Study: Oceans turning acidic at fastest pace
Source: Agencies |
March 3, 2012, Saturday
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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, according to researchers.
Looking back at this bygone warm period in Earth's history could offer help in forecasting the impact of human-spurred climate change, scientists said.
Quickly acidifying seawater eats away at coral reefs, which provide habitat for other animals and plants, and makes it harder for mussels and oysters to form protective shells.
The phenomenon has been a top concern of Jane Lubchenco, the head of the United States National Oceanic and Atmospheric Administration, who has conducted demonstrations about acidification during hearings in the US Congress.
Oceans get more acidic when more carbon gets into the atmosphere. In pre-industrial times, this occurred periodically in natural pulses of carbon that also pushed up global temperatures, the scientists wrote in the journal Science.
Human activities, including the burning of fossil fuels, have increased the level of atmospheric carbon from about 280 parts per million at the start of the industrial revolution to 392 parts per million now. Carbon dioxide is one of several heat-trapping gases that contribute to global warming.
The researchers viewed the 5,000-year hot spell 56 million years ago, likely due to factors like massive volcanism, as 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 6 degrees Celsius, 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's a fast warm-up and a quick acidification, but it's small compared to 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 (PETM) and occurring about 9 million years after the extinction of the dinosaurs, acidification for each century was about 0.008 unit on the pH scale, Hoenisch said.
Back then, many corals went extinct, as did many types of single-celled organisms that lived on the sea floor, which suggests that other plants and animals higher on the food chain died out too, researchers said.
By contrast, in the 20th century, oceans acidified by 0.1 unit of pH, and are projected to get more acidic at the rate of 0.2 or 0.3 pH by the year 2100, according to the study.
Looking back at this bygone warm period in Earth's history could offer help in forecasting the impact of human-spurred climate change, scientists said.
Quickly acidifying seawater eats away at coral reefs, which provide habitat for other animals and plants, and makes it harder for mussels and oysters to form protective shells.
The phenomenon has been a top concern of Jane Lubchenco, the head of the United States National Oceanic and Atmospheric Administration, who has conducted demonstrations about acidification during hearings in the US Congress.
Oceans get more acidic when more carbon gets into the atmosphere. In pre-industrial times, this occurred periodically in natural pulses of carbon that also pushed up global temperatures, the scientists wrote in the journal Science.
Human activities, including the burning of fossil fuels, have increased the level of atmospheric carbon from about 280 parts per million at the start of the industrial revolution to 392 parts per million now. Carbon dioxide is one of several heat-trapping gases that contribute to global warming.
The researchers viewed the 5,000-year hot spell 56 million years ago, likely due to factors like massive volcanism, as 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 6 degrees Celsius, 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's a fast warm-up and a quick acidification, but it's small compared to 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 (PETM) and occurring about 9 million years after the extinction of the dinosaurs, acidification for each century was about 0.008 unit on the pH scale, Hoenisch said.
Back then, many corals went extinct, as did many types of single-celled organisms that lived on the sea floor, which suggests that other plants and animals higher on the food chain died out too, researchers said.
By contrast, in the 20th century, oceans acidified by 0.1 unit of pH, and are projected to get more acidic at the rate of 0.2 or 0.3 pH by the year 2100, according to the study.
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