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whereas during the final 20-year period from 1976-1995, only 15% of the stations experienced
their greatest level of storm activity.
Over the period 1885-1996, Hayden (1999) determined that for the entire continent “no net
climate change in storminess [was] found,” while along the U.S. East Coast, Zhang et al. (2000)
could not find “any discernible long-term secular trend in storm activity during the twentieth
century.” In the Prairie Ecozone of western Canada, Lawson (2003) likewise could find no
significant trends in blizzard frequency in eastern and central locations over the period 1953-
1997; but there was a significant downward trend in blizzard occurrence in the more westerly
part, with “no trend in the severity of individual weather elements.”
Similarly, in the prairie provinces of Alberta and Saskatchewan in western Canada over the
period 1882 to 2001, Hage (2003) found that “all intense storms [“primarily thunderstormbased
tornadoes and downbursts”] showed no discernible changes in frequency after 1940,”
while prior to that time they had exhibited minor maxima. With respect to United States
snowstorms, on the other hand, Changnon and Changnon (2006) determined that “the
incidence of storms peaked in the 1976-1985 period,” but they report that snowstorm
incidence “exhibited no up or down trend during 1949-2000.” And in a similar finding related
to windstorm damages in the United States, Changnon (2009) found that “the peak of
incidences came during 1977-1991,” but that “the fit of a linear trend to the annual data
showed no upward or downward trend.”
With respect to Asia, and in prefacing their work, Zhu et al. (2008) noted that “a number of
studies have shown that the spring dust storm frequency (DSF) bears a negative correlation
with the local surface air temperature, and exhibits a downward trend over the past 50 years,”
citing the studies of Qian et al. (2002), Zhou and Zhang (2003), Zhai and Li (2003), Zhao et al.
(2004), Fan et al. (2006) and Gong et al. (2006, 2007) in support of this statement, after which
they explored the long-term variation of Chinese DSF in spring (March to May) and its possible
linkage with global warming and its related circulation changes in the Northern Hemisphere,
using data from 258 stations within the region surrounding Lake Baikal (70-130°E, 45-65°N)
over the period 1954 to 2007. And in doing so, they identified a “prominent warming” in recent
decades, as well as “an anomalous dipole circulation pattern” in the troposphere that “consists
of a warm anti-cyclone centered at 55°N and a cold cyclone centered around 30°N,” that leads
to “a weakening of the westerly jet stream and the atmospheric baroclinicity in northern China
and Mongolian regions, which suppress the frequency of occurrence and the intensity of the
Mongolian cyclones and result in the decreasing DSF in North China.” Similar findings were also
reported in the earlier study of Liu et al. (2004), who concluded that if global warming increases
temperatures in the northern part of China and Mongolia as predicted by climate models, “the
China-Mongolia ridge will continue to rise and suppress Mongolian cyclones and dust storm
activities in Western China-Mongolia.”
Also working in China, Xie et al. (2008) studied annual variations and trends of hail frequency at
523 stations over the period 1960-2005. And as is clearly evident in the following figure, they
report that the results of their study “show no trend in the mean Annual Hail Days (AHD) from
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