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.
https://www.bbc.co.uk/news/world-asia-56574142
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:
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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:
https://en.wikipedia.org/wiki/Kyoto#Demographics
Cherry blossoms now bloom about one week earlier than in the 19thC, which equates to between one and two degrees Celsius.
https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/joc.1594
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:
https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/joc.1594
One again we find that the BBC has not told the whole story.
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NOT A LOT OF PEOPLE KNOW THAT 
So what?
Excellent Paul. Get a complaint off to the Beeb pronto!
I haven’t read the paper, but that’s a very creative line that’s been drawn through the scatter points. I wouldn’t have advised any of my postgrads to put that in their thesis, I wonder what the p-value is for that recent droop?
This type of plotting is the art of political science (plotting and scheming to obtain the desired ends). An interesting join-the-dots observation of the latest dates for flowering shows that an almost identical situation occurred in the 13th Century. Outliers should always be used with care as they can be facts or merely reflect observational errors.
I lived in the Washington, DC area from 1969-1978. Predicting when the Japanese cherries would bloom around the Tidal Basin or along the streets of Kenwood was definitely more art than science.
Data on the Washington cherry blossom here
https://cherryblossomwatch.com/peak-bloom-forecast/
Perhaps there is scope for a comparative study.
“Countryfile” yesterday had that millionaire farmer complaining that the cold spring was delaying his rape -not so here in Cheshire according to my lungs and nasal passages- and that his poor sheep , those creatures covered in thick layers of wool, were suffering .And apparently it is extreme weather caused by climate change and will only get worse.
Now I am not a farmer but I have been growing vegetables and bedding plants for the garden for over 40 years and everyone likw me knows that putting out outdoor tomatoes is risky until the end of May( unless in SW or Scillies) . Every garden book , and seed packet, urges to delay planting out until the risk of frost is over and that this is usually mid or late May . But this farmer knows better . Frost in April, nearly 900 ft up in the Cotswold, is “extreme weather “. .I wonder how much the BBC pay him to utter such rubbish because he seems too intelligent to actually believe it .
I live in the South West and don’t dare put out the tomatoes yet so they are growing lanky in our sun room. I had hoped to get them out as normal about 2 weeks ago but the nights have been much too cold
Yes I already mentioned the presenter/farmer’s remarks. So far April is running a mere 1C or so below ‘normal’ in the CET, which is a less extreme variation than the previous March was above! You do have to go back to 1983 & 1989 to find a similarly cool April. What he is saying without realizing, is that he prefers the globally warmed world that he has got used to in recent springs!
Yes, I only mentioned him bcause I was so disappointed in his statements. I usually enjoy his contributions and our granchildren and family had a stay on his campsite one year (precovid) and greatly enjoyed it . Coming from a farming family he must know the variability of seasons , but I suppose you have to play strictly by BBC rules to appear on thier programme these days.
Spring has come early. WHAH!
We went to our local bluebell woods a week ago and there was virtually no bluebells to be seen. We were really surprised so I looked on my phone to see if I had photos for last year and there were some for exactly the same date where the woods was a carpet of blue. We suspect it will be at least another month before they get to their peak.
I concur, my woods (north west kent on the downs) have also been a little sparse on the bluebell front so far, however I have been blessed for the last month with the most prolific amount of primroses I can recall and also more pink/purple orchids as well (sorry, dont know their proper name). It was 6° this morning.I have allways noticed how sensitive the bluebells are over the years, the ones is more sheltered areas are always ahead of the ones at the higher locations (probably 60´ or so). so not all bad!
BTW fantastic Hawthorn blossom as well!
We are early in the Leap Year cycle, which in any case gives one day of variation.
“Climate Change and Cherry Tree Blossom Festivals in Japan”
Richard Primack and Hiroyoshi Higuchi Arnoldia v. 65/2
“Cherry Tree Flowering Affected by Urbanization…
As mentioned above, cherry tree flowering times have been strongly influenced by the urban heat island effect, the warming that comes from the added heating caused by removing trees and replacing them with roads, parking lots, build- ings and other aspects of a human-dominated landscape.”
Having made several complaints to the BBC over the last decade regarding their one sided climate stories. If you are really persistent you always end up with this comment. ” WE DO NOT ENTERTAIN COMPLAINTS OF BIAS BY OMMISSION” Quite how this fits with their charter of being impartial is beyond me!!!
off topic but worth a follow up .. guy on twitter talking about obvious photoshopping on ITV – looks like Lorraine Kelly re lockdown and air pollution .
. ITV joins with BBC in lying about climate
Brilliant.
Thanks.
The Heat Island effect is why the trees are blooming earlier, I think the scientist have a very blinkered view to blame the trees coming into bloom earlier using the climate change as a cause
The blossom on the wonderful old Japanese flowering cherry trees along Dovehouse Street in London SW3 reached perfection this year on March 31st. It did the same on the same day, March 31st 1990, thirty years ago. I remember it so precisely bcause of its magnificence as we drove along the street en route to my daughter’s wedding that day at St. Luke’s in Sydney Street.
So much for “unprecedented climate change” and its supposed effect on blossoming dates !
Nothing to do with cherry-blossom but on the same day as today 26 April but in 1908 my grandparents travelled back from their honeymoon in Barnstaple by train via Exeter to Sherborne and they made it. I think the London train must have run from Exeter to Salisbury. There had been a phenomenal blizzard across Wessex, the Thames Valley and much of the Midlands the day before. There was 24” of snow just outside Winchester, 20” in Farnborough, 27” in Abingdon even 13” on the island of Alderney. Would they have made the same journey under these circumstances today I wonder?
Peak blossom is surely a very subjective measure anyway, not a precise measurement.
It’s also not a particularly good measure of average temps. as it can be highly varied with short bursts of temperature variation.
And plants adapt, and different varieties may be involved….
There’s just so many random factors.
Exactly. So many unplotted variables. UHI change and effect is the biggie, but also planting areas and quantities, have they changed? method of measuring ‘peak blossom’? What was considered peak in 1401 compared to now? Species variation and evolution? Since none of todays trees were growing 400yrs ago what is the genus and genetics of todays’ trees vis a vis the old ‘unevolved’ trees. Have modern trees been bred / evolved to blossom earlier? I believe many of the Japanese trees were re-introduced from trees that had been taken to Britain in the 1800s and bred on. What rootstocks are now used? Grafted trees? Not seen any science in these ‘finger in the air’ comparisons.
Goodness me. A period of cold is climate change. Well I did you ever !
Transfering all the historical dates from the old Japanese calendar system into the current Gregorian one must have been quite a task!
Not to mention the 11 days that were removed from the calendar in 1752 in the U.S. and in 1872/73 in Japan to account for the change from the Julian to Gregorian Calendar. What are the chances that all those complications were made correctly?
Good catch , the latest time seemed to decrease the same the time the earliest reduced- was that around the 1870s ?
Whats the chance the spread of dates tightened at the same time
Even more interesting
‘Before 1873, lunar calendars, which were originally imported from China, were used in Japan for many centuries. The lunar calendars were based on the cycle of the moon, resulting in years of twelve months of 29 or 30 days (the moon takes about 29 1/2 days to circle the earth), and an occasional 13th month to even out the discrepancy to the solar cycle of 365 1/4 days, i.e. the discrepancy to the seasons.’
Occasional 13th month ?
https://www.japan-guide.com/e/e2272.html
There is a lot more CO2 nowadays. It might be a key plant food ?
But there are clearly years going back to 800 when it happens this early. It’s rare but not abnormal. Every 400 years or so a couple appear. What actually appears to be happening is that there are fewer LATE blossomings, so the average is becoming earlier. That means we have fewer colder springs.
And the varieties of ornamental Cherry Blossom have changed over the years, ‘Cherry’ Ingram was the man who brought flowering Cherry blossom back to Japan after the Second World War.
See — ‘Cherry’ Ingram : An homage to the British savior of Japan’s cherry blossoms … https://www.japantimes.co.jp/culture/2019/02/09/books/cherry-ingram-homage-british-savior-japans-cherry-blossoms/
The Magnolia tree in our garden this year is a full month BEHIND the last 10 years blossoming date.
Light pollution is also a trigger for early blooms and budding. It may have a greater effect than UHI.
http://rspb.royalsocietypublishing.org/content/283/1833/20160813
Our wedding photos of 25 years ago today reflect the same cherry blossom as my wife and I witnessed today, in Preston, Lancs.
Kyoto and Osaka must be a long way further south than SE London. My cherry blossom tree only burst into bloom last Thursday (exactly – it was amazingly sudden)