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In-Depth Information
heatwave had hit Paris a month earlier, when temperatures rose for five to six
days, peaking at around 8°C above the July norm. During that earlier heatwave
an excess of around 100 deaths occurred. In early August, in contrast, tempera-
tures peaked for several days at around 12°C above the August norm, and the
heatwave lasted longer, for nine to ten days. There were several other relevant
non-meteorological differences between the two heatwaves. First, the August
event entailed high levels of several health-damaging air pollutants, especially
newly formed ozone, the increased level of which was probably largely due to the
'catalytic' effect of higher temperature. Second, more young families were out of
town on summer holidays in August, leaving many older relatives with reduced
advice and support. Even so, most of the tenfold difference in the death toll
between the two heatwaves was due to the unusually great amount of thermal
stress in the August event, occurring at a level greater than the physiological
coping capacity of many of the more vulnerable citizens. They over-heated,
became dehydrated, had serious failures of heart and lung functioning, and died.
In comparing those two heatwave impacts, a straight-line extrapolation of
health risk from lower to much higher temperatures would obviously have
seriously underestimated the actual impact of the hotter event. Simple linear
arithmetic did not apply. Instead, within that Parisian population, some threshold
of coping capacity had apparently been exceeded during the August event, and
so the death rate jumped upwards.
Climatologists have estimated that the 2003 European heatwave, historically
a once-in-several-centuries event, is on track to becoming just an average annual
heatwave by mid-century - and perhaps an average summer day by later in this
century (Stott et al., 2004). Note, however, that those estimates were based
on climate change scenarios from around a decade ago, scenarios that entail
warming of around 2-3°C by later this century. We are on notice that an increase
of 4°C is now looking likely by 2100 (see Christoff, 2013a,
Chapter 1
in this
volume; World Bank, 2012).
Similar changes in the frequency of such extreme heat events are expected
proofed cities, towns and dwellings, and given that the human organism cannot
evolve biologically within a non-Darwinian timespan of just decades, rates of
serious health events and deaths due to heatwaves will almost certainly escalate,
especially since an increase in weather variability is an expected and prominent
feature of future warming. Hence there are similar projections, for Australia, of
increased frequency and (or) severity of other extreme weather events that maim,
kill and cause ensuing infections and post-traumatic stress disorders, including
floods, bushfires, coastal surges, hailstorms (particularly in eastern Australia) and
cyclones (likely to become more severe though not more frequent as offshore
ocean surface waters become warmer) (see Braganza et al., 2013,
Chapter 3
, this
volume). These projections have all been given greater plausibility by the recent
systematic analyses of evidence that, worldwide, extreme weather events are
indeed becoming more evident (Coumou and Rahmstorf, 2012).
Escalations in risks of disease, illness, injury and death due to 4°C warming
