Environmental Engineering Reference
In-Depth Information
Italian, and Canadian cities have already been shown to save a number of
lives when coupled with effective intervention plans (Ebi et al., 2004). These
systems, coupled with well-developed intervention activities, represent an
important way to lessen the potential for drastic increases in heat-related
mortality in coming decades due to climate change.
Long-Term Impacts of Heat Stress
Many of the impact studies summarized in this section and elsewhere
throughout this report focus on future projections for the next few decades;
nearly all of the impact studies in the literature, regardless of focus area, con-
fine estimates of potential impacts to this century. This limits quantification
of impacts based on GCM simulations driven by the SRES scenarios to those
associated to global mean temperature changes of 4°C or less, depending
on the GCMs and scenarios used to generate future projections.
One recent study, however, attempts to extrapolate beyond this thresh-
old by using long-term simulations reaching a global temperature change of
10°C relative to 1999-2008 (Sherwood and Huber, 2010). Recognizing that
most of the impacts studied to date depend on assumptions about future con-
ditions that cannot be reliably simulated with our current state of knowledge,
the authors instead focus on an impact that depends on a basic physiological
threshold: specifically, that associated with the need of the human body to
dissipate the heat it generates. This can happen only if the temperature to
which the skin is exposed is lower than the skin temperature itself.
The authors consider future statistics of annual maximum wet bulb tem-
peratures exceeding average human skin temperature of 35°C as a measure
of heat stress on humans and other mammals, and illustrate how, assuming
carbon emissions and climate change continue unchecked beyond this
century, the magnitude of land area that could become uninhabitable due to
heat stress could be greater than that lost to sea level rise over the same time
frame. Although exact projections of changes in inhabitable land area over
multiple centuries are sensitive to key uncertainties in carbon cycle, climate
sensitivity, and ocean-atmosphere dynamics discussed in Chapters 3 and 4,
this study raises an important point: namely, that hard-wired, physiological
limitations on human welfare have not previously been acknowledged in
evaluating the long-term risks associated with a given pathway of carbon
emissions.
