Quantitative Analysis of Climate Change and Human Crises in History - Space-Time Integration in Geography and GIScience - page 256

Human crises should be attributable to socio-economic factors instead of climate
change. Such a viewpoint and approach are also adopted by other scholars (Salehyan
2008 ;Fan 2010 ; Tertrais 2011 ). To facilitate a fruitful discussion about the climate-
crisis relationship, we try to clarify some issues here.
First, the crucial issue linking scale to explanation is whether the variables used to
explain a phenomenon are themselves located at the same scale. Causal explanation
and generalization relevant to one scale regime are unlikely to be appropriate at
others (Gibson et al. 2000 ). When employing variables at a different level to explain
phenomenon at a particular level, we must be aware of some explanatory fallacies.
Individualistic fallacies may occur when research imputes the cause of higher-level
(or macro) patterns to be the same as that causing lower-level (or micro) patterns.
Ecological fallacies are those that impute the cause of lower-level (or micro) patterns
to be the same as those operating at a higher (or macro) level. We based our
research upon aggregate statistics to conclude the climate-crisis relationship. While
our findings may not be applicable to explain every individual historical incident,
it would be conceptually wrong to simply explore individual cases to support/reject
aggregate statistical results.
Second, although social factors may explain some site-specific short-term crises
in a specific time slot, they cannot explain the widespread and simultaneous
occurrence of long-term crises across different countries which have different social
settings (i.e., characterized different stages of civilization, culture, economic devel-
opment, and resources), at least in the pre-industrial era. In fact, climate-induced
societal change can be measured at different scales, whereas the magnitude of
change depends upon the economic impact of climate deterioration. We established
the connection and underlying causal mechanisms between climate change and
various human crises at hemispheric, continental, and macro-regional scales by
scientific means. We concluded that climate change was the ultimate cause of human
crisis in pre-industrial societies at the macro-historical level.
Our research findings challenge a widely accepted basic concept of Malthusian
theory in ecological and population research, which states that subsistence level
increases arithmetically while population increases geometrically (Malthus 1798 )
(Fig. 14.8 a). According to the theory, land carrying capacity is assumed to be
essentially constant or possibly increasing monotonically. Population checks (i.e.,
famines, wars, and epidemics) and the associated population collapses/ socio-
political chaos occur when faster population growth overshoots the subsistence
level. Since the land carrying capacity was understood as relatively fixed, the
root of historical human crises has been attributed simply to excessive population
growth. In fact, Malthus ( 1798 ) is insightful in pointing out that the root cause
of human crises is the ecological imbalance between population size and land
carrying capacity, which is attributable to divergent rates of population growth and
subsistence increase. However, our studies emphasize that, given the technological
limitations of agricultural production during the time in question, long-term climate
changes would have a significant impact on food supplies, and that the constant or
possibly monotonic increase in land carrying capacity (assumed by Malthus 1798 ,