Climate Change Confuses Cherry Blossoms in Japan

Cherry blossoms and Heian Shirine(写真:GYRO_PHOTOGRAPHY/イメージマート)

Cherry Blossoms Boost Economies

After a dark, cold winter, cherry blossoms brighten up the atmosphere in spring and loosen the purse strings.

Honorary Professor Katsuhiro Miyamoto at Kansai University released his study in 2018 saying that the economic effect of cherry blossoms in two months was about 650 billion yen (6 billion dollars) per year on average nationwide, which is as big as the economic effect of the Olympics. 60 million people go out to see the spring flowers, spending money for transportation, food and drinks.

Earliest Full Bloom Since 812

This year, cherry blossom appeared much earlier than normal in many places of the country. Surprisingly, according to Osaka Prefecture University, the fact that flowers peaked in Kyoto on March 26th was probably the earliest in 1,200 years. The scholars have looked up a long-term record dating back to 812, by using many diaries and chronicles. They found out this year surpassed the previous record set in 1409 by one day.

2021 Flower Reports

So how fast have the cherry blossom season arrived in 2021? I will be focusing on the most popular kind of cherry blossoms called Somei-yoshino in this article.

According to the modern data collected by the Japan Meteorological Agency (JMA), 26 out of 45 major cities in the four main islands of Japan have seen the earliest start to the cherry blossom season since records began in 1953 as of April 8th. The cities include Tokyo, Osaka, Kyoto, Hiroshima, Kanazawa, Fukushima and Sendai.

Astonishingly, the season began about a couple of weeks earlier than normal years. It was on March 14th in Tokyo, which ties the earliest record set last year. It was on March 16th in Kyoto, 12 days earlier than normal, and on March 28th in Sendai which was 14 days earlier than average.

Definitions of “First Bloom” and “Full Bloom”

So what are the definitions of first bloom and full bloom?

JMA defines the first bloom as when an observation tree has five to six flowers in bloom. Full bloom is the stage when 80% of flowers on an observation tree bloom. There are 58 observation trees nationwide from Okinawa to Hokkaido. The one in Tokyo is located in Yasukuni Shrine. It is easy to find the tree as many media people flock to the tree to broadcast the conditions of the flowers.

Reasons For The Early Bloom

So what exactly is the reason for this year’s early blooming?

Of course, recent warm weather is a significant factor. Japan experienced an unusually warm February followed by a record warmest March. For example, the mean March temperatures in Kyoto was 11.6 degrees Celsius, which was 3.2 degrees higher than normal and the highest since 1881.

However, the warmth is not the only reason. Cherry blossoms are unique as they need to experience cold weather in order to prepare for blooming. It’s called “hibernation break” or “kyumin-daha” in Japanese. Like bears and squirrels, cherry flowers need to hibernate under cold weather to get active in spring. The temperature needed is said to be lower than 5 degrees Celsius.

This year, Japan experienced one of the coldest Januarys on record, possibly blamed on La Nina. That being said, this year had a perfect recipe for early blooming.

What's "400-Degree Rule"?

Ever since JMA stopped forecasting the timing of flowering, several private weather companies compete for the forecast every year based on their own methods and weather models.

However, there is a unique and easy rule of thumb that even non-experts might be able to use. Statistics show that when the sum of daily average temperatures since February 1st reaches 400 degrees Celsius, cherry blossoms begin opening. There is also a 600-degree rule, which is a sum of daily high temperatures since February 1st.

To verify the credibility of these rules, the total daily average temperatures from February 1st to March 13th, a day before Tokyo saw the first bloom were 386.1 degrees, while the sum of daily high temperatures were 593.3 degrees. Almost right!

Climate Change Confuses Cherry Blossoms

In Tokyo, the timing of the first bloom has been pushed back by 7 days over the last 50 years, as the average temperatures are on the rise. The timing could continue to arrive earlier due to climate change, but the trend may reverse at some point.

As stated earlier, cherry flowers need to hibernate under cold weather. If climate change continues to bring warm winters to Japan, temperatures may not reach the level needed for hibernation. If that happens, the flowers may start to bloom later, or they may not even reach their full bloom.

Scientists say the global warming is already distracting cherry blossoms in southwestern Japan’s Kagoshima Prefecture. Although the average temperature for March has risen by 2.5 degrees over the last 50 years, the timing of first bloom has not been changed.

(●=Areas where cherry blossoms may not bloom by 2100. Brown=areas where cherry blossoms may not reach full bloom by 2100.)

Second Quiet Season In A Row

This was the second year of quiet cherry blossom seasons because of the coronavirus. According to aforementioned Professor Miyamoto of Kansai University, this year's economic boost from cherry blossoms will plummet by about 500 billion yen (4.6 billion dollars), which is a 75% drop compared to 2018.

Hope the pandemic will come to an end soon and we can enjoy the cherish of the spring season as it used to be.