Even if the entire United States were to adopt 100% eco-friendly practices, or stop existing entirely, it wouldn't dent the global carbon footprint. Your facts are irrelevant if they can't be put into practice. There is no practical solution. Catastrophe is inevitable, because most of the Eastern world is in the process of massive industrialization. You can't stop that. Migrants and wars and food shortages don't affect those with high enough profit margins to sustain themselves in a high rise penthouse.
This doesn't make the person you were replying to correct, but it makes the whole argument irrelevant in the first place. What people should be worrying about is how to sustain their own lives after the effects start to really settle in.