As winter approaches, China has ordered its northern cities, along with Beijing and Tianjin, to cut emissions by 4%.

The government also ordered more than 5 million households to stop using coal heaters.

These eerie photos show why China has spent the last six years aggressively trying to cut down its pollution.

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Although no one knows the exact amount of carbon that China emits each year, the country has some of the most polluted air in the world.

As winter approaches, and people crank up the heat, China's government is ordering than 5 million homes to stop using coal heating, and switch to gas or electricity, by the end of October.

China also ordered 26 of its northern cities, along with Beijing and Tianjin, to cut PM2.5 emissions by 4%. PM stands for particulate matter, a mixture of solid particles and liquid drops in the air, that damages lungs.

The country has been trying to cut down its pollution for the last six years. At the end of 2016, pollution got so bad that an "airpocalypse" halted everyday life in Beijing. Cars couldn't be driven, planes were grounded, and schools had to be temporarily closed.

Here are 32 photos showing life in China, through the smog.

Jack Sommer and Cyrus Engineer contributed reporting to a previous version of this article.