Hacker News Reader

They got around this problem by not considering the hybrids, but Prunus jamasakura. Here is what they wrote in one of the source papers on how they inferred the species of the trees in the historical record(1).

"First, we determined the species of the most common cherry tree at Kyoto during the historical period. In the modern phenological observations by the Japan Meteo- rological Agency, Prunus yedoensis (Japanese common name, Somei–Yoshino) is considered representative of all cherry trees, and its full-ﬂowering dates are observed by most meteorological stations in Japan, except those in Hokkaido District and the Ryukyu Islands. However, P. yedoensis is an ornamental tree developed in the mid- dle of the 19th century, and it did not exist before that. Many descriptions in old documents suggest that a native species, Prunus jamasakura (Japanese common name, Yamazakura), was grown in Kyoto and its suburbs, and it was planted also in the ground of the imperial palace from ancient times. Therefore, P. jamasakura was the most common species of cherry tree in Kyoto until the middle of 19th century"

1. https://rmets.onlinelibrary.wiley.com/doi/10.1002/joc.1594

This ignores the fact that temperature has a known strong effect on flowering time [1]. It’s the obvious and evidence-based reason for the phenomenon, so there isn’t any basis to invent some other reason to do with hybrid genetics. Especially since there is no evidence for your hybrid hypothesis whatsoever.

There is also no reason for corn getting bigger when climate change happens so a ‘similar plot’ would not make us conclude anything of the sort. This is therefore a terrible analogy. In fact the evidence is that climate change will reduce corn yield [2].

[1] https://enveurope.springeropen.com/articles/10.1186/s12302-0...

[2] https://exhibits.stanford.edu/data/feature/corn-and-climate-...

> A similar plot could made us conclude (wrongly) that the corn is getting much bigger in the last 1000 years "by climate change", instead because people selected more modern varieties of corn.

Surely this conclusion would only make sense if we believed that relevant climatic changes were occurring over the same time frame as the changes in size.

In the case of the cherry trees, the shift in the full-flowering date corresponds very well with the shift in the local temperature record (also provided at [0]), lending credence to that being the explanatory factor. Other factors are, of course, possibly relevant, but I don't think that the link is as weakly founded as your counter-example suggests.

[0] http://atmenv.envi.osakafu-u.ac.jp/aono/kyophenotemp4/

Actually a really good point. This is just a correlation with an imprecise causal link, even if global warming is clearly the most likely factor.

Direct observations of the warming over centuries are direct proof of climate change, in addition to proof in ice cores, tree rings, and sedimentary deposit patterns (among others) of prior rates of change being much more gradual.

It could be a coincidence but honestly if we see too many of these records, it may, actually be a forest.

> Could be that and explanation to the final part of the curve?

In principle yes of course, but 1) there's an obvious mechanism which gives you a clear prior and 2) this is not the first time people have looked at this type of data and the results are consistent across species and locales [1].

Makes looking for "alternative explanations" look like motivated reasoning to me.

You might have a point if you actually had particular insight on how the species and cultivars used in Japan changed over time.

[1] https://en.m.wikipedia.org/wiki/Phenology for a starting point.