What is the Paris agreement?

The Paris Agreement is a deal reached between 195 countries to gradually reduce emissions that cause climate change in order to prevent a major increase in the global temperatures that could raise sea levels, spark major droughts, and lead to more dangerous storms. The agreement, which was negotiated in 2015 and took effect in November 2016, was spurred by the overwhelming global scientific consensus that rising global temperatures over the last several decades are caused by man-made activity. The United Nations Intergovernmental Panel on Climate Change, which pools scientific research from around the world, concluded that emissions caused were "extremely likely to have been the dominant cause of the observed warming since the mid-20th century" with more than 95 percent confidence. Climate change is already impacting the planet, but the specific goal of the Paris Agreement is to prevent the planet from warming by more than 2 degrees Celsius (3.6 degrees Fahrenheit), which scientists warn could have especially damaging consequences.

What does the U.S. have to do?

The agreement, which is not a binding treaty, calls on countries to make voluntary national pledges to reduce emissions and provide periodic updates on their progress. President Barack Obama committed America to a goal of lowering emissions by 26 percent to 28 percent below 2005 levels by 2025. These targets aren't fixed forever, though, and the broad aim is to increase them over time. The agreement also hinges on developed countries like the United States, whose economies have contributed more emissions historically, helping to finance developing countries' transition to cleaner forms of energy. The plan is to raise $100 billion a year through a mix of public and private sources. On the U.S. side, Obama transferred $1 billion out of an initial $3 billion commitment to the United Nations Green Climate Fund before leaving office. But the recent spending deal in Congress, which funds the government through September, left out any contributions to the fund.

Why would Trump want out?

There are a number of aspects of the climate deal that run counter to the president's worldview. One, Trump does not accept the dominant scientific consensus on climate change and has a penchant for conspiracy theories that cast experts like researchers, doctors, or government agencies in the role of villain. He has repeatedly tweeted and said in campaign speeches that climate change is a "hoax" and even suggested that China — another frequent Trump target — was behind the plot. Trump later said the accusation was a joke, but he has said he doesn't believe China will follow through on its promises to reduce their use of fossil fuels. Two, Trump is a skeptic of international agreements and institutions in general, which he often complains tie America down with obligations that don't provide enough concrete benefits in return. In addition to the Paris Agreement, Trump has rattled allies by criticizing trade agreements and military alliances. Three, Trump is not a fan of the regulations and spending that the previous administration proposed to meet its goals, which he warns will reduce economic growth. He appointed a prominent climate skeptic to run the Environmental Protection Agency, Scott Pruitt, and is rolling back the Obama administration's Clean Power Plan, which was set to reduce power usage by coal plants in favor of cleaner forms of energy. Trump campaigned on reviving the coal industry and has expressed displeasure with some forms of renewable energy, especially wind. These objections aren't unique to Trump. Many conservatives opposed the Paris Agreement on similar grounds and have pushed him to withdraw.

What happens if the US withdraws from the agreement?