9:00 AM - 9:15 AM
[ACG34-01] Detecting the climate change impacts on extreme ocean warming events observed around Japan for 1982-2022
Keywords:Climate change, Global warming, Sea surface temperature
Global warming has potentially caused regional record-high sea surface temperatures (SSTs), such as marine heatwaves, but it is not yet clarified to what extent climate change has increased the frequency of discrete extreme ocean warming (EOW) around Japan. Here, we examine the impact of climate change on EOW events observed from January 1982 to December 2022 in multiple Japanese monitoring areas, operationally used by the Japan Meteorological Agency (JMA). We analyzed the historical and SSP2-4.5 scenario simulations of 24 CMIP6 climate models that have the equilibrium climate sensitivity between 2 K and 5 K. The probabilities of occurrences of monthly SST in each calendar month and each monitoring area for 1982-2022 are estimated under the present (5-year periods centered at each year) and preindustrial (1850) conditions, referred to as P1 and P0 respectively. The EOW event is defined as high monthly SSTs of which the return periods exceed 20 years at the preindustrial level (i.e., P0<0.05). The fraction of attributable risks (FAR=1-P0/P1) is used to quantify the impact of climate change on the observed monthly SST levels.
While the occurrences of EOW events are gradually increased over the past 41 years, the most frequent EOW events occurred around 1998 and in the mid-2010s, especially in southern Japan. The impact of climate change was not yet dominant around 1998 but has multiplied the occurrence probability of most EOW events by at least twice (FAR>0.5) since 2000. In southern Japan, the occurrence probability of a sizable number of events is increased more than tenfold (FAR>0.9) since the mid-2010s. Our analysis further indicates that all the EOW events identified in 2022 around Japan are attributable to climate change. The regional and seasonal differences of the climate change impact on EOW events are also discussed.
While the occurrences of EOW events are gradually increased over the past 41 years, the most frequent EOW events occurred around 1998 and in the mid-2010s, especially in southern Japan. The impact of climate change was not yet dominant around 1998 but has multiplied the occurrence probability of most EOW events by at least twice (FAR>0.5) since 2000. In southern Japan, the occurrence probability of a sizable number of events is increased more than tenfold (FAR>0.9) since the mid-2010s. Our analysis further indicates that all the EOW events identified in 2022 around Japan are attributable to climate change. The regional and seasonal differences of the climate change impact on EOW events are also discussed.