Abstract: Here we present a comparison between the proxies and observational data during the past decades using a short core (TSLC) from Lake Toson.Lake Toson (37°04'~37°13'N,96°50'~97°03'E) is a closed saline lake located in Delingha,NE Tibetan Plateau.The surface area of the lake is approximately 165.9km2 with an elevation of 2808m a.s.l.The maximum water depth is 23.6m.According to data from Delingha Meteorological Station,the mean annual temperature is 4℃,and the regional annual precipitation is about 160~170mm,most of which falls as rain from May to September.The potential evapotranspiration is about 2000mm.The current salinity of the lake water is ca.27.8g/L,and the pH of the lake water is 8.38.Modern vegetation in this region is dominated by desert plant communities.The lake is fed by water from Bayin River flowing through Lake Hurleg,which is 3km to the north of Lake Toson.Such a hydrologic pattern make it sensitive to climate change and human activities,hence being an ideal site to study human activities impact on sedimentary records.Core TSLC (37°07'36"N,96°57'01"E;35.5cm in length) were recovered at the water depth of 23.6m in Lake Toson,and the resolution was 5mm and 1cm of top to 20.5cm and 20.5cm below of the sample from the cores TSLC,respectively.The short core was dated using 210Pb.Proxies including grain-size,carbonate content and carbonate oxygen isotopes (δ18Ocarb) were compared with instrumental data in Delingha in the last 52 years and the reconstructed regional precipitation by tree-ring and A/C ratio of Lake Gahai.The δ18Ocarb values were attributed to changes in precipitation/evaporation (P/E) ratios (effective humidity).High (low) authigene carbonate content indicated salinization (desalination) of Lake Toson,and carbonate content changes was consistent with δ18Ocarb,which could reveal the changes of effective humidity of lake areas.During the period of 1883~1975A.D.,proxies indicated a low effective humidity and a gradual increasing trend,but effective humidity decreased and then increased during 1960~1970A.D.Effective humidity increased during 2004~2011A.D.Results revealed that regional effective humidity indicated by proxies was consistent with the precipitation reconstructed by tree-ring and the observed precipitation during 1883~1975A.D.and 2004~2011A.D.During the period of 1975~2004A.D.,however,proxies was indicating a reduced P/E ratio,conflicting with the increased precipitation suggested by both the instrumental data,the tree-ring-based reconstruction and A/C ratio of Lake Gahai.During this period the regional evaporation decreased due to reduced wind speed and the annual sunshine hours,though the temperature was increasing.The resulted effective humidity,therefore,was increasing.The inconsistency between the reduced effective humidity recorded by proxies and the increased humidity by the observational data was caused by the regional agriculture development.Increased water consumption for irrigation during this period reduced the water supply for Lake Toson through the Bayin River.After 2004A.D.,the agricultural water consumption reduced and the climate indicated by proxies became consistent with the instrumental data again.Our result suggests that recent human impacts should be evaluated before the relationship between proxies and climate factors are used for paleoclimate reconstruction in regions with intensive human activities.Meanwhile,the resolution of observational data should be match with proxies resolution when we analyze observational data.