves have shown substantial negative impacts on public health. At the same time, climate change towards increasing air temperatures throughout Europe will foster such extreme events, leading to the population being more exposed to them and societies becoming more vulnerable. Based on two climate change scenarios (Representative Concentration Pathway 4.5 and 8.5) we analysed the frequency and intensity of heat waves for three capital cities in Europe representing a North–South transect (London, Luxembourg, Rome). We used indices proposed by the Expert Team on Sector-Specific Climate Indices of the World Meteorological Organization to analyze the number of heat waves, the number of days that contribute to heat waves, the length of the longest heat waves, as well as the mean temperature during heat waves. The threshold for the definition of heat waves is calculated based on a reference period of 30 years for each of the three cities, allowing for a direct comparison of the projected changes between the cities. Changes in the projected air temperature between a reference period (1971–2000) and three future periods (2001–2030 near future, 2031–2060 middle future, and 2061–2090 far future) are statistically significant for all three cities and both emission scenarios. Considerable similarities could be identified for the different heat wave indices. This directly affects the risk of the exposed population and might also negatively influence food security and water supply.
Highlights
The Intergovernmental Panel on Climate Change (IPCC) concludes in its Fifth Assessment Report (AR5) that the mean global near-surface air temperature showed a warming of 0.85 ◦ C for the period from 1880 to 2012 and a warming of the climate system is unequivocal [1]
An increase of the mean annual air temperature of 1.5 ◦ C until end of this century is predicted for RCP4.5 and 2.5 ◦ C for RCP8.5 (Figure 1a), respectively
With 8.1 ◦ C, the reference period in Luxembourg is more than one degree colder than London but the projected increases for the Representative Concentration Pathways (RCPs) are in comparable range at 1.6 ◦ C (RCP4.5) and 2.8 ◦ C (RCP8.5) (Figure 1b)
Summary
The Intergovernmental Panel on Climate Change (IPCC) concludes in its Fifth Assessment Report (AR5) that the mean global near-surface air temperature showed a warming of 0.85 ◦ C for the period from 1880 to 2012 and a warming of the climate system is unequivocal [1]. In the Special Report on Extremes (IPCC SREX), the IPCC highlights three possible changes in extreme events due to elevated air temperature: (a) increases in the mean temperature, (b) increases in the variability and (c) changes in the symmetry of the probability distribution [2]. Even though it is difficult to attribute such a heat wave to climate change, those extreme events are projected to become more frequent as greenhouse gas concentrations are increasing [4,5]. Even small changes in the annual mean air temperature can result in large changes on the severity of such extreme events [6]. Changes in the frequency and intensity of heat waves (HWs) will have profound impacts on the natural environment and the human society [4]
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