Approximately 3 million years ago, during the Pliocene epoch, atmospheric carbon dioxide levels were similar to today. Global temperatures averaged about 2 to 3 degrees Celsius above pre-industrial levels (a temperature increase we’re on track for in coming decades, unless we significantly reduce global greenhouse gas emissions). And the global mean sea level was upward of 65 feet higher than present, thanks to ice melt. That’s right: 65 feet higher, an increase that would submerge most of the state of Florida, and nearly all of New York City.
