Commissioned by Germany's Siemens AG and carried out by the United Kingdom's Economist Intelligence Unit, the Asian Green City Index evaluated the environmental performance of the cities in several categories, including carbon dioxide emissions, energy, buildings, transport, water, waste and land use, air quality and environmental governance.
Amy Kohl, mayor of the southwest district of Singapore, said the index should encourage Asian cities to work together for the environmental challenges they face in an increasingly urbanized Asia.
"We live in a more resource-constrained world," Khor said in a statement. "Higher energy prices, climate change and rising raw material prices all mean that we have to be more prudent with our use of resources."
As an example of how Singapore manages its scarce resources while achieving economic growth, Khor cited the city's NEWater project, which turns wastewater into a clean resource for drinking and industry use through micro-filtration, reverse osmosis and ultra-violet technology.
The Asian Green City Index shows that air pollution is a serious problem across Asia, with average levels of the three pollutants evaluated in the Index exceeding the safe levels set down by the World Health Organization.
The average annual carbon dioxide emissions per capita for Asian cities is 4.6 tons, compared with 5.2 tons for Europe, the study says, with Chinese cities showing the highest carbon emissions per capita and energy consumption per unit of gross domestic product in Asia.
Siemens Chief Sustainability Officer Barbara Kux said Asian cities have the potential to reduce emissions by up to 30 percent, which could help to limit global warming to 2 degrees Celsius.
Other rankings for the Asian Green City Index:
Designated "above average" after Singapore's "well above average" ranking: Hong Kong; Osaka, Japan; Seoul; Taipei, Taiwan; Tokyo and Yokohama, Japan.
Karachi, Pakistan was the sole city to be considered "well below average."
Rated "below average" in the study: Bangalore, India; Hanoi, Vietnam; Kolkata (formerly Calcutta), India; Manila, the Philippines and Mumbai.
Tokyo was ranked as the category leader for energy and carbon emissions; Singapore for waste; Hong Kong for land use and buildings; Singapore, Tokyo and Yokohama for water.
No cities earned leader ranking for the sanitation, air quality and environmental governance categories.
This is the third Siemens/EIU Green City Index. Curitiba, Brazil came out as a leader for the Latin American Green City Index in 2010 and Copenhagen, Denmark for the 2009 European Green City Index.