The cost of the warming planet will not be just that of building seawalls or moving coastal towns or irrigating desertified croplands or keeping salt out of groundwater. It will also be the cost of handling mass migrations from zones, sometimes whole nations, that have become uninhabitable.
People on dangerous boat crossings from Morroco to Spain, or coming from C.America to seek admittance at our southern border, is just a gentle sprinkle compared to the deluge to come. Building catchment basins and reservoirs in Guatemala is a better investment of our money than giant walls.
I live in a state that's noted for getting over 70% of its power from renewable energy sources (wind, hydro). How long will that last if everyone here, in a state where many homes don't have or need central AC, decide they need it as summers become more like, say, Oklahoma summers? We could handle that shift with more windfarms (we always have plenty of wind), if we start planning for that now and don't let the fossil fuel boosters be the loudest voices.
This pinpoints the vicious circle in states where fossil fuel reigns for electricity production:
1. We burn fossil fuels to cool our houses.
2. The climate gets hotter due the resulting carbon pumped into the atmosphere. So...
3. We burn more fossil fuels to cool our houses.