## 1 Introduction  
Located in the hinterland of Eurasia, the arid region of Central Asia has a typical continental arid climate and one of the most vulnerable terrestrial ecosystems [1]. A comprehensive understanding of the environmental issues resulting from climate change and human activities in Central Asia is of great significance for the ecological protection and improvement of the region, national security, and sustainable development of the social economy [2, 3, 4]. Over the past 100 years, air temperature in the arid region of Central Asia, which is mainly controlled by westerly winds, has clearly shown an increasing trend [5, 6]. Annual precipitation in this region also shows an overall increasing trend, but with spatial differences [7, 8]. Under the combined effect of climate change and human activities,regional surface processes are undergoing strong and brand-new changes, which are highlighted by changes in arid hydrological processes and consequent changes in the ecological environment [9; 10; 11]. The underlying surface structure of the arid region in Central Asia is complex, and a large number of mountain-oasis-desert systems exist in the region [12; 13]. Water resources in arid regions typically originate in mountain systems. The Tian Shan comprises the largest mountain range in Central Asia, traversing the central part of Xinjiang in China, Kyrgyzstan, and Uzbekistan, and extending into four countries including Kazakhstan at the western end. Major rivers in Central Asia such as the IIi, Syr Darya, Amu Darya, Tarim, and Chu rivers all have their headwaters in the Tian Shan [14]. Within the context of global change, important changes in the climate and hydrology of the Tian Shan have occurred [2; 4; 11; 14; 15; 16]. In particular, owing to the lack of weather monitoring stations in high-altitude areas such as the Tian Shan, there is a major knowledge gap regarding temperature and precipitation trends, and available data are typically poor and often unreliable, which has a negative impact on the ability to predict the occurrence and intensity of extreme weather events [17]. As modern instruments are not able to record historic climate changes, their data are representative of only a short period in the evolution of a climatic environment [18; 19]. Some historically significant climate mutations and their environmental responses cannot be recorded by modern instruments, making it difficult to grasp the current state of environmental changes and to predict future trends [20; 21]. On the one hand, the climate data has a relatively short time scale, e.g., climatic research unit (CRU) data began in 1901 [22]. On the other hand, since most of the weather stations in arid regions of China began to observe in the 1950s, the applicability of the CRU data covering Chia is also worthy of exploring. In recent years, many scholars in Central Asia have integrated tree rings into their studies [23; 24; 25; 26; 27; 28; 29; 30] to recover and reconstruct long-term changes in temperature, precipitation, or humidity. Compared with tree rings, lake sediments effectively record information on lake hydrology, regional temperature, precipitation, and vegetation, and extracting climate information from lake records is one of the basic means for studying paleoclimate and paleoenvironment [31; 32; 33; 34]. However, previous studies have not provided effective links between long-term paleoclimate reconstruction and modern investigations regarding climate and environmental parameters. In this study, while focusing on the importance of environmental changes in the Tianshan Mountains and significant spatial heterogeneity of precipitation in this area, lake sediment representative of the last 100 years from a lake in the Tian Shan was chosen as the research object.