Pederson et al. (2001) developed tree-ring chronologies for northeastern Mongolia and used them to reconstruct annual precipitation and streamflow histories for the period 1651-1995. Working with both standard deviations and 5-year intervals of extreme wet and dry periods, they found that "variations over the recent period of instrumental data are not unusual relative to the prior record." They note, however, that their reconstructions "appear to show more frequent extended wet periods in more recent decades," but they say that this observation "does not demonstrate unequivocal evidence of an increase in precipitation as suggested by some climate models." Spectral analysis of the data also revealed significant periodicities around 12 and 20-24 years, which they suggested may constitute "possible evidence for solar influences in these reconstructions for northeastern Mongolia."

Kripalani and Kulkarni (2001) studied seasonal summer monsoon (June-September) rainfall data from 120 east Asia stations for the period 1881-1998. A series of statistical tests they applied to these data revealed the presence of short-term variability in rainfall amounts on decadal and longer time scales, the longer "epochs" of which were found to last for about three decades over China and India and for approximately five decades over Japan. With respect to long-term trends, however, none were detected. Consequently, the history of summer rainfall trends in east Asia does not support climate-alarmist claims of intensified monsoonal conditions in this region as a result of CO2-induced global warming. As for the decadal variability inherent in the record, the two researchers say it "appears to be just a part of natural climate variations."

Taking a much longer look at the Asian monsoon were Ji et al. (2005), who used reflectance spectroscopy on a sediment core taken from a lake in the northeastern part of the Qinghai-Tibetan Plateau to obtain a continuous high-resolution proxy record of the Asian monsoon over the past 18,000 years. This project indicated that monsoonal moisture since the late glacial period had been subject to "continual and cyclic variations," among which was a "very abrupt onset and termination" of a 2,000-year dry spell that started about 4200 years ago (yr BP) and ended around 2300 yr BP. Other variations included the well-known centennial-scale cold and dry spells of the Dark Ages Cold Period (DACP) and Little Ice Age (LIA), which lasted from 2100 yr BP to 1800 yr BP and 780 yr BP to 400 yr BP, respectively, while sandwiched between them was the warmer and wetter Medieval Warm Period, and preceding the DACP was the Roman Warm Period. Time series analyses of the sediment record also revealed several statistically significant periodicities (123, 163, 200 and 293 years, all above the 95% level), with the 200-year cycle matching the de Vries or Suess solar cycle, implying that changes in solar activity are important triggers for some of the recurring precipitation changes in that part of Asia. Hence, it is clear that large and abrupt fluctuations in the Asian monsoon have occurred numerous times and with great regularity throughout the Holocene, and that the sun played an important role in orchestrating them.

Also working on the Tibetan Plateau were Shao et al. (2005), who used seven Qilian juniper ring-width chronologies from the northeastern part of the Qaidam Basin to reconstruct a thousand-year history of annual precipitation there. In doing so, they discovered that annual precipitation had fluctuated at various intervals and to various degrees throughout the entire past millennium. Wetter periods occurred between 1520 and 1633, as well as between 1933 and 2001, although precipitation has declined somewhat since the 1990s. Drier periods, on the other hand, occurred between 1429 and 1519 and between 1634 and 1741. With respect to variability, the scientists report that the magnitude of variation in annual precipitation was about 15 mm before 1430, increased to 30 mm between 1430 and 1850, and declined thereafter to the present. These several findings suggest that either (1) there is nothing unusual about the planet's current degree of warmth, i.e., it is not unprecedented relative to that of the early part of the past millennium, or (2) unprecedented warming need not lead to unprecedented precipitation or unprecedented precipitation variability ... or both of the above. We must conclude, therefore, that the findings of this study provide absolutely no support for the climate-alarmist contention that global warming leads to greater and more frequent precipitation extremes.

Based on analyses of tree-ring width data and their connection to large-scale atmospheric circulation, Touchan et al. (2005) developed summer (May-August) precipitation reconstructions for several parts of the eastern Mediterranean region (Turkey, Syria, Lebanon, Cyprus and Greece) that extend back in time anywhere from 115 to 600 years. Over the latter length of time, they found that May-August precipitation varied on multiannual and decadal timescales, but that on the whole there were no long-term trends. The longest dry period occurred in the late 16th century (1591-1595), while there were two extreme wet periods: 1601-1605 and 1751-1755. In addition, both extremely strong and weak precipitation events were found to be more variable over the intervals 1520-1590, 1650-1670 and 1850-1930. Consequently, the results of this study also demonstrate there was nothing unusual or unprecedented about late 20th-century precipitation events in the eastern Mediterranean part of Asia that would suggest a CO2 influence. If anything, as this region transited from the record cold of the Little Ice Age to the peak warmth of the Current Warm Period, May-August precipitation actually become less variable, in contrast to the climate-alarmist claim that extreme weather phenomena become more variable in the face of rising temperatures.

Last of all, Davi et al. (2006) used absolutely dated tree-ring-width chronologies obtained from five sampling sites in west-central Mongolia to derive individual precipitation models, the longest of which stretches from 1340 to 2002, additionally developing a reconstruction of streamflow that extends from 1637 to 1997. In the process of doing so, they discovered there was "much wider variation in the long-term tree-ring record than in the limited record of measured precipitation," which for the region they studied covers the period from 1937 to 2003. In addition, they say their streamflow history indicates that "the wettest 5-year period was 1764-68 and the driest period was 1854-58," while "the most extended wet period [was] 1794-1802 and ... extended dry period [was] 1778-83." For this part of Mongolia, therefore, which the researchers say is "representative of the central Asian region," there is no support to be found for the climate-alarmist contention that the "unprecedented warming" of the 20th century has led to increased variability in precipitation and streamflow. In fact, any tendencies that may be present in the data suggest just the opposite, which is pretty much the same story told by the other studies we have described in this summary.

References
Davi, N.K., Jacoby, G.C., Curtis, A.E. and Baatarbileg, N. 2006. Extension of drought records for Central Asia using tree rings: West-Central Mongolia. Journal of Climate 19: 288-299.

Ji, J., Shen, J., Balsam, W., Chen, J., Liu, L. and Liu, X. 2005. Asian monsoon oscillations in the northeastern Qinghai-Tibet Plateau since the late glacial as interpreted from visible reflectance of Qinghai Lake sediments. Earth and Planetary Science Letters 233: 61-70.

Kripalani, R.H. and Kulkarni, A. 2001. Monsoon rainfall variations and teleconnections over south and east Asia. International Journal of Climatology 21: 603-616.

Pederson, N., Jacoby, G.C., D'Arrigo, R.D., Cook, E.R. and Buckley, B.M. 2001. Hydrometeorological reconstructions for northeastern Mongolia derived from tree rings: 1651-1995. Journal of Climate 14: 872-881.

Shao, X., Huang, L., Liu, H., Liang, E., Fang, X. And Wang, L. 2005. Reconstruction of precipitation variation from tree rings in recent 1000 years in Delingha, Qinghai. Science in China Series D: Earth Sciences 48: 939-949.

Touchan, R., Xoplaki, E., Funkhouser, G., Luterbacher, J., Hughes, M.K., Erkan, N., Akkemik, U. and Stephan, J. 2005. Reconstructions of spring/summer precipitation for the Eastern Mediterranean from tree-ring widths and its connection to large-scale atmospheric circulation. Climate Dynamics 25: 75-98.