GLOBAL SEA-LEVEL RISE: SHOULD I SELL MY SHORE HOUSE?

Rising sea level poses a threat to coastal communities, yet the extent of this threat is often exaggerated in the media, from an “Inconvenient Truth” to the New York Times, scaring citizens into thoughts of a real estate exodus. Recent studies have documented that sea level is rising today at 3.3±0.4 mm/y, accelerating from a 20th century rise of 1.8±0.3 mm/y. We show that the maximum global rate of rise prior to 1850 was 0.5-1.0 mm/y and thus can attribute <<30% of the modern rise to natural causes. By 2100, the IPPC best estimate is that global sea level will rise by at least 40 cm (1.2 ft). However, this is not a reason to flee the beaches in panic; Atlantic City saw 40 cm of rise in the 20th century. Most regions will also see additional relative rise due to subsidence, ranging from 10-20 cm along the U.S. east coast to over a meter in southern Louisiana and Bangladesh. In the latter cases, regionally high subsidence rates are the prime concern, not global rise due to warming. The most important effects of sea-level rise in the next century will continue to be its exacerbating influence on coastal storms, the loss of marshlands, and the continued costs to fight the inexorable march back of the beaches. But we note the following concern: Rahmsdorf et al. (2007) show that we are tracking at the high end of the IPCC estimates and conclude that 80 cm (2.4 ft) is the most likely global rise by 2100. This higher rate of rise is a major concern: it will result in loss of land (1-3% of the U.S. east coast), loss of marshland, higher beach erosion, and high costs to society. A major unknown is that the upper limit of 80 cm of rise by 2100 is not well constrained. If the rate of Greenland melting continues to increase, it is possible that the global rise by 2100 will exceed 80 cm. In that case, higher ground is preferred.