From: https://www.esquire.com/news-politics/a25422366/trump-ambass...
"The fourth and latest National Climate Assessment put together by 300 scientists from 13 agencies of the U.S. government and released last month found that climate change is real, man-made, and will cost the U.S. 10 percent of its economy by 2100. Midwestern farmers will lose 75 percent of their crop yields, and trillions of dollars in coastal real estate will be at risk. The wildfires out west, already unprecedented in their destruction, will get worse. Hurricanes and typhoons will grow more ferocious. Epidemic diseases will flourish."
And that's just for the US. Large portions of Africa and the Middle East are predicted to become uninhabitable. The threat to human life on a time-scale of 100 years or more is gargantuan.