Study: Global warming worsening watery dead zones

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Study: Global warming worsening watery dead zones
A woman sunbathes on the beach in Brighton on July 18, 2014, as parts of the country were expected to experience the hottest day of the year so far and the Met Office issued a heatwave alert for southern England and the Midlands. AFP PHOTO / CARL COURT (Photo credit should read CARL COURT/AFP/Getty Images)
National Oceanic and Atmospheric Administration and NASA both agree that 2014 is the hottest year on record ever. Matt Sampson has the details.
A woman sunbathes in central London on July 18, 2014 as parts of the country were expected to experience the hottest day of the year so far and the Met Office issued a heatwave alert for southern England and the Midlands. AFP PHOTO/BEN STANSALL (Photo credit should read BEN STANSALL/AFP/Getty Images)
People gather on the beach in Brighton on July 18, 2014, as parts of the country were expected to experience the hottest day of the year so far and the Met Office issued a heatwave alert for southern England and the Midlands. AFP PHOTO / CARL COURT (Photo credit should read CARL COURT/AFP/Getty Images)
Fishermen choose a picturesque spot to cast their lines from the rocks at Seal Beach, California, as the sun prepares to set on June 28, 2014. Summer in California this year is expected to be the hottest and driest on record as nearly one-third of the state experiences 'exceptional' drought levels, the highest percentage ever recorded by the Drought Monitor, whch began monitoring in 2000, according to reports last week from the National Climatic Data Center. AFP PHOTO/Frederic J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)
A life guard keeps watch on the beach in Brighton on July 18, 2014, as parts of the country were expected to experience the hottest day of the year so far and the Met Office issued a heatwave alert for southern England and the Midlands. AFP PHOTO / CARL COURT (Photo credit should read CARL COURT/AFP/Getty Images)
A couple rest in the heat of the day in Sydney on January 6, 2015. Australia experienced its third-hottest year on record in 2014, paving the way for an early start to the bushfire season, scientists said on January 6 as hundreds of firefighters battled blazes in three states. AFP PHOTO / Peter PARKS (Photo credit should read PETER PARKS/AFP/Getty Images)
SYDNEY, AUSTRALIA - MAY 23: A general view of swimmers at Bondi Icebergs on May 23, 2014 in Sydney, Australia. Sydney is experiencing it's hottest May on record, already recording it's hottest week for this time of year in over 150 years. (Photo by Ryan Pierse/Getty Images)
SYDNEY, AUSTRALIA - MAY 23: A general view of swimmers at Bronte Beach on May 23, 2014 in Sydney, Australia. Sydney is experiencing it's hottest May on record, already recording it's hottest week for this time of year in over 150 years. (Photo by Ryan Pierse/Getty Images)
SYDNEY, AUSTRALIA - MAY 23: A general view of sunbathers at Bondi Beach on May 23, 2014 in Sydney, Australia. Sydney is experiencing it's hottest May on record, already recording it's hottest week for this time of year in over 150 years. (Photo by Ryan Pierse/Getty Images)
SYDNEY, AUSTRALIA - MAY 23: A general view of Bronte Beach on May 23, 2014 in Sydney, Australia. Sydney is experiencing it's hottest May on record, already recording it's hottest week for this time of year in over 150 years. (Photo by Ryan Pierse/Getty Images)
SYDNEY, AUSTRALIA - MAY 23: Children play in a pond on May 23, 2014 in Sydney, Australia. Sydney is experiencing it's hottest May on record, already recording it's hottest week for this time of year in over 150 years. (Photo by Ryan Pierse/Getty Images)
A fisherman sleeps on his boat as children swim behind him in a river to beat the summer heat in Manila on May 26, 2014. The Philippines has been experiencing the hottest days of the year with temperatures of 35 degrees Celsius (95 Fahrenheit) recorded in parts of the city. AFP PHOTO / NOEL CELIS (Photo credit should read NOEL CELIS/AFP/Getty Images)
(NOAA)
(NOAA)
Sunspots (shown in white) vary across multi-year cycles, causing solar irradiance, which influences the Earth's climate, to also fluctuate.
Solar irradiance from sun spots (shown in white) was high at the turn of the century. It led climatologists to believe temperatures would keep rising.
High levels of irradiance from the sun spots (shown in white) continued through about 2001.
This chart shows dramatic spikes in solar irradiance across the 1980s and 1990s before leveling off for the previous 14 years.
The sun spots then all but vanished around the beginning of 2002 and have yet to return. Scientists believe that when they do, global warming will also resume.
This image provided by NASA shows a 'Blue Marble' image of the Earth taken from the The Visible/Infrared Imager Radiometer Suite or VIIRS instrument aboard NASA's most recently launched Earth-observing satellite - Suomi NPP. This composite image uses a number of swaths of the Earth's surface taken on Jan. 4, 2012. The NPP satellite was renamed 'Suomi NPP' on Jan. 24, 2012 to honor the late Verner E. Suomi of the University of Wisconsin. Suomi NPP is NASA's next Earth-observing research satellite. It is the first of a new generation of satellites that will observe many facets of our changing Earth. Suomi NPP is carrying five instruments on board. (AP Photo/NASA)
Volcanic eruptions, like this one August 13 at Mount Etna on the southern Italian island of Sicily near Catania, have also contributed to the slow down in global warming buy launching particulates into the air that further diluted the sun's rays.
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WASHINGTON (AP) -- Global warming is likely playing a bigger role than previously thought in dead zones in oceans, lakes and rivers around the world and it's only going to get worse, according to a new study.

Dead zones occur when fertilizer runoff clogs waterways with nutrients, such as nitrogen and phosphorous. That leads to an explosion of microbes that consumes oxygen and leaves the water depleted of oxygen, harming marine life.

Scientists have long known that warmer water increases this problem, but a new study Monday in the journal Global Change Biology by Smithsonian Institution researchers found about two dozen different ways - biologically, chemically and physically - that climate change worsens the oxygen depletion.

"We've underestimated the effect of climate change on dead zones," said study lead author Andrew Altieri, a researcher at the Smithsonian's tropical center in Panama.

The researchers looked at 476 dead zones worldwide- 264 in the United States. They found that standard computer climate models predict that, on average, the surface temperature around those dead zones will increase by about 4 degrees Fahrenheit (slightly more than 2 degrees Celsius) from the 1980s and 1990s to the end of this century.

The largest predicted warming is nearly 7 degrees (almost 4 degrees Celsius) where the St. Lawrence River dumps into the ocean in Canada. The most prominent U.S. dead zones, the Gulf of Mexico and the Chesapeake Bay, are projected to warm 4 degrees (2.3 degrees Celsius) and nearly 5 degrees (2.7 degrees Celsius) respectively.

Warmer water holds less oxygen, adding to the problem from runoff, said co-author Keryn Gedan, who is at both the Smithsonian and the University of Maryland. But warmer water also affects dead zones by keeping the water more separate, so that oxygen-poor deep water mixes less.

"It's like Italian dressing that you haven't shaken, where you have the oil and water separate," Altieri said.

When the water gets warmer, marine life's metabolism increases, making them require more oxygen just as the oxygen levels are already dropping. Other ways that climate change affects dead zones includes longer summers, ocean acidification and changing wind and current patterns, the study said.

Donald Boesch, a University of Maryland ecologist who wasn't part of the study and works at a different department than Gedan, said there is not enough evidence to say that climate change has already played such a big role in the spread of dead zones. But he said the study is probably right in warning that future warming will make the problem even worse.
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