The United States, for its part, remains the world’s leading importer of what the researchers call “embodied carbon.” If the United States were held responsible for all the pollution worldwide that resulted from manufacturing the cars, clothing and other goods that Americans use, the nation’s carbon dioxide emissions would be 14 percent bigger than its domestic-only numbers suggest.

Between 1995 and 2015, the report found, as wealthier countries like Japan and Germany were cutting their own emissions, they were also doubling or tripling the amount of carbon dioxide they outsourced to China.

Under the Paris climate agreement, countries are held responsible only for the emissions produced within their own borders. Experts have long debated whether that makes sense. Is it unfair that China and India are blamed for emissions that occur because they’re making goods for richer nations? What about the fact that they also benefit from having those factories and jobs?

The migration of industries like cement and steel overseas can also shift production to less-efficient factories governed by looser pollution rules. An earlier study that Dr. Hasanbeigi led at Lawrence Berkeley National Laboratory found that China’s steel industry, on average, emits 23 percent more carbon dioxide per ton of steel produced than American and German manufacturers do. One big reason? China’s power grid relies more heavily on coal.

Since the financial crisis in 2008, however, the outsourcing of emissions from wealthy countries to developing countries has started to slow. More recently, much of the growth in carbon outsourcing is occurring between developing countries, according to a recent study in Nature Communications.

“Just as China’s starting to deal with its emissions, it’s been pushing some of its more carbon-intensive activities into countries like Cambodia, Vietnam and India,” said Steven J. Davis, a scientist at the University of California, Irvine and co-author of that study.

“From a climate policy context,” he added, “it’s like a game of whack-a-mole.”

The Unlikely ‘Tax’ Solution

One possible solution to all this emissions shifting would be for all countries to work together to enact a global carbon tax that applied equally everywhere. But in the real world, that is unlikely to happen anytime soon. And, while some politicians like President Emmanuel Macron of France have suggested that Europe put its own carbon tax on imported products, that idea has not gained traction.