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Warming temperatures are triggering the earliest spring on record in parts of the eastern US

Spring has started unusually early in the eastern United States. From parts of the Gulf Coast all the way up to southern New England, leaves are springing up from shrubs and trees days or even weeks ahead of schedule. Some areas are experiencing their earliest spring on record, meaning communities are also experiencing an unusually early allergy season. Experts say rising temperatures, one of the most visceral consequences of unchecked burning of fossil fuels, are playing a role in this year’s accelerated spring.

Phenologists — people who study biological life cycles — use two metrics to describe the changing seasons: first flowering, when plants begin to flower, and first leaf budding, when leaves unfold. This year, first blooms and leaf sprout started creeping in three to four weeks ahead of schedule on the east coast. That’s not entirely unusual; Natural fluctuations in the seasons lead to an early spring every few years. But in some places, spring came extremely early — earlier than at any time in four decades.

Parts of central Texas and the Louisiana coast, southern Arkansas, southern Ohio, the DC area, New York City and the New Jersey coast were all experiencing their earliest spring on record, said Theresa Crimmins, director of the National Phenology Network, a group which collects data on seasons and other natural cycles. The organization uses mathematical models that combine historical observations of first leaf and bloom with temperature and weather data to predict when lilacs and honeysuckles, typically the first plants to turn green each year, will begin to become active. The group then compares that initial growth to an average baseline from the three decades between 1991 and 2020. The network’s models show that spring arrived a full 20 days ahead of schedule in locations in the eastern United States. The trend was particularly evident in the mid-Atlantic region.

Heat has everything to do with when trees start to bud and leaves start to open. This year, a particularly mild winter in the eastern United States and a series of very warm days in recent weeks created ideal conditions for an early spring. “That’s really why things were so ahead of schedule,” Crimmins said.

Pinning climate change to a specific early leaf burst in a specific location is difficult, but evidence for anthropogenic warming is evident in how the timing of the seasons in the US has changed over the past few decades. “Over the longer term, there is a clear underlying trend for the spring season to start earlier and earlier in much of the country, particularly much of the eastern US,” Crimmins said. “This is the result of steadily increasing average global temperatures.”

Earlier springs are associated with a variety of human health problems. Recent research shows that the lengthening of the growing season in North America has resulted in an allergy season that is 21 percent more intense and, on average, 20 days longer. Shortened winters allow disease-carrying insects, such as ticks and mosquitoes, to become active earlier and spread pathogens to other animals and humans.

“If you suffer from seasonal allergies and live in the eastern two-thirds of the United States, there’s a good chance you’re already feeling the effects of an early bloom,” Ben Noll, a weather forecaster who tracks the weather in New York’s Hudson Valley, said grist.

And early spring is a nightmare for farmers across the country who are already struggling to adapt to rapidly changing environmental conditions. Mississippi’s blueberry crop was threatened a few weeks ago when a hard freeze swept across the state after a spate of unusually warm days caused blueberry bushes to bloom early. One farmer in the state estimated that the frost destroyed 80 percent of his crops.

“These seasonal changes can make life particularly tough for farmers whose livelihoods depend on the weather and who ultimately produce the food we consume,” Noll said.