"It is in cities that the battle to tackle climate change will be won or lost," London Mayor Ken Livingstone said.
Mayors and local leaders from more than 30 cities kicked off the conference, known as the C40 Large Cities Climate Summit, which first met in 2005 in London. Organizers say cities bear a significant responsibility to address climate change because they cover less than 1 percent of the Earth's surface but are overwhelmingly responsible for polluting it, generating 80 percent of heat-trapping greenhouse gases.
"We cannot sit around and watch our environment deteriorate and put this world in jeopardy," Bloomberg said. "The public wants action, and if you have a void, the mayors are going to fill that void."
The summit drew mayors from cities big and small — from Seoul to Sao Paulo, from Albuquerque to Addis Ababa. During the gathering, which ends Thursday, participants hope to learn from each other by trading advice and sharing experiences on the ways their cities have gone green.
Clinton did not attend Tuesday but was expected the following day.
Many said the meeting of local government officials comes at a crucial time, while many countries worldwide are struggling to have similar conversations that would lead to global and national standards for reducing carbon dioxide emissions.
Just this week, U.N. delegates are meeting in Germany to gear up for a December gathering where negotiations will begin on a new set of international rules for controlling greenhouse gas emissions. The new accord would succeed the Kyoto Protocol, which ends in 2012.
And in June, the summit of the Group of Eight major industrialized countries — the U.S., Britain, France, Germany, Japan, Italy, Canada and Russia — will also meet in Germany, and climate change is a top priority on the agenda.
Meanwhile, mayors said Tuesday, that local governments cannot wait around.
"Where national governments can't or won't lead, cities will," Toronto Mayor David Miller said.
Trenton, New Jersey Mayor Douglas Palmer, who is president of the U.S. Conference of Mayors, said Tuesday that 500 of the nation's mayors have now signed the organization's climate agreement, a pledge that is essentially in line with the Kyoto Protocol.
That 1997 international treaty requires the industrialized countries that signed it to cut emissions by 5 percent below 1990 levels by 2012; the U.S. did not join the pact.
"Mayors are leading, quite frankly, because we have to," Palmer said. "Mayors took action because the federal government was silent."
Throughout the first day of the conference, participants attended panels on various topics, including energy, water use and transportation.
There was great interest in the transportation discussion, where the mayor of the Brazilian city of Curitiba described his city's solutions, which include a Bus Rapid Transit system. It is an option that many cities, including New York, are exploring.
Bus Rapid Transit systems offer some of the same features of a subway system — exclusive busways unimpeded by traffic signals and congestion, fare collection prior to boarding, frequent schedules and quick passenger loading and unloading.
At the same panel, Livingstone described London's program to reduce traffic by charging motorists extra money in the city center.
Bloomberg recently announced his intention to begin a similar charging scheme in Manhattan, which was applauded by environmental groups but encountered skepticism among lawmakers representing commuters in the city's outer boroughs and suburbs, including some state officials who would have to approve the proposal.
At a news conference after the panel, Livingstone told Bloomberg how to respond to those who oppose congestion pricing.
"Ignore them," Livingstone said. "We can't solve the problems of climate change without getting a better balance between mass transit and the motor car."
Under the pricing scheme in London, traffic congestion dropped by 20 percent, and carbon emissions in the central zone similarly decreased, Livingstone said. The fee — equal to about $16 (euro12)
has gone up since it started in 2003.
"People may not like paying the 5 pounds a day, but they certainly didn't want to live with that style of congestion," Livingstone said.
He said the city's next goal is to charge more for higher-polluting cars, a pricing scale that could mean a $50 (euro37) equivalent charge for the worst offenders.
Some local leaders attending the transportation session asked Livingstone how their cities could adopt congestion pricing. One official from Bangkok, Thailand, wondered whether his city could do it if residents do not have adequate mass transit choices as alternatives to driving.
This was key to London's success, Livingstone said.
"You can't do this in isolation," he said. "You have to make certain that for the people giving up the car, whether they wish to or not, that there is a relatively cheap option available."
Conference organizers, who invited a number of CEOs and business leaders to this year's gathering, also said they hope to involve the private sector in the movement at the city level. They hope to convince companies that going green — through innovative construction, transportation alternatives and other environmental changes — is a profitable economic move.