Global Climate/Local Change: One in a series of occasional articles about the regional effects of climate change and how we're coping.

Even though she'd been walking in the woods for only a few minutes, Jen McIntyre was in distress.

Tears were running down her cheeks. She couldn't breathe through her nose.

"I feel like this is our new reality," McIntyre said recently of the allergies that have begun to plague her.

McIntyre, 43, of Mount Airy, never had allergies, aside from reactions to the odd dog or horse. Now, she feels as though her body has gone beyond some sort of tipping point.

Did something happen to her? Or did it happen to the world around her?

Perhaps both.

Earlier springs and later fall frosts linked to climate change have already lengthened the pollen season - in some areas, significantly, by two weeks or more, studies show.

Plants are blooming earlier and staying in bloom longer. On top of that, plants are pumping out more pollen. And there are indications that the "allergenicity" - the potency of the pollen - is increasing.

The number of people who are sensitized to pollen is rising as well.

Climate change is neither a polar phenomenon nor something in the future. It is "already affecting the health of individuals within our communities," said George Luber, associate director for climate change at the Centers for Disease Control and Prevention in Atlanta.

There's "clear evidence" that airborne allergens are being influenced by warming temperatures and rising carbon dioxide levels, he said.

"It's a big deal . . . it's really important for health," said Kim Knowlton, an environmental health professor at Columbia University and a senior scientist with the Natural Resources Defense Council.

She and Luber wrote the human health chapter of the draft 2013 National Climate Assessment, regular reports that Congress required in 1990 legislation.

Allergies "can diminish productivity at work. They can keep kids out of school," Knowlton said.

Add asthma - allergies are often the start - and "it can be more than an inconvenience," she said. "It can send people to the emergency room."

What triggers the bouts of sneezing and other symptoms for most sufferers is tree pollen in the spring, grass and weeds in the summer, and ragweed in the fall, although ragweed could gear up any day now.

The relationship between airborne allergens and climate change is complex. Long-term changes are sometimes difficult to distinguish from short-term weather effects.

For example, studies have shown that increased carbon dioxide supports the growth of poison ivy - another plant that many are allergic to. But so does abundant rainfall, which the region has certainly had this year, resulting in lush vines of the stuff all over the place.

For those sensitive to poison ivy's allergen - urushiol - studies at Duke University have also shown that increased carbon dioxide leads to increased potency.

The more data researchers analyze, the more evidence that climate change is driving a rise in allergens - and allergies.

Take ragweed. It is slowly, but perceptibly, blooming earlier and earlier, said Leonard Bielory, an allergy expert at Rutgers University. "It's now to about the second week in August."

Ragweed season is also the longest among those that involve airborne allergens, and is believed to affect the most people.

There are indications, as McIntyre's predicament suggests, that those numbers have been increasing.

A national study that compared rates of various allergies found that the percentage of adults allergic to ragweed rose from 10 percent in 1976-1980 to 26 percent in 1988-1994.

Another national health survey and an analysis of two million patient visits by Quest Diagnostics, a leading provider of diagnostic testing, also showed more people sensitive to ragweed. From 2005 through 2008, ragweed sensitization grew 15 percent, more than any other allergy analyzed.

The study ranked Philadelphia eighth among the nation's 30 largest cities for allergies.

Studies also show that people with allergies are sensitive to more substances than patients of two decades ago. "It used to be one or two" allergens, Bielory said. Now, it's common for patients to be allergic to five or six.

An EPA report on climate-change indicators was updated last year, partly to add ragweed to the 25 the agency watches.

It highlighted a study by Lewis Ziska, a plant physiologist with the U.S. Department of Agriculture, that looked at changes in the length of the ragweed pollen season in 10 cities in central North America.

The change becomes more pronounced from south to north, reaching a season that has lengthened by 26 days in southern Canada.

When Ziska looked at the effect of temperature and carbon dioxide on ragweed, he found a model for the effects of climate change near his office - in and around Baltimore.

The city has both higher temperatures and higher CO2 than the rural area around it. He studied what happened along the gradient between the two and found that urban ragweed plants grew faster, flowered earlier, were bigger, and made more pollen.

Some of the differences were striking. He found that a rural plant produced 2,300 grains of pollen per cubic meter of air, while an urban plant produced more than 12,000.

It's bound to get worse, officials say.

A National Wildlife Federation report on allergies and climate change noted that warmer temperatures could allow for "significant" expansion of the habitat for oaks and hickories, both highly allergenic tree species. Pennsylvania was among the states listed as an "allergen hotspot" for this expansion.

Another study warned that increases in airborne pollen will "increase the efficiency of windborne pollination." Translation: More plants.

Bielory and others are hoping that researchers will develop a better way to predict pollen levels. Then patients could start medications ahead of time, which would likely lessen, or perhaps eliminate, their symptoms.

For now, scientists like Bielory collect air samples in rooftop devices and measure the pollen content on any given day.

Sufferers can track counts on an iPhone app, iPollenCount, and at the website for the National Allergy Bureau (

This year, Bielory has seen the highest levels in a quarter century of monitoring. He noted that some of it may have to do with heavy rains last year, including Sandy - which scientists say was likely intensified by climate change.

"It's been a very interesting year," he said.

And doesn't Jen McIntyre know it.

An environmental attorney who now heads the Pennsylvania division of the Moms Clean Air Force, an advocacy group, she is reluctant to take medication "that makes me feel like a zombie." So she's been using a Neti pot, dosing with an herbal remedy, and taking more frequent showers. Shoes and jackets, potential pollen-bearers, come off in the vestibule of her house.

"I think I have to get a lot more regimented about my life," she said.

She and her husband plan to install an air purifier at home.

"I truly believe this is all here to stay," she said, "and it's only going to get worse."

Ways to Ease Reactions to Pollen

Sufferers can track pollen counts on an iPhone app, iPollenCount, and at the website for the National Allergy Bureau:

Avoid peak times for pollen exposure (hot, dry, windy days, often between 10 a.m. and 4 p.m.). If you must be outside, a dust mask may help.

Wash your clothes more often.

Shower and wash your hair before going to bed. Even wiping your hair, skin, and equipment before coming inside can help.

Don't dry clothes outside on high-pollen days.

Talk to your health-care professional about whether pre-medicating will help.

Source: Kim Knowlton, Mailman School of Public Health, Columbia University EndText