Reasoning:

• Donald Trump made these remarks during his address to the United Nations General Assembly on September 23, 2025¹².
• PBS NewsHour reported the exact phrasing: "It's the greatest con job ever perpetrated on the world, in my opinion," as part of his speech disparaging climate science and UN predictions².
• Columbia University's Sabin Center for Climate Change Law also documented Trump calling climate change "the greatest con job ever perpetrated on the world" during that same UN speech¹.
• ABC News fact-checked the speech and reported Trump calling it "the greatest con job perpetrated by the world," a slightly different but clearly matching version of the same quote³.
• Multiple independent, credible sources confirm the attribution and context of the statement.

Overall validity: 95%

1. President Trump Makes Several False Statements about Climate Change at UN | Sabin Center for Climate Change Law
2. WATCH: Trump calls climate change ‘the greatest con job ever perpetrated on the world’
3. Fact-checking what Trump said about climate change during the UN General Assembly - ABC News