leaves (copy)

Glimpses of the yellows and browns characteristic of fall are the result of carotenoids — pigments that change the color of foliage when the weather cools down.

There’s something special about fall that can bring an air of magic to any ordinary day. As the leaves change colors and begin to fall, a wonderland of possibilities surrounds us. A long drive with the windows down, the heat blasting on my feet, my favorite playlist blaring and a scenic drive through a winding road is my favorite longstanding seasonal tradition. It’s a small opportunity to unwind and reconnect to the nature that's always present. 

So what happens when seasonal patterns begin to change and fall no longer looks quite as magical as it always has in the past? Why did fall only last a short month this year, with dull leaves that took forever to turn color? As someone who quite possibly survives by the overwhelming joy of the fall season each year, I had to find answers. 

Fall is a time for sweaters, hot lattes and cozy blankets, but across the U.S., fall is getting warmer. In Columbia, this September was the hottest on record, tying for the title with temperatures in 1897. This heat has a huge effect on how and why leaves change color, along with precipitation in the air and on the ground, and the wind patterns, among other complex environmental factors. 

“September acted more like August, with daily high temperatures reaching the 80’s and 90’s and minimum temperatures dropping into the 60’s and 70’s,” wrote state climatologist Pat Guinan in his September report.  

For Missouri, it was the second hottest September on record and the hottest September since 1931. Data shows that on average across the state, that’s a 6.4 degree increase above the long-term average. Across the U.S., fall is getting warmer, according to Climate Central. After analyzing 244 cities, 95 percent saw an increase in fall temperatures, and Columbia was among them. 

Fall colors (copy)

We all know leaves change color in autumn. But do you know the science behind it? Leaves have yellow and orange pigments all year long, but they’re invisible under the green that covers them. The green appearance is caused by chlorophyll in the leaves that helps convert light into energy through photosynthesis. Once the chlorophyll breaks down due to the change of daylight and temperature in autumn, the green fades out, exposing the bright color underneath.

Needing the drop in temperatures and change in daily sunlight to help facilitate leaf color changes, the picturesque nature of fall is negatively influenced by heat stress, which makes the leaves turn color more quickly and disappear faster. Along with on-average increasing temperatures, the state experienced variable precipitation patterns, which also affects fall foliage. 

Richard Primack, professor of biology at Boston University, studies climate change’s effect on plants, birds and insects. He said that New England has also seen warmer than average autumn temperatures combined with higher than average rainfall. This combination, along with having more daylight throughout the day, leads to trees keeping their leaves longer, staying green longer and then often just turning brown and falling off. 

“So this year we’re having an uninspired autumn landscape,” he said. 

Primack said that the fall landscape will vary from year to year depending on conditions, but that things will continue to change whether we like it or not. Seasonal patterns deeply influence interconnected ecosystems. 

“So as a scientist, we have the opportunity to see things changing in front of us and to see really new phenomena and how things are responding to warming temperatures,” he said.

Hotter and longer summers aren’t the only season changes we should expect in the coming years. Fall and spring are shifting and winters are becoming shorter and warmer. Though it may not feel like it in the moment, especially with polar vortexes, cold snaps and snow in October, winters are warming. Columbia’s winters have warmed 4.1 degrees on average. The days below freezing temperatures are also decreasing as the planet’s climate warms. 

As someone who considers the fall season to be a part of my personal and cultural identity, the idea of losing the beauty of a colorful landscape sounds horrifying. It may not be the worst consequence of climate change that we will see in our lifetimes, but the loss of vibrant scenery is a pretty big loss in my book.  

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