PARIS — As United Nations climate conferees meet near here, Eric Feunteun wishes everyone could agree: If the world is going to curb climate change, there is no choice but to stop driving cars that burn fossil fuels.

“If we want affordable, practical and fully green technology,” Mr. Feunteun said in an interview in an office building on the edge of Paris, “the electric vehicle is the answer at this stage.”

Mr. Feunteun is hardly an unbiased source. He heads the electric car program at the French automaker Renault, which sells more electric vehicles in Europe than any other company — and with its Japanese alliance partner, Nissan, accounts for half the all-electric vehicles now on the world’s roads.

For all Mr. Feunteun’s optimism, the delegates to the United Nations climate conference in nearby Le Bourget, France, confront a sobering fact: The number of automobiles on the world’s roads is on pace to double — to more than two billion — by 2030. And more likely than not, most of those cars will be burning carbon-emitting gasoline or diesel fuels.