Model behaviour: Karlie Kloss, month of June on the Pirelli calendar, is involved with Donna Karan’s Tents Today Homes Tomorrow initiative. Photograph: Steve McCurry  During its illustrious history, attempts to portray the Pirelli calendar as more than just a lavish collection of nude photographs have occasionally come close to bathos. Last year, for instance, discussing Mario Sorrento's Corsican shoot, the American supermodel and actor Milla Jovovich made the implausible argument that "the thing about Pirelli is the really great tyres. They're strong and modern and they work, so in the shoot you've got these really strong, amazing modern women. So there's this relationship between these really strong tyres and these really strong women."  Well, up to a point. This time round, however, Pirelli's claim to be offering something beyond the female form in a state of partial or total undress looks more solid. To celebrate its 40th calendar, the Italian company has decided to abandon the normal roster of fashion photographers such as Mario Testino and Terry Richardson, who transformed a trade publication into an annual celebration of "glamour" shots to grace the garage wall. Instead, for 2013, Pirelli turned to one of the world's most famous war photographers and sent him to Rio, host to the next football World Cup and Olympic Games, and vibrant hub of a country which is booming like never before.  Steve McCurry made his name documenting Afghanistan in the early 1980s, having smuggled himself into the country by growing a beard and wearing traditional dress. The American's photograph of Sharbat Gula, a teenage Afghan refugee with vivid, haunted green eyes, became one of the most famous images in 20th-century photography after featuring on the cover of National Geographic. Describing himself as a "street photographer doing found situations", the 62-year-old McCurry has since travelled and worked in places such as Beirut, Baluchistan, Cambodia, India and Japan. So how did he wind up with 11 of the world's leading models, shooting a Pirelli calendar?  "Well, I certainly didn't think of myself as an obvious choice," McCurry admits. "I'm not a fashion photographer. But Pirelli said they wanted me to do it my way, in my style."  The result is an act of homage to a city and a country that Pirelli recognises as one of its most important future markets. "You can photograph nudes anywhere," says McCurry. "But these models are clothed, and each of them has her own charity. They are purposeful and idealistic people. I wanted to photograph them in a special place, and Rio was perfect for that."  There is a temptation to be somewhat cynical when it comes to models and good works, but in McCurry's company it is hard to be world-weary. Stocky, white-haired now and brimming with enthusiasm for a city with "the best views on the planet", this native of Philadelphia has lost none of his photographic ambition. And his version of "the Cal", as Pirelli types like to call it, is simply fabulous to look at. Rio is the true star of the 34 images, described by McCurry as a "mythic" place, with "mountains, beaches and incredible light".  Loyal to his street aesthetic, McCurry ignored the famous sand of the Copacabana and Ipanema and headed into Rio's urban and historic heart, usually at night. This is a Rio of shadows, sultry allure and moments of ethereal beauty caught on the hoof. "I wasn't interested in doing the beach type of thing," he explains. "I was more interested in the darker, moodier places. So we went to areas like Lapa and Santa Teresa, places where there's more texture and more life. Where there's people hanging out on the street, people barbecuing, people dancing, bars with all kinds of characters in them. I became fascinated by the graffiti. That could have been a book in itself. We went into the favelas, too. They were teeming with life pressed together. We found this hotel in a favela – called Bob's Place, I think – and we shot there for a couple of days against this amazing backdrop of Rio."  Some of the images feature ordinary cariocas – as Rio inhabitants are known – rather than models. One extraordinary photograph shows a young couple walking high above the city at sunset, looking down on a landscape that seems too beautiful to be real. "This is the best view of any city in the world," says McCurry. "I knew that spot because a few years ago I was in Rio and I wanted to get a cityscape kind of photo. I saw this high point in the distance and I thought if we could find it there would just be a fabulous view of the city. By luck we found the location and on the top of the hill there was a park. So we went back this time and these people were just out walking. Look at that light! It's just amazing."  When the models appear, they seem to be offering an invitation to savour the drama of the city that is unfolding behind them. Petra Nemcova, the Czech model and actress, sits in front of an open window which looks out on the heart of nighttime Rio. Karlie Kloss (see picture above) leans against a graffiti-covered tram as a bus departs for the city and a shadowy figure passes by unseen. In another shot, a dark silhouette walks away from the camera, across the famous Lapa viaduct, heading for the warmth and light of Rio's skyscrapers. "I wanted the models to be part of the environment and have life swirling around them, to be integrated into the city," says McCurry.  There was also a sincere desire to showcase the various causes promoted by the women he chose to photograph. Since 2004, when Nemcova lost her fiancé in the tsunami which overwhelmed Thailand, she has run the Happy Hearts Fund, dedicated to assisting child victims of natural disasters. Kyleigh Kuhn, who graduated from Berkeley university in California, has founded a campaign dedicated to the funding of schools for Afghan girls. The calendar gives a meticulous account of each model's campaigning activities. "Working with Steve on a project like this was an amazing opportunity to publicise the causes we're trying to help," said Kuhn. "I've tried to use my modelling as a platform from which to promote these projects, and this was the perfect situation." According to Kloss, "the fact that the models are clothed helps take away attention from the women's bodies and direct it to their causes".  That may be overstating it a little. But McCurry is lost in admiration for his subjects. "Spending time with the girls outside the shoot and finding out about their work and causes was for me maybe the best thing about doing the calendar. You've got this false stereotype of models who don't have much to say… so to get to know them as real people was just fascinating and inspiring."  The launch of "Steve McCurry's Rio", compered by Sophia Loren, was an opportunity for Milanese executives to bask in the acclaim of Pirelli's first "social" calendar. Even Luiz Inácio Lula da Silva, the left-wing former Brazilian president, turned up. But for some seasoned observers of Pirelli calendars past, the combination of McCurry, clothed models and social commitment was just a little too baffling. In its early years, a calendar launch was a very different affair, populated exclusively by members of the tyre-making industry and that year's collection of models. As Loren presented Lula with a Pirelli award for "social engagement", there were those who remembered those simpler days with a degree of nostalgia.  "I can't quite figure out what the point of it is any more, I'm afraid," observed one veteran of a motoring publication. "What's the connection between nice pictures of Rio and Pirelli? You know, when you used to have the distinctive tyre tread painted on a model's bottom, you could see the marketing strategy. Not now."  You can't please all the people all of the time. But as McCurry's friend, the travel writer Paul Theroux, pointed out in a commentary written to accompany the launch, the photographer has certainly succeeded in one very basic sense. "It is impossible," writes Theroux, "to see the Steve McCurry photographs of Rio and its people and not wish to be there."
To create its 40th calendar, the tyre company headed to Rio to do something out of character – get the great Steve McCurry to shoot  the models with their clothes on. Julian Coman investigates