Progress in studies of the climate of humid period and the impacts of changing precession in early-mid Holocene

Studies on the climate of humid period and the impacts of changing precession in the early-mid Holocene are reviewed in this paper. High-resolution proxy data indicated that the African Humid Period, strong summer monsoon from the Arabian Sea to South Asia, northward migration of ITCZ ( Intertropical Convergence Zone) over the northern South America, and the humid period of China appeared in 10.5-5.5 kaBP, 10.0-6.0 kaBP, 10.5-5.4 kaBP, and 11.0-8.0 kaBP, respectively. Modeling studies proved that summer insolation over the Northern Hemisphere increased following the changes of precession in the early Holocene, which increased the land-sea temperature contrasts, intensified the summer monsoon circulation in the Northern Hemisphere, and finally induced a humid climate over the area under the influence of summer monsoon. However, modeling results underestimated the increase of precipitation and the degree of northward extension of monsoon rain belt compared with palaeo-environmental data. These discrepancies between the modeling results and the palaeo-environmental data may be associated with the changes of North Atlantic circulation, sea ice and vegetation covers. Moreover, climate of the humid period was not stable, in which several droughts were inlaid on centennial scale. In this review, perspectives for further studies of the climate change of the humid period in the early-mid Holocene are also proposed. (c) 2008 National Natural Science Foundation of China and Chinese Academy of Sciences. Published by Elsevier Limited and Science in China Press. All rights reserved.