Global Warming

The impact onhuman health 177

health from increased malnutrition and from a prevalence of conditions
more likely to lead to the spread of diseases from a variety of causes.
How about direct effects of the climate change itself on human
health?^56 Humans can adapt themselves and their buildings so as to live
satisfactorily in very varying conditions and have great ability to adapt to
a wide range of climates. The main difficulty in assessing the impact of
climate change on health is that of unravelling the influences of climate
from the large number of other factors (including other environmental
factors) that affect health.
The main direct effect on humans will be that of heat stress in the
extreme high temperatures that willbecome more frequent and more
widespread especially in urban populations (see box and Figure 6.6). In
large cities where heat waves commonly occur death rates can be doubled
or tripledduring days of unusually high temperatures.^57 Although such
episodes may be followed by periods with fewer deaths showing that
some of the deaths would in any case have occurred about that time,
most of the increased mortality seems to be directly associated with the
excessive temperatures with which old people in particular find it hard
to cope. On the positive side, mortality due to periods of severe cold in
winter will be reduced. The results of studies are equivocal regarding

Heat waves in Europe, 2003

Record extreme temperatures were experienced in Europe during June,

July and August 2003. At many locations temperature rose over 40◦C.

In France, Italy, the Netherlands, Portugal and Spain, over 21 000 ad-

ditional deaths were attributed to the unrelenting heat. Spain, Portugal,

France and countries in Central and Eastern Europe suffered from in-

tense forest fires.^58 Figure 7.14 illustrates the extreme rareness of this

event.

Figure 7.14Distribution

of average summer

temperatures (June, July,

August) in Switzerland

from 1864–2003 showing

a fitted gaussian

probability distribution –

standard deviation 0.94◦C.

Average temperatures with

10,100 and 1000 year

return periods are also

indicated. The 2003 value

is 5.4 standard deviations

from the mean showing it

as an extremely rare event

(from Schar et al. 2004,

Nature427, 332–6).