MANAUS, Brazil — Joe Biden on Sunday became the first sitting American president to set foot in the Amazon rainforest, as the incoming Trump administration seems poised to scale back the U.S. commitment to combating climate change. The massive Amazon, which is about the size of Australia, stores huge amounts of the world’s carbon dioxide, a greenhouse gas that drives climate change when it’s released into the atmosphere. But development is rapidly depleting the world’s largest tropical rainforest. Joined by Carlos Nobre, a Nobel-Prize winning scientist and expert on how climate change is impacting the Amazon, and Biden climate adviser