Over the past decade, both the United States and Europe have made major strides in reducing their greenhouse gas emissions at home. That trend is often held up as a sign of progress in the fight against climate change.

But those efforts look a lot less impressive once you take trade into account. Many wealthy countries have effectively “outsourced” a big chunk of their carbon pollution overseas, by importing more steel, cement and other goods from factories in China and other places, rather than producing it domestically.

Britain, for instance, slashed domestic emissions within its own borders by one-third between 1990 and 2015. But it has done so as energy-intensive industries have migrated abroad. If you included all the global emissions produced in the course of making things like the imported steel used in London’s skyscrapers and cars, then Britain’s total carbon footprint has actually increased slightly over that time.

“It’s a huge problem,” said Ali Hasanbeigi, a research scientist and chief executive of Global Efficiency Intelligence, an energy and environmental consulting firm. “If a country is meeting its climate goals by outsourcing emissions elsewhere, then we’re not making as much progress as we thought.”

Hasanbeigi is an author of a new report on the global carbon trade, which estimates that 25 percent of the world’s total emissions are now being outsourced in this manner. The report, written with the consulting firm KGM & Associates and ClimateWorks, calls this a “carbon loophole,” since countries rarely scrutinize the carbon footprint of the goods they import.