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Vladimir B. Aizen, Elena M. Aizen, John M. Melack, and Jeff Dozier

Abstract

The authors analyze climatic and hydrologic data from 110 sites collected from the middle of the twentieth century to the present in the Tien Shan, one of the largest mountain systems of central Asia. In spite of a few confounding interregional variations in the temporal changes of surface air temperature, precipitation, runoff, glacier mass, and snow thickness in the Tien Shan, it has been possible to establish statistically significant long-term trends in these key hydroclimatic variables. The average rise in air temperature was 0.01°C yr−1 over the range, with slightly lower values below 2000-m elevation. The precipitation in the Tien Shan increased 1.2 mm yr−1 over the past half-century. The precipitation increase is larger at low altitudes in the northern and western regions than at altitudes above 2000 m. A decrease in snow resources occurred almost everywhere in the Tien Shan; the maximum snow thickness and snow duration have decreased on average 10 cm and 9 days, respectively. The annual runoff has dropped or did not change significantly in Tien Shan rivers. The main factor determining the change in river runoff is the type of precipitation (liquid or solid). Over the last few decades, periods of glacier decline have coincided with declining river runoff.

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Pavel Ya. Groisman, Elizabeth A. Clark, Vladimir M. Kattsov, Dennis P. Lettenmaier, Irina N. Sokolik, Vladimir B. Aizen, Oliver Cartus, Jiquan Chen, Susan Conard, John Katzenberger, Olga Krankina, Jaakko Kukkonen, Toshinobu Machida, Shamil Maksyutov, Dennis Ojima, Jiaguo Qi, Vladimir E. Romanovsky, Maurizio Santoro, Christiane C. Schmullius, Alexander I. Shiklomanov, Kou Shimoyama, Herman H. Shugart, Jacquelyn K. Shuman, Mikhail A. Sofiev, Anatoly I. Sukhinin, Charles Vörösmarty, Donald Walker, and Eric F. Wood

Northern Eurasia, the largest landmass in the northern extratropics, accounts for ~20% of the global land area. However, little is known about how the biogeochemical cycles, energy and water cycles, and human activities specific to this carbon-rich, cold region interact with global climate. A major concern is that changes in the distribution of land-based life, as well as its interactions with the environment, may lead to a self-reinforcing cycle of accelerated regional and global warming. With this as its motivation, the Northern Eurasian Earth Science Partnership Initiative (NEESPI) was formed in 2004 to better understand and quantify feedbacks between northern Eurasian and global climates. The first group of NEESPI projects has mostly focused on assembling regional databases, organizing improved environmental monitoring of the region, and studying individual environmental processes. That was a starting point to addressing emerging challenges in the region related to rapidly and simultaneously changing climate, environmental, and societal systems. More recently, the NEESPI research focus has been moving toward integrative studies, including the development of modeling capabilities to project the future state of climate, environment, and societies in the NEESPI domain. This effort will require a high level of integration of observation programs, process studies, and modeling across disciplines.

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