Cherry Blossom & UHI

By Paul Homewood


This story comes around almost as regularly as the cherry blossom does!





The cherry blossom season, Japan’s traditional sign of spring, has peaked at the earliest date since records began 1,200 years ago, research shows.

The 2021 season in the city of Kyoto peaked on 26 March, according to data collected by Osaka University.

Increasingly early flowerings in recent decades are likely to be as a result of climate change, scientists say.

The records from Kyoto go back to 812 AD in imperial court documents and diaries.

The city has experienced an unusually warm spring this year.

The previous record there was set in 1409, when the season reached its peak on 27 March.

Graphic of peak cherry blossom day in Kyoto from 812 to 2021


Apparently we are all supposed to be alarmed that cherry blossom arrived a day earlier this year than it did in 1409!


According to the BBC, “scientists” say that increasingly early flowerings in recent decades are likely to be as a result of climate change.

But real scientists know that urbanisation has made cities like Kyoto much warmer than they used to be. One Japanese study for instance found that urbanisation has added a “few degrees per century” to temperatures in large cities. UHI is also significant in slightly urbanised sites with much lower population density:




Not only is Kyoto a large city, it has massively expanded since pre-war, and from the point of view of buildings and infrastructure is now unrecognisable from those earlier days:




Cherry blossoms now bloom about one week earlier than in the 19thC, which equates to between one and two degrees Celsius.




However, the author of the study referred to by the BBC, Yasuyuki Aono, found in an earlier study in 2007, that UHI accounted for 1.1C of the warming at Kyoto since 1940:


Although he calculates that March temperatures have risen by 2.2C since 1826, after allowing for urbanisation, most of this actually occurred pre-1940. Aono does point out, by the way, that the 1820s marked one of the much colder periods, so some warming since is to  be expected.




When UHI is allowed for, it appears there is very little difference in cherry blooming times now and prior to the Little Ice Age:




One again we find that the BBC has not told the whole story.


April 26, 2021 at 05:51AM

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