The world's biggest polluter is about to make a big pledge.
Cap-and-trade systems theoretically give the government the ability to control carbon emissions. They set a total limit for the whole country and issue permits to pollute up to that limit. Companies then buy and trade the permits.
China's announcement isn't totally out of nowhere. The country has been experimenting with smaller cap-and-trade markets for several years. The new plan would more or less just consolidate them.
It's also not surprising that the announcement is happening now. The UN's climate summit in Paris is just over two months away, and countries have been announcing their plans ahead of time. (Video via The White House)
This video includes images from Getty Images.