President Trump has risked starting a trade war by deciding to pull the U.S. out of the Paris climate accord.

That's the assessment of trade experts who argue that other countries could respond by slapping tariffs on American products that are cheaper to produce as a result of the move.

"It's not a pretty picture by any means," said Dirk Forrister, head of the International Emissions Trading Association. "This isn't something that businesses typically like."

Dropping the Paris agreement could help American companies produce products like steel at a lower cost than global rivals.And punitive trade measures would be one way for U.S. trading partners to level the playing field.

The tool they could use is called a "carbon tariff," which would act as a tax on U.S. goods crossing their borders. The more carbon pollution used to make a product, the higher the tax would be.

"It's basically throwing the fairness issue back in the face of the Trump administration," said Jeff Schott, a trade expert and senior fellow at the Peterson Institute for International Economics.