Where are the effects of global warming already having a major impact? In places like South Florida and especially Miami, which faces major long-term threats from a slow but stealthy adversary: sea level rise. In this region, sea levels already have risen by about a foot since 1880. By the end of this century, according to the latest assessment report from the Intergovernmental Panel on Climate Change, they're expected to rise by another 1 to 3 feet, and possibly as high as 5 to 6 feet. This poses dire threats to Miami's fresh water supplies, which already are being affected...