Although global warming over the past century has been confirmed, the response of different regions to it is still uncertain. We developed a tree-ring width chronology based on tree-ring samples from juniper trees from the Xiqing Mountains in the northeast Tibetan Plateau, the central headwater area of the Yellow River. Using this tree-ring chronology, the minimum winter half-year (October–April) temperature for the research area was reconstructed for the past 425 years. The reconstruction shows that temperature variability was minimal over past four centuries prior to the warming that began in 1941. During the 50 years from 1941 to 1990, the minimum temperature of the winter half-year increased 2.5 °C. This degree of warming relative to the past 400 years suggests that the eastern Tibetan Plateau is highly sensitive to global warming. Copyright © 2007 Royal Meteorological Society