Reconstruction of annual net accumulation using ice cores from the Dasuopu glacier reveals monsoon precipitation variability in the central Himalayas over the past three centuries. We found that the broad features of the snow accumulation are reverse to the Northern Hemisphere temperature reconstruction over the past 300 years. On average, a 0.1¿C change in Northern Hemisphere temperature is associated with about 100 ¿ 10 mm change in snow accumulation in the Dasuopu ice core. Especially during the period 1920--1995 the snow accumulation in the Dasuopu ice core decreased about 500 mm while Northern Hemisphere temperature increased about 0.5¿C, which contrasts with previous studies that indicate an increase of summer monsoon precipitation in High Asia is a consequence of global warming. For the period 1900--1995 Indian monsoon precipitation in the Himalayas, Nepal, Bangladesh and northern India highly correlate with the thermal contrast between the Tibetan Plateau and the tropic Indian Ocean. Although the Tibetan Plateau has experienced statistically significant warming until to the early 1960s, the linear warming trend on the Tibetan Plateau is still less than that in the tropical Indian Ocean during the period 1900--1995, suggesting a decreasing thermal contrast between the Tibetan Plateau and the tropical Indian Ocean. We infer that transportation of water vapor from the tropical Indian Ocean to the Himalayas is decreasing as a result of the decreasing thermal contrast between the Tibetan Plateau and the tropical Indian Ocean.