An avid adventurer works to bring solar ovens to the mountains of Mexico.

When John Markowitz first heard about solar ovens, he knew exactly what he wanted to do with them: He wanted to give them away.

John Markowitz is a smiling, six-foot-tall, 67-year-old native of New Jersey who works as a nurse’s assistant in the emergency room of a New Hampshire hospital. Trained as a shop teacher and football coach, he’s also an avid mountain climber. In 1999, he and his friend Sonny decided to climb the third-highest peak in North America, an 18,000-foot sleeping volcano about 120 miles east of Mexico City called El Pico de Orizaba.

Markowitz used a mountain-guiding service for this climb operated by Gerardo Reyes, who is also a medical doctor. Known locally for his excellent mountain-rescue work, Reyes had recently been appointed the head of the local chapter of the Red Cross—but he had no staff, no ambulance, and no budget. In his clinic, for instance, Reyes still uses a gurney made in 1895.

When Reyes and Markowitz visited some of the mountain villages on the way to the glaciers of Pico de Orizaba, Markowitz says he was “incredibly touched by the experience. The people there are warm and friendly, but they are very, very poor, and we Americans have so much.” So Markowitz decided he’d try to get Reyes an ambulance.

The roads in the area that Reyes covers are unpaved, eroded, mountainous, and often rutted and filled with boulders, however, so any ambulance wouldn’t do. Markowitz found a 1960 Mercedes Unimog for sale in Arizona that seemed ideal. It was old and in need of repair, but the Unimog had independent, articulating wheels and a ground clearance of over two feet. It can drive over boulders, through deep water and snow. It cost $4,000, money Markowitz didn’t have.

But through slide shows and talks, Markowitz managed to recruit 16 other climbers, who each paid an additional $250 above the cost for a trip to El Pico de Orizaba. That provided enough to buy the Unimog. Such are the vagaries of Mexican customs, however, that it would take him another two years to get it across the border.

Now Markowitz was hooked: whenever he could, he traveled to Mexico and visited with Dr. Reyes, increasingly drawn less to the mountaineering than to the charity work. He raised money for warm clothes, a computer for a school, and hand surgery for a local boy who had been born with an extra thumb. After the surgery, the boy’s mother told Markowitz, “Now he will be able to marry.”

Markowitz also collected out-dated, but still decent, medical supplies from his hospital in New Hampshire. He held bake sales. He found local knitters to make sweaters and hats. And he approached a magazine, National Geographic Adventure, about buying a photograph from one of his Orizaba ascents, and put the $700 they paid toward his Mexican charity work. The editor he dealt with there told him about her parents, who ran an organization called the Solar Oven Society, which uses volunteer labor to build ovens that run entirely on the power of the sun.

These solar ovens are essentially a heavily insulated box, black on the interior, with a clear-plastic cover coated with a special heat-collecting film. Even in the winter, they can generate temperatures of around 300 degrees—not hot enough to bake a pizza, but hot enough to function like a solar crock-pot. You can put diced meat and vegetables into the pots that come with the oven without adding any water, direct it at the sun, and a few hours later enjoy cooked food. It can also pasteurize water.

While a solar oven may seem like a toy in the modern world, it has tremendous potential to benefit people in places like Hidalgo, a little village near El Pico de Orizaba. According to the Solar Oven Society, roughly two billion people on the planet struggle to find or afford the fuel necessary to boil water or cook food, increasing their risk of disease. Their constant search for firewood can be so time-consuming, and involve such long walks, that the women and children who do this work rarely have time for school. The need for firewood has also been blamed for deforestation in developing countries, and resulting erosion and desertification.

Consider also that a cooking fire releases about 1,000 grams of soot per year, which is a major cause of climate change. Given that about two billion people are building cooking fires every day, this adds up to arguably one of the biggest—and most easily fixed—causes of climate change on the planet.

It’s also a huge health problem. Many families in developing countries cook their food in leaky or un-vented stoves inside the same space where they live and sleep. Markowitz says that when he travelled to Madagascar, he could tell which window in a house was the kitchen because it was completely black. That wood smoke contains carcinogenic chemicals such as benzene, formaldehyde and dioxin. The World Health Organization estimates that indoor smoke kills about a million people every year, while also increasing the rates of emphysema, bronchitis, pneumonia, cancer and such birth defects as cleft palate.

Markowitz, when he first heard about solar ovens, thought about Olga and Carlos Sanchez, parents of two boys who he met in Hidalgo. Olga cooked over a small metal box that looked like it had been cut out of an oil drum. Carlos worked as a sharecropper, tilling potato fields, so the tank of propane they bought every three months represented a major share of their income. And Hidalgo is usually sunny.

Markowitz raised more money and tried to ship solar ovens south, but again was confounded by Mexican customs. (He’s been waiting a year for a shipment of medical supplies to reach Dr. Reyes.) So he again used the power of his mountaineers. Now when his groups fly to Mexico City to climb El Pico de Orizaba, Markowitz uses their luggage allotments to pack solar ovens. So far he’s brought down 18 ovens.

The last time he visited, Carlos Sanchez told Markowitz that he now takes a solar oven to the fields with him, where he sometimes must camp overnight, and his food cooks while he works. Olga served Markowitz potato tacos she’d cooked in a solar oven. Now their tanks of propane last nearly three times longer. With the help of some priests, he has also brought about 61 ovens to needy people in Madagascar.

“I don’t do this to stand up and say ‘look at me,’” Markowitz says. “I do it because there’s such a disparity between what they have and what we have. Trying to help them just feels good. And it’s made our trips to these mountains a lot more than climbs—they’ve become very rich adventures.”

Nathaniel Reade has been an editor and writer for scores of magazines, including GQ, Spirit and SKI, on subjects ranging from West Nile Virus to snowshoeing in Labrador. The comic young-adult novel he recently wrote with his 12-year-old son, The Pencil Bandits, has been described as “Oliver Twist meets The Marx Brothers meets The Boxcar Children.”