In an appearance on CBS’s “Face the Nation” on Earth Day, Bloomberg said he would give $4.5 million of his personal fortune towards the U.S.’s pledge of up to $3 billion by 2020 to support climate change initiatives. Only $1 billion of that had been paid when the U.S. withdrew from the deal. His net worth is an estimated $50.9 billion. Bloomberg said that all Americans share the responsibility to uphold deals the government makes, and that since he is able to, he would send a check to the organization as though nothing had changed.

The Paris climate agreement is the first to unite all of the world’s nations in a single accord to fight climate change. The U.S.’s withdrawal last year made it effectively the only nation in the world that is not a participant.

One estimate indicates that without the resources committed by the U.S., the globe will see an additional 0.3 degree Celsius rise in global temperature by 2100.

The $4.5 million pledge from Bloomberg will not make up the entire shortfall from the U.S.’s departure. Bloomberg’s foundation, Bloomberg Philanthropies, and several partners have been working together to collect the country’s full contribution and significantly reduce emissions at home by 2025 through an organization called America’s Pledge.

There are some indications that Trump may decide to re-enter the deal if it were amended to be more favorable to the U.S. Bloomberg told CBS the president should “change his mind” on the deal.