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Japanese kids born in 2020 could face extreme rain, heat unseen by grandparents: study

This Oct. 12, 2019 file photo shows a severely swollen river in Hakone, Kanagawa Prefecture, during Typhoon Hagibis. When the typhoon struck Japan, 922.5 millimeters of rain fell on the town of Hakone in a single day -- the most ever recorded in Japan. Research suggests that children born now may experience three torrential rain events beyond their grandparents' experience. (Mainichi/Haruo Sawa)

TOKYO -- Should climate change grind on unchecked, a Japanese person born in 2020 is expected to see about three major torrential rain events beyond anything experienced by the generation born in 1960, as well as around 400 more days of intense heat, over the course of their lives, new research shows.

    We know more frequent and intense weather disasters are expected because of global warming. But researchers including at Japan's National Institute for Environmental Studies (NIES) have asked just how many more torrential rains and heatwaves today's children across the world might experience compared to previous generations. Their estimates have been published in the Japanese journal Science Research Communications.

    The team based its predictions on hypothetical individuals born in 1960, referred to as the grandparent generation, who would live to be 80 and welcome their first grandchild in 2020. The researchers then predicted how many extreme weather events exceeding the intensity of any seen by the grandparents could befall their grandchildren by the latter's 80th birthday.

    It is thought that if global temperatures continue to rise, and bring with them more hot days, then torrential rains will become more common in Japan due to an increase in atmospheric water vapor.

    If efforts to reduce global emissions do not progress and average global temperatures hit 4.8 degrees Celsius higher than pre-Industrial Revolution norms by the end of this century, the study predicts, over the course of their lives the grandchildren would see about three rainfalls exceeding the maximum single-day amount experienced by the grandparent generation. The grandchildren would also experience some 400 days hotter than the hottest day of their grandparents' lives.

    But if global temperatures rose only by 2 C, the grandchildren would see around 2 days of rain beyond their grandparents' experience, and some 20 days of extraordinary heat. The results showed that if emissions are reduced sooner, then future generations' risks of encountering weather disasters could be brought down.

    Looking to other parts of the world, if average temperatures at the end of this century reach 4.8 C higher than pre-Industrial Revolution levels, then young people including in Southeast Asia, Central Africa and northwestern South America are expected to witness five or more rain events beyond anything their grandparents will have experienced. In North Africa and tropical parts of South America, the grandchild generation is predicted to experience at least 1,000 days of extraordinary heat.

    Many countries in these regions produce relatively low emissions. With the coming of each generation, it is thought that the inequality in climate change damage experienced by low-emissions producing nations and high-producing ones will be perpetuated further.

    Hideo Shiogama, head of the Earth System Risk Analysis Section at NIES and one of the people behind the research, said, "It shows us that realizing the goals of the Paris climate change agreement, which aims to keep average global temperature rises below 2 C, and to 1.5 C if possible, will help fix generational and geographical inequalities.

    "I want people to think of global warming, which will bring with it more grave repercussions in the future, as an issue that our children and grandchildren are significantly affected by."

    The report can be read in English at the following link:

    (Japanese original by Shuichi Abe, Science & Environment News Department)

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