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| Ozone Layer cartoon |
Ozone is Earth's natural sunscreen, shielding life from excessive amounts of ultraviolet radiation. But Earth's ozone layer has been damaged by well-intentioned chemicals - chlorofluorocarbons, used for refrigerants and aerosol spray-cans - that have the unintended consequence of destroying ozone molecules.
A huge Arctic ozone hole opened up over the Northern Hemisphere for the first time this year, an international research team.
The hole covered 2 million square kilometres - about twice the size of Ontario - and allowed high levels of harmful ultraviolet radiation to hit large swaths of northern Canada, Europe and Russia, the 29 scientists say.
The discovery of the "unprecedented" hole comes as the Canadian government is moving to reduce staff in what Environment Minister Peter Kent calls the "streamlining" of its ozone monitoring network.
Environment Canada scientists say the "chemical ozone destruction over the Arctic in early 2011 was - for the first time in the observation record - comparable to that in the Antarctic ozone hole."
It also highlights the importance of Environment Canada's ozone networks, which scientists have warned could be drastically reduced. Department officials say ozone monitoring will continue but will be "streamlined" to eliminate "redundancy."
The scientists say maintaining "comprehensive" data is "critical" to understanding Arctic ozone depletion and the threats it poses.
They used U.S. and European satellites, along with ground stations and scientific balloons - including those operated by Environment Canada - to find and track the hole. "The satellites, ground stations and balloons each provide a piece of the puzzle", says co-author Kaley Walker, at the University of Toronto. "It is important to have them all."
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| The peak of the Ozone Layer in late March |
The hole formed over the Arctic in February and March, then swung across northern Canada, northern Europe and Central Russia to northern Asia, prompting scientists to issue warnings this spring about excess radiation.
A report shows just how big and remarkable the hole was and how it moved. It also points to what scientists are calling "ominous" changes in the Arctic stratosphere, about 20 kilometres above the surface, which may be linked to climate change and increasing greenhouse gas emissions.
The ozone-destroying chlorine compounds have been banned internationally, but they are so "long-lived" the scientists expect them to stay in the atmosphere for decades. Scietists say it will likely be about 70 years - "a full generation of humans" - before the chlorine compounds disappear from the atmosphere. Meantime a cooling trend in the stratosphere, which is thought to be tied to increasing greenhouse gases like carbon dioxide, could create more ozone holes.
They also say "more acute Arctic ozone destruction could exacerbate biological risks from increased ultraviolet radiation exposure, especially if the vortex shifted over densely populated midlatitudes, as it did in April 2011." The "polar vortex" is the frigid air mass that circles the polar region in winter and can dip as far south as New York and Rome.
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| I love the Ozone Layer sticker |
The lowest value (deepest hole) ever recorded was 73 Dobson Units on September 30, 1994, while the broadest hole occurred on September 29, 2000, when the ozone-depleted area stretched 29.9 million square kilometers. The record for mean size of the ozone hole - the greatest extent over a one-month window - was September 7 to October 13, 2006, when the hole reached 26.2 million square kilometers. The mean ozone hole in 2010 was 22.2 million square kilometers.
In 2010 report, the science advisers to the Montreal Protocol found that:
- Global ozone and ozone in the Arctic and Antarctic is no longer decreasing, but is not yet increasing.
- The ozone layer outside the Polar Regions is projected to recover to its pre-1980 levels some time before the middle of this century. The recovery might be accelerated by greenhouse gas-induced cooling of the upper stratosphere.
- The ozone hole over the Antarctic is expected to recover much later.
- The impact of the Antarctic ozone hole on surface climate is becoming evident in surface temperature and wind patterns.
- At mid-latitudes, surface ultraviolet radiation has been about constant over the last decade.
Ozone hole 2011, compared to previous years:
