Arctic ozone layer fell to an unprecedented low in 2011
Prepare for an '80s flashback.
NASA scientists this week published a study reporting that the ozone layer over the Arctic fell to unprecedentedly low levels over the winter and spring of 2011. Of course, back in the '80s, the concern was about the ozone hole over Antarctica, but still ... we all stopped using that CFC-spewing hairspray decades ago. Shouldn't this be over by now?
According to atmospheric scientists Michelle Santee and Nathaniel Livesey, two of the co-authors of the new study, the answer is no. Although industry and scientists around the world came together to stop the release of new ozone-destroying CFCs (chlorofluorocarbons) in the '90s, the CFCs that had already been released into the atmosphere have a long shelf life. It will be another 50 or so years before the level of CFCs in the stratosphere start noticeably decreasing.
Scientists are not surprised that the ozone hole continues to show up in Antarctica. But a new hole emerging in the Arctic? That's troubling.
What happened in the Arctic is that the temperature in the stratosphere stayed colder for longer in 2011, and CFCs break down ozone faster when the stratosphere is colder.
"The challenge facing the scientific community is to try to tease out why this winter was so much colder," said Livesey in an interview with The Times.
Although climate change is causing warmer temperatures on Earth's surface, Santee said, it appears to be causing colder temperatures in the stratosphere. Scientists are continuing to investigate how the two phenomena are linked, she told The Times.
Their study was published Oct. 2 in the journal Nature.
And in case you've forgotten why the ozone layer is important, here's a quick refresher: The ozone layer protects life from the sun's harmful ultraviolet radiation. It is essential to the make-up of our stratosphere.
"I don't want to convey a sense of alarm about the specific health consequences of this Arctic winter," said Santee. "The ozone layer was low only for a few weeks, so not that huge a population was exposed to harmful levels of UV."
Don't sigh with relief just yet.
She adds: "The thinning ozone over the densely populated northern and middle latitudes is a concern if we see a thinning in the future."
-- Deborah Netburn
Image: At left, an ozone map of Earth's stratosphere at the North Pole from an altitude of approximately 12 miles in mid-March, near the peak of the 2011 Arctic ozone loss. At right, chlorine monoxide -- the primary agent of chemical ozone destruction in the cold polar lower stratosphere -- on the same day from the same vantage point. Credit: NASA / Jet Propulsion Laboratory/Caltech