Fall foliage is a traditional sign of the change of seasons. In New York City, peak color is normally around the last week of October. This year, however, we did not hit the peak until somewhere between the second and third weeks of November. Is this delay of fall color a sign of climate change?
Fall foliage displays are strongly influenced by the weather and therefore vary from year to year. The late arrival of the fall colors this year could be an anomaly related to the exceptionally warm and wet conditions of the early autumn in the northeast. Delayed color changes, however, are also happening elsewhere around the globe. Climate change studies in both Europe and Asia have shown that leaves there have been changing color later in the season.
Scientists working with satellite data at the Seoul National University in South Korea have shown that the growing season in the northern hemisphere was extended by 6.5 days from 1982 to 2008. Another study at the University of Southampton in England found that increased levels of carbon dioxide in the atmosphere is delaying the change of color in autumn leaves. Researchers there conducted an experiment with poplar trees and found that the those exposed to higher levels of carbon dioxide, a key component of photosynthesis, stayed green longer.
Climate change is a complex subject. No one knows for certain how different aspects of the natural world, like the timing of fall foliage, will respond to changing environmental conditions. This highly nuanced subject, in my opinion, warrants closer study.