Paleoclimate Records

Until recently, researchers have found it difficult to compare the relative ages of China's Quaternary glaciations with each other, let alone with global ice ages. However, absolute numerical dating now allows China's glaciations to be placed into the pre-existing worldwide framework. Based on these new dating results, Yi Chaolu and others have determined that most Asian Quaternary glaciations in the last 100,000 years were synchronous with global glacial events. One glacial advance between 44,000 and 54,000 years ago in southeastern Tibet was not synchronous with global cooling, and might have been caused by greater precipitation during a locally colder period. Chinese researchers have identified more Quaternary glacial periods before the Wisconsin Glaciation than have been identified in other regions of the world. The uplift of Tibet during the Cenozoic could be responsible for these differences.

As one of the thickest ice caps in central Asia, the Guliya Ice Cap, on the crest of the Kun Lun Mountains, provides valuable information for this critical region about the past climatic and environmental changes. Yang Meixue and others report that the Guliya ice core demonstrates periodic oscillations of the temperature and precipitation over the past 1,700 years. The results show various oscillations in the ice core records, with multiple timescales (200, 150, 70, 40, and 20 years). Their amplitude, phase, and frequency vary with time. Temperatures recorded since 1700 c.E. show that precipitation correlates well with temperature in this region.

Yao Tandong and others used data from an ice core from the Puruogangri Icefield on the central

Tibetan Plateau to construct a temperature history for the region based on the temperature proxy, 51sO. Reconstructing temperatures back to 1000 c.E. shows changes on the plateau generally similar to those in other parts of the Northern Hemisphere on a multi-decadal timescale. These data indicate that the 20th century warming in China was abrupt and exceptional, and that the 20th century was warmer than any time during the past 1,000 years.

Unlike much of the Northern Hemisphere, temperatures throughout the Tibetan Plateau showed no widespread cooling trend from 1000 c.E. to the late 19th century. They show, instead, slightly increasing temperatures. For the northern portion of the plateau, however, temperatures exhibited a very slight cooling trend from 1000 c.E. to the late 19th century. This reconstruction confirms the existence of the Medieval Warm Period and the Little Ice Age in China. However, the Little Ice Age was not as relatively cold as in other regions of the Northern Hemisphere.

The impressive Tibetan Plateau contains the largest ice mass on Earth outside the polar regions, with almost 37,000 catalogued glaciers that have a combined area of nearly 50,000 km2.

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