Glacial features in the geological record provide essential clues about past behavior of climate. Of the numerous physical systems on earth, glaciers are one of most responsive to climate change, especially small glaciers, their direct marginal response taking only a few years or decades to be expressed. Accelerating recession of modern glaciers raises the issue of the climate's impact on water runoff. Data based on topographic maps and Advanced Spaceborne Thermal Emission and Radiometer (ASTER) imagery show the trends that are highly variable over time and within the region. An analysis of the local topographic settings of very small (<0.5 km 2 ) glaciers was conducted to investigate their influence on recent changes in these glaciers. Among 137 glaciers, 12 disappeared completely. The study reveals that glaciers situated in favorable locations had tiny relative area reduction, while those in less favorable settings generally had large area loss or even disappeared. It is suggested that most of the small glaciers studied have retreated as far as they are likely to under the climatic conditions of the late 20th century. Undoubtedly, the strong retreating of small glaciers exerts adverse effects on the hydrologic cycle and local socioeconomic development.

During the past five decades, fluctuations of glaciers were reconstructed from historical documents, aerial photographs, and remote sensing data. From 1956 to 2003, 910 glaciers investigated had reduced in area by 21.7% of the 1956 value, with a mean reduction for the individual glacier of 0.10 km 2 . The relative area reductions of small glaciers were usually higher than those of large ones, which exhibited larger absolute loss, indicating that the small glaciers were more sensitive to climate change than large ones. Over the past ~50 years, glacier area decreased by 29.6% in the Heihe (黑河) River basin and 18.7% in the Beidahe (北大河) River basin, which were the two regions investigated in the Middle Qilian (祁连) Mountain region. Compared with other areas of the Qilian Mountain region, the most dramatic glacier shrinkage had occurred in the Middle Qilian Mountain region, mainly resulting from rapid rising temperatures. Regional differences in glacier area changes are related to local climate conditions, the relative proportion of glaciers in different size classes, and other factors.

The eastern Xinjiang Basin is desperately short of water. Most rivers in the basin originate in the high eastern Tianshan, which has abundant precipitation and numerous alpine glaciers. Fieldwork conducted on three reference glaciers around Mt. Bogda in 1981 and suggests that they all strongly melt in summer, a process that has tended to accelerate in recent decades. Based on topographic maps from 1962 and 1972 and 2005/2006 . South-facing glaciers lost more of their area than those that are north facing, yielding an areal loss of 25.3% and 16.9% for southern and northern slopes of Mt. Bogda, respectively, and 12.3% and 6.6% for the comparable slopes of Mt. Harlik. Glaciers smaller than 0.5 km 2 in area experienced the strongest retreat, whereas glaciers larger than 2 km 2 in area experienced gentle recession but may be the main contributors in the future to river runoff. Glacial ablation in eastern Xinjiang tends to be strong, and the water resources in this region are deteriorating. Also, a heavy reduction in the capacity of the local karez system, as well as a significant change in river runoff, can be related to glacial retreat. Combined, this will adversely affect the downstream city of Urumqi and the Turfan Basin. Climate change is of great concern the world over, particularly regarding the effect of humanity on the existing environment and vice versa. Under continued warming over the last several decades, alpine glacier retreat has accelerated. Surface melting has occurred even on high-altitude glaciers [1]. Moreover, about 75% of the fresh water of the world comes from glaciers [2], thus retreating glaciers will have a strong influence on the regional hydrologic balance and economic sustainability. Climate warming, regardless of whether it is caused by anthropogenic factors or by nature, has led to strong global glacier recession. In fact, changes in alpine glaciers are one of the best natural indicators of climate change because a small change in climatic parameters will result in pronounced geometric changes in glacier shape and size. Many studies show that strong glacial wastage has been the major trend [3,4] over the period from 1993 to 2003 during which time sea level has risen about 0.77 ± 0.18 mm as a result, primarily, of that glacier melting [5]. Using two climate models, sea level is estimated to rise 0.046 m and 0.051 m as a result of mountain glaciers and ice caps melting by 2100 [6]. The estimate of China's potential contribution to cryospheric change is a sea level rise of 0.14-0.16 mm a 1 , of which the contribution of meltwaters from glaciers is assessed at about 0.12 mm a 1 [7]. The problems associated with strong mountain glacier melt are glacial hazards such as glacial lake outburst floods and

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