Studying the evolution of the Late Holocene monsoon climate will help to understand and predict future climate changes more accurately in the monsoon regions.In the eastern and western coasts of the Pacific Ocean where the global monsoon is concentrated,a large number of paleoclimate records have been published in these regions.However,there is still a lack of comparative and integral studies on abrupt climate events in the four monsoon regions.To address this problem,comparing the delta~(18)O of stalagmite records in 11 caves and Ti of 1 lake record which from four monsoon regions,namely Asian monsoon region,Indonesian-Australian monsoon region,American monsoon region,and the results show that the delta~(18)O values of stalagmites show a positive trend in the Late Holocene,which mean summer monsoon declined.On the other hand,weak summer monsoon events of 1.5 kaB.P.and 2.7 ka B.P.are observed in four monsoon regions.Furthermore,it also recorded a series of weak summer monsoon events on decadal to centennial timescales with decreasing trend in the east and west Pacific.However,this feature is different from the see-saw" pattern between northern and southern hemisphere.Because of the enhanced ENSO (El Nino-Southern Oscillation)activity in the Late Holocene,which played an important role in the weakening of the summer monsoon between the northern and southern hemispheres of both sides of the Pacific Ocean.During El Nino events,the Walker circulation weakens and its rising limb shifts eastward away from the western Pacific warm pool.At the same time,the western North Pacific subtropical high (WPSH) strengthens and stretches westward,which resulted into the weakening of the Asian summer monsoon.Note that,the Walker circulation and its rising limb shifts eastward also led to the declining of sea surface temperature (SST) in Indo-Pacific Warm Pool(IPWP),then Indo-Australian summer monsoon weakened as Madden-Julian Oscillation (MJO) weakened.Furthermore,during El Nino events,a rising of SST in the eastern equatorial Pacific led to the weakening of the temperature gradient in the eastern and western Pacific.Consequently,the low Level Jet(LLJ) in the South American monsoon region weakens with South America summer monsoon declined.Contemporary,an enhanced LLJ (low level jet) stream over North American Caribbean,result in enhanced subsidence in this monsoon region,and it turns out that North American summer monsoon may be declined in this period.Our conclusion suggests that ENSO activity enhanced could lead to a weakening summer monsoon trend in the east and west Pacific during the Late Holocene.