250 feet (76 meters)

Despite uncertainties in reserve sizes, it is clear that if we burn all the fossil fuels, or even half of the remaining reserves, we will send the planet toward an ice-free state with sea level about 250 feet higher than today. It would take time for complete ice sheet disintegration to occur, but a chaotic situation would be created with changes occurring out of control of future generations.
James Hansen in Inside Climate News, 15 Jul 2009