Rising Seas

RISING SEAS

Sea level didn’t change much for nearly 2,000 years, judging from sediment cores. It began to rise in the late 19th century, as Earth started to warm. If sea level continues to track temperature, it could rise three feet or more by 2100. The great unknown: the future of the ice sheets. NOAA’s four scenarios, shown here, span the range of possibilities for 2100. The sea will keep rising after that.

Local measurements of sea level with tide gauges became common after 1880; satellites began global measurements in 1992. They’ve shown a clear acceleration: At an eighth of an inch a year, sea level is rising twice as fast as it was a few decades ago.

LAWSON PARKER, NGM STAFF. SOURCES: JOSH WILLIS, NASA/JPL; JOHN CHURCH AND NEIL WHITE, COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION; ANDREW KEMP ET AL., 2011; R. STEVEN NEREM et aL., 2010; NOAA