- After absorbing nearly half of humankind's industrial
emissions of carbon dioxide for the past 200 years or so, the Earth's oceans
are becoming more acidic -- a chemical change that could significantly
harm sea life and speed up global warming.
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- That's the gist of several reports in today's Science
magazine from an international team led by researchers at Seattle's Pacific
Marine Environmental Laboratory, operated by the National Oceanic and Atmospheric
Administration.
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- Carbon dioxide is a so-called "greenhouse gas,"
and its atmospheric increase, largely because of fossil fuel use, is one
of the main drivers of global warming. But only half of the total carbon
dioxide produced by human activity has remained in the atmosphere. The
rest has disappeared, and scientists, until now, have debated where it
went.
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- It turns out "the oceans have done us a great service"
by absorbing much of this carbon dioxide, said Christopher Sabine, an oceanographer
at the Seattle NOAA station -- but at a price, other researchers say.
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- Sabine was principal investigator for the international
research project that, for the first time, quantified just how much of
the atmospheric carbon dioxide is being absorbed and recycled by the oceans.
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- Working with teams from elsewhere in the United States,
Australia, Canada, Spain, Japan, South Korea and Germany, Sabine and others
reviewed nearly 10,000 measurements of oceanic carbon concentrations worldwide
taken on some 95 research cruises.
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- Using sophisticated methods to track how the atmospheric
carbon is slowly absorbed and "processed" in the surface waters
of the oceans, the scientists estimated that the oceans had taken up some
118 million metric tons of atmospheric carbon dioxide during the past two
centuries -- about 48 percent of all fossil fuel emissions during the same
time period.
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- "Their results show that the oceans store a major
proportion" of the carbon dioxide produced by human activity, and
provide a better understanding of the carbon cycle, said Columbia University's
Taro Takahashi, who wrote a commentary on the findings in the journal.
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- Richard Feely, Sabine's colleague at the Seattle lab,
was principal author of another report in today's Science that examined
some of the chemical and biological impacts on the oceans acting as one
of the primary carbon sinks for our industrial effluent.
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- "We are changing the chemistry of the oceans,"
said Feely. Carbon dioxide is an acid, he noted, and the oceans are becoming
more acidic -- a chemical change that could potentially upset the entire
marine ecosystem.
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- To test the long-term impact of this change, Feely and
colleagues studied marine creatures -- such as plankton, coral or snails
-- that take in carbon as calcium carbonate to form their shells. In the
lab, they exposed these creatures to higher levels of carbon dioxide to
simulate the atmospheric levels of this gas by the end of this century
if current trends continue.
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- "The shells appeared to be malformed," Feely
said. But more importantly, he noted, the creatures' ability to absorb
carbon was diminished as carbon dioxide levels and seawater acidity increased.
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- The changes under way in the oceans' chemistry, Feely
said, could trigger significant adverse effects on the entire marine food
chain. It's too soon to say if this is happening now, he noted, but the
studies indicate such negative effects could occur if current trends continue.
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- All of life on Earth, most of the molecules in our bodies
and much of what we consider "natural" on this planet depend
upon carbon and a process called the carbon cycle -- the planetary production,
absorption and reconstitution of carbon in its many chemical forms.
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- Fossil fuels are also mostly carbon and our tendency
to burn lots of them has produced today's unprecedented amount of carbon
dioxide gas, among other things, which has to go somewhere.
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- Sabine said his research indicates the oceans are now
at about one-third of their total capacity to absorb carbon dioxide.
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- But as Feely's findings show, he added, there are other
consequences to consider if we continue to expect the oceans to sop up
our excess carbon.
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