Category Archives: ozone depletion




(or, thoughts on atmospheric chemistry…)



As usual, we were out tramping this weekend.  We hiked across New Zealand! To be more precise, we sorta hiked across Stewart Island/Rakiura from Mason Bay to Freshwater Landing – a whopping 14 kilometers!  I’ll write more about that at a later date when I figure out a way to make it sound more exciting and adventurous than it really was…



So, yes, sunburned.  You know, when your skin receives a bit too much ultraviolet (UV) radiation from the sun and then turns red and hurts a little or a lot.  In my case, the pain is relatively mild.  I’ve had terrible sunburn in my life, like the time when I fell asleep in a canoe in the middle of the Missouri River reservoirs in Montana – that was a bad one!  Or, at the beginning of the summer when I was a swimming pool lifeguard about 35 years ago.  As I reflected on this sunburn, I wasn’t too surprised.  I’m not a person who enjoys wearing sunscreen unless I know that I’ll be able to take a shower and wash it off – I just don’t like the feel of it on my skin, clogging my sweating pores.  I was wearing a short-sleeved shirt, shorts and my ever-present cap while we were hiking, here at the beginning of the austral summer.  The season here is akin to June in the northern hemisphere, and I lost the bit of sun tan that I had from my boreal summer before we moved to New Zealand in August.  It’s time to get my skin back in shape.



The other reason that I reflected on my sunburn is because I had a bit of sunburn back in September here – at the end of the austral winter, when the daylight periods are so much shorter – and I remember being surprised that I had a sunburn.  I know that a lot of people get sunburned in the winter in the States, particularly when they’re skiing and the sun is reflecting off of the snow and up into their exposed faces.  But, in our winter in New Zealand, there wasn’t any snow and the sunburn on my hands, face and lower lip only came from direct, overhead exposure to the sun.  I remember in August and September that there were various admonitions to put on sunscreen, particularly coming from the teachers at our kids’ school.  And, I also remember thinking at the time that this was quite odd – why would folks put on sunscreen in the winter??  Yes, I’ve been exposed to many cultural  differences here in New Zealand, but this one just didn’t quite click for some time…



And then, in late October/early November, it struck me why I had received a sunburn in September here!  Ozone depletion!  I learned quite a bit about ozone depletion back in the day when I was a real environmental scientist and I’ll try to share a bit about ozone depletion.  The difference now is that I’m living in a place where ozone depletion has consequences!



Way back in the 1970’s, we all became aware of the likelihood of ozone depletion and then the actuality of it.  If you’re about my age or older, you’ll likely recall that aerosol containers, like deodorants sprays, were pressurized with chlorofluorocarbon (CFC) gases and refrigerators and freezers used halocarbon gases in their vapor compression/energy exchange cycles.  I once visited a US Department of Energy installation that was losing a million pounds of CFCs a year!  (I can’t say where because they might terminate me!)  Most of these CFCs were lost to the atmosphere. (We still use CFC-like gases in our refrigerators and freezers, but they’re now more benign and we’ve gotten much better about capturing and recycling these gases.) Once in the atmosphere, sunlight dissociates the CFCs into chlorine and bromine radicals (I’ll try to keep the chemistry to a minimum).  Basically, though, a chlorine radical is extremely reactive and it loves to react with an ozone molecule and destroy the ozone molecule.



The ozone is in our atmosphere and is created when the high energy sunlight (UV radiation) reacts with oxygen molecules (O2) to form oxygen atoms (O).  These oxygen atoms react with oxygen molecules to form the ozone (O3).  This whole cycle goes on and on, creating and destroying oxygen and ozone molecules.  The UV radiation is absorbed in the process and releases infrared/thermal energy.  In this way, the ozone molecules protect us from excessive UV radiation: continuously (and slowly!) absorbed by various forms of oxygen- pretty cool, huh?  [And, if any of my former professors are reading this, yes, I know that my ozone chemistry presentation here is simplistic…  🙂 ]  So, if something comes along and destroys the ozone, which is a good absorber of UV radiation, then we have a problem.



Now, here’s the really interesting part of all of this chemistry (yes, I know that you’re on the edge of your computer chairs, heavily panting) – these ozone-destroying reactions occur at a greater rate/frequency in the Arctic and Antarctic atmosphere! Why? you ask…  Catalysis!  (Here we go again with the chemistry stuff!) A catalyst is a compound that accelerates a chemical reaction, but doesn’t participate in the reaction and isn’t changed by the reaction. As atmospheric scientists were monitoring atmospheric ozone concentrations back in the 1970’s, they were (unpleasantly) surprised to find that ozone depletion was greatest over the North and South Poles, and that “ozone holes” were forming in the respective winters of the Poles.  During these polar winters, the cold atmosphere more readily formed ice crystals in the earth’s stratosphere (between about 20 kilometers and 50 kilometers above the earth’s surface) and these ice crystals provided a “catalytic” surface on which chlorine atoms very readily destroyed ozone.  The quantity of ozone destruction is so great over the Poles that we now have seasonal “ozone holes.”  When these ozone holes appear, greater quantities of UV radiation reach the earth.   And, when people (and any organism, for that matter) are beneath these ozone holes, we are at risk for sunburn and other UV-inspired damage.



I don’t know why (I can’t find the information, but I hope that someone knows), but the Arctic ozone hole does not seem to be as large as the Antarctic ozone hole.  This means that those people who live in the Southern Hemisphere, and particularly those live as far south as we are currently living (~ 46 degrees southern latitude) have greater potential for UV exposure than folks in the Northern Hemisphere who live at ~46 degrees northern latitude.  Since we are living as far from the South Pole as someone who lives in northern Wisconsin lives from the North Pole, you’d expect to see ozone hole/UV issues in northern Wisconsin, if the ozone depletion was the same in each hemisphere, but we I don’t recall anyone in northern Wisconsin being told to put on sunscreen in the winter.



Here’s a time-lapse ozone monitoring animation from over the Antarctic, starting on 1 July 2012, courtesy of NASA on a separate page (please “click” on the link below to open it).  The dark blue area represents the extent of the ozone hole.



2012 Antarctic Ozone Monitoring Animation




I hope that you’ll notice that in the lower right-hand corner, down by the date, that’s the southern tip of New Zealand – where we’re living!  We’re definitely NOT under the worst area of the ozone hole, but occasionally the fringe of the hole floats over southern New Zealand, which helps to explain (in part) my September sunburn.



This has been a long post about sunburn and ozone depletion…  But, this isn’t the point of the post.  Read on, if you dare…



When the science of ozone depletion was being discussed in the 1970’s, there was quite a group of naysayers.  Yes, I know – GASP!  How can that be?   Here’s are some lines that I’ve copied from the Wikipedia page regarding ozone depletion:


“The Rowland–Molina hypothesis was strongly disputed by representatives of the aerosol and halocarbon industries. The Chair of the Board of DuPont was quoted as saying that ozone depletion theory is “a science fiction tale…a load of rubbish…utter nonsense”.[66] Robert Abplanalp, the President of Precision Valve Corporation (and inventor of the first practical aerosol spray can valve), wrote to the Chancellor of UC Irvine to complain about Rowland’s public statements (Roan, p 56.) Nevertheless, within three years most of the basic assumptions made by Rowland and Molina were confirmed by laboratory measurements and by direct observation in the stratosphere.”



Does this sound remotely familiar to you???  Does this sound like a position that’s similar to the contemporary climate change denial community??   I’ll readily grant you that proving that the annual cycles of ozone depletion are real was a whole lot easier than proving that slow and noisy climate change is real.  Ozone depletion and changes to how we use CFCs were a whole lot easier to tackle than making the necessary changes for climate change.  But, climate change is real.  Deny it, if you will, not at your own peril, but at the peril of your children and your children’s children.



In the twenty plus years that I’ve been living in Wisconsin, there are too many anecdotes of my life there that have changed in that short period:


  • Winters are warmer; it used to be common to spend a week in the -20 degrees F range; now, we hardly see -10 degrees F;

  • The winter and spring of 2012 that wasn’t – have we ever had such a warm spring?

  • Superstorm Sandy – tell it to New York City and the East Coast.

  • We went to Glacier National Park in 2011 – the glaciers are receding and may be gone in fifty years.  The glacial retreat in New Zealand is similar.

  • Polar bear lives are seriously disrupted by the lack of Arctic sea ice, which means that they’re unable to fish, feed and survive as in the past.



These are all just anecdotes – points on the noisy, discontinuous, apples & oranges continuum…  And, I’m as guilty as anyone else about the size of my carbon footprint.  I don’t always make the best choices.  But, I’m also not able to make as good as choices as I’d like to make because of the society in which I live and the technologies and ways of living that it encourages (like our increasing use of natural gas and the loss of methane [another extremely strong component of global climate change] through our new found interest in “fracking” – and, don’t get me started about all of the groundwater pollution that comes from fracking!) and the technologies and lifestyles that are not encouraged like more solar power and a focus on more pedestrian- and bicycle-friendly communities.



If you haven’t seen it and are so compelled, I highly recommend the movie An Inconvenient Truth.  As a person who enjoys charts and graphs, the charts and graphs presented by Al Gore seem to me to be beyond compelling – and that was in 2006!



So, my blog about CFCs and ozone depletion is over.  Unfortunately, global climate change is just beginning.  Which leaves me with the question: how will your children, grandchildren and great grandchildren survive?  I’m scared for my offspring…  toasted and roasted…



Dr. Tim Mulholland (a.k.a. 46 S EnZed) signing off…



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