National Geographic August 27, 2013 Oceans Levels Are Getting Higher. Can We Do Anything About It? I f e s 3 4 , , d . 50min:nceitio*.olt, vs. Fwd. WOW* hpe tun , ak,o el a (St," 0 Idectes135milmee,gio /me noree" '9O, Tht rock Irate clotO•effingt pas trosaVs al coal ans. weVaiw. Mtn rwearrg incitec lox; n 2004., era tn•Nitifwaalmaolts.2040, tetl,ec<4., Core samples, tide gauge readings, and, most recently, satellite measurements tell us that over the past century, the Global Mean Sea Level (GMSL) has risen by 4 to 8 inches (to to 20 centimeters). However, the annual rate of rise over the past 20 years has been 0.13 inches (3.2 millimeters) a year, roughly twice the average speed of the preceding 8o years. Over the past century, the burning of fossil fuels and other human and natural activities has released enormous amounts of heat-trapping gases into the atmosphere. These emissions have caused the Earth's surface temperature to rise, and the oceans absorb about 8o percent of this additional heat. The rise in sea levels is linked to three primary factors, all induced by this ongoing global climate change: Thermal expansion: When water heats up, it expands. About half of the past century's rise in sea level is attributable to warmer oceans simply occupying more space. Page I 1 of 2 EFTA01114028