President Donald Trump dismissed climate change as “the greatest con job” in the world during his address to the United Nations General Assembly on Tuesday, doubling down on his skepticism of global environmental initiatives and multilateral institutions.

Scientists say climate change is real, mostly caused by humans, and getting worse. They point to rising temperatures, stronger storms, and melting ice as clear signs. Groups like the UN have warned that waiting too long to act could cause serious damage to the planet and people.