The Intergovernmental Panel on Climate Change (IPCC) estimates that sea levels will rise between 0.18 and 0.59 meters (0.59 to 1.9 feet) by 2099 as warming sea water expands, and mountain and polar glaciers melt. These sea level change predictions may be underestimates, however, because they do not account for any increases in the rate at which the world’s major ice sheets are melting. As temperatures rise, ice will melt more quickly. Satellite measurements reveal that the Greenland and West Antarctic ice sheets are shedding about 125 billion tons of ice per year—enough to raise sea levels by 0.35 millimeters (0.01 inches) per year. If the melting accelerates, the increase in sea level could be significantly higher.