Wednesday, February 24, 2021

What's up with the Ozone Layer?

[This is a transcript of the video embedded below.]

Without the ozone layer, life, as we know it, would not exist. Scientists therefore closely monitor how the ozone layer is doing. In the past years, two new developments have attracted their attention and concern. What have they found and what does it mean? That’s what we’ll talk about today.

First things first, ozone is a molecule made of three oxygen atoms. It’s unstable, and on the surface of Earth it decays quickly, on the average within a day or so. For this reason, there’s very little ozone around us, and that’s good, because breathing in ozone is really unhealthy even in small doses.

But ozone is produced when sunlight hits the upper atmosphere, and accumulates far up there in a region called the “stratosphere”. This “ozone layer” then absorbs much of the sun’s ultraviolet light. The protection we get from the ozone layer is super-important, because the energy of ultraviolet light is high enough to break molecular bonds. Ultra-violet light, therefore, can damage cells or their genetic code. This means, with exposure to ultraviolet light, the risk of cancer and other mutations increases significantly. I have explained radiation risk in more detail in an earlier video, so check this out for more.

You have probably all heard of the ozone “hole” that was first discovered in the 1980s. This ozone hole is still with us today. It was caused by human emissions of ozone-depleting substances, notably chlorofluorocarbons – CFCs for short – that were used, among other things, in refrigerators and spray cans. CFCs have since been banned, but it will take at least several more decades for the ozone layer to completely recover. With that background knowledge, let’s now look at the two new developments.

What’s new?

The first news is that last year we have seen a large and pronounced ozone hole over the North Pole, in addition to the “usual” one over the South Pole. This has happened before, but it’s still an unusual event. That’s because the creation of an ozone hole is driven by supercooled droplets of water and nitric acid which are present in polar stratospheric clouds, so clouds that you find on the poles in the stratosphere. But these clouds can only form if it’s cold enough, and I mean really cold, below about −108 °F or −78 °C. Therefore, the major reason that ozone holes form more readily over the South pole than over the North Pole is quite simply that the South Pole is, on average, colder.

Why is the South Pole colder? Loosely speaking it’s because there are fewer high mountains in the Southern hemisphere than in the Northern hemisphere. And because of this, wind circulations around the South Pole tend to be more stable; they can lock in air, which then cools over the dark polar winter months. Air over the North Pole, in contrast, mixes more efficiently with warmer air from the mid latitudes.

On occasion, however, cold air gets locked in over the North Pole as well, which creates conditions similar to those at the South Pole. This is what happened in the Spring of 2020. For five weeks in March and early April, the North Pole saw the biggest arctic ozone hole on record, surrounded by a stable wind circulation called a polar vortex.

Now, we have all witnessed in the past decade that climate change alters wind patterns in the Northern Hemisphere, which gives rise to longer heat waves in the summer. This brings up the question whether climate change was one of the factors contributing to the northern ozone hole and whether we, therefore, must expect it to become a recurring event.

This question was studied in a recent paper by Martin Dameris and coauthors, for the full reference, please check the info below the video. Their conclusion is that, so far, observations of the northern ozone hole are consistent with it just being a coincidence. However, if coincidences pile upon coincidences, they make a trend. And so, researchers are now waiting to see whether the hole will return in the Spring of 2021 or in the coming years.

The second new development is that the ozone layer over the equator isn’t recovering as quickly as scientists expected. Indeed, above the equator, the amount of ozone in the lower parts of the stratosphere seems to be declining, though that trend is, for now, offset by the recovery of ozone in the upper parts of the stratosphere, which proceeds as anticipated.

The scientists who work on this previously considered various possible reasons, from data problems to illegal emissions of ozone-depleting substances. But the data have held up, and while we now know illegal emissions are indeed happening, these do not suffice to explain the observations.

Instead, further analysis indicates that the depletion of ozone in the lower stratosphere over the equator seems to be driven, again, by wind patterns. Earth’s ozone is itself created by sunlight, which is why most of it forms over the equator where sunlight is the most intensive. The ozone is then transported from the equatorial regions towards the poles by a wind cycle – called the “Brewer-Dobson circulation” – in which air rises over the equator and comes down again in mid to high latitude. With global warming, that circulation may become more intense, so that more ozone is redistributed from the equator to higher latitudes.

Again, though, the strength of this circulation also changes just by random chance. It’s therefore presently unclear whether the observations merely show a temporary fluctuation or are indicative of a trend. However, a recent analysis of different climate-chemistry models by Simone Dietmüller et al shows that human-caused carbon dioxide emissions contribute to the trend of less ozone over the equator and more ozone in the mid-latitudes, and the trend is therefore likely to continue. I have to warn you though that this paper has not yet passed peer review.

Before we talk about what this all means, I want to thank my tier four supporters on Patreon. Your help is greatly appreciated. And you, too, can help us produce videos by supporting us on Patreon. Now let’s talk about what these news from the ozone layer mean.

You may say, ah, so what. Tell the people in the tropics to put on more sun-lotion and those in Europe to take more vitamin D. This is a science channel, and I’ll not tell anyone what they should or shouldn’t worry about, that’s your personal business. But to help you gauge the present situation, let me tell you an interesting bit of history.

The Montreal protocol from 1987, which regulates the phasing out of ozone depleting substances, was passed quickly after the discovery of the first ozone hole. It is often praised as a milestone of environmental protection, the prime example that everyone points to for how to do it right. But I think the Montreal Protocol teaches us a very different lesson.

That’s because scientists knew already in the 1970s, long before the first ozone hole was discovered, that chlorofluorocarbons would deplete the ozone layer. But they thought the effect would be slow and global. When the ozone hole over the South Pole was discovered by the British Antarctic Survey in 1985, that came as a complete surprise.

Indeed, fun fact, it later turned out that American satellites had measured the ozone hole years before the British Survey did, but since the data were so far off the expected value, they were automatically overwritten by software.

The issue was that at the time the effects of polar stratospheric clouds on the ozone layer were poorly understood, and the real situation turned out to be far worse than scientists thought.

So, for me, the lesson from the Montreal Protocol is that we’d be fools to think that we now have all pieces in place to understand our planet’s climate system. We know we’re pushing the planet into regimes that scientists poorly understand and chances are that this will bring more unpleasant surprises.

So what do those changes in the ozone layer mean? They mean we have to pay close attention to what’s happening.


  1. The Montreal Protocol worked fairly well because it mostly called for the replacement of CFCs with other compounds. This turned out to be fairly easy to do from an economic standpoint. Eliminating CO_2 emissions is a much more difficult problem.

    I learned a while back that Earth has an EM wave of 8Hz that is confined by the ionosphere. This is a standing wave that covers Earth. It has a multipolar form of harmonics in Legendre polynomials and so forth. At 8Hz this is what one would expect if an EM wave were wrapped around the Earth as a standing wave. This is associated with the electrical and electromagnetic dynamics of the Earth’s atmosphere, where there is everywhere a constant varying electric field. Some spiders use their webs as dipoles to surf these electric fields. These variations are higher harmonics of this, and the extreme harmonics are found in electrical storms. It was rather fascinating learning this. These were not something I had ever encountered or even thought of. This is of course how science tends to operate. It is maybe less often that a great discovery is shouted with “Eureka,” but more often a confused muttering of “Well that is odd.”

    I had been largely of the mind that the ozone hole problem may not have been solved, but things were better. Things may be problematic. The polar region has been the most effected by climate change with warming as much as 7C or so. This means the temperature difference that drives the polar vortex that bottles up cold air over the poles has less kinetic energy from the temperature gradient with latitude. We just got a big breakdown and a dump of arctic air here. I would presume this means the north pole is much warmer. This will vary, and one thing that global warming is doing is driving larger fluctuations in energy and temperature. So, while the poles on average are warming up, there may be more temperature variance that bring episodes of colder temperatures. This means there could over time be more of these colder periods with a loss of ozone.

    1. Interesting. There is also a tangential discovery of Laplacian pressure waves in atmosphere oscillating in different modes. "[Takatoshi Sakazaki] was initially focused on temperature variations, and he viewed the pressure peaks as unwelcome noise." The article:

      It's certainly tightly related phenomena, it also seems that abrupt atmospheric pressure changes observed around the globe (not directly connected to Laplacian) affect the organism even more than mere temperature fluctuations (if they could've happened on their own). So more of severe headaches to some folks, probably linked to pressure adaptation & the vegetative nervous system (deep breathing with retentions helps in regulation). And presumably more... irrational behavior.

      It seems that all those effects combined will make it close to impossible to make weather forecast.

    2. “We just got a big breakdown and dump of arctic air here.” That was a pretty impressive breakdown of the polar vortex. Monitoring the climatereanalyzer site, from the University of Maine daily, I noticed a huge blob of ultra cold purple air break off from the polar region and descend into central, south Canada just before it plunged into the US. Looking at pictures and news footage of highways and homes in Texas was quite shocking. The cold wave lasted about a week but caused staggering damage. I can understand why this happened. Checking Accuweather’s temperature means for Dallas, Texas it’s clear that such extreme cold is quite rare, so residents and businesses really had no impetus to winterize their homes and facilities.

      Back in February, 1977 I took a bus from New York City to Dallas, Texas to visit my brother who was then working there. On one of the days I was there it reached 83 degrees F. (28.3 C.). It was so delightful I strapped my brother’s cat carrier to the back of his bike and pedaled down to a nearby park, letting the cat roam free while I basked in the sun. It was such a nice break from long winters we have in the northeast.

    3. Back in the 80's the old frig in my apartment used the banned CFC's, but if memory serves couldn't operate on the replacement chemical that wasn't as harmful to the ozone layer. When this refrigerant started running low the technician I contacted had a supply of the old CFC and was able to recharge it. I've long since moved from that apartment, but I would imagine the landlord has replaced the out of date frig.

      Talk about refrigeration. Here in the northeast it seems like we're in a refrigerator. For some four days the winds will be howling and highs for the days will either not even reach freezing or be just above it. Our seemingly permanent snow cover just won't melt at these temps. Overall the planet is warming based on long-term data, but our local climate regime continues to torture us with mind numbing cold.

  2. My question is, how do we know the ozone hole isn't just a natural feature of the stratosphere? We only noticed the hole once we were able to actually measure it, but doesn't it seem logical that it has always been there, given, as this article says, it is also caused by cold temperatures?

    35 years of Montreal hasn't really affected it much...not in data that I have seen, ,but I'm no expert...and even if there is a trend towards "recovery" how much is is our actions on cfc? How much of it is the natural warming of the climate? How much is anthropogenic warming?

    If we just can't tell, and have no idea, can we claim any victory?

    Just wondering...

    1. Roland,

      The British Antarctic Survey began their measurements in the late 1957, before the ozone hole appeared for the first time. This information is easy to find if you had bothered to look for it. Why did you not look for this information? Is it maybe because you thought you knew the answer? Do you come here deliberately to waste my time?

    2. You seem to jump to conclusions of my beliefs and knowledge that are not supported by anything you could have possibly read in my question.

      So again, the same questions apply. How can we tell the difference between it being a natural feature of the atmosphere and being manmade, when the data shows no change since montreal? The yearly changes are huge compared to any possible trend in the data post montreal.

      Still just wondering...

    3. I have had to endure sufficiently many people like you who are "just wondering" but can't be bothered to do anything else than post their "just wondering" comments. I will not approve further comments from you. Do your reading.

  3. Sorry if this comment doesn't add to discussion of this video.
    So, I had the impression/I think I read somewhere that ozone depletion was easing up and that the polar holes were shrinking. I'm disconcerted that I had it so wrong, how/where the heck did this erroneous impression come from? Or did I just make it up?

    1. The ozone hole over the South Pole has indeed been getting better. The ozone hole over the North Pole, as I said, is a somewhat unusual occurrence, and it's unclear whether it'll become a more frequent visitor. As to the overall amount of ozone. My understanding is it's roughly recovering as expected, but the bad news is that the distribution is changing, which means it's not recovering as quickly as expected over the equator, and instead adding up in mid-to-high latitudes. This seems to be a trend (note, as I said, paper has not been peer reviewed) and it could be climate-change driven. I think it's something to keep an eye on that we'll almost certainly hear more about in the next years.

    2. I guess the brief summary is you didn't get it wrong, it's just that the news you read was somewhat incomplete.

  4. So I hit up Google to answer my question, the consensus seems to be that the Ozone Layer is recovering, and expected to be fully recovered circa 2060.
    It would seem though that we can't collectively sigh with relief yet.

  5. There is a view that ozone holes contribute to global warming by admitting more UV which warms the oceans disproportionally. That view is not widely held or popular. The greater effect of UV vs. other frequencies on water EM energy absorption is considered generally crackpot. That hypothesis is based on water having a different phase (structure) in certain circumstances. The effect of volcanos on increased ozone formation is another hypothesis with little support or interest.

    1. Morris,

      You have it backwards. Ozone is a greenhouse gas, so actually ozone depletion has a cooling effect. Please remember that to get a greenhouse effect, it doesn't matter what goes through (as you write) but what gets stuck. Ozone doesn't have large effect on the overall temperature though, and compared to CO2 it's entirely negligible. I don't think this a controversial topic and I don't know why you make it sound like one. There is a good summary here.

    2. I think that you misread your source on Ozone effects on temperature, I quote: "The major ozone losses that have been observed in the lower stratosphere due to the human-produced chlorine- and bromine-containing gases have a cooling effect on the Earth's surface. On the other hand, the ozone increases that are estimated to have occurred in the troposphere because of surface-pollution gases have a warming effect on the Earth's surface, thereby contributing to the "greenhouse" effect."

      The ozone losses in ozone holes occur in the stratosphere, so, according to the article you cite, they have a cooling effect. The effect of an absorbing gas depends on where it is in the atmosphere. Morris is correct, and you are mistaken.

    3. Is this comment addressed at me? I wrote ozone depletion (yes, in the stratosphere) has a cooling effect. Morris is the one who claims it contributes to warming. I think you're wrong about who is wrong, or else, I don't understand who or what you are talking about.

    4. To morris...

      You are correct, water does not absorb blue/uv as much as other wavelengths, that is what water looks blue. UV also does not have the energy to penetrate deep enough in to oceans to cause any significant warming.

      As a civil engineer, I know many (if not most) wastewater treatment plants use UV disinfection before effluent is released. These systems release hundreds, if not thousands of times more UV than the sun in to the effluent to kill microbes, but basically all added heat is from the bulbs themselves (they have to be close) and not from warming by the UV light


    5. To Sabine
      I am not advocating the view ozone is not a greenhouse gas. What I wrote does not contradict the consensus view or is promotion of controversy. What I do suggest is that there are other views about ozone holes, UV, water structures volcanos and which might contribute to global warming to some (unknown) degree. Individually these ideas are not at all popular for unrelated reasons. There is no evidence that they can be combined to affect climate. On the other hand they are interesting notions that tend to be dismissed out of hand.
      You seem to assume that I am attacking the consensus view. That is not warranted given what I said but seems like lack of tolerance.

    6. To morris,

      I personally don't have a problem with attacking some sort of "consensu" but I do have a problem.with bad physics...

      Anything that can be easily tested and proven incorrect (like uv light increasing global temperatures through heating water) SHOULD be dismissed out of hand...

      My only issue is with the unknowns...feedbacks, natural variability, etc...but this is a Ozone hole post, not a global warming post, so no need to get in to all that...


    7. Started as such, true, but ended with a spot-on warning about our hubris. Implicitly hubris in general I gather, even though explicitly in regard to climate.

      Only final-solution segue of all these debates; obsessive consumerism, greed, wealth inequality, abuse, violence, addictions, ... you name it, is, I'm afraid, human psyche. In this particular example, portion of it that covers convenience. Because nobody intelligent enough to be able to learn to speak and write can be dumb enough not to see writing on the wall, unless their head is deep in the sand if I leave the other place, often more aptly describing situation, aside. Changes required are inconvenient. And convenience thread has very high priority in hierarchy of brain processes. It's a survival thing. That piece of code must date back to first proto-neurons if not earlier. So one could say: "But then it's ok, it's natural. Can't expect us to go against nature even if it is to save Nature!" Probably some are even saying that.

      Except we've so far removed ourselves from nature that we have absolutely no business calling her to our defense. We either live by her rules and accept that not everybody should survive and breed, that no idiot could assume lead role, that population is controlled by *locally* available resources, ...

      Or we say that we've evolved far enough to implement that intellect and start acting above and beyond hormone driven mess of base code snippets evolution has written in.

      Kinda funny how we're so quick to jump to extremes but in this case we stubbornly stick to middle path.


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