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How tiny plankton could give global warming a significant boost

A new study suggests that as oceans become more acidic, plankton could produce less of a compound that is key to cloud formation. Clouds help keep earth cool.

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The setting sun highlights Arctic clouds near Barrow, Alaska. Ocean acidification could affect cloud formation, adding to global warming, according to a new study.

Beth Ipsen/Arctic Sounder/AP/File

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Global warming may get a nudge from its "evil twin," ocean acidification.

That possibility is raised in a new study that suggests that the activities of a tiny plankton – affected by the growing acidity of the world's oceans – could raise average global temperatures by as much as 1 degree Fahrenheit above current estimates.

The study, published Sunday in Nature Climate Change, represents a first cut at the issue and so faces a range of uncertainties. Trends in greenhouse-gas emissions, for example, could impact the findings.

Still, the work is "important" and "unique," says Richard Feely, a senior scientist at the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory in Seattle.

"I don't think any of the previous modeling includes the effect of acidification on biological feedbacks" to the atmosphere, says Dr. Feely, who was not a member of the research team.

This "biological feedback" involves a compound produced by the plankton, called (rather unmercifully) dimethylsulfoniopropionate. Mercifully, scientists have reduced the name to the acronym: DMSP.

DMSP breaks down into forms that, once they reach the atmosphere, are readily converted into tiny aerosol particles. These aerosols, in turn, serve as the seeds for thick, low-level clouds over the ocean – clouds that are effective at reflecting sunlight back into space.

Lab and field experiments have shown that when seawater becomes more acidic, planktons' output of DMSP drops. The potential effect on cloud formation globally could be significant. By the end of the century, reduced cloud cover from this feedback could raise projected global average temperatures from 0.23 to 0.48 degrees Celsius (roughly 0.4 to 0.9 degrees Fahrenheit), according to the research team led by Katharina Six, with the Max Planck Institute for Meteorology in Hamburg.

Sulfur-based gases are the primary raw materials for aerosols that stimulate cloud formation, Feely says. Bacteria in the ocean break down DMSP into two byproducts, one of which is dimethyl sulfide (DMS) – said to be the atmosphere's single largest source of sulfur. DMS also is responsible for the smell of the sea as you approach the beach.

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