NEW YORK: Speaking at the close of the U.N. Climate Summit, Barack Obama said the one issue that would define the current century more than any other is the urgent and growing threat of a changing climate.

"Deepening scientific evidence says this once distant threat has moved firmly into the present; no nation is immune," he said. "The climate is changing faster than our efforts to address it. The alarm bells keep ringing. Our citizens keep marching. We cannot keep pretending we do not hear them. We have to answer the call."

According to the International Atomic Energy Agency (IAEA), a shift to sustainable, low-carbon transport by the middle of the century could save governments, companies and individuals up to US$70 trillion.

The U.N. says with transport contributing 25 percent of global energy-related CO2 emissions and 20 percent of energy use, a "business as usual" model will result in a 50 percent increase in emissions by 2030.

In a bid to reduce this possibility, by 2030 the Urban Electric Mobility Initiative - supported by Michelin – aims to increase the number of electric vehicles in cities to least 30 percent of all new vehicles sold annually.

"Mobilizing support from the private sector is vital to enable us to implement technological breakthroughs in urban mobility" commented Joan Clos, UN-Habitat executive director.

Another initiative, the International Association of Public Transport Declaration on Climate Leadership, brings together 1,300 organizations from 92 countries to provide access to climate-savvy public transportation in cities.

Meanwhile the U.N. International Civil Aviation Organization continues to develop a global CO2 standard for new aircraft and implement a measure adopting alternative fuels for international aviation from 2020 onward. So far over 100 airlines – including Virgin Atlantic and Thai Airways – have committed to the initiative.

Together with the International Union of Railways' promotion of rail as an alternative to road and airfreight, the U.N. says these four transport initiatives announced at the Climate Summit are designed to ensure a low carbon future and save trillions of dollars in fuel costs in the process.