On Route 11 north of Tuscaloosa, Ala., last April, a pickup truck pulled up next to Greta Browne, and a young man began lecturing her about global warming.
He had seen Ms. Browne's T-shirt announcing that she was "Walking for the Climate," and he wanted to set her straight. Humans, he told her, have nothing to do with heating up the planet.
Ms. Browne, 65, a Unitarian minister from Bethlehem, Pa., has encountered more than one global warming naysayer since last March, when she began a trek up the Eastern seaboard to draw attention to climate change.
"Sometimes, you just have to stand up," she said.
So far, Ms. Browne says, she has logged about 1,100 miles, walking from outside New Orleans to Rouses Point, N.Y., near the Canadian border, where she will end her journey Saturday. A grandmother of three, she blogs for adults, and for children.
When she began the trip, Ms. Browne had hoped to attract crowds of other people to walk with her (think Forrest Gump running cross country in the 1994 film). Instead, it has been a mostly solo journey, which she describes as "a meditation, a prayer," for Earth.
Still, her shirt and her beckoning smile invite people to approach. Sometimes they pull their cars over and hand her fistfuls of dollar bills - she is financing the trip with small donations, and her Social Security checks.
Sometimes people run up alongside and proffer water bottles, which she accepts, even though they violate her principles on garbage and waste. And sometimes they stop to tell her not to worry: God would never allow Earth to warm disastrously, they say. She listens patiently and argues her case.
In choosing to promote her cause this way - as opposed to, say, pressing for legislative change - Ms. Browne joins a growing list of environmental activists who are hoping to draw public attention to the issue through stunts: Colin Beavan, for example, the writer who lived without toilet paper and electricity, or David de Rothschild, a self-described "eco-adventurer" in San Francisco who has built a boat made of reused plastic water bottles and plans to sail to Sydney, Australia.
As she has plodded along, Ms. Browne said, she has come to understand her journey as a one-woman survey of the American mindset on global warming, though one, she readily concedes, that is deeply unscientific. Normally a glass-half-full type, she says the trip has made her "more pessimistic."
"Mostly people think it is a problem," she said, "but mostly they think it will not impact them anytime soon."
A longtime member of the Green Party and the founder of a vegetarian cooperative restaurant, she has been concerned for years about global warming. But after she retired last year, she joined an environmental group and read "Six Degrees: Our Future on a Hotter Planet" by Mark Lynas. The book, which argues that most of humanity could be wiped out by the end of the century if Earth's temperatures continue to warm, galvanized her.
As the child of Presbyterian missionaries, Ms. Browne lived in Brazil, China and Niger, and was used to a peripatetic lifestyle, so she decided to take to the road. Her role model was Doris Haddock, better known as Granny D, who in 1999, at age 90, walked across the country for campaign finance reform, generating both crowds and headlines.
Ms. Browne's trek has not quite turned out that way, and, she says, her adventure has other shortcomings. To make the walk logistically possible, she has lived out of a 1982 van - complete with gold-colored shag carpeting and rust velour sofas - that is, by her own admission, "a disgusting gas guzzler."
By living abstemiously on other fronts, she said she had managed to keep her carbon footprint to half that of the average American. She never eats out and, except for her T-shirts, all her clothes are second-hand. Even her white Clarks sneakers were bought from a thrift store.
On Sundays, she goes to Unitarian Universalist churches along the way. She has handed out fliers listing small actions people can take to fight global warming, like using compact fluorescent light bulbs and lobbying for schools to teach the subject.
Crowds or no, Ms. Browne says, she is convinced that she has reached people and "raised awareness." She estimates that 500 to 1,000 cars pass her on the road every day and about 1 percent, she says, honk or give her a thumbs-up.
In the end, Ms. Browne said, she thinks that most people are sympathetic and want to do something - just not too much. She was particularly discouraged by a woman who approached her after one church talk and said, "Oh, you are preaching to the choir. We already recycle."
Ms. Browne remembers thinking that recycling was "so 1980s" - perfectly good, she said, but not nearly enough in itself.
"People just don't see enough urgency to change their life," she said.
But she understands. She plans, she says, to keep the van.