As the world hurtles toward its urban future, the opportunities and challenges of urbanization become ever more apparent. Cities are the most complex, economically powerful, culturally diverse, and socially important creation of humanity, but also a key factor in climate change.

Cities drive our economies and cultures; they bring together ideas, passions, finance, and a rainbow of colorful agendas. They are home to most of the world’s infrastructure, governments, and cultural institutions, as well as Fortune 500 companies.

But storm clouds are gathering. Eighty percent of GHG emissions come from cities, and citydwellers will bear the brunt of adapting to climate change. The rapid urbanization of the coming 25 years promises that cities in developing countries will need to accommodate 2 billion additional residents who will require water, sanitation, transportation, electricity, healthcare, and education. Addressing future GHG emissions and increasing resilience must be an integral part of any city’s climate change plan.

Urban residents, governments, and businesses need to develop sustainable cities—not only because cities contribute to climate change, but also because they are particularly vulner­able to it. Low-carbon cities reduce GHG emissions as they usher in an era of cost savings, cleaner air, and better living standards.

The experiences of cities like Barcelona, Portland, and Vancouver supply important lessons, as illustrated by the video interview with Barcelona Global’s CEO in this issue. After all, cities, like people, can learn from each other as they focus worldwide on climate change mitigation and adaptation.

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50 largest cities & urban areas

Combined, the 50 largest cities and urban areas are home to 500 million people, have a total GDP of $9,564 billion, and emit 2.6 billion tonnes of CO2e per year.

1. Tokyo, Japan
2. Mexico City, Mexico
3. Mumbai, India
4. New York, U.S.A.
5. São Paulo, Brazil
6. Delhi, India
7. Calcutta, India
8. Jakarta, Indonesia
9. Buenos Aires, Argentina
10. Dhaka, Bangladesh
11. Shanghai, China
12. Los Angeles, U.S.A.
13. Karachi, Pakistan
14. Lagos, Nigeria
15. Rio de Janeiro, Brazil
16. Osaka, Japan
17. Cairo, Egypt
18. Beijing, China
19. Moscow, Russia
20. Manila, Philippines
21. Istanbul, Turkey
22. Paris, France
23. Seoul, South Korea
24. Tianjin, China
25. Chicago, U.S.A.
26. Lima, Peru
27. Bogota, Colombia
28. London, U.K.
29. Tehran, Iran
30. Hong Kong, China
31. Chennai, India
32. Bangalore, India
33. Bangkok, Thailand
34. Dortmund, Germany
35. Lahore, Pakistan
36. Hyderabad, India
37. Wuhan, China
38. Baghdad, Iraq
39. Kinshasa, Congo
40. Riyadh, Saudi Arabia
41. Santiago, Chile
42. Miami, U.S.A.
43. Belo Horizonte, Brazil
44. Philadelphia, U.S.A.
45. St. Petersburg, Russia
46. Ahmadabad, India
47. Madrid, Spain
48. Toronto, Canada
49. Ho Chi Minh City, Vietnam
50. Chongging, China

The 2006 population figures are based on censuses carried out between 2000 and 2005 and adjusted to take account of average annual population changes (www.citymayors.com).

By 2050, global urban population will double; built-up area will triple.

Top countries & 50 largest cities

in terms of population, GHG emissions, and GDP

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Source: World Bank 2010. Table is for indicative purposes only. The years of data sources vary across countries and are determined by the last available UNFCCC-reported country data.


GHG emissions & urban lifestyle

The lifestyle choices of urban residents can significantly impact emissions.  According to economist Edward Glaeser, the average household in 48 major metro areas generates up to 35 percent less GHG emissions when located in the city instead of the corresponding suburbs.  Here Handshake presents three examples that show how infrastructure, policy, and access to services are closely interrelated.
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3.5 tCO2e per year
Maria, a program assistant for a private company, lives in Bogota City. She shares a house with her husband and two children and loves to cook. She has many electrical appliances in her kitchen, including a refrigerator, microwave, stove, and blender. She also has a TV, DVD player, computer, and miscellaneous other items to make life easier. She does not have heating or AC, as it’s not needed. Maria commutes from home using the Transmilenio bus rapid transit system. She usually spends her vacations at home.
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11.5 tCO2e per year
Nathan is a student living with his parents in the suburbs of Toronto. He owns a medium-sized car which he uses to go to school (25 kms each way daily). He also travels by plane at least twice a year. He cannot imagine not having a mobile phone, iPod, and laptop. He also has other entertainment systems at home that he keeps plugged in all the time. Due to the weather, his house needs to be both heated and cooled.
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1.8 tCO2e per year
Yusuph, a Tanzanian tailor, lives in Dar es Salaam. He never has his electrical appliances plugged in unless he is using them, as he is afraid that they might overload during one of the common power cuts. He has a TV, sewing machine, radio, refrigerator, water boiler, and table fan. He lives with his wife, his three children, and two cousins in a typical Swahili house. Despite the warm weather year round, he has no air conditioning. Every day, he takes the “daladala” (minivan) to work (10 kms).