Historically, the high cost of renewables has been one of the greatest hurdles in breaking our dependency on oil and gas. But recent research indicates that advances in renewable-energy production have made it cheaper than fossil fuels. Bill McKibben, a contributing writer to The New Yorker and the founder of the environmental group 350.org, joins Dorothy Wickenden to discuss the new economic realities of renewable energy, and how they could affect the global battle against climate change.