Decades after ozone-depleting substances were banned, we’re finally seeing the results. According to a joint press release from NASA and NOAA, the hole in the ozone layer is now the smallest it’s ever been since we began measuring it. There is now a long-term trend towards an overall recovery.
The existence of a hole in the ozone layer is probably one of the first world events I consciously remember. The ozone layer above us is a critical protective layer around our planet. It blocks damaging UV radiation, including UV-C and UV-B. While some UV-B still makes it to the Earth’s surface (it’s the wavelength associated with sunburn and skin cancer), concentrations of UV-B are 350 million times higher at the top of Earth’s atmosphere than they are at the surface.
In the late 1970s, scientists discovered ozone levels in the atmosphere were dropping due to the heavy use of certain refrigerants, solvents, propellants, and foam-blowing agents. These chemicals, collectively known as ozone-depleting substances, destroy ozone as they break down in the upper atmosphere via photodissociation. Once we discovered the existence of an actual ozone hole over the Antarctic, it was clear we had to act. Various ODS substances were banned or heavily restricted in 1989 via the Montreal Protocol. Now, it’s clear those efforts are paying off.
According to NASA, the ozone layer hole is now the smallest it has been since 1982. The ozone hole is unusually small this year in part because of overall planetary weather patterns that have limited its size. Similar patterns also occurred in 1988 and 2002. NASA is warning people not to expect that recovery has suddenly accelerated as a result of these changes.
“It’s great news for ozone in the Southern Hemisphere,” said Paul Newman, chief scientist for Earth Sciences at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “But it’s important to recognize that what we’re seeing this year is due to warmer stratospheric temperatures. It’s not a sign that atmospheric ozone is suddenly on a fast track to recovery.”
But while the ozone layer may not be on the fast track to recovery, it is recovering. A plot of ozone levels shows small but definite increases in the minimum level of ozone detected by the TOMS (Total Ozone Mapping Spectrometer) since the mid-1990s.
Image by Wikipedia
There is no known connection between the size of the ozone hole and climate change. The specific reason for the smaller-than-expected depletion level this year was warming in the upper atmosphere. At ~12 miles up, temperatures were 29 degrees Fahrenheit (16 degrees Celsius) warmer than average. This weakened Antarctica’s polar vortex. This, in turn, allowed the unusually warm air to sink into the stratosphere, where it disrupted the formation of the stratospheric clouds that fuel ozone destruction. The weather patterns also diverted ozone-rich air from elsewhere in the Southern Hemisphere over the spot. The ozone hole is expected to be roughly the same size in 2070 as it was in 1980 — a substantial improvement from the declines we were seeing before.
The problem of climate change may not be directly related to the ozone layer, but the fact that we’re seeing slow improvements is itself proof that human activities shape the globe. Taking action to reduce the amount of CFCs in the atmosphere has had a real impact. It continues to have an impact. We are not simply prisoners of events and taking action at a global scale can reduce or avoid the worst outcomes associated with modern industrial activity. The fact that we’re on track to have an ozone layer in 2070 as opposed to watching its continued, active decline is proof of our own ability to effect meaningful change.
Feature image by Katy Mersmann, NASA Goddard.
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