This video podcast examines the city of London's role in C40, the international climate change organization. The majority of the world's population is now urban, making cities major sources of greenhouse gas emissions. In response, leaders from 40 cities met in London to tackle the challenge of making urban areas less polluting. The result is a worldwide network of cities - named C40 - that shares innovative strategies and advances climate change policy on the political agenda.

"e²: the economies of being environmentally conscious" is an ongoing PBS documentary series about solutions to the world's most pervasive environmental challenges. The latest addition to the series - "e² transport" - examines transportation alternatives and urban planning in cities around the world. Check your local PBS listings for television broadcast dates in your area.

The "e²" series and its video podcasts are produced by kontentreal, and distributed within the United States by PBS. More information is available at pbs.org/e2/ and e2-series.com/