Quantitative Analysis of Climate Change and Human Crises in History - Space-Time Integration in Geography and GIScience - page 234

Table 14.1 Pearson's correlation coefficients between temperature anomaly and wars in China (in
different analytical units), AD 1000-1911
Analytical units Tot al wars Rebellions Others North Central South

Phase 0.693* 0.686* 0.014 0.511 0.666* 0.525

Decadal 0.179 0.229* 0.030 0.090 0.214* 0.065

0.034
*Significant at 0.05 level (2-tailed) ( P < 0.05); **Significant at 0.01 level (2-tailed) ( P < 0.01)

Annual 0.115** 0.156** 0.026 0.060 0.133**

demonstrated a cyclic pattern, with a turbulent period followed by a relatively
tranquil one (Fig. 14.1 b) (Zhang et al. 2006 ). Eight of the ten war peaks (>25
wars/decade) coincided with cold phases. Two of the three very high war peaks (>50
wars/decade) occurred in the coldest phases (temperature is below 0.5 ºC). All
cold phases have one or two war peaks. Rebellion was the dominant war category
(Fig. 14.1 b, red line) and its variation was highly correlated with climatic changes.
Regarding the distribution of wars in different geographic regions 5 (Fig. 14.1 c),
in warm and humid South China, war frequency variations were less sensitive
to temperature changes. In contrast, war outbreaks in North China were closely
associated with cold phases. In Central China, six of the seven war peaks occurred
in cold phases, and they all closely followed cold phases. We calculated Pearson's
correlation coefficients between wars and temperature at three different time scales:
phase, decade, and annual (Table 14.1 ). At the phase scale, total wars, rebellions,
and Central China wars were significantly correlated with temperature. At the
decadal scale, rebellions and Central China wars were significantly correlated with
temperature. At the annual scale, total wars, rebellions, and Central China wars were
significantly correlated with temperature.

Fig. 14.1 Climate change, wars, population growth, and dynastic changes in China in AD 1000-
1911. ( a ) Normalized temperature change records for the last millennium for land areas in the
Northern Hemisphere north of 20 ı N: Jones et al. ( 1998 , dark blue line ); Mann et al. ( 1999 , pink
line ); Briffa ( 2000 , yellow line ); Crowley and Lowery ( 2000 , turquoise line ); Esper et al. ( 2002 ,
violet line ); and the average of these five normalized series ( bold black line ). Cold phases are
shaded as gray strips .( b ) Frequency of total wars ( sky blue line ) and rebellions ( red line ). ( c )
Frequency of wars in North China ( red line ), Central China ( sky blue line ), and South China ( bright
green line ). ( d ) Dynastic changes and population size (in million) in China (Color figure online)

5 According to the physical regionalization of China (Zhao 1986 ), China is divided into three
macro regions, namely: (1) North China - with continental humid, semi-humid, semi-arid, and
arid temperate climate influenced by both the monsoons and the westerlies. Its average annual
temperature ranges from very low to 14 ºC. Major agriculture products are spring wheat (northern
part) and winter wheat (southern part). Economic activities are mainly pastoral because of the
relatively low average annual precipitation of 50-750 mm, with >100 frost days per year; (2)
Central China - with a climate dominated by the monsoons, with annual temperature ranging
from 14 to 18 ºC, and 10-80 frost days per annum. The region has served as China's major rice
producing area; and (3) South China - with south sub-tropical and tropical climates and average
annual temperature ranging from 19 to 22 ºC. The long growing season permits double- or triple-
cropping in a year. Frost days are <10 per annum.