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The World's Water Tower
Reference
Xu, S., Lu, C., Shi, X. and Gao, S. 2008. World water tower: An atmospheric perspective. Geophysical Research Letters 35: 10.1029/2008GL035867.

What was done
The authors analyzed a half-century (1957-2006) of upper-air Chinese radiosonde observations, along with concomitant surface air temperature and precipitation data for the Tibetan Plateau or "roof of the world" region.

What was learned
Xu et al. report that in the summer half of the year, "the Tibetan Plateau acts as a strong 'dynamic pump' [that] continuously attracts moist air from the low-latitude oceans." When reaching the plateau, some of these flows rise along its south side and cause "frequent convections and precipitations," which feed its mid- and low-latitude glaciers, snowpacks and lakes, from whence originate many of Asia's major rivers, which flow system comprises "the largest river runoff from any single location in the world." Hence, they say "it is not an overstatement to call the Tibetan Plateau 'the global water tower'."

In further analyzing the data sets they employed, the four researchers found that "recent warming in the plateau started in the early 1970s, while the water vapor content showed an upward trend in the early 1980s and continues to the present time," which led to the same pattern being found in the annual precipitation data.

What it means
Xu et al. write that their findings "suggest several possible consequences." First, they note that "owing to the combined effect of the rapid melting of glaciers and increased precipitation in the Tibetan Plateau due to global warming, the downstream transport of water from the Tibetan water tower would increase in volume," and "this may cause an increase in severe flooding problems for countries along the major rivers that discharge this water." However, most climate alarmists are more concerned about these rivers drying up, because, as the four researchers continue, "the rapid retreat of glaciers over the plateau's mountains may pose a serious socio-economical issue for the water resources that feed 40% of the world's population." Hence, an alternative scenario, which seems even more likely (in that it is a mix of the two extremes) is that, as they describe it, "the increased atmospheric [moisture] supply may alleviate the problem of rapid depletion of water resources arising from the melting of glaciers," which much more optimistic view is akin to seeing doomsday on the left and doomsday on the right, but salvation in the middle.

Reviewed 28 January 2009