Urban Index

Less than 1: Percent of the earth's surface covered by cities (1)
75: Percent of global energy consumed by cities (2)
80: Percent of global greenhouse-gas emissions contributed by cities (1)

6.7 billion: World population in 2007 (3)
50: Percent of world population expected to live in urban areas by the end of 2008 (3)
70: Percent of world population expected to live in urban areas by 2050 (3)

840: Mayors who have signed the U.S. Mayors Climate Protection Agreement (4)
50: States from which those signatories hail (4)
80 million: Citizens those signatories represent (4)
3: Actions those signatories agree to take (strive to meet or beat Kyoto goals in their communities; urge state and federal leaders to meet or beat Kyoto goals; urge Congress to pass bipartisan greenhouse-gas reduction legislation) (4)
110: Mayors who attended the November 2007 U.S. Conference of Mayors Climate Summit, the largest-ever meeting of U.S. mayors devoted solely to climate protection (5)

1,200: Tons of annual carbon emissions cut by replacing regular traffic-light bulbs with LEDs in Warwick, R.I. (6)
1,100: Tons of annual carbon emissions cut with free home energy retrofits in Houston, Texas (2)

30: Percent increase in public transportation use in the U.S. between 1995 and 2006 (7)
24: Percent increase in vehicle miles traveled in the U.S. during the same time (7)
88: Percent of all trips taken by car in the U.S. (8)

48: Percent of U.S. greenhouse gases contributed by the building sector, primarily through energy consumption (9)
50: Percent of the "built environment" expected to be rebuilt by 2030 (10)
1.7 billion: Estimated tons of carbon that could be saved by large-scale conversion to greener buildings in North America by 2030 (11)
418: Percent increase in number of cities with green building programs between 2003 and 2007 (12)

Sources: