Toronto is among 22 cities around the world joining former U.S. president Bill Clinton in the battle against climate change.

The Clinton Climate Initiative is aimed at increasing energy efficiency in everything from street lights to building materials and promoting clean-burning fuels and energy conservation.

The initiative brings together Clinton and his presidential foundation with the Large Cities Climate Leadership Group — an alliance of cities that have pledged to cut greenhouse gas emissions.

One of the aims of the group is to create a purchasing consortium to buy energy saving products. The group would also gather experts to help cities lower greenhouse gas emissions.

"This is a very, very serious problem, but also a phenomenal opportunity," Clinton said Tuesday at the University of California, Los Angeles, where he signed the pact.

Urban areas are responsible for over 75 per cent of all greenhouse gas emissions in the world, according to the Clinton Foundation website.

The alliance cites a number of ways cities can reduce greenhouse gas emissions and become more energy efficient. These include using:

• More energy efficient traffic and street lights.
• More energy efficient lighting, windows, heating and ventilation systems in buildings.
• Cleaner electric generation systems.
• Hybrid technologies for city buses, garbage trucks and other vehicles.