Where were the monsoon regions and arid zones in Asia 1 prior to the Tibetan Plateau uplift ?

12 The impact of the Tibetan Plateau uplift on the Asian monsoons and inland arid climates is an 13 important but also controversial question in studies of paleoenvironmental change during the 14 Cenozoic. In order to achieve a good understanding of the background for the formation of the 15 Asian monsoons and arid environments, it is necessary to know the characteristics of the 16 distribution of monsoon regions and arid zones in Asia before the plateau uplift. In this study, we 17 discuss in detail the patterns of distribution of the Asian monsoon and arid regions before the 18 plateau uplift on the basis of modeling results without topography from a global coupled 19 atmosphere-ocean general circulation model, compare our results with previous simulation studies 20 and available bio-geological data, and review the uncertainties in the current knowledge. Based on 21 what we know at the moment, tropical monsoon climates existed south of 20°N in South and 22 Southeast Asia before the plateau uplift, while the East Asian monsoon was entirely absent in the 23 extratropics. These tropical monsoons mainly resulted from the seasonal shifts of the Inter24 Tropical Convergence Zone. There may have been a quasi-monsoon region in central-southern 25 Siberia. Most of the arid regions in the Asian continent were limited to the latitudes of 20-40°N, 26 corresponding to the range of the subtropical high pressure year-around. In the meantime, the 27 present-day arid regions located in the relatively high latitudes in Central Asia were most likely 28 absent before the plateau uplift. The main results from the above modeling analyses are 29 qualitatively consistent with available bio-geological data. These results highlight the importance 30 of the uplift of the Tibetan Plateau in the Cenozoic evolution of the Asian climate pattern of 31 dry-wet conditions. Future studies should be focused on effects of the changes in land-sea 32 distribution and atmospheric CO2 concentrations before and after the plateau uplift, and also on 33 cross-comparisons between numerical simulations and geological evidence, so that a 34 comprehensive understanding of the evolution of the Cenozoic paleoenvironments in Asia can be 35