PARIS, Oct. 7 (UPI) -- The European Space Agency says scientists have determined the 2008 ozone hole is larger than last year's ozone hole but smaller than the 2006 hole.
"This year the area of the thinned ozone layer over the South Pole reached about 27 million square kilometers, compared to 25 million square kilometers in 2007 and a record ozone hole extension of 29 million square kilometers in 2006, which is about the size of the North American continent," the ESA said.
Scientists said the depletion of ozone is caused by extremely cold temperatures at high altitude and the presence of ozone-destructing gases such as chlorine and bromine, originating from man-made products like chlorofluorocarbons, which were phased out under the 1987 Montreal Protocol but linger in the atmosphere.
Julian Meyer-Arnek of the German Aerospace Center which monitors the hole annually, said since the polar vortex remained undisturbed for a long period, the 2008 ozone hole has become one of the largest ever observed.
The annual analysis is based on data provided by instruments aboard the ESA's Envisat, ERS2 and MetOp satellites.