Springtime in Japan is a visual spectacular. Millions of cherry trees erupt into bloom, heralding the arrival of the new season.

This iconic time of year, which attracts high numbers of tourists, is such an important event that the Japan Meteorological Agency (JMA) makes a huge effort to forecast peak blossom every year.

And that diligence in predicting the cherry blossom has highlighted a worrying pattern that suggests global warming is affecting Japan’s climate. In each passing decade the blossom is arriving earlier.

The JMA has been monitoring the blossoms since 1953. By looking at trees in 59 locations it’s found that the flowers are appearing earlier - at a rate of 4.8 days every 50 years.

Japan’s Acer trees provide a second spectacular show later in the year. When the leaves turn in the Autumn they set off a blaze of colour that spreads across the landscape. But the timing of this event is changing too.

The JMA uses 52 observation stations to track the Acer’s transition from summer green to Autumn hues. It’s found the leaves are changing colour 16.1 days later every 50 years.

Image: Japan Meteorological Agency

A brief history of blossom

Japan has been keeping records of the blossom since long before the JMA got involved. Some records go back centuries and the data from them paints a similar picture to more modern surveys.

Yasuyuki Aono, a professor of environmental sciences at Osaka Prefecture University, assembled a set of blossom flowering dates from 800 AD to the present in Kyoto.

Zeke Hausfather, a climate and energy scientist at the University of California, Berkeley, used the data to plot two graphs. The first shows that the cherry blossom has been arriving consistently earlier since around 1850.

The second shows the relationship between the day of the year the flowering takes place and the average March temperature in Kyoto since 1881. These direct correlations have led to predictions that by 2100, the cherry trees will flower around 30 days earlier than they do now.

Blossom and the bottom line

Household purchases of alcohol rise by around 10% in March, as blossom viewing parties begin. Major brands use the blossom season to increase sales by repackaging their products to cash in on the celebratory atmosphere. The number of tourists arriving from other parts of Asia has grown in recent year providing another line of profit.

But the blossom boost is short-lived. Within a week or two of the peak, the petals begin to wither and fall to the ground.

In Japanese culture the cherry blossom represents more than the coming of Spring. It is an apt, annual reminder of the fragility of life.