New Paper Shows Antarctic Ozone Hole Receding

False color images of the Antarctic ozone hole left (in September, 2000) and right (in September 2014. According to a recent paper the hole area has shrunk by 4.5 million square kilometers. (Blue tones indicate areas of extremely low O3 concentrations)

One of the events that got me interested in solar research occurred when a massive solar flare shredded the ozone layer in the early 1970s. The then Skylab orbital observatory reported up to 80 percent of the ozone layer "eroded" by one single super flare (class 4B optical, and X 9 x-ray). The event also aroused my curiosity regarding the ozone layer and its importance for Earth - or rather the organisms that inhabit the Earth.

By now most people know that ozone O3 - is a form of oxygen - and fond 20-30 km above Earth's surface or at the lower edge of the stratosphere. It basically is critical in protecting life forms from the effects of the Sun's ultraviolet (UV) radiation. Take that layer away and you will behold sunburns the likes of which would rival 20 hours straight in a tanning bed, not to mention an explosion of skin cancers.  Minus the ozone layer, in other words, life as we know it would not exist.

So, it is important what happens to that layer.

What disturbed many space and atmospheric scientists is that the ozone layer over the Antarctic appeared to be especially susceptible to erosion, but not from solar flares. We became aware of this via tracking of ozone concentrations by NASA satellites since the 1970s. This paved the way for a study that tapped into that database thereby discovering the adverse role of chlorfluorocarbons or CFCs.

This ground breaking research by Susan Solomon and her team discovered that these chemicals - often released via hair sprays, spray deodorants etc. - reduced stratospheric ozone concentrations all over the world. At that time (1986) industries also used CFCs in refrigeration and dry cleaning. The reduction was observed to be especially bad over Antarctica hence the term "ozone hole".

One by product of the work was to explicate the processes underlying ozone hole formation. It was known, for example, that CFCs destroyed Antarctic ozone every spring. But only later was it revealed that the process begins even before winter.  It commences, in fact, at the summer solstice or shortly thereafter when the Sun rises causing light to strike the ambient CFCs, breaking its chemical dons and freeing chlorine (e.g. CCl₃F → CCl₂F^. + Cl^.    )

The freed chlorine atoms (at the end of the right side of the above equation) then strip the oxygen  (O2) from the ozone (O3) to form other chemicals destroying the ozone itself. This leads to the emergence of an "ozone hole" which generally reaches peak area in October.

The latest research by Solomon et al, published on June 30th, e.g.

http://bit.ly/science-ozone

shows the extent to which changes in atmospheric chemistry and human activity are inextricably linked. Specifically, the authors show how public policy efforts i.e. (to ban CFCs) over decades have paid off by shrinking the Antarctic ozone by more than 4 million square miles (a 16 percent decrease) since 2000.

The obvious question is whether the success of activated public policy as it pertained to CFCs - to significantly reduce the ozone hole -could also have relevance to global warming and cutting CO2 emissions. We know that every 2 ppm increase in CO2  concentration in the atmosphere increases the effective solar insolation value by 2.0 w/  m²  .

This means the impact of CO2 on greenhouse heating is analogous to the impact of CCl₃F on ozone depletion. It makes sense then that dramatically reducing the source, CO2, can make for an improved situation with anthropogenic global warming. The problem, of course, is that carbon - which gives rise to CO2-  is a far more contentious substance with vast economic import. This is because it is part and parcel of the fossil fuels which when converted in factories or automobile engines, spawns CO2. Resistance to cutting CO2 emissions really signals opposition to altering, lowering economic growth.

Hence, naturally then there will be far more opposition to limiting fossil fuels (and by association carbon deposition) than eliminating CFCs for refrigeration or hair sprays - since alternatives can easily be found for the latter/

Never mind! A way must be found to sanely balance energy demands and needs with the worst effects of the CO2 that issues from carbon burning.

Ozone Hole Continues to Increase - Projected At Least Until 2040

Antarctic ozone hole as it appeared in 2006, highlighted in purple and blue. It marked the largest hole area yet observed at more than 273 million square kilometers. (From EOS Transactions, Vol. 96, No. 10, p.28).


It seems strange that many believe the problem of the growing ozone hole over Antarctica is now solved, and no longer a problem. Nothing could be further from the truth and new research reveals the extent of the problem. In truth, atmospheric scientists have observed as the ozone hole has formed every spring from the Southern Hemisphere.

The origin is no mystery and the erosion of the ozone layer,  caused by enormous inputs of CFCs or chloro-flourocarbons, has been known for at least 40 years. Each CFC molecule, as the late Carl Sagan pointed out in a 1979 article, is capable of eliminating tens of thousands of ozone molecules (each composed of 3 oxygen atoms) that form the protective barrier against harsh UV or ultraviolet radiation. The type that causes more skin cancers and cataracts. Humans caused this massive ozone erosion, which reached up to 70% of the ozone layer over the South Pole by late 1979- through the use of chemicals including: aerosols, solvents and refrigerants.

When these CFCs reach the stratosphere, the chlorine atoms are liberated by ultraviolet radiation from the Sun, which incept the erosion of the ozone. The peril arising from this erosion reached the point that by 1987, the nations of the world agreed to the "Montreal Protocol" to halt the harmful emission of these CFCs.  As a result the hole quit growing by the mid-1990s.

That's the good news. The bad news is that recovery of the protective ozone shield has been slow because many of the ozone depleting chemicals can last in the atmosphere up to 100 years - a lot of time to keep causing damage, erosion.

Despite the fact CFCs are no longer being emitted in any vast quantities, atmospheric scientists don't forecast the ozone hole to disappear until at least 2070.  They calculate that the gradual destruction of CFCs already in the atmosphere causes chlorine to decline each year by roughly 20 parts per trillion or 0.5%. However, as reported in EOS Transactions, Vol. 96, No. 10, p.28, Earth-orbiting satellites indicate that the natural variability of chlorine levels over Antarctica is up to ten times larger than the expected annual decline. 

In fact, in some years the chlorine levels have declined as much as 200 parts per trillion or 5% but in other years it increased by 150 ppt.  According to Strahan et al (Journal Of Geophysical Research - Atmospheres, 2014) it will take a decade of exclusive chlorine declines to be certain that the Montreal Protocol has caused the ozone hole to shrink.

Currently, it is low temperatures in the Antarctic that play the largest role in determining the size of the ozone hole. For example, in 2006, the combination of very low temperatures and high chlorine levels produced the largest ozone hole ever. It won't be until 2040, according to the authors, that we'll be able to expect the chlorine levels to have fallen enough that the ozone hole will he smaller than it is today, even given a very cold year.

Given these natural fluctuation issues, we are left with years of monitoring both temperature and chlorine levels before it can definitively be said that the declining trends can be attributed to the Montreal Protocol. Yes, the Protocol has evidently worked, but the inordinate lifetimes of the CFCs has made full removal extremely difficult, and requiring an extended time frame. 

This is also a cautionary tale for those who deny climate change-global warming, since an analogous situation applies. As reported in EOS Transactions of the American Geophysical Union (Vol. 91, No. 30, 27 July, 2010),  CO2 is so long-lived in the atmosphere (~ 100 years for each molecule from the time deposited) and so much has been injected by humans, "it could effectively lock the Earth and future generations into warming not just for decades or centuries but literally for thousands of years."

Something to think about!