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Global warming blamed for late autumn, early spring in west Japan prefecture

The sample maple tree is seen at Momijidani Garden in the city of Wakayama on Dec. 17, 2020. (Mainichi/Satoshi Yamaguchi)

WAKAYAMA -- Global warming is believed to have triggered late autumn foliage and early cherry blossoms in the west Japan prefecture of Wakayama, according to the local meteorological observatory.

    In 2020, the Wakayama Local Meteorological Observatory determined that the official "autumn leaves day" based on its sample maple tree was Dec. 14, even though the day usually fell in November half a century ago. The day is declared when the majority of leaves on the sample tree are observed to have turned red. The observatory official also said that the cherry blossom season has been starting earlier year by year, and it is suspected that global warming is affecting those seasonal changes.

    The sample maple tree is at Momijidani Garden on the grounds of Wakayama Castle in the city of Wakayama, and the local observatory has been monitoring it since 1953.

    The latest autumn leaves day was Dec. 21, 2006, and the earliest was Nov. 8, 1953. Between 1953 and 1980, except for some early years where no records remain, the day fell in November 20 times, and in December only five times. Since 1981, the day gradually shifted to December, and it's fallen in December since 2003.

    A calculation of seasonal changes between 1953 and 2020 by the Wakayama observatory indicates that autumn leaves day is moving backward at a pace of about 15 days every 50 years. Similar trends have been seen around the country, and the day is moving backward nationwide at a pace of 14 days every 50 years. Meanwhile, the cherry blossom season in Wakayama is moving forward at a pace of 3.5 days every 50 years.

    Changes in average temperatures, which are deeply connected to plant growth, have also been observed. In Wakayama, the average temperature rose by some 1.5 degrees Celsius over the last 100 years.

    "It's certain that autumn leaves day is statistically becoming later," said a meteorological official at the observatory. "We suspect that the fact that global warming is proceeding due to increasing emissions of greenhouse gasses and urbanization is a contributing factor."

    (Japanese original by Satoshi Yamaguchi, Wakayama Bureau)

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