“Made in China” products surround us, yet few consumers have anything more than a foggy idea of where in China their phones, computers, and other goods come from. Hunan Province in South Central China is not only the home of spicy food, but the world’s largest mines for non-ferrous metals used in many electronic devices. Nearly all the glass panels for Apple and Samsung smartphones are manufactured in Hunan as well. While this multibillion-dollar phone industry has been a boon for Hunan’s economy, it has also produced seriously polluted rivers and soil.

It was some point in May last year, shortly after ISIS surged into the city of Ramadi, and I was working on a story about Iraq’s fast-disappearing Mesopotamian Marshes. Keen to fact-check a few statistics with the Ministry of Water Resources and to hear the government line on the wetlands’ struggles, I dialed its Baghdad offices. After being passed from official to official like a hot potato, a young employee, Hussein, finally gave it to me straight. “No, no, we don’t have this sort of information,” he said, clearly impatient to get off the phone. “There are much more important things in Iraq right now.”

In December 2015, Beijing issued its first-ever “red alert” for smog, its highest air pollution warning, which closed schools and restricted the number of cars on the road. Less than two weeks later, it issued its second.

The recent news that China has been underreporting its already globe-leading coal consumption by nearly 20 percent for the last decade underscores the scale of its air pollution crisis.

The announcement in Washington on September 24 that President Xi Jinping is committing China to a national carbon trading system is the latest step in an important partnership between the two biggest carbon emitters in the world.