The first blossoms of the season popped open last week in Tokyo. At the Yasukuni Shrine, a lone Somei Yoshino tree revealed just enough blooms—five, to be exact—for the Japan Meteorological Agency to declare the 2025 cherry blossom (also called sakura) season officially underway.

While the blossoms are as beautiful as ever, something’s wrong. Lately, their timing has gone rogue. The trees are blooming faster and faster. Yes, it’s yet another proof that climate change is taking its toll on the planet.

Cherry data doesn’t lie

Kyoto’s cherry blossoms have been tracked for more than 1,200 years. That’s over a millennium of handwritten notes, royal diaries, and temple records describing when these trees flowered. This data has been digitzed and it’s very useful to track proxies about weather and climate.

There were ups and downs in the blooming, but in the long term, the trend has remained constant century after century; until the 20th century, that is.

As climate change started kicking in, the cherry trees (called sakura in Japan) started blooming increasingly earlier. In 2023, Kyoto’s trees reached peak bloom on March 25—the earliest date in twelve centuries.

It’s not that this is one of the most important effects of climate change. However, this is one of the most visible signs of impact you can get.

The timing of a cherry blossom’s bloom is exquisitely sensitive to temperature. Even a few degrees of warming can shift it by days—or weeks. Trees need a prolonged chill period in winter before they can blossom. Without it, they may bloom erratically. But what we’re seeing now isn’t an erratic behavior; it’s a clear trend towards trees blooming earlier.

And it’s not just cherry trees. Apple orchards, peach groves, even forests of oak and maple—all of them depend on a timeline between cold seasons and spring emergence. We just don’t have written data on them going as far back as we have on sakura.

Climate, science, and culture

Early bloom could also have significant environmental impacts. It could send local ecosystems into disarray. When that timing breaks down, ecosystems follow.

Insects may emerge too early or too late to pollinate. Birds may arrive after their food supply has peaked. It’s a domino effect—one that starts with a flower opening too soon.

Japan offers one of the best data sets in the world for understanding phenology—the study of the timing of biological events like flowering and migration. In addition to the blossom tracking, since 1953, the Japan Meteorological Agency has tracked over 120 different events, from frog calls to butterfly appearances, across more than 100 weather stations nationwide.

Yet the cherry blossoms are particularly striking due to their cultural importance.

In Japan, the cherry blossom is more than a tree. It’s a symbol of impermanence, of life’s fleeting beauty. It’s also the centerpiece of hanami—flower-viewing festivals that mark not just the arrival of spring, but the beginning of the school and fiscal year.

The arrival of spring is a feeling the entire country shares, but that feeling is shifting. What once arrived in early April now comes in March. Researchers expect it to come even earlier in the future. Under a medium-emissions climate scenario, Kyoto’s blossoms could bloom another couple of weeks earlier by the end of this century. Under a worst-case emissions path, the changes could be even more dramatic.

The trees are talking to us and trying to tell us something. Hopefully, we’ll start listening.