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Current Carbon Levels Driving Ocean Acidification at the Fastest Rate in 3 Million Years

“The world’s oceans are turning acidic at what could be the fastest pace of any time in the past 300 million years, even more rapidly than during a monster emission of planet-warming carbon 56 million years ago,” as reported by “Scientific American” from the March 2012 “Science” journal .

“Oceans get more acidic when more carbon gets into the atmosphere. In pre-industrial times, that occurred periodically in natural pulses of carbon that also pushed up global temperatures, the scientists wrote.”

“The events that seemed similar to what is happening now included mass extinctions about 252 million and 201 million years ago, as well as the warming period 56 million years in the past.”

“The researchers reckoned the 5,000-year hot spell 56 million years ago, likely due to factors like massive volcanism, was the closest parallel to current conditions at any time in the 300 million years.  During that span, the amount of carbon in the atmosphere doubled and average temperatures rose by 10.8 degrees F (6 degrees C), the researchers said. The oceans became more acidic by about 0.4 unit on the 14-point pH scale over that 5,000-year period, the researchers said.”

“That is a fast warm-up and a quick acidification, but it is small compared with what has happened on Earth since the start of the industrial revolution some 150 years ago, study author Baerbel Hoenisch of Columbia University’s Lamont-Doherty Earth Observatory said.”

“During the warming period 56 million years ago, known as the Paleocene-Eocene Thermal Maximum, or PETM, and occurring about 9 million years after the extinction of the dinosaurs, acidification for each century was about .008 unit on the pH scale, Hoenisch said.”

“By contrast, in the 20th century, oceans acidified by .1 unit of pH, and are projected to get more acidic at the rate of .2 or .3 pH by the year 2100, according to the study.”

“Those skeptical of human-caused climate change often point to past warming periods caused by natural events as evidence that the current warming trend is not a result of human activities. Hoenisch noted that natural causes such as massive volcanism were probably responsible for the PETM. She said, however, that the rate of warming and acidification was much more gradual then, over the course of five millennia compared with one century.”

For the “Science” study in its entirety, visit The Geological Record of Ocean Acidification

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