A study published in Nature Geoscience by researchers, from Imperial College London and their academic partners shows that 5-3 million years ago in the Pliocene, the last time it was as hot as it is going to be in this century, antarctic ice shelf melting caused a sea level rise of as much as 20 meters (65 feet).
At 65 feet sea level rise, we basically lose Louisiana and most of Florida, according to this useful intractive map:
In both cases, the warming was caused by the hothouse gas carbon dioxide, which traps the heat of the sun in earth’s atmosphere and prevents it from radiating back out to space. (Venus is a torrid hell with rivers of molten lead because it has a lot of hothouse gases in its atmosphere). In past times, C02 built up over millions of years because of volcanic activity. In our time, we are conducting a massive experiment on ourselves by running up parts per million of carbon in the atmosphere from 287 in the 18th century when the United States was founded, to 400 ppm today; we are rapidly going toward 450 and even 500 ppm, which could destabilize the climate and endanger human life on earth. Coal plants, natural gas plants, and burning petroleum to fuel vehicles are the major sources of C02, i.e. we are doing this to ourselves.
Although we will like go to a 4 degrees C./ 7.2 degree F. increase in this century, the full effects of it won’t be felt for centuries. Note that that is a higher concentration than in the Pliocene! In this century we will likely see 4 to 5 feet sea level rise if we go on like we are now. dumping the raw sewage of C02 into our air in amounts of 35 billion metric tons annually.
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