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. [emphasis, links added]
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 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 the 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 phenomenon in which as a location experiences population growth and densification, the development associated with it 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 affected.
Concerning Tokyo, as explained in the February 2024 Climate Fact check posted at Climate Realism, even as Tokyo’s unbiased average annual temperature has declined since 1997, the impact of the UHI effect there has been to artificially boost the average temperature there by 5.4℉ over the past century, far above the average rise measured for the island nation as a whole.
This bias results in earlier spring-like conditions with higher nighttime lows, resulting in early bloom.
Research published in the peer-reviewed journals Geophysical Research Letters and Environmental Pollution explain that the UHI effect could shift blooming dates by several days to weeks in large metropolitan areas when compared to trees and flowering plants in nearby rural locations.
Another peer-reviewed study published in the Journal Climate specifically discussed the UHI signature of Washington D.C. The figure below from that study shows maps of the UHI signature of Washington, D.C. in the morning, afternoon, and at night.
The maps above show that the UHI dominates the downtown core, where Washington, D.C.’s cherry trees are located along the tidal basin. So, it isn’t surprising that the cherry trees react accordingly and bloom earlier as the UHI signature has grown over time.
Measured temperatures in Washington, D.C. have risen more than the nationwide average, largely as a result of population growth and the resultant UHI effect over the past century.
Washington, D.C.’s population has grown by more than 331 percent since 1950, associated with a huge amount of development.
The National Park Service has been tracking the peak cherry blossom bloom since the early 1920s, and its data, displayed on the Environmental Protection Agency’s website, shows that the annual peak bloom has shifted earlier as the population has grown there. (See the graph below.)
ABC News ignores the research and data that strongly suggest that the UHI [effect] is wholly responsible for earlier spring peak cherry blossom blooms due to fewer late-season frosts and warmer average nighttime temperatures.
But, of course, this is in line with the narrative that the mainstream media pushes concerning climate change, that it causes everything bad.
The facts may not support this, but then the facts don’t inspire a compelling news story, which is all that ABC and other outlets seem to really care about — generating public interest, attention, clicks, and ad sales, rather than reporting the truth.
Read more at Climate Realism
