Tue Oct 25, 2005
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While climatologists might still argue over why our climate has warmed in recent decades, Mother Nature has already reacted to the change. Hi, I’m Bryan Yeaton for The Weather Notebook.
Climatologists prefer directly measured data to determine climate trends, but often the best indicators come from just watching nature. And this is what naturalists do in a field called “phenology.” Phenologists observe recurrent natural events, such as the flowering of lilacs over many years, to determine how nature reacts to changing seasonal conditions.
One climate change feature phenology can study is the onset of Spring. Because the timing of Spring flowering and leafing is largely controlled by heat accumulation above a temperature threshold, researchers have found that many physical and biological indicators of Spring have begun occurring earlier in the year.
The onset has advanced, by about 5-6 days across North America over the 35-year period beginning in 1959. In the Northeast States, lilacs now bloom four days earlier than in 1965, as do New York apples and grapes. In Washington, DC, Japanese cherry trees bloom about a week earlier than 30 years ago. In Alaska, the Nenana Ice Classic, an annual wager on the ice breakup date on the Tanana River, has seen the breakup advance by 5.5 days since 1917.
Several European Spring indicators show a five-to-10 day advancement over the last half century. In Britain, first flowering for 385 plant species has advanced between 4 and 55 days over the last decade. In Western Canada, Spring flowering of some woody plants now comes ten days earlier than 45 years ago. Plants whose Spring flowering depends on daylength rather than temperature, however, show no significant changes for their blossoming: a confirmation of warming trends.
Thanks to our contributing writer, meteorologist Keith Heidorn. Our show is funded by Subaru of America. Find us online at www.weathernotebook.org.
Lilacs Say Northeast Spring Coming Earlier
Earlier Springs in the Western United States