Scientists at NASA have shared evidence proving that levels of ozone-destroying chemicals in the atmosphere are declining. For the first time, there is full scientific proof that a worldwide ban on CFCs is working.
Image: NASA's Goddard Space Flight Center/Katy Mersmann
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Direct satellite observations by NASA show that the global ban on chlorofluorocarbons (CFCs) has caused the hole in the ozone layer to shrink.
In a new study published in the journal Geophysical Research Letters, scientists said ozone depletion had dropped by about 20 percent since 2005.
CFCs are long-lived, chlorine-based chemicals that rise into the stratosphere layer of Earth's atmosphere, where the sun's ultraviolet radiation breaks their compounds apart, releasing chlorine atoms that destroy ozone molecules.
Stratospheric ozone protects life on Earth by absorbing ultraviolet radiation, which is potentially harmful as it can cause skin cancer and cataracts, compromise the immune system and damage plants.
"We see very clearly that chlorine from CFCs is going down in the ozone hole, and that less ozone depletion is occurring because of it," said lead author Susan Strahan, an atmospheric scientist at NASA's Goddard Space Flight Center.
Strahan and co-author Anne R. Douglass used data from the Microwave Limb Sounder (MLS) aboard the Aura satellite, which has been making measurements continuously around the globe since mid-2004.
"The Antarctic ozone hole is healing slowly because levels of the man-made chemicals causing the hole have long lifetimes," the study stated.
Ozone layer still decades away from full recovery
The study is the first to use measurements of the chemical composition inside the ozone hole to confirm that ozone depletion is decreasing as a direct result of the decline in use of CFCs. Past studies have had to rely only on statistical analyses of changes in the ozone hole's size to suggest that the ozone is healing.
The Antarctic ozone is expected to continue to recover gradually as CFCs leave the atmosphere; however, a complete recovery is expected to take decades, as the ozone layer faces other threats.
"CFCs have lifetimes from 50 to 100 years, so they linger in the atmosphere for a very long time," Douglass said. "As far as the ozone hole being gone, we're looking at 2060 or 2080. And even then there might still be a small hole."
Two years after the discovery of the Antarctic ozone hole in 1985, countries around the world agreed to sign the Montreal Protocol on Substances that Deplete the Ozone Layer, which regulates ozone-depleting compounds. The agreement was ratified in 1989 and has been amended multiple times since in order to completely phase out the production of CFCs.
NASA's IceBridge in the Arctic Circle
IceBridge is part of NASA's Cryosphere Program, which uses remote sensing to monitor Earth's major ice sheets - including the extent to which they are changing.
Image: Getty Images/M.Tama
Mapping the ice
Operation IceBridge studies the processes that link the polar regions with the Earth's climate system. Rapidly changing polar ice means researchers need to use highly sophisticated airborne technology to measure annual changes in thickness and movement - onboard a retrofitted 1966 Lockheed P-3 aircraft.
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Ready for takeoff
It's all part of a six-year project under NASA's Cryosphere Program, in which researchers are carrying out a series of eight-hour flights over Greenland (from March to May) and Antarctica (October to November) in order to accurately model a three-dimensional view of ice sheets, ice shelves and sea ice.
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Ice meets cloud
In 2003, NASA launched a satellite called ICESat (Ice, Cloud, and Land Elevation Satellite) for the purpose of monitoring changes in polar ice. However, it suddenly stopped collecting data in 2009. With ICESat-II not expected to be ready for launch until 2018, researchers needed to somehow bridge the nine-year data gap between the two satellites.
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Keeping an eye on things
Enter operation IceBridge, which has been keeping a close eye on the polar ice - as well as its cute inhabitants - while ICESat-II is prepped for launch next year. Or is the hare rather watching over these strange bipeds?
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Climate change in action
The data collected during these missions is critical for researchers in predicting the effects climate change is already having on the polar ice, including a rise in sea levels. According to NASA scientists, on March 7, 2017, sea ice in the Arctic reached the lowest maximum wintertime extent ever recorded.
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Seeing past the surface
A glacier is visible through mist above Ellesmere Island. Operation IceBridge allows scientists gather valuable data by using special ice-penetrating radar, which only functions properly when used in lower altitudes.
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Melting landscape
Scientists have long warned that the Arctic Circle will be one of the regions hit hardest by climate change - and effects are already becoming evident. The darker the color, the thinner the ice.
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Rugged terrain
Once ICESat-II is up and running, it will have the ability to take continuous measurements over a much wider area - unlike the current aircraft-based method, which is limited only to annual surveys.
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Trapped icebergs
Icebergs are locked in sea ice, as seen from the research aircraft along the Upper Baffin Bay coast above Greenland. Aircraft-based research allows its human pilots to focus on specific areas of scientific interest, rather than simply conducting a flyover on a fixed path.
Image: Getty Images/M.Tama
Ice on the retreat
As in Greenland, the ice fields of Ellesmere Island in Canada are also gradually retreating due to warming temperatures. The future of ICESat-II is now in question, as US President Donald Trump has pledged to strip funding for NASA's entire earth science program.
