Yan Hong, Professor of Institute of Earth Environment, Chinese Academy of Sciences (IEECAS). He was born in Yueyang, Hunan Province of China in 1986, and received a BS and a PhD from University of Science and Technology of China in 2008 and 2012, respectively. He joined IEECAS as an Associate Professor in 2012 and was hired as a Professor in 2015. He was appointed deputy director of the State Key Laboratory of Loess and Quaternary Geology in 2016, deputy director of IEECAS in 2021, and director of State Key Laboratory of Loess Science in 2024. He obtained the Excellent Young Scientists Fund and the National Science Fund for Distinguished Young Scholars in 2015 and 2020, respectively.

His research focuses on multi-scale tropical climate changes and has made multiple advances in the study of Tridacna and dynamics of tropical hydroclimate changes; his work has promoted the widespread application of the Tridacna in past global change research, opened up new directions of paleoweather study, and proposed the hypothesis of ITCZ contraction/expansion. He has published more than 100 papers, in which more than 50 were first/corresponding-author papers, including 4 first-author papers on Nature series journals and on PNAS. His work has been cited more than 3,000 times, was selected as research highlights by Nature China, International Geochemical Association and NSFC, and was reported by scientific media such as BBC, Asian Scientist and China Global Television Network (CGTN), etc. He received the "Special Award of the President of the Chinese Academy of Sciences", "Shaanxi Youth Science and Technology Award", "Liu Tungsheng Prize for Outstanding Youth", "Young Scientist Award of the Chinese Academy of Sciences" and other honors. He actively participates in organizing youth academic exchange activities in China and serves as the leader of the National Youth Geoscience Forum (2016 to present), making contributions to promoting academic exchanges among Earth science youth of China.

ITCZ contraction/expansion hypothesis

Most of the tropical rainfall occurs in the Intertropical Convergence Zone (ITCZ). The changes of the ITCZ are not only important for tropical area, but also can affect climate change in mid-latitudes and even the world through atmospheric circulation such as monsoons. Both paleoclimate reconstructions and climate modeling have demonstrated that the past changes of the ITCZ were mainly characterized by north- south migration. These migrations should be associated with the occurrence of weaker (stronger) East Asia Summer Monsoon and stronger (weaker) Australia Summer Monsoon, which caused the opposite rainfall variations between the two hemispheres. However, through the study of hydrological records from the Asian-Australian summer monsoon area, Yan Hong and coauthors found that the precipitation in East Asia continent and northern Australia decreased synchronously during the Little Ice Age (~AD 1400-1850). The unusual spatial variation of paleoclimate records documented a distinctly different rainfall pattern that violated the expectation of ITCZ southward migration. Thus the authors proposed an alternative dynamic scenario: rather than strict north-south migration, the apparent mode of multi-decadal to centennial change for the western Pacific ITCZ is contraction/expansion in response to external forcings such as solar irradiance variation and large volcanic eruptions. This work indicated that in addition to the orbital parameters and north Atlantic melt water, solar activity and uneven distribution of aerosol concentrations may also lead to changes in the ITCZ. Even subtle changes can have significant impacts on tropical water and energy distribution, as well as global climate. This is also one of the key issues that we need to pay attention to in understanding and predicting future climate change. The ITCZ contraction/expansion hypothesis has broken through the universality of the ITCZ migration theory and provides a new perspective for understanding the dynamics of long-scale tropical hydrological changes. This work has received widespread attentions and a large number of subsequent studies have demonstrated it from the perspective of paleoclimate records and simulations