Japan‘s famous cherry blossoms have reached their flowery peak in many places earlier this year than at any time since the first records began in 812 AD, over 1,200 years ago.
Amid an exceptionally warm March in Japan, the cherry blossoms in peaked Friday, March 26th, the earliest in more than 1,200 years of records. The record bloom fits into a long-term pattern toward earlier spring flowering, a compelling indicator of climate change, experts say.
The March 26, 2021, peak bloom date surpassed the previous record holder of March 27, 1409, nearly a century before Christopher Columbus sailed to America. The long-term record dates back to A.D. 812, about 12 years after Charlemagne was crowned Holy Roman Emperor.
“The Kyoto Cherry Blossom record is incredibly valuable for climate change research because of its length and the strong sensitivity of flowering to springtime temperatures (warmer springs = earlier flowering, typically),” Benjamin Cook, a research scientist at Columbia University who specializes in reconstructing climate data from the past, said in an email.
Japan’s favourite flower, called ‘sakura,’ used to reach their peak bloom in April, just as the country celebrates the start of its new school and business year.
Yet that date has been creeping earlier and now most years the blossoms are largely gone before the first day of the Japanese school year, which starts in April.
The data was collected by Yasuyuki Aono, a researcher at Osaka Prefecture University, using diaries and chronicles written by emperors, aristocrats, governors, and monks.
This year’s bloom is also the earliest since the Japan Meteorological Agency started collecting the data in 1953 and 10 days ahead of the 30-year average. Similar records were set this year in more than a dozen cities across Japan.
Aono said the earliest blooms he has found before this year were March 27 in the years 1612, 1409 and 1236, though there are not records for some years.
The time of the peak bloom in Kyoto had been moving earlier in the year, from mid-April to the start of the month, from 1800 onwards, data shows.
‘We can say it’s most likely because of the impact of the global warming,’ said Shunji Anbe, an official at the observations division at the Japan Meteorological Agency.
Yasuyuki Aono, a researcher at Osaka Prefecture University, has tracked the data back to 812.
“I have searched and collected the phenological data for full flowering date of cherry tree (Prunus jamasakura) from many diaries and chronicles written by emperors, aristocrats, governors and monks at Kyoto in historical time,” he wrote.
Phenology is the study of seasons and recurring biological events. Since about 1800, the data suggest the peak date in Kyoto has gradually been moving back from mid-April towards the beginning of the month.
Unique for its longevity, the cherry blossom time series shows the average peak bloom date was relatively stable for about 1,000 years, from about 812 to 1800. But then, the peak bloom dates slope abruptly downward, revealing a shift earlier and earlier in the spring.
Since the 1800s, warming has led to a steady trend toward earlier flowering that continues to the present day, Some of this warming is due to climate change, but some is also likely from an enhanced heat island effect due to increased urbanization of the environment over the last couple of centuries.