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Comment by malingo | Hacker News Reader

The Economist published a remarkable chart last year that shows 1200 years of cherry blossom data: https://www.economist.com/graphic-detail/2017/04/07/japans-c...

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Note that is for the cherry blossoms of Kyoto. So I'd say that the graph means next to nothing in terms of global or even national climate trends. This is about a very small city-dominated local climate. Any variation from a norm could have more to do with the heating/cooling of buildings and local traffic rather than global warming. The trend towards the use of glass in new buildings could have as much an impact as global carbon.

Despite the down votes this is a perfectly valid point. In the last 100 years Kyoto has turned from a quiet backwater into a city of over 1 million, liberally slathered in concrete like every other Japanese city. This will have an impact on the local climate, above and beyond global warming as a whole.

The population of Kyoto has been over 1 million since 1932.

It was also hardly a backwater... The Fall of Edo was only 150 years ago and before that Kyoto was the seat of the Emperor.

Not a political or historical backwater, but also not the booming metropolis that was Tokyo. It was a backwater in terms of urbanization and urban heat island impacts.

>quiet backwater

Wow.

Kyoto was the capital of Japan for close to a millennium.

Yes, but it stopped being the seat of power in 1603 and even the Emperor moved to Tokyo in 1868.

The point, though, is not the politics, but that modern Kyoto bears very little resemblance to pre-1900 Kyoto.

People down voting this are ignorant of how cities affect the local climate. Urban effects would dwarf global climate changes pretty much always.

I can't speak for how it affects the data, but note that Kyoto city (京都市, the administrative area to which this data seems to apply) is about two-thirds mountains and small rural towns.

See the satellite image here (there should be a red border around Kyoto city): https://goo.gl/maps/FZZbj7UFi4m

This is an interesting figure. Naturally, the sharp decline in the last 100 years or so captures one's attention, and would fit in with globally rising temperatures.

However, one other thing differentiates the older and newer epochs: The variance is much larger for older data. On the one hand it could be that increased variance is due to natural phenomenon (cooler weather?) or random error of less reliable measurements. However if that larger variance is due to systematic error (e.g., different methodologies/sources which were not accounted in the model (e.g., using hierarchical modeling), then there is a possibility that the difference between older and newer data are not that dramatic. What an interesting (and alarming) figure.

It looks like the confidence interval is larger in earlier years because there are fewer data points.

Whats interesting to me is how big the spread is until the 1900s where not only is the blossom date trend increasing, but the individual blossom dates are grouping much closer together as well. I wonder if this is an error in measurement or if there is natural explanation for this variance reduction in the last 100 years.

Ignore the error bars for a bit and look at the actual data points. The distribution is much broader than it is for the last 50 or so years.

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