Saturday, August 10, 2013

Ozone hole might slightly warm planet

A press release from the America Geophysical Union: A lot of people mix up the ozone hole and global warming, believing the hole is a major cause of the world’s increasing average temperature. Scientists, on the other hand, have long attributed a small cooling effect to the ozone shortage in the hole.

Now a new computer-modeling study suggests that the ozone hole might actually have a slight warming influence, but because of its effect on winds, not temperatures. The new research suggests that shifting wind patterns caused by the ozone hole push clouds farther toward the South Pole, reducing the amount of radiation the clouds reflect and possibly causing a bit of warming rather than cooling.

 “We were surprised this effect happened just by shifting the jet stream and the clouds,” said lead author Kevin Grise, a climate scientist at Lamont-Doherty Earth Observatory of Columbia University in New York City. Grise notes this small warming effect may be important for climatologists trying to predict the future of Southern Hemisphere climate.

The work is detailed in Geophysical Research Letters, a journal of the American Geophysical Union. Grise collaborated on the study with Lorenzo Polvani of Columbia University, George Tselioudis of NASA Goddard Institute for Space Studies, Yutian Wu of New York University, and Mark Zelinka of Lawrence Livermore National Laboratory.

...Dennis Hartmann, an atmospheric scientist at the University of Washington in Seattle unrelated with the project, points out that since predicting cloud behavior is so challenging, the model used in Grise’s study could be underestimating clouds north of the jet stream being pulled toward the equator and in turn reflecting more light, potentially reducing or even negating the warming effect. Hartmann added that he also has some concerns about the modeling of the low-level cloud response. Still, “this is certainly a very interesting topic and potentially important from a practical perspective of predicting Southern Hemisphere climate and even global warming rates,” he commented...

The ozone hole via NASA, on September 22, 2012

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