ABC News ran a story this week reporting on the early bloom of the cherry blossom trees in Washington, D.C., attributing the early bloom to climate change. This is false. Although the cherry blossom bloom has arrived earlier in recent years, the cause is the population increase in D.C, and development that has caused a localized heat biases from the urban heat island (UHI) effect, causing fewer late season freezes and higher average nighttime temperatures in the area. The same is true for Tokyo.

The reporter in ABC News item, “Cherry blossoms blooming earlier due to climate change,” says that “Washington’s iconic cherry blossoms are approaching peak bloom, and it’s happening earlier due to human-amplified climate change.” This change, while not catastrophic is disrupting travel to see the blooms, causing travelers who come to D.C. to see the bloom annually to have to plan for earlier vacations.

Similar stories have run in past years around this time of year over the past decade, including in the Washington Post in 2023, and the BBC describing a similar situation in Tokyo in 2024.

It may be true that cherry blossoms are reaching peak bloom days earlier in recent years than they have in past decades, but if so, population growth and the associated UHI effect are to blame, not a modest rise in global average temperatures. The UHI effect is a well established phenomena in which as a location experiences population growth and densification, the development associated with comes with artificial sources of heat, such as, surfaces like concrete, asphalt, buildings, engines, furnaces, boilers, and air conditioner exhausts. These heat sources absorb sunlight and heat during the day only to release it slowly at night, which tends to raise the average temperatures for nighttime, biasing the overall average temperature for any location so effected.