Knowledge of the past variability of climate at high northern latitudes during astronomical analogues of the present interglacial may help to inform our understanding of future climate change. Unfortunately, long-term continuous records of ice-sheet variability in the Northern Hemisphere only are scarce because records of benthic (18)O content represent an integrated signal of changes in ice volume in both polar regions. However, variations in Northern Hemisphere ice sheets influence the Siberian High (an atmospheric pressure system), so variations in the East Asian winter monsoon (EAWM)--as recorded in the aeolian dust deposits on the Chinese Loess Plateau--can serve as a useful proxy of Arctic climate variability before the ice-core record begins. Here we present an EAWM proxy record using grain-size variations in two parallel loess sections representative of sequences across the whole of the Chinese Loess Plateau over the past 900,000 years. The results show that during periods of low eccentricity and precessional variability at approximately 400,000-year intervals, the grain-size-inferred intensity of the EAWM remains weak for up to 20,000 years after the end of the interglacial episode of high summer monsoon activity and strong pedogenesis. In contrast, there is a rapid increase in the EAWM after the end of most other interglacials. We conclude that, for both the 400,000-year interglacials, the weak EAWM winds maintain a mild, non-glacial climate at high northern latitudes for much longer than expected from the conventional loess and marine oxygen isotope records. During these times, the less-severe summer insolation minima at 65° N (ref. 4) would have suppressed ice and snow accumulation, leading to a weak Siberian High and, consequently, weak EAWM winds.

Abstract. We correlate the China loess and Antarctica ice records to address the inter-hemispheric climate link over the past 800 ka. The results show a broad coupling between Asian and Antarctic climates at the glacial-interglacial scale. However, a number of decoupled aspects are revealed, among which marine isotope stage (MIS) 13 exhibits a strong anomaly compared with the other interglacials. It is characterized by unusually positive benthic oxygen (δ 18 O) and carbon isotope (δ 13 C) values in the world oceans, cooler Antarctic temperature, lower summer sea surface temperature in the South Atlantic, lower CO 2 and CH 4 concentrations, but by extremely strong Asian, Indian and African summer monsoons, weakest Asian winter monsoon, and lowest Asian dust and iron fluxes. Pervasive warm conditions were also evidenced by the records from northern high-latitude regions. These consistently indicate a warmer Northern Hemisphere and a cooler Southern Hemisphere, and hence a strong asymmetry of hemispheric climates during MIS-13. Similar anomalies of lesser extents also occurred during MIS-11 and MIS-5e. Thus, MIS-13 provides a case that the Northern Hemisphere experienced a substantial warming under relatively low concentrations of greenhouse gases. It suggests that the global climate system possesses a natural variability that is not predictable from the simple response of northern summer insolation and atmospheric CO 2 changes. During MIS-13, both hemispheres responded in different ways leading to anomalous continental, marine and atmospheric conditions at the global scale. The correlations also suggest that the marine δ 18 O record is not always a reliable indicator of the northern ice-volume changes, and that the asymmetry of hemispheric climates is one of the prominent factors controlCorrespondence to: Z. T. Guo (ztguo@mail.iggcas.ac.cn) ling the strength of Asian, Indian and African monsoon circulations, most likely through modulating the position of the inter-tropical convergence zone (ITCZ) and land-sea thermal contrasts.

The understanding of the ongoing climate change needs high-resolution records of the past, which are difficult to obtain in north-central China. Historical documents are unique materials for high-resolution (up to season) climate change reconstruction. Here, we report an attempt of quantitative climate reconstruction covering the main part of north-central China, by combining historical drought/flood index and tree-ring data. The rigorous verification tests confirm the fidelity of transfer functions used in the reconstructions. The precipitation and temperature anomalies/intervals were then defined based on the reconstructions. Finally, the intensity of several big droughts recorded in historical documents was re-examined and the dominant and recessive patterns of heat/water changes within the study area were identified. We concluded that (1) the droughts, occurred during the years of

No abstract