Sea Level
Rising Sea Levels Affect Millions Around the World, and Billions of Dollars in Property
Sea level is rising and the rate of change is accelerating. The combination of warming ocean water expanding and rapidly increasing melt of land and polar ice has increased the rate of sea level rise from about 6.8 inches average during most of the 20th C to a current rate of 12 to 14 inches per century. Based on this increase in rate of change, scientists are estimating that by the end of this century, the oceans will be from 20 inches to more than three feet higher -- and increasingly the higher levels seem probable.
“The big gorillas in terms of sea level are Greenland and Antarctica,” polar glacier scientist Eric Rignot told Gary Braasch for his book Earth Under Fire. “The response of those ice sheets to climate warming will be bigger than predicted.” Also, studies of many other past climate records show that at no time in the past 800,000 years, and perhaps much longer, has the CO2 concentration been as high as the present 387 parts per million (ppm). Jonathan Overpeck and coworkers, who figured out the temperatures during the last interglacial period, calculate that a continued increase in CO2 levels this century could bring us to a temperature equal to that which existed 130,000 years ago. At that time sea level rose several meters, fed by Greenland meltwater.
Sea level is measured now not only by direct tide gauges, but by an array of satellites which measure the height of the open ocean where no tide gauges could be placed.
In the United States, said a report by the U.S. Climate Change Science Program in January 2009, "rising sea levels are submerging low lying lands, eroding beaches, converting wetlands to open water, exacerbating coastal flooding, and increasing the salinity of estuaries and freshwater aquifers." Four of the top 20 cities with populations and infrastructure assets most exposed to increasing sea level and storm damage are in the United States: New York, Virginia Beach, Miami and New Orleans (study by Robert Muir-Woods and colleagues; see first link, above. Other cities listed in this study are Amsterdam, Rotterdam, Alexandria, Mumbai, Kolkata, Ho Chi Minh City, Bangkok, Guangzhou, Shenzhen, Hong Kong, Ningbo, Shanghai, Tianjin, Osaka, Tokyo and Nagoya).
World View of Global Warming has been documenting these changes since 1999, and in March 2010 we completed a re-photography expedition to North Carolina, Florida, and parts of Chesapeake Bay.
Warming Winds, Rising Tides: Florida and the Atlantic Coast
The entire coast of Florida is threatened by rising seas and stronger surges during storms, which is already having high economic costs. Looking ahead only 40 years, a study in 2007 by Tufts University and the Stockholm Environment Institute—US Center estimated that Florida’s average annual temperatures will be 5º F higher than today in 2050. Sea-level rise will reach 23 inches by 2050, and 45 inches by 2100. Maps in the report show an approximation of Florida’s coastline at 27 inches of sea-level rise, which is projected to be reached by around 2060 if little action is taken to control greenhouse gases.
