Oceans Found to Absorb Half of All Man-Made Carbon Dioxide

John Pickrell
for National Geographic News
July 15, 2004

Around half of all carbon dioxide produced by humans since the industrial revolution has dissolved into the world's oceans—with adverse effects for marine life—according to two new studies.

Scientists who undertook the first comprehensive look at ocean storage of carbon dioxide found that the world's oceans serve as a massive sink that traps the greenhouse gas.

The researchers say the oceans' removal of the carbon dioxide from Earth's atmosphere has slowed global warming.

But in a second, related study, scientists say the sink effect is now changing ocean chemistry. The resulting change has slowed growth of plankton, corals, and other invertebrates that serve as the most basic level of the ocean food chain. The impacts on marine life could be severe, scientists say.

"The oceans are performing a great service to humankind by removing this carbon dioxide from the atmosphere," said Christopher Sabine, a geophysicist with the National Oceanic and Atmospheric Administration in Seattle, Washington. "The problem is that this service has potential consequences for the biology and ecosystem structure of the oceans."

Sabine is a co-author of both studies, which are described in tomorrow's edition of the research journal Science.

Missing Sink

A greenhouse gas, carbon dioxide traps solar heat in Earth's atmosphere. The gas is known as the biggest contributor to global warming of the planet.

Since mass consumption of fossil fuels began with the industrial revolution around 1800, the concentration of carbon dioxide in the atmosphere has grown from an estimated 280 parts per million to around 380 parts per million.

Today's current level of atmospheric carbon dioxide is only around half of what scientists have predicted atmospheric levels should be, based on estimates that humans have contributed 244 billion metric tons of carbon dioxide to Earth's atmosphere.

"The other half of the emitted carbon dioxide was the so-called missing sink, which was thought to be taken up by either the oceans or the land plants," Sabine said. (Plants absorb carbon dioxide and use it to produce energy.)

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