By Timothy Gardner

NEW YORK, May 12 (Reuters) Mexico City's mayor wants to learn how to prevent flooding from climate change, London's wants lessons on making energy from waste, while New York wants to compare notes on reducing emissions-belching traffic.

Mayors from some of the world's 40 largest cities, which form the climate group C40, will meet in New York next week to share information on cutting greenhouse gas emissions linked to global warming that scientists say could cause deadly floods, droughts and heat waves.

''While we are competitors in many other fields, we have all committed to work together in terms of tackling climate change,'' Mark Watts, the climate change adviser to London Mayor Ken Livingstone, said in a telephone interview.

City traffic, buildings and manufacturers emit 70 per cent of the world's greenhouse gases.

While the leaders of countries consider whether to join international agreements on cutting emissions, cities are where many of the basic reductions are made. Cities encompass many of the systems vulnerable to climate change, such as freshwater transportation, energy and sewage lines.

''We do have the power, we are the ones that arrange public transportation and set the standards for just about everything,'' Fernando Menendez, senior adviser to Mexico City Mayor Marcelo Ebrard, said in a telephone interview.

In the early 1990s, when Mexico City had the world's worst air pollution, Ebrard, then head of the city's interior department, helped limit car use.

Now the capital city wants to cut heat-trapping gas emissions to prevent flooding -- even though, as a developing country, Mexico is not mandated by the UN's Kyoto Protocol to fight output of the gases. Experts say climate change could lead to more more rainfall in some regions and heighten the risk of floods. Menendez said flooding would overwhelm Mexico City's drainage systems and ''would cost so much money it would be absurd.'' To cut emissions, Mexico is expanding express bus lines and building new subway lines to take passengers for the first time anywhere in the city.

CONGESTION FEE New York Mayor Michael Bloomberg is also seeking to cut traffic emissions as part of his plan to cut the city's greenhouse emissions 30 per cent by 2030. He plans to charge drivers 8 dollars to enter the heart of America's most-populous city, taking a cue from London, which has used congestion pricing since 2003. Polls show New York drivers solidly opposed to that high a fee.

London, whose mayor is chair of C40, can learn from U S cities, Watts said. London wants to produce more energy within its boundaries and learn from Western U S cities how to make fuel from waste, perhaps from the gases emitted from sewage and garbage.

Ideas germinating from cities can add practical solutions to international ones on fighting warming. ''Cities are a lot closer to the ground,'' said Kathyrn Wylde, president and CEO of the Partnership for New York City, which is organizing the meeting for New York. ''We haven't had this kind of leadership from the federal level,'' she said.

REUTERS CS HT0910