An unusually cool March has kept seasonal allergy sufferers in Hampton Roads indoors, out of the line of fire of springtime pollen — and breathing easier because of it.
But the word from climate scientists and allergists is to enjoy it while it lasts: As average global temperatures and atmospheric carbon dioxide levels increase, so does the length of the allergy season and the potency of many allergens.
Experts say it's nothing to sneeze at.
"As the temperature rises, some of the species that cause allergies are going to have a longer growing season," said James Perry at the Virginia Institute of Marine Science in Gloucester Point. "So you get more pollen over more and more time."
The risk extends beyond those who already suffer from seasonal plant allergies, or what's commonly known as hay fever.
"We have a certain amount of immunity to some of these allergens," Perry said. "But if we're exposed over and over and over again, we'll eventually develop a reaction. …You will wear out your immune system, because it's constantly fighting things off."
At particular risk, he said, are the elderly and the young, whose immune systems are either weaker or poorly developed.
According to Lew Ziska, a research plant physiologist with the U.S. Department of Agriculture, "Given how many people already have respiratory problems like asthma, a longer, more intense allergy season can be a real public health concern."
Last week, Ziska and others with the Union of Concerned Scientists released a summary of multiple lines of research that indicate real changes have already begun.
Change can vary by year or by region, the group said, but on average March is warmer by 2.1 degrees Fahrenheit since record-keeping began in the 1880s, with many species of flora and fauna struggling to adapt. The time it takes for the so-called "green wave" of trees to leaf out in the spring from Miami to Maine, for instance, has shrunk dramatically from 74.7 days to 59.1 days. And many plants are pollinating days or weeks earlier.
The engine for climate change is greenhouse gases like carbon dioxide, or CO2, caused by burning fossil fuels like oil and coal. For plants, CO2 is a kind of Miracle-Gro, supplying the carbon they need for photosynthesis. Greenhouse gases also trap heat in the atmosphere.
"And as the planet warms, the ecosystem responds," explained Bruce Wielicki, senior scientist at NASA Langley Research Center in Hampton. "Those responses can be a change in the length of the growing seasons."
There's no research yet to pinpoint change on a scale as small as Hampton Roads, he said, but regional changes are being studied.
"There's no question those changes are going on," Wielicki said.
Those changes could go further still. If we continue with business as usual and fail to curb our appetite for fossil fuels, he said, "we're literally talking about Virginia's climate zone moving down to where Florida is now."
'It'll get worse'
Local doctors say the most troublesome allergens in the spring in Hampton Roads are trees like elm, cedar, birch, poplar, cottonwood and red maple, which pollinate February into May. Grass pollen kicks in during April. The local ragweed season is generally mild, starting around September and going until first frost. Running throughout the season are outdoor mold spores.
A year ago, when March was warmer and milder, all the pollen seemed to arrive at once, said Angela Hogan, a pediatric allergist at the Children's Hospital of the King's Daughters in Norfolk.
"We had really heavy pollen loads very quickly," Hogan said. By comparison, this year was a slow start, she said, "but we're catching up now."
In practice since 1990, Hogan says she is now noticing more individuals with symptoms to regional pollens and a longer season for ragweed, which is beginning to crop up locally as early as July.
According to the Union of Concerned Scientists, the fall ragweed season has expanded by up to 27 days as late fall temperatures increase. Ragweed pollen production has risen 60 percent to 90 percent, while its potency has likewise increased. It's also shifted from a rural problem to an urban one, since cities have higher temperatures and higher concentrations of CO2.
Slow start this year
In Newport News, pediatrician and allergist Ann Zilliox said she usually has "lots of miserable, tree pollen-allergic folks" in her office in March. Not this year. She blames — or credits — the cold, rainy weather.
"Nobody's been outside to experience it," Zilliox said. "If a tree falls in the forest and no one's around to hear it, does it make a sound? If there's tree pollen outside and nobody's around to breathe it in …"
But she cautioned against being lulled by the mild start to the allergy season. There's a difference between short-term weather and long-term climate, she said, and "really good data" supports warming temperatures and higher CO2 levels, both of which tend to drive up pollen counts and, by extension, allergy statistics.
According to the Centers for Disease Control and Prevention, 16.9 million adults and 6.7 million children had diagnosed hay fever in 2012.
"All the numbers for every allergic disease have been rising for quite some time now," Zilliox said. "I imagine it'll get worse."
Whether there's a limit to how much worse depends on how radically different the climate becomes in the long term, if very different plants show up and what pollens they bring. At this point, she said, it's hard to prognosticate.
"We've never been here before," Zilliox said.
To limit your exposure to pollens
•Keep track of pollen levels and alerts in your area
•Keep windows closed during pollen season, especially during the day
•Stay inside during midday and afternoon hours when pollen counts are highest
•Take a shower, wash your hair and change clothes after working or playing outdoors.
Information comes from the American College of Allergy, Asthma & Immunology.
For more information and a link to a pollen map, go to http://www.aaaai.org, the website of the American Academy of Allergy, Asthma & Immunology.