Publication details

Anthropogenic Aerosols Cause Recent Pronounced Weakening of Asian Summer Monsoon Relative to Last Four Centuries

Authors	LIU Yu CAI Wenju SUN Changfeng SONG Huiming COBB Kim M. LI Jianping LEAVITT Steven W. WU Lixin CAI Qiufang LIU Ruoshi NG Benjamin CHERUBINI Paolo BÜNTGEN Ulf SONG Yi WANG Guojian LEI Ying YAN Libin LI Qiang MA Yongyong FANG Congxi SUN Junyan LI Xuxiang CHEN Deliang LINDERHOLM Hans W.
Year of publication	2019
Type	Article in Periodical
Magazine / Source	Geophysical Research Letters
MU Faculty or unit	Faculty of Science
Citation
Web	https://doi.org/10.1029/2019GL082497
Doi	http://dx.doi.org/10.1029/2019GL082497
Keywords	tree-ring width; annual precipitation; east-asia; china; climate; variability; reconstruction; region; index
Description	The Asian Summer Monsoon (ASM) affects ecosystems, biodiversity, and food security of billions of people. In recent decades, ASM strength (as represented by precipitation) has been decreasing, but instrumental measurements span only a short period of time. The initiation and the dynamics of the recent trend are unclear. Here for the first time, we use an ensemble of 10 tree ring-width chronologies from the west-central margin of ASM to reconstruct detail of ASM variability back to 1566 CE. The reconstruction captures weak/strong ASM events and also reflects major locust plagues. Notably, we found an unprecedented 80-year trend of decreasing ASM strength within the context of the 448-year reconstruction, which is contrary to what is expected from greenhouse warming. Our coupled climate model shows that increasing anthropogenic sulfate aerosol emissions over the Northern Hemisphere could be the dominant factor contributing to the ASM decrease. Plan Language Summary Monsoonal rainfall has a certain influence on agriculture and industry in the regions of Asian Summer Monsoon (ASM). An understanding of the spatial-temporal variability of the ASM and the associated dynamics is vital for terrestrial ecosystems, water resources, forests, and landscapes. We have developed a 448-year ASM reconstruction back to 1566 CE using 10 tree ring chronologies from the margin region of ASM. We find that historical severe droughts and locust plague disasters during weak ASM events. The recent decreasing ASM trend persisting for over 80 years is unprecedented over the past 448 years. Coupled climate models show that increasing anthropogenic aerosol emissions are the dominant underlying factor. Our aim is that the time series will find a wide range of utility for understanding past climate variability and for predicting future climate change.