“Today, President-elect Biden will sign an Executive Order that takes critical first steps to address the climate crisis, create good union jobs, and advance environmental justice, while reversing the previous administration’s harmful policies,” the transition team said in a statement.

First on the list of climate policies for Day One is an executive order to rejoin the Paris Agreement, one of Biden’s campaign pledges, and a direct rebuke and reversal of Trump’s removal of the U.S. early in his term. The U.S. officially left the Paris Agreement on November 4, 2020, as poll results of the election were coming in.

In a statement, Biden’s team said notice to rejoin would be given to the United Nations by the end of the day, and would go into effect 30 days later.

“Best available science”

The incoming president also announced a sweeping directive to direct all government departments and agencies to review the executive actions of the last four years that were “harmful to public health, damaging to the environment, unsupported by the best available science, or otherwise not in the national interest.”

That includes instructing agencies to look at revising fuel and emissions standards, methane-emissions standards, reviewing the boundaries of national monuments, and revoking the presidential permit granted to the Keystone XL pipeline, among others, the statement said.

A more granular breakdown of agency actions under review cover legislation on everything from efficiency standards for dishwashers, to the to the regulation of toxic chemicals, to the designation of the critical habitat of the Northern Spotted Owl.

While Biden had pledged to reverse environmental policies put in place by Trump and to advance policies to promote clean energy, energy and climate experts had warned that his ability to make lasting change would be heavily dependent on whether the Democrats’ would gain control of the Senate. Now, after that party’s victory in the Georgia run-offs earlier this month, Biden will have greater legislative control to put momentum behind his environmental policies.

That’s not to say that the Administration’s efforts are likely to be nothing but smooth sailing. A Conservative-leaning Supreme Court may present legal challenges and constraints on some policies, some experts have warned, while Biden is also taking up the top post amid a deep economic and public health crisis that is sure to divide public attention and the government’s resources.

Meanwhile, the U.S.’ international credibility on climate policy has also taken a dent over the last four years, particularly in Europe. Other nations will be watching to see whether legislation on climate change truly has wide backing—and therefore staying power—back home, says Amos Hochstein, the former Obama and Biden special envoy for international energy.

“Making this transition more acceptable and palatable to a broader swath of the American population is going to be critical to the success of the administration,” he said.