Large areas in western China were wetlands or less arid between 40 and 30 ka, corresponding to the “Greatest Lake Period” on the adjacent Tibetan Plateau. During the last glacial maximum, some of these western Chinese deserts again experienced wetter conditions; however, at the same time the sandy lands in the eastern Chinese desert belt experienced an activation of aeolian dunes. While interpretations of the mid-Holocene environment in the deserts of China are controversial, it is quite likely that it was more humid not only in the eastern areas influenced by monsoon climate systems but also in the western deserts where moisture is currently associated with westerlies. Evaluation of lacustrine records in the lakes recharged by dryland rivers and the complex interactions of these systems, as well as other paleoenvironmental proxies such as theArtemisia/Chenopodiaceae ratio, should be interpreted with greater caution. Facing the highlighted uncertainties in our understanding of climate changes in Chinese deserts, it is hoped that this special issue will improve our knowledge considerably.

Significance: In contrast to earlier assertions that deserts in northern China are 10 ⁶ years old, our multidisciplinary investigation in the Hunshandake Sandy Lands, located in the eastern portion of China’s desert belt, shows that this desert is ca. 4,000 years old. This study documents dramatic environmental and landscape changes in this desert during the last 10,000 years. For the first time to our knowledge we present a case of desertification mainly triggered by changes in the hydrological and geomorphological system, associated with climate change at ca. 4.2 ka. Our research on the human–environment interactions in the Hunshandake suggests Chinese civilization may be rooted in the marginal areas in the north, rather than in the middle reaches of the Yellow River.

We appreciate very helpful reviews by Dr. Martin Stokes and three anonymous reviewers and editor Dr. Richard Marston. We also appreciate the encouragement for writing this paper from Dr. Timothy Horscroft. We acknowledge support of the sponsors of the Fluvial Systems Research Group consortium, BP, BG, Chevron, ConocoPhillips and Total.Peer reviewedPostprin

Tree ring data have been used to reconstruct the mean late-season (June through January) temperature at a timberline site in the Sierra Nevada, California, for each of the past 2000 years. Long-term trends in the temperature reconstruction are indicative of a 125-year periodicity that may be linked to solar activity as reflected in radiocarbon and auroral records. The results indicate that both the warm intervals during the Medieval Warm Epoch (∼A.D. 800 to 1200) and the cold intervals during the Little Ice Age (∼A.D. 1200 to 1900) are closely associated with the 125-year period. Significant changes in the phase of the 125-year temperature variation occur at the onset and termination of the most recent radiocarbon triplet and may indicate chaotic solar behavior.