If this happened very, very slowly, there's a good chance we could adapt. After all, the geological record shows lots of climate changes and the animals and plants evolved to adapt to the new environment. The problem is the rate of change. Climate change is happen at a fast (geologically speaking) rate already and we're making it faster, not slower. The real question is whether we, as a species, can adapt to the changing climate at the rate we're causing the climate to change. Sure, everyone in a low-lying coastal area could be relocated to higher ground over time. Can you relocate New York City, London, most of the Boston-Atlanta metropolitan axis, about half of India, and who knows how much of China to higher ground as fast as the storms are flooding places? Who's going to accept the refugees from NYC or Miami Beach? Where are we going to house them. Who's going to pay for all this? Same story for crops. If the Salinas Valley becomes too dry for farming, there might be somewhere else in the world that opens up. How do you get the infrastructure there as fast as we need it to happen so worldwide food production doesn't dip for a decade or more? Where's the infrastructure come from? How are you going to move all the people to the new place? What do you do with all the people who are already there? Who pays for this?
The last question is really the big one. We're living in a world crippled by debt, facing declines in energy affordability, with only higher costs in the future. How are we going to pay for the massive global upheaval required to adapt to a warmer climate as fast as we're causing that climate to change?