The big news for the environment today is whether or not President Trump is planning on pulling the U.S. from the Paris accord or not.

But what is the Paris Accord, and what does it mean to withdraw? Let’s take a look. The Paris Accord was an agreement negotiated within the UN Framework Convention on Climate Change between 195 countries to make an effort to try and combat climate change. It was negotiated in Paris in November and December of 2015. It went into effect on 4 November 2016. 147 countries had ratified the agreement as of last month, including the U.S.

Nations Following Paris Climate Change Agreement Commit To Cut CO2

The key elements of the deal are to keep global temperatures less than 3.6F (2.0C) above what they were in pre-industrial times and to limit the greenhouse gases emitted by human activity to the level that trees, soil, and oceans can absorb. That temperature limit is set at a level that scientists say can prevent dangerous and irreversible levels of climate change. The agreement sees countries committing to reduce emissions, and for more wealthy countries to help developing countries financially to meet their own goals.

Under the Obama Administration, the U.S. set a goal of reducing greenhouse gas emissions by 26 to 28 percent from 2005 levels by 2025. President Obama signed the agreement in April last year, but by executive order, not through the Senate. That is why President Trump has the option to either continue in the accord or back out.

So what does it mean if the U.S. withdraws from the accord? It could hurt the country’s image internationally. There are 194 other countries in the agreement, so a withdrawal puts the US in a group with countries like Syria that aren’t participating. It could also significantly impact the climate. The U.S. has one of the highest levels of carbon emissions and had committed to one of the largest reductions. The loss of that commitment would make it more difficult for the rest of the world to make a meaningful impact.

President Trump has said that combatting climate change costs American business trillions of dollars. He has tweeted that “the concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive.”

President Trump has announced that he will make his decision on the Paris accord at 3 pm eastern time today.