1.1 Changes in high temperatures and projections for Europe

In several countries, despite increasing episodes of extreme temperatures, heat-related health impacts seem to be decreasing. This highlights the effectiveness of current prevention measures. Nevertheless, projections for the Region clearly indicate that without adequate efforts for heat–health adaptation to climate change, heat-related exposures and the associated health impacts could increase substantially. Such projections, combined with long-term trends of ageing and urbanization, strongly warrant the adoption of a long-term perspective to manage the health effects of temperature in the context of a changing climate.

The WHO European Region is warming, fast and dangerously. The year of inception of this report (2019) was the warmest calendar year on record in the northern part of the Region, as well as the second warmest year globally ever recorded. It was not an outlier, however: according to the European Centre for Medium-Range Weather Forecasts (ECMWF), 11 of the 12 warmest years in the Region have all occurred since 2000 (ECMWF, 2020). Both annual and seasonal average temperatures show a clear warming trend over the last four decades. Warming trends in the Region are consistently measured and statistically significant (Gil-Alana & Sauci, 2019); they are routinely evaluated by comparing recent measurements with climate data dating back to pre-industrial times (Fig. 1).

Beyond average temperatures, heat waves are also growing in frequency, in relative and absolute intensity and in duration, with a significant increasing trend in the Region since 1950 (Donat et al., 2013). The number of hot days has increased by 10 days per decade since 1960 in most of southeastern Europe and Scandinavia (Russo, Sillmann & Fischer, 2015). A comprehensive study of 59 weather stations in the eastern part of Europe, the Caucasus, the Russian Federation and Central Asia, using data from 1951 to 2010, found a clear increasing trend in the frequency of extremely hot summers (with an average temperature equal to or greater than the long-term average plus two standard deviations). While one extremely hot summer occurred during the first 30 years, five occurred during the last 10 years of the study period (Twardosz & Kossowska-Cezak, 2013).

An increasing trend in heat-wave frequency and intensity has been observed in Poland, although the increase is statistically significant at only about 60% of analysed stations (Wibig, 2017).

 A recent study examining 100 years of data (1917– 2016) found significant increasing trends in the frequency, intensity and duration of heat waves in most of central Asia (which in this study refers to Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan), and especially during the last 50 years in western central Asia (Yu et al., 2020). In Georgia, statistical analysis demonstrated significant increases in the number, intensity and duration of low- and high-intensity heat waves (Keggenhoff, Elizbarashvili & King, 2015). Data also indicate that the frequency and duration of heat waves increased in the western part of Turkey between 1965 and 2006 (Unal, Tan & Mentes, 2013). Other parts of the WHO European Region, including most countries in the Mediterranean basin, have also experienced an increase in the frequency and intensity of heat waves, as has Israel (Green et al., 2013), where record high temperatures were registered as recently as May 2019 (WMO, 2019).

The Copernicus Climate Change Service (C3S) provides access to quality-controlled data about the past, the present and the future of global climate. These include historical observations, global hourly data about all main meteorological parameters extending from 1979 to near-real-time (five-day latency), seasonal predictions for the next six months, and global and regional climate projections. Given the impact, climate variability and change is having on societies, and the complexity of the processing procedures associated with the analysis of climate data, C3S makes high-quality, up-to-date datasets available in an unrestricted manner to all users. The service also provides a free cloud environment in which to process the data and transform it into usable and useful information.

 The following example represents a way in which C3S data can be used to inform stakeholders and policy-makers. Fig. 2 shows the trend in change in degrees per year of the surface air temperature for the summer months (June, July and August) during 1979–2019. The values were calculated using a linear trend on the ECMWF re-analysis data for the surface temperature. The figure shows European surface air temperature anomalies relative to the 1981–2010 average, from January 1979 to August 2019. The first graph shows the mean anomalies for every month and the second graph shows the running 12-month averages.

 The plot and the code to generate this plot are freely available online on the C3S Climate Data Store platform for anyone to consult or reproduce. The user can also analyse past temperature anomalies for specific months and years through the C3S monthly climate bulletin explorer application.

Greater temperature increases are expected in the north of the Region in winter (potentially decreasing cold-related mortality), and in the southeast and the Balkans in the summer (EEA, 2017). The increase in warming magnitude is expected to be most dramatic in the central southern part of the Region, while the increase in the duration of hot conditions is expected to be most pronounced in the Mediterranean (Guerreiro et al., 2018). Nevertheless, extreme heat events may also occur in northern areas that are currently not strongly affected by heat waves (Nikulin et al., 2011). 

  In central Asia, assuming a 4 °C increase in global temperatures by the end of the century, around 80% of the land area could be affected by events hotter than three standard deviations beyond the long-term temperature average, and about 50% of the land area could be affected by events hotter than five standard deviations by 2071–2099 (Reyer et al., 2017). In general, solid high extremes temperature projections under climate change are comparatively scarce in the published literature for most areas of the Region beyond EU countries. This scarcity poses a clear challenge for evidence-based heat–health action and health adaptation in these areas.