I recall years ago though reading a debate between a peak oil "doomer" and someone saying climate change was the bigger problem. The latter kept saying we have more oil at higher prices and that the real problem is we have "enough carbon to destroy the world." If we really got desperate and decided we didn't want Florida we could do deep in situ conversion of massive conventionally unreachable reserves of very deep coal into gas ("water gas reaction"), then liquids. That could, he said, keep our liquid based transport economy going for thousands of years but would send Earth back to the Permian.