Paper Reviewed
Zhang, Y., Tian, Q., Guillet, S. and Stoffel, M. 2017. 500-yr. precipitation variability in Southern Taihang Mountains, China, and its linkages to ENSO and PDO. Climatic Change 144: 419-432.

According to Zhang et al. (2017), "a plethora of millennia-long tree-ring chronologies have been developed for the western part of China," yet they lament the fact that "only a very limited number of chronologies have reached beyond AD 1700 so far in eastern China," which lack of data has "prevented a reliable estimate of drought variability in eastern China." Thus, intending to help remedy this situation, the team of four researchers set out to develop a long-term precipitation reconstruction for this data-deprived region.

To accomplish their design, Zhang et al. collected tree-ring samples from 22 whitebark pine (Pinus bungeana) trees located on Shennong Mountain in the southern Taihang mountain range of Henan province, China (35.21°N, 112.80°E). The cores were cross-dated and processed using standard dendrochronological procedures, ultimately producing a reconstructed May precipitation chronology for the period 1510-2013, depicted in Figure 1 below.

In describing this record, the scientists note that it reveals the presence of long-term fluctuations in wet and dry intervals. And to this end, they note that "obvious wet periods include the 1530s-1570s, 1840s-1870s, and the 1950s-present," whereas relatively dry conditions prevailed during the 1630s-1650s, 1680s-1700s and 1770s-1780s. Zhang et al. also report that correlation and wavelet analysis revealed a close linkage between precipitation and ENSO and the PDO, which relationship was anti-phase (climate is drier in years with a high PDO and El Niño event) over the past 300 years.

All in all, in viewing the precipitation reconstruction of the Southern Taihang Mountains, it appears to us that there is nothing unusual, unnatural or unprecedented about the more recent portion of this record, as anomalies during the 20th and 21st century are all well within their long-term range. And that suggests there has been no discernible impact of rising atmospheric CO2 (i.e., global warming) on this record. Instead, changes in ENSO and the PDO seem fully capable of explaining its periodic fluctuations, suggesting natural climate change is the predominant driver of precipitation fluctuations there.

Figure 1. Precipitation reconstruction with the mean (dotted line) and a smoothed 13-yr. running mean (blue line). Source: Zhang et al. (2017).