Spring seemed to arrive early in much of the United States this year, and nearly everyone with seasonal allergies noticed. As climate change makes winters warmer and plants start flowering earlier, studies have shown that the pollen that causes allergy symptoms has arrived earlier than in decades past.
Here’s a breakdown of how warmer winters lead to a longer growing season for plants and how that affects millions of Americans with hay fever.
A hot and humid winter in the eastern United States
“February continued the unusually mild start to 2023, with much of the eastern United States experiencing record or near-record warm temperatures,” according to the National Oceanic and Atmospheric Administration (NOAA).
“The average temperature across the contiguous United States last month was 36.5 degrees F, 2.7 degrees above the 20th century average, ranking in the warmest third of the 129-year climate record. “, said the agency in a report published last week.
Virginia had its hottest February on record. Eight other states east of the Mississippi River had their second hottest February ever, and three had their third hottest.
However, there was one exception: Six western states — Arizona, California, Colorado, Idaho, Nevada and Oregon — experienced colder than normal February temperatures this year.
Although there is yet another week of winter on the astronomical calendar, which is based on the Earth’s position relative to the Sun, “meteorological winter” refers to the coldest three months of the year. , and it is considered December-February.
NOAA reported last week that the average meteorological winter temperature was 2.7 degrees warmer than the 20th century average, making it the 17th warmest meteorological winter on record. Massachusetts had its warmest winter ever, and seven states in the northeast, Appalachia and upper Midwest had their second warmest winter on record. 21 other states had one of their 10 warmest winters.
Average winter precipitation totals for the December-February meteorological winter of 2022-2023 have so far been 0.90 inches above the historical average. Wisconsin had its wettest winter ever and six other states had one of their 10 wettest winters. Studies have shown that more rain during a plant’s growing season leads to earlier and faster growth.
Early flowering in the eastern half of the country
“Observers report very early leaves of common lilac in Pennsylvania, brilliant yellow flowers of forsythia in Maine and American witch hazel in New York,” USA Today reported late last week. A study of more than 140-year-old records at the Missouri Botanical Garden found that violets are responding to increased rainfall and higher temperatures by budding earlier, the journal reported.
“I’m sitting outside on March 7 and all my daffodils are blooming, and that’s ridiculous,” Lois Krauss, a local environmental activist in Westfield, NJ, told Yahoo News.
The National Phenology Network, which tracks the onset of spring by tracking the flowering of plant species nationally common and typically among the first to sprout leaves, such as honeysuckles and lilacs, reported in late February that leaves were sprouting the earliest they ever had in parts of the eastern United States. In New York, buds appeared 32 days earlier than the historical average.
“The spring leaf outflow continues to spread northward, arriving several days to several weeks earlier than average (the period 1991-2020) across much of the Southeast, lower Midwest and central Atlantic. Kansas City, MO is 9 days ahead, Nantucket, MA is 35 days ahead,” the National Phenology Network reported Monday. The group added that “the spring bloom also arrived in southern states days to weeks earlier in the southeast,” including 22 days earlier in Norfolk, Virginia.
“It’s a bit disturbing, it’s definitely something beyond the boundaries of when we would normally wait for spring,” said Teresa Crimmins, director of the National Phenology Network and environmental scientist at the University of Arizona, at the Guardian, about the early blooms. “It may not be surprising, given the trajectory our planet is on, but it is surprising when you experience it.”
However, this is not uniformly true nationally. “West is a mix of beginning and end,” the band noted. “UT Southwest is days over a week behind and Portland, OR is 2 days behind… Spring Bloom is 10 days behind Las Vegas, NV.”
A new report from Climate Central, a nonprofit climate research organization, analyzed temperature data from 203 U.S. cities since 1970, to measure the length of the growing season for plants – the interval between the last frost in or before spring and the first of the following fall or winter. The group found that 85% of cities have longer growing seasons than in 1970. On average, the frost-free season increased the most in the West, 27 days, followed by the Southeast (16 days), Northeast (15 days), South (14 days) and Central United States (13 days).
“Due to climate change, we are now seeing an earlier and longer growing season for plants, which of course produce pollen, which is the enemy of many Americans with pollen allergies – and allergies mold as well,” Lauren Casey, a meteorologist with Climate Central, told CNN. “Pollen can also trigger an asthma attack, which is of course much more serious for people with asthma.”
Warmer weather, heavier rains and earlier flowering are consistent with climate change
Although the weather still varies from year to year, temperatures are steadily rising, averaging 0.14 degrees Fahrenheit since 1880, due to climate change, according to the federal government. Average global temperatures have increased by 2 degrees Fahrenheit since the Industrial Revolution, due to increased concentrations of greenhouse gases such as carbon dioxide in the atmosphere.
“Winter is getting warmer,” Matthew Barlow, a professor of climatology at the University of Massachusetts Lowell, told Yahoo News. As a result, the cold duration is shortened on both sides.
Climate change is also causing more precipitation. “As the Earth’s average surface temperatures increase, evaporation occurs, which, in turn, increases overall precipitation,” says the Environmental Protection Agency (EPA). “Therefore, a warming climate is expected to increase precipitation in many regions. Since the turn of the 20th century, precipitation in the 48 contiguous states has increased at an average rate of 0.20 inches per decade, according to the EPA.
It’s not just climate change that contributes to early germination. The carbon dioxide emissions that cause climate change also stimulate earlier and faster plant growth. Since plants absorb carbon dioxide during photosynthesis, higher atmospheric concentrations of carbon dioxide accelerate this process.
“Carbon dioxide (CO2), in addition to being the main greenhouse gas, can also be considered a plant food – it is the source of carbon necessary for the manufacture of sugars during photosynthesis”, explained a 2016 research article in the journal Environmental Health Perspectives. . “When exposed to warmer temperatures and higher CO2 levels, plants grow more vigorously and produce more pollen than they would otherwise.”
Earlier and faster plant growth leads to an earlier and more severe allergy season
Seasonal allergies, also known as ‘hay fever’, are caused by allergic reactions to plant pollen and mold spores in the air. As higher CO2 concentrations, higher temperatures and more precipitation contribute to earlier and faster plant growth, the allergy season is prolonged and exacerbated.
For example, Atlanta “saw pollen counts reach ‘extremely high’ levels on March 6, the earliest in 30 years,” Forbes recently reported.
The Washington Post reported in mid-February that “unusually high winter temperatures led to a historically early and intense tree pollen explosion” in the nation’s capital. DC’s first high tree pollen count occurred on February 8, marking the third highest recorded pollen count and the third since 2017.
A number of studies in recent years have identified longer and more intense pollen seasons due to climate change.
The QA 2021 paper published in the Proceedings of the National Academy of Sciences between 1990 and 2018 from 60 pollen count stations in the United States and Canada, found a 21% increase in pollen concentrations and a average annual pollen season 10 days longer over the 38-year period.
“Trend data suggest that the prevalence of asthma, including forms of the disease triggered by pollen, mold and other allergenic substances, is increasing,” reported a 2016 article in the journal Environmental. Health Perspectives.
For many, allergies are only a minor annoyance, but for asthmatics they can be life-threatening, as allergies are a major cause of asthma attacks.
Eighty-one million Americans, about 26% adults and 19% children, were diagnosed with asthma in 2021, according to the Asthma and Allergy Foundation of America.
Although some allergy treatments exist, including antihistamine medications and allergy shots, none are 100% effective and some are quite expensive or time consuming. Ultimately, environmental and public health organizations advocate for reducing greenhouse gas emissions to limit the severity of climate change.
“We are already experiencing the effects of climate change with every breath we take in the spring,” William Anderegg, an associate professor of biology at the University of Utah, told NPR last year. “Acting on climate change is really important for people’s health.”