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Last Time Oceans Acidified as Fast as Today was 56 Million Years Ago
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| The Financial Express (New Delhi) , Monday, March 05, 2012 |
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| Our oceans acidified by 0.1 unit of pH through the 20th century, and it is estimated that they will acidify by another 0.2-0.3 pH in this century. In order to understand the impact of future acidification by looking at past examples, a group of American, British, Dutch, German and Spanish researchers reviewed geological studies of the past 300 million years, finding the closest parallel in the Paleocene-Eocene Thermal Maximum period about 56 million years ago. Further, they delved into fossils from the period buried under the Southern Ocean off Antarctica. Their findings, funded by the US National Science Foundation and published in last week’s edition of Science, are that when the oceans became more acidic by about 0.4 unit over a 5,000-year period back then, it was enough to push as many as half of all species of seabed-dwelling single-celled creatures to extinction, thereby sharply diluting the ability of the oceans to absorb atmospheric carbon dioxide—they absorb about a third today. Although the researchers underline that no past event can perfectly parallel future projections, if a gradual acidification spread over five millennia instead of a century was so impactive, there is definite cause for concern about ongoing disruptions in ocean carbonate chemistry.
Climate change sceptics often look for their evidence in the zigzag nature of scientific reports, and in the fact that human civilisation has evolved over many natural, cataclysmic cycles. After all, we don’t know exactly what mix of tectonic upheavals, volcanic activity and comet impact caused the carbon overload 56 million years ago. Yet here we are, where we weren’t. But surely there’s a monumental difference between a hedonistic experiment and being haplessly sucked into ‘a wholesale rearrangement of life’ by Nature.
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