Thursday, September 15, 2011

New paper shows global sea level rise of only ~ 2.5 inches over past 36 years

Al Gore's "Climate Reality" stream featured Paul Higgins, Associate Director of the American Meteorological Society Policy Program, attempting to answer some basic questions such as "how much has the sea level risen in the past 50 years?" Higgins says he doesn't know, but it's "less than half a meter [~ 20 inches]." He was right that it was "less than" 20 inches - by a factor of 5.7 times. A paper published today in the journal Geophysical Research Letters finds that the sea-level rise from 1972 to 2008 measured by tide gauges was 1.8 mm/yr, equivalent to ~ 2.5 inches over the 36 year period; a rate of 3.5 inches per 50 years or 7 inches per century.

Reasons why tide gauges are more accurate than satellite altimetry
Satellite altimetry data alterations resulting in a false exaggerated trend here and here
Sea level rise is decelerating


Revisiting the Earth's sea-level and energy budgets from 1961 to 2008

John Alexander Church et al

We review the sea-level and energy budgets together from 1961, using recent and updated estimates of all terms. From 1972 to 2008, the observed sea-level rise (1.8 {plus minus} 0.2 mm yr-1 from tide gauges alone and 2.1 {plus minus} 0.2 mm yr-1 from a combination of tide gauges and altimeter observations) agrees well with the sum of contributions (1.8 {plus minus} 0.4 mm yr-1) in magnitude and with both having similar increases in the rate of rise during the period. The largest contributions come from ocean thermal expansion (0.8 mm yr-1) and the melting of glaciers and ice caps (0.7 mm yr-1), with Greenland and Antarctica contributing about 0.4 mm yr-1. The cryospheric contributions increase through the period (particularly in the 1990s) but the thermosteric contribution increases less rapidly. We include an improved estimate of aquifer depletion (0.3 mm yr-1), partially offsetting the retention of water in dams and giving a total terrestrial storage contribution of -0.1 mm yr-1. Ocean warming (90% of the total of the Earth's energy increase) continues through to the end of the record, in agreement with continued greenhouse gas forcing. The aerosol forcing, inferred as a residual in the atmospheric energy balance, is estimated as -0.8 {plus minus} 0.4 W m-2 for the 1980s and early 1990s. It increases in the late 1990s, as is required for consistency with little surface warming over the last decade. This increase is likely at least partially related to substantial increases in aerosol emissions from developing nations and moderate volcanic activity.

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