One new study suggests lower natural gas prices may be saving households up to $725 per year. Others find lower numbers. Here's why they differ.
The White House just raised its estimate of the price of carbon 50 percent. That's a big shift.
The World Bank reports that more than 60 carbon-pricing schemes or either underway or planned for the years ahead, from California to the European Union to South Korea.
Externalities, trade-offs, and the challenges of getting the math right on what carbon really costs the world.