Monday, June 25, 2012

National Research Council Releases New Report That Estimates Higher Rates Of Sea Level Rise Than Previously Reported

A report released Friday June 22, 2012 by the National Research Council projects that the sea level off most of California is expected to rise about one meter over the next century, an amount slightly higher than projected for global sea levels, and will likely increase damage to the state's coast from storm surges and high waves.  

The report presents data indicating that global sea level rose during the 20th century, and provides estimates that it will rise at a higher rate during the 21st century.  A warming climate causes sea level to rise primarily by warming the oceans -- which causes the water to expand -- and melting land ice, which transfers water to the ocean.  However, sea-level rise is uneven and varies from place to place.  Along the U.S. west coast it depends on the global mean sea-level rise and regional factors, such as ocean and atmospheric circulation patterns, melting of modern and ancient ice sheets, and tectonic plate movements.   

Among its key findings, the committee that wrote the report projected that global sea level will rise 8 to 23 centimeters by 2030, relative to the 2000 level, 18 to 48 centimeters by 2050, and 50 to 140 centimeters by 2100.  The 2100 estimate is substantially higher than the United Nation's Intergovernmental Panel on Climate Change's projection made in 2007 of 18 to 59 centimeters with a possible additional 17 centimeters if rapid changes in ice flow are included. 

For the California coast south of Cape Mendocino, the committee projected that sea level will rise 4 to 30 centimeters by 2030, 12 to 61 centimeters by 2050, and 42 to 167 centimeters by 2100.  For the Washington, Oregon, and California coast north of Cape Mendocino, sea level is projected to change between falling 4 centimeters to rising 23 centimeters by 2030, falling 3 centimeters to rising 48 centimeters by 2050, and rising between 10 to 143 centimeters by 2100.  The committee noted that as the projection period lengthens, uncertainties, and thus ranges, increase. 

Interestingly, the committee noted that tectonic activity may also be a factor in predicting impacts of sea level rise on the west coast.  For instance, the committee's projections for the California coast south of Cape Mendocino are slightly higher than its global projections because much of that coastline is subsiding, exacerbating the effects of rising waters.  The lower sea levels projected for northern California, Washington, and Oregon coasts are because the land there is rising.  In this region, the ocean plate is descending below the continental plate at the Cascadia Subduction Zone, pushing up the coast. 

The study was sponsored by the states of California, Washington, and Oregon; National Oceanic and Atmospheric Administration; U.S. Geological Survey; and U.S. Army Corps of Engineers.  More information and a link to the entire report can be found on the National Academy of Sciences website by clicking here.

If you have any questions concerning this topic, please contact Hanspeter Walter from our office, or the KMTG attorney with whom you normally consult.

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