We saw two early signs of that this week. On Tuesday, more than 300 companies called on the president-elect to remain in the Paris Agreement and continue helping the U.S. move toward a “low-carbon economy.” These firms include DuPont, Intel, General Mills, the Kellogg Company, Mars Incorporated, L’Oréal, and the Craft Brew Alliance. Many of the companies have donated thousands or tens of thousands of dollars to Republican lawmakers or campaigns in the past.

And on Wednesday, China’s vice foreign minister, Liu Zhenmin, promised that his country had not invented climate change as a hoax. Four years ago, Trump tweeted that “the concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive.”

“If you look at the history of climate-change negotiations, actually it was initiated by the [Intergovernmental Panel on Climate Change] with the support of the Republicans during the Reagan and senior Bush administration during the late 1980s,” said Liu.

In other words, a Chinese diplomat had to assure the U.S. president that, no, his country hadn’t invented a widely documented scientific phenomenon (which was discovered in part by American scientists).

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When it was ratified last month, the Paris Agreement became the first truly global treaty to address climate change. It is largely non-binding for the United States, and it does not legally require this country to reduce its emissions.

During the campaign, Donald Trump promised he would withdraw the United States from the Paris Agreement if he were elected.

Technically, the U.S. could not withdraw from the Paris Agreement for four years. But it could summarily stop participating in the annual meetings that the treaty requires. It could also announce its withdrawal from the much older overarching treaty, the UN Framework Convention on Climate Change adopted by President George H.W. Bush in 1992.

Due to a fluke in terms, it would only take the United States one year to withdraw from the broader UNFCCC. But leaving the UNFCCC would carry broader problems for American firms.

The Obama administration had hoped to meet the non-binding promises that it made at Paris through a set of EPA regulations called the Clean Power Plan. Generally, these rules pushed states to build fewer coal-burning plants while installing more renewable-energy capacity. It also set up the basics of an interstate cap-and-trade structure.

The Clean Power Plan, however, was put on hold by the Supreme Court earlier this year, and the D.C. Circuit is now examining whether it can pass legal muster. The Trump campaign promised to repeal these executive actions on the first day of the administration. To start, it could simply decline to defend them in the courts.

But to truly undo them, it would have to go through a lengthy rule-making process. The EPA must regulate carbon dioxide as an air pollutant thanks to a 2007 Supreme Court decision, Massachusetts v. EPA. Were Congress to amend the Clean Air Act such that the EPA no longer had this obligation, Republicans could open up greenhouse-gas-emitting companies (like factories and manufacturers) to private litigation under a 2011 Supreme Court decision.