President Donald Trump on his first day in office again withdrew the U.S. from a landmark global pact to fight climate change. So what is the Paris Agreement? And what happens to it now?

The Paris agreement is a mostly voluntary climate pact originally written to both try to reduce warming and withstand the changing political winds in the U.S.

Trump’s day-one actions on energy come as climate change-fueled fires ravage Southern California, following the globe’s hottest year on record.