New York City ? A global summit of leaders including former President Clinton convenes here this week to exchange ideas on addressing the threat of global warming.

Mayors and governors of more than 30 localities from Colombia to South Korea, along with executives from a number of international companies, will join Clinton and New York City Mayor Michael Bloomberg for the C40 Large Cities Climate Summit that begins today.

It is the second such gathering; the first was held in 2005 in London, drawing representatives of 18 cities.

The theory behind the conference is that cities must play a major role in reversing climate change, since they contribute 80 percent of the world’s greenhouse gas emissions even though they cover less than 1 percent of the Earth’s surface.

“Cities must take responsibility for our contribution to global climate change,” said Los Angeles Mayor Antonio Villaraigosa, who is one of the participants. A spokeswoman said he will announce his own city’s carbon-reduction plan Tuesday in California before attending the conference.