It could be a very warm 21st Century:
By the 2060’s, if carbon-cycle feedbacks prove to be strong, the world could be 4°C warmer, and 40 to 70 percent of assessed species could be headed irreversibly toward extinction. And by the end of the century, my grandchildren and great grandchildren will live in a world where sea levels could be between three and seventeen feet higher than they are now. The abandonment of many of the world”s great cities will be well underway.