Without the warming effects of urban environment and climate change, cherry blossoms in Kyoto, Japan, would not bloom 11 days in advance. Last year, cherry blossoms in Kyoto bloomed on March 26, the earliest in more than 1000 years of records. Although this year's Kyoto Cherry Blossom bloomed on April 1, which is in line with the typical characteristics of the current climate, it is still earlier than the average record before the 1930s.
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Nikolaos christidis of the Met Office and colleagues designed a computer model to estimate when urban cherry blossoms would bloom without urban warming and human induced climate change.
The researchers used records of the cherry blossom season in Kyoto since 1200. "This information can be found in a variety of materials." Christidis said that because the cherry blossom in Kyoto has been a major event in Japan since ancient times, it represents the arrival of spring in Japanese tradition.
In a recent study published in the environmental research letters, the research team pointed out that under the current climate conditions, the urbanization of Kyoto has led to cherry blossoms blooming five days in advance, while the impact of climate change has led to cherry blossoms blooming six days in advance.
Christidis said that there are several reasons why urbanization leads to higher temperatures, such as changing the way solar heat interacts with the urban surface.
Japanese cherry blossoms begin to bloom when the ambient temperature is maintained at a certain level, usually around March every year.
Christidis pointed out that the average temperature in Kyoto in March is about 9 to 10 degrees Celsius, but if there is no human influence, the temperature should be 5 to 6 degrees Celsius.
The researchers also found that if temperatures continue to rise as expected this century, cherry blossoms will open a week earlier by 2100. As last year, the possibility of flowering very early will also increase.
"Such extreme events are expected to occur at least once a century." Christidis said.