Delegations from Berlin to Beijing and London to Los Angeles are expected at the C40 Large Cities Climate Summit, billed as dedicated to reducing carbon emissions and developing more energy-efficient infrastructure.

The first such summit was held in London in 2005, bringing together environmental officials from around 20 cities for what was mostly an opportunity to exchange ideas and set up the large cities network.

This year's summit counts mayors and senior officials from some 46 cities committed to tackling climate change and reducing their carbon footprint and for the first time brings in top business leaders from around the world.

The key to the summit is the financial case for addressing climate change, said Kathryn Wylde, president of the Partnership for New York City, a non-governmental business leadership group organizing the summit.

"The feeling was it was important for this summit to focus on the potential economic benefits of cities taking action to reduce carbon emissions and address climate change," she told AFP.

Former World Bank chief economist Nicholas Stern last year warned that the fallout of climate change could be on the scale of the two world wars and the Great Depression of the 1930s unless urgent action was taken.

Wylde said that by bringing together city authorities, companies who can provide technological solutions and the financial institutions to back new initiatives, the summit was much more than a mere talking shop.

"You've had lots of people that are abstractly talking about global warming and advocating policy change, but these are people who actually write checks and let contracts, who are making a public commitment," she said.

"It's no longer a matter just of rhetoric. Mayors are 'roll up your sleeves' guys that really have to run a city and do things," she said. "These are mayors with real budgets, real local obligations."

The summit was expected to include several joint initiatives based on leveraging the cities' combined purchasing power, Wylde said, while refusing to be drawn on what those initiatives might involve.

The event is being organized in conjunction with the The Clinton Climate Initiative, part of the foundation set up by former US president Bill Clinton, who is due to address the four-day summit on Wednesday.

Other topics up for discussion include beating congestion, making water systems more efficient, adopting renewable energy sources, increasing recycling levels, reducing city waste and improving mass transit systems.

Cities are responsible for around three-quarters of the world's energy consumption and considered critical to reducing carbon emissions.

Wylde said the summit gave mayors of US cities an opportunity to do something about climate change regardless of the national policies of President George W. Bush, who has refused to sign the Kyoto Protocol on climate change.

"It's particularly significant for the cities of the US where our national government hasn't made a commitment to do anything about it. Even in the absence of action on the national level, cities can take action," she said.

In addition, the summit allowed cities to pool their influence to create a movement that could make a real change to tackling global warming, she said.

Among the cities attending the summit are Bangkok, Beijing, Cairo, Delhi, Dhaka, Istanbul, Jakarta, Johannesburg, Karachi, Lagos, Melbourne, Mumbai, Paris, Rio de Janeiro, Seoul, Shanghai, Singapore, Sydney and Tokyo.

Sydney's Lord Mayor Clover Moore will be asking other cities to follow Sydney by implementing an "Earth Hour" during which businesses and homes turn off their lights for one hour to reduce energy consumption.

The city's first "Earth Hour", on March 31, was hailed as a success which cut normal energy use by 10 percent.

"I'll be reinforcing the message that it's how we live, what we do, and how we consume that can ensure a habitable earth for our children," she said.

"Sydney is the first global city to blaze with fireworks for the New Year. Next year we want to be the first in a chain of cities to turn out the lights as a signal of our united commitment to a sustainable planet."

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