Ocean acidification: another problem with CO₂ emissions

We tend to measure time by the span of a human life, making a century seem like an era and a millennium a mega-stretch of time. In this perspective, a million years is an eternity. So it can be revealing to consider our place in geologic history measured in hundreds of millions of years.

This is what a group of researchers from the United States and four other countries did recently. They reviewed existing evidence on the impact of changes in the atmospheric concentration of carbon dioxide (CO₂), the main global warming gas, from decades of research on fossilized remains and other evidence from Earth’s geologic record.

Published earlier this month, their findings reinforce warnings from many climate scientists that the world’s oceans, a vital source of fish food protein, may be turning acidic faster today from human CO₂ emissions than they did during four major episodes of animal and plant extinctions in the last 300 million years, when natural surges of CO₂, probably from catastrophic volcanic eruptions or meteor strikes, sent global temperatures soaring.

Of the four episodes, the closest analogue for the present is what happened some 56 million years ago, a period known as the Paleo-Eocene Thermal Maximum (PETM), when oceans changed fast but not nearly as fast as today.

The scientific review suggests that acidification is now happening at least 10 times more quickly than during PETM, raising “the possibility that we are entering an unknown territory of marine ecosystem change.” For an ocean-oriented nation like Japan, where fish is such an important part of the national diet, this is a warning that should be taken seriously.


Michael Richardson, The Japan Times, 15 March 2012. Full article.

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