Former New York Mayor Michael Bloomberg aims to use his new role as U.N. envoy on cities and climate change to help “frustrated” U.N. chief Ban Ki-moon motivate world leaders to cut greenhouse gas emissions by showing them progress made by large cities.

Bloomberg, who left office in December after 12 years as New York’s mayor, said he would help Ban drum up support for a U.N. summit on climate change in September by spreading the message that tackling the issue does not have to be controversial or cost a lot of money.

Ban is seeking to re-energize the global climate change debate and boost the role of the United Nations, which diplomats say has been side lined since a 2009 summit in Copenhagen failed to secure a deal on a binding treaty on reducing emissions.

Ban probably is a little bit frustrated that the nations of the world haven’t come together,” Bloomberg told reporters on Tuesday ahead of a meeting in Johannesburg of the C40 Cities Climate Leadership Group, an international group of mayors created in 2005. Bloomberg is now president of the C40 board.

“There’s nothing inconsistent between what we do at the city level and what he would like to get done at a national level,” said Bloomberg, the billionaire philanthropist who was appointed to the U.N. role on Friday.

There are 63 cities - including New York, Rio de Janeiro, London and Sydney - that are part of the C40 group, representing 600 million people. They share ideas to tackle climate change like bus rapid transit systems, environmentally friendly outdoor lighting, and bike sharing schemes.

“Mayors don’t have time to debate politics, they have to deliver results, and mayors around the world increasingly recognize the threats climate change poses to our cities,” Bloomberg said.

“Cities account today for 70 per cent of the world’s carbon emission and more than three-quarters of the world’s energy use, and so the action that they take today to confront climate change really will have a global impact,” he said.

Bikes, lights and fast buses

The second Climate Action in Megacities survey, released by C40 on Wednesday, found that in 2013 36 C40 members had implemented bike-sharing programs, up from six in 2011, and 80 per cent of the total C40 group had introduced cycle lanes.

More than 90 per cent of C40 cities are taking action to reduce emissions from outdoor lighting, and 35 cities have or plan to develop bus rapid transit systems, following the lead of Curitiba in Brazil and Bogota in Colombia, the survey found.

Improving energy efficiency in buildings accounted for 20 per cent of all of the projects and policies being undertaken by C40 cities to tackle climate change.

“Mayors have real power to cut emissions and improve climate resilience, and they are taking action,” said C40 chairman, Rio de Janeiro Mayor Eduardo Paes. “C40’s networks and efforts on measurement and reporting are accelerating city-led action at a transformative scale around the world.”

Bloomberg had promoted his own environmental accomplishments in December before leaving office, announcing that New York’s greenhouse gas emissions have dropped by 19 per cent since 2005, putting the city nearly two-thirds of the way to meeting the goal he had set five years ago.

Bloomberg trumpeted measures ranging from hybrid taxi cabs to making municipal building more energy efficient. He spearheaded the introduction of bike lanes and a bike-sharing program in New York, but failed to win state approval for a congestion pricing program designed to discourage driving in Manhattan’s busiest areas during peak travel periods – modeled after a program in London.

The United Nations Intergovernmental Panel on Climate Change said in September that it is at least 95 per cent probable that human activities, led by the burning of fossil fuels, are the dominant cause of global warming since the 1950s, up from 90 per cent in a 2007 assessment.

The world has agreed to work out a global U.N. deal by the end of 2015, entering into force from 2020, to fight climate change. But progress has been sluggish, with discussions shifting to bilateral talks between key world powers and the Group of 20 club of major developed and developing nations.

Ban has also appointed former Ghana President John Kufuor and former Norwegian Prime Minister Jens Stoltenberg as special envoys on climate change to build momentum for the September conference.