IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability Heatwaves

Hot days, hot nights and heatwaves have become more frequent (IPCC, 2007a). Heatwaves are associated with marked short-term increases in mortality (Box 8.1). There has been more research on heatwaves and health since the TAR in North America (Basu and Samet, 2002), Europe (Koppe et al., 2004) and East Asia (Qiu et al., 2002; Ando et al., 2004; Choi et al., 2005; Kabuto et al., 2005).

A variable proportion of the deaths occurring during heatwaves are due to short-term mortality displacement (Hajat et al., 2005; Kysely, 2005). Research indicates that this proportion depends on the severity of the heatwave and the health status of the population affected (Hemon and Jougla, 2004; Hajat et al., 2005). The heatwave in 2003 was so severe that short-term mortality displacement contributed very little to the total heatwave mortality (Le Tertre et al., 2006).

Eighteen heatwaves were reported in India between 1980 and 1998, with a heatwave in 1988 affecting ten states and causing 1,300 deaths (De and Mukhopadhyay, 1998; Mohanty and Panda, 2003; De et al., 2004). Heatwaves in Orissa, India, in 1998, 1999 and 2000 caused an estimated 2,000, 91 and 29 deaths, respectively (Mohanty and Panda, 2003) and heatwaves in 2003 in Andhra Pradesh, India, caused more than 3000 deaths (Government of Andhra Pradesh, 2004). Heatwaves in South Asia are associated with high mortality in rural populations, and among the elderly and outdoor workers (Chaudhury et al., 2000) (see Section 8.2.9). The mortality figures probably refer to reported deaths from heatstroke and are therefore an underestimate of the total impact of these events.

Box 8.1. The European heatwave 2003: impacts and adaptation

In August 2003, a heatwave in France caused more than 14,800 deaths (Figure 8.2). Belgium, the Czech Republic, Germany, Italy, Portugal, Spain, Switzerland, the Netherlands and the UK all reported excess mortality during the heatwave period, with total deaths in the range of 35,000 (Hemon and Jougla, 2004; Martinez-Navarro et al., 2004; Michelozzi et al., 2004; Vandentorren et al., 2004; Conti et al., 2005; Grize et al., 2005; Johnson et al., 2005). In France, around 60% of the heatwave deaths occurred in persons aged 75 and over (Hemon and Jougla, 2004). Other harmful exposures were also caused or exacerbated by the extreme weather, such as outdoor air pollutants (tropospheric ozone and particulate matter) (EEA, 2003), and pollution from forest fires.

Figure 8.2

Figure 8.2. (a) The distribution of excess mortality in France from 1 to 15 August 2003, by region, compared with the previous three years (INVS, 2003); (b) the increase in daily mortality in Paris during the heatwave in early August (Vandentorren and Empereur-Bissonnet, 2005).

Figure 8.2

A French parliamentary inquiry concluded that the health impact was ‘unforeseen’, surveillance for heatwave deaths was inadequate, and the limited public-health response was due to a lack of experts, limited strength of public-health agencies, and poor exchange of information between public organisations (Lagadec, 2004; Sénat, 2004).

In 2004, the French authorities implemented local and national action plans that included heat health-warning systems, health and environmental surveillance, re-evaluation of care of the elderly, and structural improvements to residential institutions (such as adding a cool room) (Laaidi et al., 2004; Michelon et al., 2005). Across Europe, many other governments (local and national) have implemented heat health-prevention plans (Michelozzi et al., 2005; WHO Regional Office for Europe, 2006).

Since the observed higher frequency of heatwaves is likely to have occurred due to human influence on the climate system (Hegerl et al., 2007), the excess deaths of the 2003 heatwave in Europe are likely to be linked to climate change.