The first zero-carbon city in the world may sound like something out of a science-fiction movie: instead of cars, transportation will consist entirely of light rail and automated "pods" that act like small, driverless taxis. But the city is becoming a reality, with construction having begun in February in the United Arab Emirates. Masdar City, in the emirate of Abu Dhabi, is expected to have a population of 50,000. The 6-square-kilometer city will exist entirely on renewable resources, with solar power providing much of the energy in this sun-drenched region. AM buildings will be low-rise and built to counter the oppressive heat; natural air conditioning will ...