President Trump visited the Environmental Protection Agency on March 28, to sign a sweeping executive order that instructs regulators to rewrite key rules curbing U.S. carbon emissions and other environmental regulations. (The White House)

Polls show a majority of Americans want President Trump to stay in the global Paris climate change deal.

But if he does leave it, it will be a rare moment where the president does exactly what Republicans in Congress asked him to do.

Last week, more than 20 high-profile Republican senators sent a letter to Trump urging him to back out of the deal of nearly 200 nations agreeing to significantly cut carbon emissions by 2030.

We don't know how much this letter influenced the president, who has yet to announce his decision. But we do know that his administration is split on whether to split from the Paris climate agreement, and this letter arrived just days before he's expected to make his decision.

Given all that, it's worth walking through the arguments these Senate Republicans are making about why Trump should leave the Paris climate deal — and the argument environmentalists are making about why he should stay.

Argument one for leaving the Paris agreement: You've basically already pulled out of it

With coal workers at his side, Trump signed an executive order in March that pulled the plug on a number of Obama climate-change rules, his clearest signal yet he wasn't going to enforce Obama's greenhouse-gas emission limits for power plants. Trump ordered the federal government to:

  • Rewrite its rules on how much carbon power plants can emit
  • Lift a moratorium on coal leasing on federal lands
  • Remove the requirement that ALL federal workers consider the impact of climate change when making a decision

“The order has taken the legs out from under the Paris climate agreement that President Obama signed in his last year in office,” Sen. John Barrasso (R-Wyo.), chair of the Senate's environment committee, argued in a March Washington Times op-ed.

In their letter, senators argue that Trump would be giving mixed signals if he stays in a global agreement to cut carbon emissions while he increases limits on carbon emission back home.

What the other side says: Environmentalists acknowledge Obama's domestic commitments to lower greenhouse gas emissions are a key part of the United States' international commitments. But they don't want Trump to leave either.

President Trump has decided to pull the U.S. out of the Paris Agreement. Here's what you need to know. (Daron Taylor/The Washington Post)

Argument two: If you stay in the Paris agreement, you'll get sued. A lot.

Trump's goal appears to be to eventually unwind the Clean Power Plan, which Obama put in place in 2014 to require states to reduce carbon dioxide emissions by about one-third of 2005 levels over the next 15 years.

Republican lawmakers HATE this plan. It's filled with regulations they worry will hurt energy companies in their state, like coal workers in Senate Majority Leader Mitch McConnell's Kentucky.

But environmentalists saw the Clean Power Plan as the best way to reduce emissions in the absence of a Congress reluctant to. The political tension pretty much guarantees that as Trump rolls back greenhouse gas emission regulations, environmental groups will sue him for it. (In April, a federal court granted the Trump administration a 60-day pause on all lawsuits about the Clean Power Plan while the Trump administration reevaluates it.)

These Republican senators argue that if Trump is still in the Paris deal, environmental groups can hang their lawsuit on it. “It is clear that those advocating for greenhouse gas regulations will use the Paris Agreement as a legal defense again,” the letter reads.

What the other side says: Trump's going to get sued anyway. “Tearing the rules down require going through the same process it took to build them up,” David Doniger, director of the Natural Resources Defense Council’s climate and clean-air program, told The Washington Post in March. “We will make them face the music at every step.”

Argument three: If you stay in the agreement, China will win


A man wears a mask as he rides his bike during a polluted morning in 2015 in Beijing. (Kevin Frayer/Getty Images)

The United States is one of the world's largest greenhouse-gas emitters, and its participation was expected to make up 21 percent of the emissions the Paris deal would cut, says The Post's Chris Mooney.

By comparison, China gets off easy under the Paris agreement, GOP senators argue. Barrasso in the Washington Times:

“The Paris deal imposed on the United States unrealistic targets for reducing our carbon emissions. It set America’s standards higher than for much of the world, while giving countries like China a free pass for years to come.”

What the other side says: Since signing the Paris agreement, China has stepped up its game on reducing carbon emissions, largely because its pollution is so bad it has no choice. China's appetite for coal is declining, and “both China and India look set to overachieve their Paris Agreement climate pledges,” predicted the Climate Action Tracker in a May report. If China follows through on its intent to lower emissions more than it promised in Paris, it could even cancel out any increased emissions from the United States.