Quantitative Analysis of Climate Change and Human Crises in History - Space-Time Integration in Geography and GIScience - page 231

Since the mid-1990s, there has been rapid advancement in high-resolution paleo-
climate reconstructions and a growing concern about the possible catastrophic
consequences of global warming. Against this background, research about the
climate-crisis relationship in human history has been revitalized. Nevertheless, the
proof of the relationship in recent studies remains vague, owing to the reliance on
individual cases (e.g., deMenocal 2001 ; Cullen et al. 2000 ; Polyak and Asmerom
2001 ; Yancheva et al. 2007 ). As there is not much quantitative evidence about the
relationship, no one can say with certainty how far and to what extent human crises
are really caused by climate change. At the same time, for those studies which
suggest the climate-crisis relationship, the causal mechanism that describes how
climate deterioration is eventually translated into human crises has rarely been
investigated. Therefore, the relationship remains in a black box. This probably
explains why climate-crisis relationship is one of the most controversial topics in
academia.
Driving to the heart of the controversy about the climate-crisis relationship
over the past few years, we took a pioneering approach to examine quantitatively
the connection between deteriorating climate 2 and human crises. In addition, the
causal mechanism responsible for the connection was also scientifically explored.
It is worth mentioning that we based our work on high-resolution paleo-climate
reconstructions and fine-grained historical socio-economic datasets to verify the
climate-crisis relationship, and our findings were derived from all of the known
cases, instead of individual examples. By doing so, we provided important scientific
evidence about the climate-crisis relationship in recent human history. This topic
chapter is a brief summary of our recent research findings that have been published
in the journals Chinese Science Bulletin , Climatic Change , Global Ecology and
Biogeography , Human Ecology ,andthe Proceedings of the National Academy of
Sciences of the United States of America , respectively.

14.2 Quantitative Analysis of Climate-Crisis Relationship

Since the mid-2000s, we have conducted a series of studies verifying the connection
between climate change and human crises (in recent human history) via quantitative
and statistical methods (Zhang et al. 2005 , 2006 , 2007a , b , 2011a , b ). Our
study areas include China, Europe, and other countries/regions in the Northern
Hemisphere during the pre-industrial era. To facilitate our research, we posited a set

2 Deteriorating climate refers to climatic cooling or warming. Cooling shortens the crop growing
season and reduces farmland area (Galloway 1986 ); warming shortens the duration between sowing
and harvesting and increases evapotranspiration (Lobell and Field 2007 ). Both are detrimental to
agricultural productivity, especially to a primarily agricultural economy characterized by a low
level of technology and high dependence on climate. Together with the side effects of climate
change, such as shifts in rainfall pattern, the carrying capacity of the agro-economy shrinks
significantly in a deteriorating climate.