The question of when human pressures began to fundamentally change the Earth System is also the question of when the Anthropocene began, but this question remains unanswered due to the gradual intensification and time-transient nature of human influences on the Earth System.

　In this study, the research group investigated traces of human impact in geological records at 7700 locations around the world over the past 137 years and identified three periods. In particular, from 1948 to 1953 (1952±3), numerous signals reflecting advanced technological revolutions were observed on a global scale, including the first detection of organic pollutants such as PCBs and microplastics, and a sharp increase in radioactive nuclides such as plutonium from atmospheric nuclear explosions, and it was found that this unprecedented rapid increase in the number of traces of human impact occurred almost simultaneously in all regions.

　This reflects the fact that human activity has had such a powerful force that it has been able to leave a variety of traces of human activity on a global scale in geological records. Since then, irreversible changes have occurred in the Earth system, such as deviations from natural climate change due to greenhouse gases. This would not have been possible in the Holocene epoch (after 11700 years ago), when human influence was not dominant in the Earth system.

　The sudden increase in human traces around 1952±3 is seen as the start of the "unofficial Anthropocene," and is said to be of increasing importance in future discussions about the beginning of the Anthropocene.

*Other participants include the University of Tokyo, Australian National University, Matsuyama University, Kyoto University, Shimane University, and the National Institute of Advanced Industrial Science and Technology.

Paper information:[Proceedings of the National Academy of Sciences of the United States of America] Toward defining the Anthropocene onset using a rapid increase in anthropogenic fingerprints in global geological archives