/sudden unexpected infant death syndromes (SIDS/SUID) (Jhun et al. 2017). Elevated temperatures also cause worsening mental health, as described in the Mental Health subsection later in Section 3.
The severity and duration of high temperatures influence the health impacts resulting from extreme heat. In addition, air pollution and population vulnerability (Basu 2009) compound these impacts. Vulnerability is also a function of the typical temperatures to which a population is exposed, plus the extent to which a population adapts (Curriero et al. 2002; Baccini et al. 2008; Ho et al. 2015).
Workers, especially those who work outdoors or in hot indoor environments, are at increased risk of heat stress and other heat-related disorders, occupational injuries, and reduced productivity at work (Levy and Roelofs 2019). Workers in the agricultural sector face increased risk of heat strain and dehydration due to repeated exposures to high air temperatures, arduous physical exertion, and limited fluid intake. These risk factors may result in acute kidney injury (Moyce et al. 2017), as well as increased heat-related traumatic injuries (Spector et al. 2016). Spector et al. (2016) suggest that efforts should be made to address heat-related illness and prevent occupational injury for high-risk populations exposed to high temperatures and high physical exertion.
The impacts of increased air temperature may increase workers’ exposure to hazardous chemicals and, thus, the adverse health effects of those chemicals (Spector et al. 2016). Global warming is also increasing ground-level ozone concentrations with adverse effects on outdoor workers (Levy and Roelofs 2019).
Assessing heat impacts specific to Montana
Multiple studies—covering wide ranges of temperature, time, and geographic area—have sought to assess the health impacts of extreme heat (e.g., Morabito et al. 2014; Zhang et al. 2014). Some studies estimate how heat-related mortality differs between rural and urban landscapes (reviewed by Ho et al. 2015). Other studies develop indices to identify heat-vulnerable populations (Vescovi et al. 2005; Reid et al. 2009; Reid et al. 2012; Chuang and Gober 2015).
Human health vulnerability to heat is most often expressed as a combination of three factors: adaptive capacity, exposure to heat, and sensitivity to heat (Smit and Wandel 2006; Füssel 2010; Inostroza et al. 2016) (see sidebar). In our analysis, heat vulnerability was calculated as a combination of a) the historical land-surface temperature and future projections of heat to describe exposure; and b) county-level socioeconomic factors to describe sensitivity and adaptive capacity (see Appendix A for details). We will refer to the climate impacts as exposure, and the socioeconomic factors as sensitivity, with sensitivity inclusive of adaptive capacity, but no health factors were directly included due to incomplete county health factor data.
Factors Considered in Determining Vulnerability to Extreme Heat
Vulnerability, in the present context, is the extent to which a person is susceptible to the impacts of climate change. As described in the text and below, many factors go into calculating a person’s vulnerability to extreme heat. Three key terms bear definition:
- adaptive capacity.—The ability of a person (or society) to cope with climate change.
- exposure.—The type and magnitude of a climate change.
- sensitivity.—How easily affected a person is by climate change.
Vulnerability (the “V” in the diagram below) is assumed to be the intersection of adaptive capacity, exposure, and sensitivity (Smit and Wandel 2006; Füssel 2010; Inostroza et al. 2016). We combine adaptive capacity and sensitivity into one group, which is based on socioeconomic factors (see Appendix A for details). We continue to use the intersection of the three areas to determine vulnerability; and assume adaptive capacity is simply implicit in the socioeconomic layers that comprise our sensitivity factor.
Heat exposure is modeled as the combination of historical land-surface temperatures and projected heat. To determine