U.S. President Barack Obama arrived at Joint Base Andrews in Maryland on Sunday from Brisbane, Australia where he attended the G20 summit.
During the meeting, Obama pledged up to $3 billion to the United Nation's Green Climate Fund (GCF) which helps poor nations cope with global warming.
G20 leaders put a spotlight on climate change despite efforts by host Australia to focus more narrowly on economic growth.
Last week, the United States and China set goals for curbing climate change.