Li, V., Wang, S., Niu, J.,
Fang, K., Chao, Y., Li, X.
and Li, Y.
2016
"Tree-ring-based reconstruction
of drought variability (1792-2011)
in the middle reaches of the
Fen River, North China."
Dendrochronologia 40: 1-11
SUMMARY:
The recent drought event of the 2000s
is nothing unusual or unnatural,
nor does it suggest any effect of CO2,
when viewed as part a long-term
perspective, of this two-century-long
PSDI ( drought index ) reconstruction.
The 11-year smoothed data, as shown
in the chart below, chronicles epochs
with persistently dry years that occurred
in the 1790s, 1840s, 1920s-1930s and 2000s.
Persistently wet periods occurred
in the 1850s, 1880s and 1940s-1950s.
Additional analysis revealed statistically
significant periodic cycles associated
with Pacific Ocean temperature cycles,
that are unrelated to CO2 levels:
The ENSO ( El Nino Southern Oscillation ),
and the PDO ( Pacific Decadal Oscillation ),
likely explain much of the PSDI oscillation
in the past two centuries.
DETAILS:
Drought events tend to cause hardship
such as crop failures, especially during
extreme and/or long lasting droughts.
There are claims that CO2-induced global
warming is causing more drought.
Li et al. (2016), who developed
"a robust May-July Palmer Drought
Severity Index (PSDI) reconstruction
for 1792-2011" for the middle reaches
of the Fen River, North China.
The seven Chinese scientists
collected 52 tree-ring samples
from 25 old-growth Chinese pine trees
(Pinus tabulaeformis) located in the
Tianlong Mountain Natural Reserve
(37.73°N, 112.37°E).
They were able to construct
a history of drought variability
in this region since 1792.
There were several years
of extremely moist
or extremely dry conditions
in the record, which conditions
were defined as years in which
the PSDI values were more than
1.5 standard deviation units
above or below the mean
of the record.
The resultant chronology
is smoothed with an
11-year moving average
shown on the chart below:
