Yet unless there are major advances in technology, it will be difficult for the United States to meet its commitments under Paris without using rules similar to the current regulations.

As details of the order leaked to the public, nearly every environmental or climate-centric group castigated it as a costly step backward. Andrew Steer, the president and CEO of the World Resources Institute, said that the administration was “taking a sledgehammer to U.S. climate action.”

An administration official, speaking anonymously to reporters on Monday so as to preview the order, described it in softer terms, as something between a strategic reset and an adolescent rite-of-passage. “When it comes to climate change, we want to take our course and do it in our own form and fashion,” the official said.

There is a lot going on in the order: Months of rumored environmental action have been distilled into this document. Its policy goals can be separated into two categories. First, some policies require rule-making processes that Trump can only set in motion and point toward certain goals. The second group of policies are just executive directives reserved to the president. Trump can issue them by himself, just as Obama did, and they will enter force immediately.

The largest shift in U.S. climate policy contained in the order falls into the first category. President Trump will command the EPA to review and rewrite the Clean Power Plan, the signature climate policy of the Obama administration.

The Clean Power Plan sought to replace coal-fired power plants with natural-gas, solar, wind, and hydroelectric plants; the EPA and outside studies estimated that it would save more than 1 billion tons of carbon-dioxide emissions by 2030. The EPA also predicted that the plan would reap more than $55 billion in public-health benefits per year by 2030. The electricity sector is responsible for about 30 percent of U.S. carbon emissions.

To the Trump administration and its allies, the Clean Power Plan constituted the advance front of Obama’s “war on coal.” (Most energy economists say that the coal business is collapsing not because of recent regulations, but because domestic fracking has made natural gas cheap and plentiful.) Some Constitutional law scholars, including Laurence Tribe of Harvard University, argued that aspects of Obama’s rule amounted to executive overreach.

Trump cannot reverse the Clean Power Plan immediately, but he can tell the EPA what goals to pursue. The EPA must then revisit the science and policy justifying that rule and go through the arduous process of drafting a new one. (It took the Obama administration more than six years to issue the first version of the rule.) And throughout all that time, the Clean Power Plan will likely stay out of effect: It has been on pause since the Supreme Court stayed it in February 2016.