New Delhi, Sept. 24 -- Championed by Big Oil as the fastest way to reduce emissions and reviled by environmentalists who say the world needs to ditch all fossil fuels -- the debate over natural gas may be one of the controversial aspects of climate change.

The arguments will get an airing as politicians, activists and business leaders gather for Climate Week in New York. On Monday, CEOs of the world's largest oil companies are expected to speak at an event organized by the Oil and Gas Climate Initiative where they'll likely defend the idea that gas is integral to a low-carbon future.

Here are six key arguments about gas, starting with the case for the fuel:

1. Gas is killing coal

When burned cleanly, gas releases about half as much ca...