What was done
The authors employed more than 200,000 ring-width measurements from 384 trees obtained from 20 individual sites ranging from the lower to upper timberline in the Northwest Karakorum of Pakistan (35-37°N, 74-76°E) and the Southern Tien Shan of Kirghizia (40°10'N, 72°35'E) to reconstruct regional patterns of climatic variations in Western Central Asia since AD 618, noting that these high-elevation sites are "exceptionally sensitive to climatic variations" and that "conspicuous interactions exist between [their] ecosystems and climate."

What was learned
The long ring-width record the authors developed provides an important perspective on the Medieval Warm Period and Little Ice Age.  The authors note, for example, that early in the seventh century the Medieval Warm Period was already firmly established and growing even warmer.  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 authors report that "the twentieth-century trend does not approach the AD 1000 maximum."  In fact, there is almost no comparison between the two periods, with the Medieval Warm Period being far more conducive to good tree growth than the Modern Warm Period.  As the authors describe the situation, "growing conditions in the twentieth century exceed the long-term average, but the amplitude of this trend is not comparable to the conditions around AD 1000."

What it means
Contrary to the climate-alarmist claim that the last decade of the 20th century was the warmest of the past millennium, it is readily evident from the authors' data that the great bulk of the first century of the past millennium in Western Central Asia was much warmer than any part of its last century.  And that wasn't even the warmest period of the past 1300 years.  "The warmest decades since AD 618 appear between AD 800 and 1000," say the authors.  Hence, it can be appreciated that the "unprecedented warming of the past century," as climate alarmists like to describe it, does not even come close to meriting that appellation, especially in Western Central Asia.  In fact, in this region of the world, the warming of the past two centuries is pretty pathetic, giving absolutely no hint of any possible anthropogenic influence.