The Chinese government may have just signaled that it’s serious about fighting climate change—although, as with all political developments in China, it’s difficult to be sure.

The signal came on Monday, when Beijing’s Municipal Environmental Protection Bureau announced its intention to ban coal consumption by 2020. That is an ambitious goal, considering that coal supplies a quarter of Beijing’s energy for 21 million people. Just a few years ago, no one would have said China is on the verge of making one of its largest cities coal-free in less than a decade.

The announcement is meaningful for two reasons. First, it means that people in and around Beijing may be able to breathe easier in the future. Studies haves shown that the city’s thick, choking air pollution has shaved 16 years off of life expectancy in Beijing. According to the Associated Press, coal accounts for 22 percent of the fine particle pollution that’s choking Beijing’s residents.

But the announcement should reverberate in this country, as well. For some time, American conservatives have been skeptical that China would do its part on climate change—and they’ve used that assumption as an argument for why the U.S. should not take action on its own. The latest news could mean that skepticism is wrong.

Among the hopeful is Jake Schmidt, Natural Resources Defense Council's international climate policy director, who notes that China has already taken some other steps, like establishing cap-and-trade policies in some of the provinces. “There is a very serious conversation about when [China’s] emissions will peak,” Schmidt said. “Two years ago you would be lucky to say they would peak by 2050, or 2030 if you really pushed them.” Now, he says, it’s possible China would be ready to limit emissions well before then. That’s a prerequisite for reaching an international agreement to limit greenhouse gases, in time to forestall some of the worst effects of global warming.

Still, it’s too early to celebrate. One big question is what energy sources Chinese officials use to replace coal. They could, for example, rely heavily on a process that converts coal into synthetic natural gas. Synthetic gas might make the air seem cleaner, but the conversion process results in 82 percent more carbon pollution than burning coal. It also relies heavily on water. China might also move aggressively into fracking for natural gas, which produces its own environmental hazards. Without the right safeguards, fracking can contaminate water supplies and leak methane—another, even more potent greenhouse gas. 

And interpreting signals from Chinese officials is always difficult. For about a day in early June, it looked like the country was considering an absolute cap on carbon. Then officials indicated the reports were wrong; they weren’t thinking about any sort of limit. They were merely looking at ways to slow its growth. That’s problematic, because China's intentions are key to a meaningful international agreement at the next big round of negotiations—in Paris next year. “As China goes into Paris that is critical,” Schmidt said. “If China doesn’t propose a strong target and the U.S. doesn’t, then it doesn’t matter what the rest of the world does, the deal won’t come together."