Michael Bloomberg says he'll pay $4.5 million to help fulfill the U.S.' commitment to the Paris climate agreement.
The agreement was struck while President Barack Obama was in office, and 195 countries committed to reducing their carbon emissions.
But President Donald Trump announced last year that the U.S. would be withdrawing from the agreement, citing an unfair burden on the U.S.
Bloomberg has been a vocal advocate for the Paris accord. He helps lead a group of state and local institutions from all over the country in an effort to make sure the U.S. meets its emissions goals, even if it's not formally part of the accord.