Global warming reports, NOAA data, but wait?

yes, the warming has been happening for some time. we've been adding CO2 since the early 1800's. I do not understand 'all' underwater. If sea levels rise by 20 feet, coasts will change but I doubt that the world will be under water. The effect since the 1920 has been about 20 centimeter ( 5 inches) not enough to put a city under water..