1.2 How heat affects health and projections for Europe
Heat extremes have serious impacts on public health in Europe. The effects of heat mostly occur on the same day and in the following three days. The observed increase in frequency and intensity of heat waves – for which there is no globally agreed definition, but for the purposes of this report means periods of hot weather lasting for several days – has had significant effects on human health across Europe, particularly among elderly people and in cities due to the urban heat island effect. Age, pre-existing medical conditions and social deprivation are key factors that make people experience more adverse health outcomes related to heat and extreme temperatures. The effects of exposure can be directly related to heat (heat stress and dehydration or heatstroke) or indirectly related – such as a worsening of cardiovascular and respiratory diseases, kidney diseases or electrolyte disorders (WHO Regional Office for Europe, 2018).
1.1. Observed heat-related mortality impacts and trends
The Global Heat Health Information Network (GHHIN) was initiated in 2016 and launched publicly in 2018 as a joint initiative of the WMO, WHO and United States National Oceanic and Atmospheric Administration to respond to coordination and technical advisory needs identified by the global meteorological and public health communities (GHHIN, 2020). The Network largely serves as a community of practice and a knowledge broker for both individuals and institutions across a broad range of disciplines focused on addressing the human health risks posed by extreme heat. Several studies indicate that heat-related health impacts are generally decreasing over time in many parts – but not all – of the WHO European Region, although this reduction is not homogeneous or generalized. Similar reductions (with similar caveats) have been observed in other parts of the world, including Australia, Japan and the United States of America. Studies of trends in human vulnerability to extreme heat in several countries in the WHO European Region are presented in Table 1, mainly adapted from the review by Sheridan & Allen (2018). The majority of the studies considered mortality health outcomes, probably due to the availability of health data and a lack of information on indirect impacts or health service delivery.
Within the WHO European Region, clear decreases in some measure of vulnerability to heat or health impacts of heat have been observed in France (Fouillet et al., 2008; Pascal et al., 2018), Ireland (Pascal et al., 2013; Paterson & Godsmark, 2020), Italy (Schifano et al., 2012; de’Donato et al., 2018) and Spain (Achebak, Devolder & Ballester, 2018; Díaz et al., 2018). On the other hand, no consistent evidence of a significant decrease has been found for the United Kingdom (Gasparrini et al., 2015), and although no significant excess mortality was observed there in a recent severe heat wave in 2013 (Green et al., 2016), the overall evidence suggests that heat-related mortality may be increasing (Arbuthnott & Hajat, 2017). In Czechia, a recent analysis points to a comparative increase (Urban, Davidkovova & Kyselý, 2014). Relatively comparable heat waves in Finland in 2014 and 2018 resulted in 330 and 380 deaths, respectively (THL, 2019). A study carried out in Slovenia found greater heat-related mortality among vulnerable groups in 2015 than in 2013 (Perčič et al., 2018).
1.2 Projections in heat-related health impacts
Before considering projections of heat impacts, it is worth noting that a proportion of the observed heat extremes is confidently attributed to climate change (ECMWF, 2020a). Moreover, some of the heat-related burden of illness in the WHO European Region is also already attributable to climate change (Vicedo- Cabrera et al., 2019). The warming the Region has already experienced is countering prevention efforts, strengthening the argument for climate action from a public health perspective. Moreover, wherever a reduction of heat impacts on health is observed, the warming climate is moving countries further from the goal of minimizing the heat-related burden of illness throughout the Region.
In addition to climate change, several variables and long-term trends affect the relationship between temperatures and health in the Region – the main factors being population ageing and urbanization. Population ageing strongly affects the relationship between heat and population health. Given the epidemiological profile of high temperatures as a health threat (in which elderly and chronically ill people are at higher risk), ageing and population structures is a key dynamic factors to account for in HHAPs. The WHO European Region is ageing: the median age of the population in EU countries increased by 4.2 years between 2002 and 2017, and the proportion of people aged 65 years and over increased by 2.4% in the last decade (Eurostat, 2018). While the non-EU eastern European and central Asian Member States have younger populations overall, these are also ageing faster due to migration and rapid fertility declines (Bussolo, Koettl & Sinnott, 2015).
Urbanization increases heat exposures and their impacts, as this report explores in Chapters 5 and 8. Reduced vegetation, heat-conserving urban materials, urban geometry and abundant heat sources all contribute to the urban heat island effect (UHI, 2014). Other factors, like household insulation, access to air-conditioning and individual vulnerability may also increase heat-related risks for some urban populations (Wolf, McGregor & Analitis, 2009; Wolf & McGregor 2013). Moreover, higher population density, all else being equal, increases the population at risk in urban areas. Albeit at a slowing pace, the overwhelmingly urban WHO European Region is still becoming more urbanized (UNDESA, 2014). This has practical consequences for heat–health prevention, as the urban landscape's aggravation of heat-related health impacts, further highlights the importance of a broad perspective in heat–health action planning. Limiting the urban heat island effect through city adaptation plans can not only protect local populations but also significantly enhance international mitigation efforts – for instance, through a reduction of energy use for cooling (Estrada, Botzen & Tol, 2017).
The scientific consensus is that without
strong levels of adaptation, climate
change is bound to increase the
heat-related burden of disease (mortality and morbidity). A large
number of scientific studies published in the last
decade give projections of
heat-related health impacts in the WHO European Region, in EU countries, and at the national, subnational and local
levels. Within the Region,
those increases would
be sharpest in central and southern Europe (Gasparrini et
al., 2017). Estimates under an optimistic scenario
(RCP 4.5) assess additional annual heat-related premature mortality of over 85 000
deaths in the 27 countries in the EU from 2020, plus
Switzerland and Norway, in 2046–2055
compared with 1991–2000 (Orru et al.,
2019). In an assessment including 38 countries
in the WHO European Region, Kendrovski et
al. (2017) projected an overall excess of 46 690 and 117 333 premature deaths per year under the RCP 4.5 and RCP 8.5 scenarios respectively for the period 2071–2099, in addition to the 16
303 additional deaths estimated under
the historical scenario.
Mediterranean countries and those in the eastern
part of the Region would be
the most affected by heat,
but a non-negligible impact would still be registered in northern continental countries.
In addition to regional estimates, many projections of heat-related health impacts have been made under various climate scenarios at the national and sub-national levels (Ciscar et al., 2014; Hajat et al., 2014; Petkova, Gasparrini & Kinney, 2014; Roldán et al., 2014; Wu et al., 2014; Forzieri et al., 2017). Several of these projections of the possible impact of heat on future mortality consider a fixed, unchanging threshold temperature based on retrospective observations. Under this hypothesis, and as a consequence of the increase in temperatures associated with climate change (Smith et al., 2014; IPCC, 2018), important increases in mortality attributable to heat have been suggested. This assumption, however, needs to be analysed carefully in terms of its operational implications. Wherever they have been analysed across a long enough time frame, temperature thresholds of heat-related mortality have shown change over time. Population ageing (widely observed throughout the WHO European Region) would have an influence on such a threshold, lowering it by increasing the pool of vulnerable individuals (mainly people over 65 years of age) (Montero et al., 2012; Carmona et al., 2016).
The impact of heat on health in European cities is expected to worsen under likely climate change scenarios (Kendrovski et al., 2017). In fact, climate change-driven increases in daily maximum temperatures may already have increased the number of heat-related deaths substantially (Christidis, Stott & Brown, 2011). How far the resulting health impacts might be minimized due to acclimatization is unclear (Baccini et al., 2011; Honda et al., 2013; Martinez et al., 2018). Also unclear is whether milder winter temperatures in a climate that is more variable overall might lead to a decrease in cold-related deaths. Studies suggest that cold-related mortality has either remained constant or increased (Gasparrini et al., 2015; Díaz et al., 2015; Linares et al., 2016). The IPCC (Smith et al., 2014) concludes that by the middle of the 21st century, heat-related deaths will outweigh health gains due to fewer cold periods in temperate areas like the WHO European Region, and later studies have confirmed those findings (Díaz, López-Bueno et al., 2019).
On the other hand, although valid as a counterfactual scenario for policy advocacy, a complete absence of adaptive processes is unlikely. Variable levels of autonomous and planned adaptation are to be expected, even in the absence of large and concerted efforts. From the “institutional” side, these would include further empowerment of the population to adopt protective behaviours against heat (Bobb et al., 2014); implementation of prevention plans (Schifano et al., 2012; Van Loenhout & Guha-Sapir, 2016);
improvements in health services (Ha & Kim, 2013); and improvements in socioeconomic circumstances and housing (Carmichael et al., 2020; Samuelson et al., 2020). In addition, a certain degree of “autonomous” adaptation may be expected from individuals and families, not least in the form of improved shading, insulation and/or an increase in the number of air-conditioning units (Díaz et al., 2018; Watts et al., 2018). In addition to active adaptation, there is a certain degree of physiological acclimatization to heat, although this is assumed to be quite limited until reaching “peak heat stress” (Sherwood & Huber, 2010). As a result of these factors, the threshold temperature used to define a heat wave will vary over time in most locations (Díaz, Sáez et al., 2019).
Despite these caveats, current and forthcoming trends and projections of climate change, ageing and urbanization strongly warrant and advocate adopting a long-term perspective in managing the health effects of temperature in the context of a changing climate. Yet against this background, most HHAPs operated by national and subnational authorities follow a largely reactive, static approach. The existing evidence highlights that long-term measures show the lowest levels of implementation within HHAPs, as do surveillance and plan evaluation (Bittner et al., 2014). As the responses to a survey of heat–health action planning undertaken by the WHO Regional Office for Europe in 2019 show (the results are highlighted throughout the chapters of this report), most current HHAPs in the Region do not explicitly address the question of whether and how their core elements should evolve in a changing climate, shifting demographics and increasingly urban populations. HHAPs can benefit from the rapidly expanding knowledge and practice of overall climate change adaptation, and become prime examples of effective health adaptation. This report is designed to help HHAP administrators and practitioners in their efforts to create an anticipatory and adaptive approach to the prevention of heat impacts on health.
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