Monday, July 23rd 2012, 5:04 PM EDT
Surely someone would have seen this coming?
The last interglacial period (LIG)—the Eemian—is commonly believed by scientists to have been warmer than the current Holocene interglacial. Along with that balmier climate there is evidence that sea levels were significantly higher than today. Previous studies have pegged Eemian sea levels at 4 to 6m higher than today. Recently, a new investigation raises that estimate, reporting that ancient sea levels peaked between 6.6 and 9.4 m (~20 to 30 feet). Modern day accounts of flooding in low lying coastal areas and tropical islands abound, with ominous suggestions of links to global warming. How high the oceans will rise is a topic of debate for IPCC members, the news media and assorted climate alarmists, but they are asking the wrong question. Instead, they should ask why are sea levels so low?
Perhaps no speculative outcome of anthropogenic global warming (AGW) is more threatening than a significant rise in sea level. Given that most of Earth's human population lives in littoral regions, the prospect of flooded cities and millions of refugees fleeing inundated coastal plains is a threat that strikes fear in the hearts of people everywhere. Predicting future sea-level rise requires an understanding of various climate conditions and potential ice-sheet instability. Unfortunately, efforts to accurately forecast the rising and falling of sea levels have proven inadequate. To try and gain some insight into the mechanisms at work, scientists have been studying the warm period prior to our own—the Eemian interglacial that occurred ~125,000 years ago.
In a report in the July 13, 2012, edition of Science, A. Dutton and K Lambeck present a new assessment of Eemian sea levels based on a a new global database of U-Th ages and elevations of fossil corals. In “Ice Volume and Sea Level During the Last Interglacial,” the authors argue that during the previous warm period significantly more Antarctic ice must have melted to generate the calculated ancient sea levels. Here is the article’s abstract, which sums up their findings nicely:
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During the last interglacial period, ~125,000 years ago, sea level was at least several meters higher than at present, with substantial variability observed for peak sea level at geographically diverse sites. Speculation that the West Antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice-sheet dynamics during this time interval. We provide an internally consistent database of coral U-Th ages to assess last interglacial sea-level observations in the context of isostatic modeling and stratigraphic evidence. These data indicate that global (eustatic) sea level peaked 5.5 to 9 meters above present sea level, requiring smaller ice sheets in both Greenland and Antarctica relative to today and indicating strong sea-level sensitivity to small changes in radiative forcing.
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