Geoscience Reference
In-Depth Information
members of the actual
Homo
genus. Indeed, in those mid-Miocene times the
great ape lineage was still emerging from smaller and more primitive primates.
It is, in principle, possible that in a Four Degree World, if sustained over many
centuries (and probably becoming still warmer as amplifying feedback processes
kicked in), there would once again be few (if any) humans.
Globally, it is very likely that a Four Degree World would seriously erode the
essential foundations, the underpinnings, of human population health discussed
earlier - food yields, water supplies, natural constraints on infectious disease
rates and ranges, the many 'providing and protecting' functions of ecosystems
and the physical security of settlements. In rich countries these foundations can
seem abstract and distant, and lacking apparent relevance to human health.
Reinforced by the prevailing individualistic 'world-view' recently fortified by the
ascendance of neoliberal values and assumptions, 'health' is widely viewed as the
personal outcome of free-range consumer choices and behaviours, a few dodgy
genes and a quota of day-to-day luck.
However, the profile and real significance of the risks to human population
health in a Four Degree World can only be properly understood by recognizing
that climate change and its environmental and social consequences are
systemic
and ecological
in character. They are outside the conventional frame within
which we think about 'environmental risks to health'. Climate-related risks
generally impinge on whole communities, whole populations, and will typically
act over long periods of time, often via complex multi-stage causal paths. That
is, these climatic-environmental changes are
not
just another entry on the list
of discrete environmental hazardous exposures (such as the many documented
toxic workplace exposures, elevated lead concentrations in local air, water and
soil, and locally generated air pollutants) that predominantly affect unlucky
individuals, occupational groups or local communities (McMichael, 1999).
Current mainstream modelling studies (Braganza et al., 2013; Whetton et al.,
of Australia's climate in a Four Degree World include temperature increases
of 3°C to 5°C in coastal areas and 4°C to 6°C in inland areas; a likely decline
in rainfall in southern Australia (particularly in winter) of up to about 50 per
cent and uncertain rainfall changes in other regions; sea level rise of up to
about 1.1 metres in 2100, increasing to more than 7 metres during subsequent
centuries, even with no further global warming; and increases in extremely high
temperatures, extreme rainfall, extreme fire weather, large hail on the east coast,
increased tropical cyclone intensity, and greater storm-related coastal flooding.
While the size of the temperature rise is of primary concern, the actual
duration
of over-heating at
1
4°C would be a very important determinant of the
extent and chronology of adverse health impacts in Australia and elsewhere. For
example, if
1
4°C conditions persisted for centuries, as is likely (Stager, 2011),
and if the Himalayan glaciers disappeared, then life-supporting river flows in
China, South Asia and South East Asia would dwindle markedly. This would
include many of the great rivers of the region, including the Yangtze, Ganges,
Brahmaputra, Meghna and Mekong. The ensuing cascade of adverse health
