Farman et al. (1985)

Farman et al. (1985)

Ozone (O3) is an amazing molecule. In the Stratosphere, it is a vital layer that shields us from harmful UV rays. Near ground level, it is a pollutant that causes acute and long term side effects that are harmful to us. In this famous paper, Farman discovers the “hole” in the ozone layer above Antarctica. He attempts to find the source of this loss of ozone by measurements of [ClOx] and [NOx] and how they interact. Could it be halocarbons caused by freons? Sun spots? NO and NO2 caused by supersonic jets?

Tune in this Friday for the answers!


11 Responses to “Farman et al. (1985)”

  1. Josh Ellsworth Says:

    The paper does a good job at linking the drop in ozone over the antarctic to rising concentration of CFC’s in the atmosphere, even if the axes on the graphs are ambiguously labeled if at all. Even though at this point it would be strictly an academic exercise, could the effect of anthropogenic NO production on the ozone layer prior to the widespread use of CFC’s be extrapolated?
    What is the “high activation energy” required for reaction #1 in table one, and is the uv radiation at high altitudes sufficient to overcome the barrier even at low temperatures? Even though the formation of chlorine radicals obviously has a greater impact on ozone depletion, is it safe to assume that NO production in the absence of CFC’s can be disregarded?

    • Daniel Begay Says:

      There is data on NOx use before CFCs but I was unable to get a hold of it. CFCs are extrememly stable molecules, that is how they are able to bypass the troposphere into the stratosphere. The UV light up in the stratosphere is extremely intense. So intense, it is able to break the bonds of the sturdy CFCs.

      In the paper, Farman discusses the effects from both ClOx and NOx. He was able to observe that NOx could still break down O3, just not at the significant rate as ClOx.

  2. Adam Settimo Says:

    My question has to do with the background of this paper. I was reading that at first he didn’t believe the data, saying that it couldn’t be correct because others would’ve seen it by now as well. NASA, for instance didn’t observe the loss of ozone because the lower limits of their instrumentation was above the measured limits. Wouldn’t having no readings, even back ground, be an indication of something being wrong, even if it was unrelated to the ozone?

    Also, in figure 2 are the amounts of F11 and F12 in the same units as the total ozone? showing an inverse relationship between the halocarbons and ozone concentration?

    • Daniel Begay Says:

      I also questioned this, I would suspect that NASA was looking at ‘average’ values, and maybe didn’t bother to look at numerous amounts of individual raw data. As I found out, the satellites that NASA used were programmed to ignore any data that seemed ‘fishy’. It was thrown out as incorrect. However, nothing is ever really thrown out. After Farman’s data, they were able to pull those numbers back up and saw the exact same losses of O3.

      F-11 and F-12 are in units of pptv (parts per thousand by volume). Not the same units.

  3. Antony Says:

    This question might sound silly but how do we know we have a hole in the atmosphere and not a doughnut considering that the measurements were taken not from the south pole but from Haley Bay on the coast of Antarctica and some Argentine islands? Also is there not a hole in the ozone in the north pole because of the fact that most of the land mass in earth is on the northern hemisphere heating the northern polar vortex and disrupting it? Is it in the south because of the giant land mass continent, Antarctica, is stabilizing the colder temperature and thus the polar vortex?

    • Daniel Begay Says:

      Back in 1985, it wouldn’t be a silly question. Now? Maybe. NASA has an entire website dedicated to watching daily changes in the ozone in the Southern Hemisphere. Even in 1985, they had satellites that were able to measure the ozone.

      For the Northern Hemisphere, they don’t have the same conditions as the Southern Hemisphere. The S.H. is isolated by the air and sea currents (same ones that create the polar vortex). The heat plays a significant factor in the stability of the polar vortex. The heat is what causes the polar vortex in the N.H. to dissipate while in the polar night. On the other hand, the S.H. vortex is stable through the polar night and doesn’t dissipate until a couple weeks into spring (when the sunlight hits it).

  4. Hunter Burgin Says:

    Antarctica is the most unpopulated continent on earth due to the uninhabitable climate seen year round. Why is it exactly we are seeing the most significant damage to the ozone in a place like this and not China where the air quality pollution is the worst the planet has ever seen? As Farman discusses the summer/winter solstice have a great impact on the ozone degradation but why is it we don’t see the same extreme results in heavily industrial areas?

    • Daniel Begay Says:

      ClOx and NOx are affecting all parts of the world. The use of CFCs in the 1920s to the 1970s are still in the stratosphere to this day, and they are doing a lot of damage. Antarctica is an interesting case because of the polar vortex. The vortex causes a circulation of air current strong enough to cause weak transport of ozone in and out of the vortex. Virtually, a closed off system where chemical reactions of CFCs can cause heavy ozone loss. Due to Cl2 molecules being stored in Polar Stratospheric Ice Clouds (PSCs), photolysis form Cl radicals that are able to react with ozone, destroying it. Now that most of the ozone has been loss (and no new concentrations of ozone are able to enter this vortex) there is “hole” formed.

  5. Porter Marsh Says:

    The paper very clearly explained that there is a relationship between halogenated gasses and ozone concentration but I don’t understand what exactly happens between the two. Do halogenated gasses destroy existing ozone or merely inhibit its production? If halogenated gasses destroy existing ozone, do the halogenated gasses somehow pick up the Oxygen in ozone with a negative charge and release O2? Maybe some kind of radical chemistry because of the strong radiation?

    • Daniel Begay Says:

      These halogenated gases essentially destroy the ozone, ripping it apart into free atomic oxygen (O) and regular oxygen (O2). This is all being done by radical chemical reactions.

      Let’s say you have CCl2F2 (a CFC molecule). It is extremely stable, but dissociates under intense UV radiation. This rips off a Cl* atom (radical Cl), and it very reactive. It will react with an O3 molecule giving you a product of ClO* (radical) and oxygen gas. The newly formed ClO* will react with atomic oxygen (O) to give you another O2 molecule. Ending with the same Cl* you started with. It will then reenter the cycle.

      CCl2F2 + hv –> Cl* + CClF2
      Cl* + O3 –> ClO* + O2
      ClO* + O –> Cl* + O2

  6. Kevin Greenwood Says:

    My question on this process is more about what happens after spring. As I understand it, when the sun reappears, the UV light catalyzes ozone degradation. By around the end of spring though, the damage is done and after warmer air diffuses in from the lower latitudes carrying fresh CFCs and ozone, the ozone levels peak for the year and the cycle is ready to start again.

    How are these chlorine compounds eventually removed from the atmosphere? In studying this I read about how denitrification removes nitrogen dioxide as nitric acid sediments through polar stratospheric clouds; is there a similar mechanism for removing medium weight halogens, or halogen oxides from the atmosphere?

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