The Trump administration has started to pull the US out of the Paris climate agreement. Here's what that means and what comes next.

• On Monday, the United States began the process of formally withdrawing from the Paris climate agreement - the first nation ever to attempt to exit the accord.
• The withdrawal will be completed on November 4, 2020.
• The Paris agreement, established in 2015, is a voluntary accord between 200 countries to limit global warming to less than 2 degrees Celsius by cutting greenhouse-gas emissions.
• But the United Nations recently reported that our planet will likely blow past the warming limits set as goals in the Paris agreement.
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On Monday afternoon, US Secretary of State Mike Pompeo announced that the Trump administration had sent official notification to the United Nations that the US is withdrawing from the Paris climate agreement.

That makes the US - the world's second-largest emitter of greenhouse gases, behind China - the only nation to attempt to exit the landmark climate accord. Because of processes established in the agreement, the exit will formally take place in one year, on November 4, 2020.

The Paris agreement, adopted on December 12, 2015, set international objectives to cut greenhouse-gas emissions in order to keep Earth's climate from warming more than 2 degrees Celsius by the year 2100.

In June 2017, President Donald Trump announced his intention to pull the US out of the agreement, suggesting that it "disadvantages the United States to the exclusive benefit of other countries."

But because the United Nations stipulated that no country that entered the agreement could exit for at least three years - and the accord didn't take effect until November 6, 2016 - Trump had to wait to take the promised action. This week, that process began.

Here's what the withdrawal really entails, and what could happen next.

What is the Paris climate agreement?

The Paris climate agreement is non-binding, voluntary pledge by more than 200 countries to reduce carbon emissions. Each country submitted its own plan in pursuit of this goal, but there are no legal ramifications for member nations that fail to meet their promised emissions cuts.

At the time, the US (under the Obama administration) pledged to cut its greenhouse-gas emissions to 26% below the 2005 level by the year 2025. Other countries committed to being carbon-neutral by 2050. Both the US' pledge and others were meant as baselines that would get ramped up over time.

However, a study by the non-profit Climate Action Tracker found that in aggregate, the Paris commitments fall woefully short; current pledges would result in a 3-degree-Celsius temperature increase.

Why does Trump want out?

Trump believes that the US' pledged emissions cuts put an "unfair economic burden" on American workers, businesses, and tax payers.

The Trump administration also does not want the US to be beholden to an international agreement about emissions cuts. In his announcement about the Paris agreement on Monday, Pompeo noted that the nation's greenhouse-gas emissions dropped 13% between 2005 and 2017 - evidence that the US is already tackling climate change.

Pompeo did not mention that US carbon emissions rose in 2018.

However, Andrew Steer, CEO of the World Resources Institute, said in a statement that the Trump administration is creating a false dichotomy between climate action and economic hardship.

"By withdrawing from the Paris agreement, the Trump administration is showing that it cares neither about science nor economics. It is driven by outdated views from the last century that held that climate action was costly and hurt jobs," Steer said.

This isn't the first time the Trump administration has worked to soften environmental regulations and commitments: The president also catalyzed rollbacks of the US Endangered Species Act and the Environmental Protection Agency's Clean Water Act.

Could the US rejoin the agreement later?

According to a Yale survey, 69% of American voters (including 51% of Republicans) disapprove of Trump's decision to pull the US out of the Paris agreement.

House Speaker Nancy Pelosi has described the move as a "disastrous decision that sells out our children's future."

Once the US formally exits the agreement on November 4, 2020 (a one-year waiting period to exit is stipulated in the agreement rules), American leaders would still be permitted to attend future climate negotiations, but as observers only. The agreement requires that member nations come together every five years to set more ambitious targets.

However, every Democratic presidential candidate running in the 2020 election has pledged to re-join the Paris agreement.

If one of those candidates wins the presidential election, the US would still formally withdraw from the agreement, since the one-year mark falls within Trump's presidential term. But a new president could re-join after taking office - it would only take 30 days for the US to re-enter the agreement after a new leader sends a request to the United Nations.

"Even if [Trump] follows through, it would take just 30 days for a new president to get us back in," former vice president Al Gore tweeted on Monday. "This decision is ultimately in the hands of the voters."

The executive branch of the European Union, which co-signed the Paris agreement, tweeted on Tuesday: "We regret the US notification to withdraw from the #Parisagreement. We worked side-by-side with our American friends to build the agreement in 2015 which is now in force. It is here to stay, its door remains open and we hope the US will decide to pass it again one day."

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