Global Sea-level Rise: Faster than Ever?

sea levelIn yet another instance of the media jumping on the climate alarmist bandwagon, The New York Times this past February boldly headlined “Seas Are Rising at Fastest Rate in Last 28 centuries.” The article went on to proclaim “the worsening of tidal flooding in coastal communities is largely a consequence of greenhouse gases from human activity, and the problem will grow far worse in coming decades, scientists reported Monday.”

“Worsening tidal flooding”—“grow far worse”—scary words for coastal inhabitants, but do they help the reader understand what the two reports (here and here) actually said? More importantly, do they help the reader evaluate what was reported? Or does the NYT wording continue the intellectually shallow but emotionally potent sea-level terror theme of Al Gore’s movie, An Inconvenient Truth?

The two reports published in the Proceedings of the National Academy of Science (PNAS) made several claims. During pre-industrial history (prior to 1860), global sea level rose at an average rate of 0.1 to 0.3 mm/yr. From 1860 to 1900 it rose at an average rate of 0.4 mm/yr, and from 1900 to the present it has been rising at 1.4 mm/yr. The studies project for various hypothetical CO2 emission-increase scenarios during this 21st century a total rise in global sea level between 1 ft and 2.5 ft.

First, observe that “tidal flooding” is not the same as the spectacular “storm-surge” that accompanies severe coastal storms like Sandy or the fictionalized surge in the 2004 apocalyptic sci-fi film The Day After Tomorrow. Such surges can easily exceed the reports’ estimated increase in tidal flooding by ten times or more. You probably wouldn’t know that from media stories like the NYT piece. Mitigation of known storm surge damage could protect coastal communities from the worst guesses of sea-level rise for the rest of this century!

Second, forecasting sea-level rise involves even more guesswork than forecasting global warming. Actual sea-level direct measurement data exist only for a century and a half and only for a few regions of the earth. Even in the world’s best documented region, the eastern North Sea and Baltic region, tide-gage records of sea-level measurement are less than 200 years old. Estimates of sea-level changes over 28 centuries necessarily rely upon layers of interpretation of various proxies such as evidence of shoreline changes. Extensive modeling, therefore, is required as the two PNAS papers demonstrate. Each model element to some degree has to involve guesswork. Resulting estimates of sea-level rise rates vary from 1.15 mm/yr to about 3 mm/yr—a considerable variation for any long-term projections.

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Comments (4)

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    In a somewhat similar story, Lake Michigan has risen nearly 4 feet since January 2013, approaching the record high of 1986. During the early 2000’s very low water levels were blamed on the evaporative effects of… you guessed it…GLOBAL WARMING…

    The Gore-like doomsday predictions for Lake Michigan at the time had the place reduced to a mere puddle by the end of this century… Whoops!

    And the last time I checked, melting glaciers had very little effect on the Great Lake’s water levels.

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    Who would deny the fish a little happiness ?
    It must be upsetting to have those waterfront property owners worrying about moving their
    pool furniture an inch or so every 10 years .

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    Interesting that the study cites sea levels up to 2,800 years ago. They nicely picked the Minoan Warm Period, which was likely warmer than today. The solar output seen in the current “Modern Warm Period” is probably a close second to the warming seen during the Minoan Warm Period.

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