Kommentar till artikel om avsmältningen av Antarktis is i julinumret 2012 av Scientific American

Efter en tids frånvaro är jag åter tillbaka.

I julinumret av Scientific American skrev frilansskribenten Douglas Fox artikeln ”Witness to an Antarctic meltdown”. Artikeln är dramatisk och underhållande och vore antagligen OK i en kvällstidning. Men man hissnar över att sådant kan publiceras i Scientific American. Min replik kommer nedan :

Douglas Fox article about receding glaciers and ice shelves in Antarctica contain some spectacular descriptions. It seems, however, as if the author has been carried away in his descriptions of the uniqueness of the events which is not what one expects from a scientific magazine like SA.  

 Firstly, I happen to be located on a place where the earth’s crust is “springing back” right now by 0,5 cm per year. Not as a result of a recent glacial retreat but rather from an extremely massive glacier that rapidly disappeared 10,000 years ago. That the glacial rebound is still so large after 10,000 years is a telltale sign on how massive this meltdown was and how quickly the glacier retreated (and that the reported observation was not all that special). This glacier over northern Europe was much, much larger than the minute ones in the Antarctic peninsula – rather more a good fraction of the size of the entire Antarctic ice sheet. Massive and quick meltdowns of huge glaciers is thus nothing new (but certainly spectacular). The associated ice shelves, although not known in detail, were presumably much more impressive than the Larsen ones and there is a good chance that the disappearance of some of these shelves were witnessed somewhere by humans thereby contradicting the preamble of the article.

 Then I don’t understand the mathematics of the disintegration of the Larsen B shelf as described in the article. We are told that it was 55 times larger than Manhattan (=3000 km2) and that whales could be seen in places “…where the ice was 300 m thick…”  which I assume is a representative thickness (and not a deliberate exaggeration). The total volume is then 900 km3 of ice. The volume of the Empirate State Building, an unusually large skyscraper, is about 1 million m3 or 0.001 km3. The Larsen B shelf should thus have to be broken up into about 1,000,0000 pieces of skyscraper size. In the text we are told that it “disintegrated into hundreds of shards the size of skyscrapers”, almost 10,000 times too few! Please, these exaggerations serve no other purpose than strengthening the feeling of sceptics that conventional (or even minimal) scientific honesty is not applied when it comes to climate change.

Steven Jörsäter

Stockholm, Sweden

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