Naurzbaev and Vaganov (2000) developed a continuous near-surface air temperature record from tree-ring data obtained from 118 trees growing near the timberline in Siberia that covers the period 212 BC to AD 1996, as well as a 700-year record for the period 3300 to 2600 BC.  Because the temperature fluctuations they derived agreed well with air temperature variations reconstructed from Greenland ice-core data, they concluded that "the tree ring chronology of [the Siberian] region can be used to analyze both regional peculiarities and global temperature variations in the Northern Hemisphere."  So what did they find?

The scientists discovered a number of several-hundred-year warm and cool periods, including the Medieval Warm Period (AD 850 to 1150), the Little Ice Age (AD 200 through 1800), and the current Modern Warm Period.  In regard to the warming between the latter of these two periods, Naurzbaev and Vaganov say it is "not extraordinary" and that "the warming at the border of the first and second millennia [i.e., AD 1000] was longer in time and similar in amplitude."  They also note that temperatures of the mid-Holocene were warmer yet, averaging about 3.3°C higher than those of the past two millennia.

In another tree-ring study - this one of the Pakistan/Afghanistan border region near China and India - Esper et al. (2002) employed more than 200,000 ring-width measurements from 384 trees obtained from 20 individual sites ranging from the lower to upper timberline to reconstruct the climatic history of Western Central Asia since AD 618.  Their work revealed that early in the seventh century, the Medieval Warm Period was already firmly established.  Between AD 900 and 1000, tree growth was exceptionally rapid, at rates that they say "cannot be observed during any other period of the last millennium."  Between AD 1000 and 1200, however, growing conditions deteriorated; and at about AD 1500, minimum tree ring-widths were reached that persisted well into the seventeenth century.  Towards the end of the twentieth century, ring-widths increased once again; but the scientists report that "the twentieth-century trend does not approach the AD 1000 maximum."  In fact, the Medieval Warm Period was far more conducive to good tree growth than the Modern Warm Period.  Summing up their work, Esper et al. say that "the warmest decades since AD 618 appear between AD 800 and 1000."

Zhuo et al. (1998) reviewed what is known about the mid-Holocene period in China, noting that temperatures during the Climatic Optimum in that part of the world were also warmer than they are currently, by anywhere from 2-6°C.  They additionally reported that many glaciers across the country retreated during this period, and that some in eastern China disappeared altogether.  Also, the warmer temperatures of the mid-Holocene resulted in a retreat of the southern permafrost limit to 100 km north of its current position.

Yafeng et al. (1999) analyzed a 2000-year high-resolution ð¹⁸O record obtained from the Guliya ice cap located in the Qinghai-Tibet Plateau of China.  Their data clearly depicted the Dark Ages Cold Period of the middle of the first millennium AD, the warmth of the subsequent Medieval Warm Period, and the following "well-defined 'Little Ice Age'," which in that part of the world appeared to last until 1930.  Perhaps the most striking of their findings, however, was the occurrence of over 30 abrupt climatic shifts on the order of 3°C that took place over but two or three decades.

The Holocene in Asia, as depicted by these several records, was a period of millennial-scale climatic oscillations, the warm and cool nodes of which are typified by the Medieval Warm Period and Little Ice Age.  Another distinctive feature of the Holocene was its peak mid-period warmth, when temperatures were considerably higher than they are currently, but when atmospheric CO2 concentrations were much lower.  Also evident in the Holocene record of Asia are many rapid shifts in temperature, which - on the Guliya ice cap, at least - were even more dramatic than the "unprecedented" warming that is claimed by the IPCC to have occurred during the last decades of the 20th century.

In view of these real-world observations, there appears to be nothing unusual about the planet's current climatic state or its recent climate dynamics, particularly in Asia.  In fact, the data of Esper et al. suggest that the Modern Warm Period still has a long ways to go before it can be said to be equivalent to the Medieval Warm Period.  Hence, there would appear to be little reason to suggest that the hand of man is evident in the global warming of the past century or so.  Indeed, we would say there is no reason to make such an inference.

References
Esper, J., Schweingruber, F.H. and Winiger, M.  2002.  1300 years of climatic history for Western Central Asia inferred from tree-rings.  The Holocene 12: 267-277.

Naurzbaev, M.M. and Vaganov, E.A.  2000.  Variation of early summer and annual temperature in east Taymir and Putoran (Siberia) over the last two millennia inferred from tree rings.  Journal of Geophysical Research 105: 7317-7326.

Yafeng, S., Tandong, Y. and Bao, Y.  1999.  Decadal climatic variations recorded in Guliya ice core and comparison with the historical documentary data from East China during the last 2000 years.  Science in China Series D - Earth Sciences 42 Supp.: 91-100.

Zhuo, Z., Baoyin, Y. and Petit-Marie, N.  1998.  Paleoenvironments in China during the Last Glacial Maximum and the Holocene Optimum.  Episodes 21: 152-158.