Health and Climate Change: policy responses to protect public health Page: 1,864
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All plausible futures resulting from realistic anticipated emissions trajectories expose the global population to worsening health consequences. In
2014, WHO estimated an additional 250 000 potential deaths annually between 2030 and 2050 for well understood impacts of climate change.
WHO suggest their estimates represent lower bound figures because they omit important causal pathways. The effects of economic damage, major
heatwave events, river flooding, water scarcity, or the impacts of climate change on human security and conflict, for example, are not accounted
for in their global burden estimates.32 Without action to address continued and rising emissions, the risks, and the number of people exposed to
those risks, will likely increase significantly. WHO emphasises that the importance of the interactions between climate change and many other
trends affecting public health, stressing the need for interventions designed to address climate change and poverty-two key drivers of ill health.32
Similarly, the authors of the IPCC assessment of climate change on health emphasise that the health impacts become amplified over time.2
This report provides new insights into the potential exposure of populations, showing that when demographic trends are accounted for, such as
ageing, migration, and aggregate population growth, the populations exposed to climate change that negatively affect health risk are more
seriously affected than suggested in many global assessments. It involves new analysis on specific and direct climate risks of heat, drought and
heavy precipitation that directly link climate change and wellbeing. The number of people exposed to such risk is amplified by social factors: the
distribution of population density resulting from urbanisation, and changes in population demographics relating to ageing.
Thus, human populations are likely to be growing, ageing, and migrating towards greater vulnerability to climate risks. Such data emphasise
the need for action to avoid scenarios where thresholds in climate greatly increase exposure, as well as adaptation to protect populations from
How climate affects human health
Mechanisms linking climate and health
The principal pathways linking climate change with health outcomes are shown in figure 2, categorised as direct and indirect mechanisms that
interact with social dynamics to produce health outcomes. All these risks have social and geographical dimensions, are unevenly distributed
across the world, and are influenced by social and economic development, technology, and health service provision. The IPCC report documents
in expansive detail the scientific knowledge on many individual risks.31 Here, we discuss how these risks could change globally as a result of a
changing climate and of evolving societal and demographic factors.
Changes in extreme weather and resultant storm, flood, drought, or heatwave are direct risks. Indirect risks are mediated through changes in the
biosphere (eg, in the burden of disease and distribution of disease vectors, or food availability), and others through social processes (leading, for
instance, to migration and conflict). These three pillars, shown in figure 2, interact with one another, and with changes in land use, crop yield, and
ecosystems that are being driven by global development and demographic processes. Climate change will limit development aspirations, including
the provision of health and other services through impacts on national economies and infrastructure. It will affect wellbeing in material and other
ways. Climate change will, for example, exacerbate perceptions of insecurity and influence aspects of cultural identity in places directly affected.33
Thus, in figure 2, climate risks might be both amplified and modified by social factors. The links between food production and food security in
any country, for instance, are strongly determined by policies, regulations and subsidies to ensure adequate food availability and affordable
prices.34 Vulnerabilities thus arise from the interaction of climatic and social processes. The underpinning science shows that impacts are
unevenly distributed, with greater risks in less developed countries, and with specific subpopulations such as poor and marginalised groups,
people with disabilities, the elderly, women, and young children bearing the greatest burden of risk in all regions.31
In many regions, the consequences of lower socio-economic status and cultural gender roles combine to increase the health risks that women
and girls face as a result of climate change relative to men and boys in the same places, although the converse might apply in some instances.
Whilst in developed countries, males comprise approximately 70% of flood disaster fatalities (across studies in which sex was reported), the
converse is generally true for disaster-related health risks in developing country settings, in which the overall impacts are much greater.3536 For
example, in some cultures women may be forbidden from leaving home unaccompanied, are less likely to have learnt how to swim, and may
have less political representation and access to public services. Additionally, women's and girls' nutrition tends to suffer more during periods of
climate-related food scarcity than that of their male counterparts, as well as starting from a lower baseline, because they are often last in
household food hierarchies.37
Direct mechanisms and risks: exposure to warming and heatwaves
While societies are adapted to local climates across the world, heatwaves represent a real risk to vulnerable populations and significant increases
in the risks of extreme heat are projected under all scenarios of climate change.38 On an individual basis, tolerance to any change is diminished
in those whose capacity for temperature homoeostasis is limited by, for example, extremes of age or dehydration. There is a well-established
relationship between extreme high temperatures and human morbidity and mortality.39 There is also now strong evidence that such heat-related
mortality is rising as a result of climate change impacts across a range of localities.3'
Evidence from previous heatwave events suggests that the key parameters of mortality risk include the magnitude and duration of the
temperature anomaly and the speed of temperature rise. The risks are culturally defined, even temperate cities experience such mortality as it is
deviation from expectations that drives weather-related risks. This is especially true when hot periods occur at the beginning of summer, before
people have acclimatised to hotter weather.38 The incidence of heatwaves has increased in the past few decades, as has the area affected by
The most severe heatwave, measured with the Heat Wave Magnitude Index, was the summer 2010 heatwave in Russia.40 More than 25 000
fires over an area of 1.1 million hectares42 raised concentrations of carbon monoxide, nitrogen oxides, aerosols, and particulates (PMio) in
European Russia. The concentration of particulate matter doubled from its normal level in the Moscow region in August, 2010, when a large
smoke plume covered the entire capital.43 In combination with the heat wave, the air pollution increased mortality between July and August,
2010, in Moscow, resulting in more than 11 000 additional deaths compared with July to August, 2009.44 Projections under climate scenarios
show that events with the magnitude of the Russian heatwave of 2010 could have become much more common and with high-end climate
scenarios could become almost the summer norm for many regions.40'45
Rising mean temperatures mean that the incidence of cold events is likely to diminish. The analysis here focuses on the heat-related element
because the health benefits of reductions in cold are not established. Whilst there is an increase in deaths during winter periods in many climates,
the mechanisms responsible for this increase are not easily delineated. Most winter-related deaths are cardiovascular, yet the link between
temperature and cardiovascular mortality rates is weak. There is a stronger link between respiratory deaths and colder temperatures but these
account for a smaller percentage of winter deaths.46
The impact of cold temperatures can be measured considering seasonal means, extreme cold spells, and relative temperature changes. Seasonal
means and extreme cold spells (or absolute temperature) have relatively small or ambiguous relationships with numbers of winter deaths,
however temperature cooling relative to an area's average temperature does more clearly correlate with mortality rates.46,47 There may be modest
reductions in cold-related deaths; however, these reductions will be largely outweighed at the global scale by heat-related mortality.46 Whilst
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Watts, Nick; Adger, W. Neil; Agnolucci, Paolo; Blackstock, Jason; Byass, Peter; Cai, Wenjia et al. Health and Climate Change: policy responses to protect public health, article, June 22, 2015; Amsterdam, The Netherlands. (https://digital.library.unt.edu/ark:/67531/metadc1234369/m1/4/: accessed March 22, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT College of Arts and Sciences.