Cohen gave Tokyo high marks for its public transit system (the most-used in the world) and its focus on private-sector innovation. He said the city needs to work on commitment to renewables and a climate adaptation plan. | Credit: James Law

The densest city in the rankings, London scored well for policies like congestion pricing, for its comprehensive climate action plan, and for its adaptation measures, such as the Thames Barrier, which protects against tidal surges. | Credit: Marc Baker

Leadership from Mayor Michael Bloomberg, a relative wealth of park space, and an excellent rail transit infrastructure made New York one of only two U.S. cities on the list. | Credit: Christopher Schoenbohm

A strong political commitment to climate-friendly policies, along with an aggressive greenhouse gas reduction target, were among the factors that put San Francisco in the running. | Credit: Grant Montgomery

Paris is a leader in adaptation strategies, having recently planted 100,000 trees and 20,000 square meters of rooftop gardens. It's got a climate action plan and also boasts the highest rail use per capita in Cohen's survey. | Credit: switchhook

Topping North America in the rankings, Vancouver demonstrates solid political commitment and has aggressive greenhouse gas reduction goals. The city also gets 90 percent of its energy from renewables. | Credit: Lola Buendia

Stockholm scored well almost across the board -- on policy goals, rail use, park space, and GHG emissions targets (the city aims to be carbon-neutral by 2050). Cohen does say the Swedish capital should focus more on adaptation strategy. | Credit: Chris Goldberg

Planning for adaptation to climate change is a strong point for Barcelona, which has also led the way with an innovative solar thermal ordinance that requires new and renovated buildings to use solar thermal energy for heating water or other purposes. | Credit: Premshree Pillai

Famous for its pioneering Bus Rapid Transit program, Curitiba also gets 82 percent of its energy from renewables and is tied with Copenhagen in the survey for lowest emissions per capita. | Credit: whl.travel

Political commitment? Check. Forty percent of citizens cycling to work? Check. Lowest in carbon emissions per capita? Tied with Curitiba. All these factors combined to put this Danish city comfortably at the top of the list. | Credit: SFBC Operations