With the largest fleet of natural gas buses in the U.S. — about 2,200 — Los Angeles has become a leader in cutting carbon emissions.
Find out what makes the largest city in the United States one of the world's greenest, most environmentally friendly cities.
Once a declining industrial metropolis with steel mills spewing black smoke and soot into the sky, Pittsburgh has transformed itself into a vibrant green city.
Chicago's rooftop gardens reuse water and reduce heat, which can reduce a building's power costs. The city has 418,000 square meters of high-rise greenery.
Renewable energy resources such as solar and wind have opened up new possibilities for distributed power generation and transmission.
What type of energy do you use? The five dominant sources of renewable energy range from solar and wind to lava and biomass.
After more than 190 countries signed the Paris agreement, it moved toward going into force in only months. What's next for the landmark climate accord?
If the airline industry were a country, it would be the world's seventh-largest carbon polluter. New rules set limits on increases in aircraft emissions.
The Paris climate agreement will enter into force November 4, after the EU ratified the accord to bring it past a key threshold.