Invited Speaker

Abstract: Global societies have recognized the importance of impacts of climate changes on our lives and therefore the Paris Agreement has entered effect in 2016. The goal to keep the increase in global average temperature to well below 2 °C above pre-industrial levels is a challenging because novel technological evolutions are required to make it possible. Therefore, we can never go to the future without adaptations to climate changes to cope with. Reliable studies on these topics depend on reliable future climate projections with small uncertainties, and atmospheric science community is tackling this big issue.

Japan has experienced record-breaking torrential precipitation causing disasters for recent years as well as many countries in the world: Heavy rain in northern Kyushu Island in July 2017, Heavy rain in July 2018, Typhoon Faxai in 2019, and Typhoon Hagibis in 2019. One may wonder if this frequency and record-breaking intensity of disastrous precipitation occur by chance or an underlying cause, global warming. Climate scientists were interviewed about the cause of recent disastrous precipitation since the begging of this century but did not have a good answer. Instead, they provided information about the extreme precipitation in late 21st century based on the Intergovernmental Panel on Climate Change (IPCC) assessment reports.

New methodology to answering these questions have been emerging for a decade: event attributions. This methodology has two approaches: storyline approach and probabilistic approach. In the former, two predictions as initial value problem between under current on-going warming and non-warming conditions are compared to estimate the impact of global warming on an extreme precipitation event occurred in a real world with a regional climate model focusing on a target region. On the other hand, in the latter, two sets of huge ensemble simulations as boundary value problem with current on-going warming and non-warming conditions with a combination of a global climate model and a regional climate model. The former approach was applied to the Heavy rain in July 2018. We performed two simulations: a current on-going warming simulation with observations as they are and non-warming simulation with elimination of linear trends of summer-mean/monthly-mean temperature from 1980 to 2018. The current on-going warming simulation showed the increases in total precipitation of the Heavy rain in July 2018 by approximately 6.7% compared to the non-warming simulation.

The latter approach was applied to heavy rains in Kyushu Island to support the Heavy rain in northern Kyusyu Island in July 2017. Stationary weather fronts and typhoons bring heavy precipitation in western and eastern sides of the mountain ranges in the Kyusyu Island and have different changes under a current on-going global warming. Therefore, the changes in heavy precipitation over western and eastern sides of the mountain ranges are also different. We also investigated future projections of heavy precipitation in Kanto and associated weather patterns by large ensemble high-resolution with another approach.

Biography: Dr. Tosiyuki Nakaegawa is currently the Head of the Applied Meteorology Laboratory at Meteorological Research Institute, Japan Meteorological Agency. He is the member of the national water resources investigation committee under a future climate change by the Ministry of Infrastructure, Land, and Transport, Japan, and the member of sector-specific working group of impact assessments of climate change by Ministry of Environment.

He is the co-leader of expert team on sector-specific climate indices, the World Meteorological Organization (WMO), the member of climate change impacts on tropical cyclones (United Nations Economic and Social Commission for Asia and the Pacific/WMO), and the member of International Commission on Climate, the International Association of Meteorology and Atmospheric Science under the International Union of Geodesy and Geophysics. He is the board member of the Meteorological Society of Japan, and was the board member of the Japan Society of Hydrology and Water Resources. He is devoted to publishing peer-review international journals from Japan: Editor-in-Chief of Hydrological Research Letters, Vice Editor-in-Chief of Scientific Online Letters on Atmosphere, and an observer of Earth, Planets and Space.

He is the author of more than 120 peer-review journals. He received the Awards for Research Article Award (2012), for Scholar Award (1998), for Young Scientist Research Article Award (1995) of Japan Society of Hydrology and Water Resources, the Young Scientist Research Article Award of Remote Sensing Society of Japan (2002), Young Scientist Article Research Award of Annual Journal of Hydraulic Engineering, Japan Society of Civil Engineering (1995). He also received Certificate in appreciation of services to the WMO (2018).