The numbers offer a sobering reminder of how deeply the modern economy still depends on fossil fuels. Whenever industrial activity declines, whether because of a recession or a major disease outbreak, climate pollution tends to plummet, too.

You can see the drop in China’s coal consumption in the chart above. Every year, the nation’s coal use falls during the weeklong holiday around the Lunar New Year, which occurred on Jan. 25 this year. Coal-burning emissions then typically rise again once people return to work and factories spring back to life.

But this year, coal use has yet to rebound. In late January, the Chinese authorities extended the New Year’s holiday and restricted travel and public gatherings in an attempt to stop the coronavirus from spreading.

The effects have rippled through virtually all sectors of China’s economy.

Construction activity has slowed, which has meant reduced demand for steel and other materials. Oil refineries are producing less fuel than usual as cargo trucks sit idle and the number of flights has dropped by about 13,000 per day. Activity in key industrial sectors has declined by 15 percent to 40 percent over the last three weeks compared with the previous year. (Mr. Myllyvirta first published his analysis at Carbon Brief last week and on Tuesday updated it with another week of data.)

But economic disruptions on this scale, whether caused by disease or recession, are usually accompanied by severe human costs and rarely make it easier to fight climate change. In some cases, they can make it harder.