FULL TO THE BRIM Seas lose effectiveness in absorbing CO ²

FULL TO THE BRIM Seas lose effectiveness in absorbing CO ² Sindya N Bhanoo      The Earth’s oceans, which have absorbed carbon dioxide from emissions since the dawn of the industrial era, have recently grown less efficient at sopping it up, new research suggests.     Emissions from the burning of fossil fuels began soaring in the 1950s, and oceans largely kept up, scientists say. But the growth in the intake rate has slowed since the 1980s, and markedly so since 2000, the authors of a study write in a report in Thursday’s issue of Nature. The research suggests that the seas cannot indefinitely be considered a reliable “carbon sink” as humans generate heat-trapping gases linked to global warming.      The slowdown in the rise of the absorption rate resulted from a gradual change in the oceans’ chemistry, the study found. “The more carbon dioxide the ocean absorbs, the more acidic it becomes and the less carbon dioxide it can absorb,” said the study’s lead author, Samar Khatiwala, a research scientist at the Lamont-Doherty Earth Observatory of Columbia University and a professor at the Georgia Institute of Technology. “It’s a small change in absolute terms,” Khatiwala said. “What I think is fairly clear and important in the long term is the trend toward lower values, which implies that more of the emissions will remain in the atmosphere.”     To calculate the slowdown, Khatiwala created a mathematical model using measurements of seawater collected over the past 20 years.     Even as human-generated emissions of carbon dioxide increase, the oceans’ uptake rate growth appears to have dropped by 10% from 2000 to 2007, he said. NYT NEWS SERVICE