In Japan, cherry blossoms (or sakura in Japanese) are the epitome of spring. Hanami is known as the long standing tradition of welcoming spring1 as well as the annual appreciation of the fleeting beauty of nature. People congregate to enjoy festivities under the breath taking panorama of blooming flowers. Japanese citizens as well as tourists patiently wait to admire the beautiful flower trees that cascade the streets each year. Cherry blossom season typically begins in late March/early April, with the prime bloom only lasting up to a week.
In 1829 the peak blooming date was around April 18th. Since 1951, groups of meterologists and climatologists have been researching the advance of Japanese cherry tree blooming. According to two Japanese scientists, Yasuyuki Aono and Keiko Kazui, the full-blossom date for Kyoto’s cherry blossom trees can predict the March temperatures to within 0.1°C. The growth of cherry blossom trees is dependent on the weather in the months of February and March. As a result, the peak blooming date for cherry blossoms happens earlier in the year.
This phenomenon is not just occurring in Japan. The Japanese cherry blossom craze began in the US when the wife of the Japanese ambassador and First Lady Helen Herron Taft planted cherry tree seedlings from Japan on March 27th 1912. Since the National Cherry Blossom Festival launched in 1927, global warming has affected the blooming date in DC as well. Blooming now begins 5 days earlier than the original recorded date.
Every time I return home to Japan, I compare how warm it is compared to the previous year. However, I never think about the actual causes or the consequences of rising temperatures. Through data analysis by Yasyuki Aono, we are able to gain further insight into just how imminent the danger of climate change is in Japan. Aono estimates that temperatures have gone up at least 3.4°C (6.1°F) since 1820.
As seen by the graph above, Washington’s full bloom date has shifted five days earlier from the 6th of April to the 1st in between 1921 and 2017, whilst Kyoto’s from the 12th of April to the 5th. In Washington, D.C. as well as Kyoto, rising temperatures and earlier peak bloom dates are associated with the urban heat island (UHI) effect and growing concentrations of GHG. An urban heat island is a phenomenon in which urbanized areas may have higher temperatures than their surrounding rural landscapes. In an effort to mitigate this problem, the Diet of Japan has established the ‘Outline of the Policy Framework to Reduce UHI” in 2004, which imposes conditions such as annually monitoring measures in order to reduce temperatures in urban areas, as well as releasing a progress report to the public to diffuse the importance of the issue. 6The UHI measures also include the reduction of artificial heat emissions, avoiding the build up of heat by creating wind paths, promoting greening especially in urban farming, and improving pavement surfaces.7