Today -- right now, in fact, at 11:44 a.m. ET -- marks the beginning of fall, the season marked by cool temperatures and the brilliant changing of the leaves in northern forests.
Only, it doesn't really.
It marks the celestial start to the season, the Autumnal Equinox, when we experience equal hours of sunlight and darkness. And it's a date on the calendar.
And while some signs of the season are evident -- in the migrations of songbirds and in the blossoms of hardy mums for sale outside garden centers -- many have been noticing that the season is lagging.
Or as Robert Lowell might have said about climate change, if the poet had been as interested in environmental health as he was about mental health: the "season's ill".
Global warming has expanded the growing season across North America: Spring comes early, and summer hangs on. The changing of the leaves has complex triggers, ranging from the angle of sunlight to the degree of drought, but temperature is one key attribute. Data's hard to come by, given the subjectivity involved in pin-pointing the "peak" of fall foliage... but the signature autumn event seems to be getting later.
Data from the Mohonk Preserve in New York's Shawangunk Mountains, where naturalists have tracked the leaves for more than a century, suggest that the peak is indeed coming later -- weeks later.
It's only one consequence of global warming for northern forests. Maples, which fill the forests with crimson, prefer colder climes, and require cold winters to produce adequate sap for syrup. Over time, those trees may "migrate" north with the changing climate. Insect pests, too, are spreading north as winter freezes grow more mild, and those pests might affect not only fall color, but the value of timber harvests and the health of habitat for wildlife.
Last year, peak foliage was particularly late. It remains to be seen whether this year -- which has, across much of the U.S., experienced less dramatic high temperatures -- follows suit. The overall trend, though, is established, and the metronome of the seasons is ticking at a different pace thanks to our carbon emissions.
Keep track of the fall foliage with help from the U.S. Forest Service.
Dive into your photo archive and submit some of your best photos from falls past -- and keep your camera clicking this fall to add to The Daily Green's Fall Scenes photo gallery.
Enter your city or zip code to get your local temperature and air quality and find local green food and recycling resources near you.