With What Shall I Mend It, Dear Liza, Dear Liza?

Two years after Farman et al. (1985)’s findings were published, the ‘Montreal Protocol on Substances that Deplete the Ozone Layer’ was agreed. Under the Protocol, there are legally binding regulations to phase out (in other words, gradually reduce to nothing) the production and use of CFCs worldwide. The Protocol is now signed by 197 nations and continues to undergo revisions to set new targets for the CFC phase out process (The Australian Government: Department of the Environment, n/d). The original target was to reduce CFC production by 50% by 1999 (Hardy and Gucinski, 1989) but this progressed to a complete phase out by 1995 (The Australian Government: Department of the Environment). The Protocol does not only require CFCs to be phased out though. Other substances that can react with ozone are also targeted to be phased out. These substances are appropriately named as ‘ozone depleting substances’ (Weatherhead and Andersen, 2006). Furthermore, one fact to note is that the obligations for developing and developed countries are different. The total phase out target for developing countries is later than for developing countries, this reflects the fact that they may have a lower ability to adapt and find alternatives than developed countries.

How successful was the phase out?

There is wide consensus among academics, politicians, researchers and scientists that this protocol has been one of, if not, the most successful international treaty ever (for example, The Australian Government; Kofi Annan, former Secretary General of the United Nations; Aronson et al. 2011; Fahey, 2013; Mӓder et al. 2010). Indeed, what these scholars and politicians consider a success is the way that the agreement has reduced emissions of CFCs. By banning the production of CFCs and phasing out their usage, fewer chlorine molecules are able to react with ozone. Therefore the total layer of ozone gas should be restored. For example, Mӓder et al. ran a regression to analyse the effectiveness of the Montreal Protocol in protecting the ozone layer. The authors conclude from their analysis that their models have proven the effectiveness of the Montreal Protocol and the ozone layer is indeed protected by the regulations that came out of the Protocol.

This evidence seems convincing, right? I thought it was, until I came across a video by the National Geographic, which can be accessed here (apologies I am unable to post it up on this blog). The video states that the ozone hole (not layer!) peaked in 2008. Therefore despite the widespread appraisal of the Protocol, levels of ozone have not actually been increasing since the ban of CFCs. Additionally, when NASA measures the amount ozone in Antarctica using satellites, the results are unexpected, and counter what scientists, politicians, and the general public, believe about the success of this regulation. For instance, figure 1 shows that the amount of ozone over Antarctica through the years has only been increasing since the Protocol, with 2014 spring levels still significantly lower than in 1979. This means that since the ban of CFCs, ozone depletion has continued!

Figure 1. Ozone levels in October 1979, 1989, 1999 and 2014. Adapted from ‘Map Archives' from NASA (2015). The depth of the ozone hole is measured in Dobson units. Purple and blue indicate low levels of ozone. Green and red indicate high levels of ozone.

What can explain this? Does this mean that banning CFCs was ineffective? Not necessarily. There are many factors that affect the levels of CFCs that remain in the ozone layer. These factors can limit the effectiveness of banning CFCs. For example, the ban was implemented approximately 50 years after CFCs first came into use. This means that 50 years’ worth of chlorine and bromine molecules are currently present in the ozone layer, despite having been emitted years ago. Thus, although Montreal has been effective at preventing further chlorine and bromine molecules from reacting with ozone, it has been unable to alter the composition of CFCs that are still present in the stratosphere. Current CFCs in the stratosphere remains a challenge to address unless the international community wishes to physically remove them from the stratosphere. I am definitely not suggesting that they do this as this task is impossible to carry out! The point I would like to make is that, unfortunately, humans’ past actions are leaving an unwanted legacy on the ozone layer which is beyond human control. Solomon (2004) states that lifetimes of CFCs can be between 50 and 100 years, showing that this legacy is going to exist for a long time and will prevent the ozone layer from fully recovering in the short term.

Another influence on the ozone layer is climate. Solomon mentions that a warm spring can result in less ozone depletion, and therefore a cold spring can lead to more ozone depletion. Given this trend, global circulations such as the Arctic Oscillation can affect the levels of ozone that are observed in Antarctica. As my post on 22 October explained, the Arctic Oscillation affects the climate in Antarctica and can be used to explain the extent of ozone depletion (Zhou et al. 2001). A further climatic factor that affects the level of ozone is temperature. Weatherhead and Andersen (2006:41) mention that ‘colder conditions in the lower stratosphere promote the formation of polar stratospheric clouds which contribute to severe ozone depletion’. These factors show that climate can interfere with levels of ozone, and that ozone levels are interconnected with a whole range of natural climatic systems. This makes the analysis of ozone complicated and challenging to understand. Furthermore, because of the range of factors that affect ozone, the true effect of the Montreal Protocol will never be fully known. This means that celebrating the success of the Montreal Protocol may be naïve.

Conclusions

Although the Montreal Protocol has successfully reduced emissions of CFCs, this is not enough to deal with the problem of CFCs. CFCs are still in the stratosphere which means that the hole in the ozone layer will be present until the end of CFC lifetimes. Furthermore, climate also affects ozone levels. These additional determinants of ozone levels complicate scientists’ understanding of ozone and so it is difficult to understand how successful the Montreal Protocol really is. As figure 1 shows, ozone levels are worse now than they were before the Montreal Protocol. Because of this, perhaps celebrating the success of the Protocol is premature.

I would like to end this post with a reference to the song indicated in the title. This folk song is a story about a hole in a bucket that needs amending. In order to fix it, many actions are required until the character trying to fix it cannot because he ends up back where he started and the story forms a loop. In terms of the ozone layer, the Montreal Protocol has found a solution in the long term. However in the short term, CFC molecules will continue to destroy ozone molecules until the end of the CFC's lifetimes. This means that no additional measures can be implemented to protect the ozone layer as these attempts will only lead us back to the same problem (i.e. the problem of having chlorine and bromine molecules that were emitted in the past in the stratosphere). This post therefore emphasises that human actions from the past can continue to have effects on the Antarctic environment. This means that measures taken in the present do not compensate for the negative impacts resulting from the past. Because of this, I believe that the Protocol has achieved all it can for the moment and only time will tell how effective it is at restoring the ozone layer to natural levels. For this reason, I will award a point to the positive side. Now the score is 7-5.

My next post will sadly be my last and this is where I'll summarise the key findings from my blog. Thanks for reading!

There’s a Hole in the Ozone Layer, Dear Liza, Dear Liza

A blog about the human impacts on Antarctica would be incomplete without a post or two concerning the hole in the ozone layer. This is perhaps the most well-known human impact on the continent. Furthermore, this blog has so far considered the human impacts on the ground or on the marine environment. The atmospheric effects are also significant. 

The ozone layer lies between the stratosphere and the troposphere. The reason this layer is useful to us is that ozone molecules absorb ultraviolet (UV) radiation from the Sun and therefore protect us from the harmful effects of excessive UV radiation exposure (Martin and Hine, 2014, in ‘A Dictionary of Biology’).

The hole in the ozone layer was discovered by Farman et al. (1985). The authors collected data at the Halley Bay research station from 1957 to 1984 and, by using spectrophotometers, discovered that the ozone layer was depleting in spring (which is from September to November). The cause of ozone depletion was found to be a chemical reaction that occurs between chlorine and bromine atoms, that originate from chlorofluorocarbons, and ozone (Molina and Rowland, 1974). Chlorofluorocarbons (CFCs) were invented in the 1920s and commercially manufactured in the 1930s (The Ozone Hole, 2014). CFCs were used as cleaning solvents, in fire extinguishers, in aerosols and as refrigerants in air conditioning units (Tsai, 2014:883, in ‘Encyclopedia of Toxicology’). They were desirable because they possessed beneficial properties, including the fact that they were nontoxic and non-flammable. 

Molina and Rowland found that the reaction takes place in the presence of UV radiation. According to the NOAA (2008), during the Antarctic winter, ‘stratospheric ice clouds (PSCs, polar stratospheric clouds) form when temperatures drop below -78C. These clouds are responsible for chemical changes that promote production of chemically active chlorine and bromine’. During the winter, there is no sunlight in Antarctica. Thus, when spring arrives and the sun appears, chlorine and bromine molecules react with ozone molecules, causing it to break down. This is what creates a hole in the ozone layer during the spring. The reason why Antarctica in particular is subject to ozone depletion more than, say, the Arctic, is that cold temperatures are required for the reaction (Solomon, 2004). Figure 1 shows the monthly mean total ozone levels at Halley Bay in October, the middle of spring when ozone depletion occurs, from 1957 to 1984. The figure shows spring ozone depletion starting from the mid-1960s. CFCs have caused the ozone layer to deplete by as much as 50% (Smith et al. 1992) not just in spring, but in the winter as well (Rowland, 1986). The human invention of CFCs has therefore been the sole contribution to ozone depletion. 

Figure 1. Monthly mean total ozone levels at Halley Bay in October from 1957 to 1984. Source: Farman et al. (1985)

Effects

Without the protective shield from the ozone layer, more UV radiation reaches the Earth. For humans, greater exposure to UV can have severe health effects, such as increasing the likelihood of developing skin cancer (Norval et al. 2011), damage to DNA (Herrlich et al. 1992) and eye damage (Longstreth et al. 1995).

But I think it would be more relevant to focus on the effects of ozone depletion on species living in Antarctica. For instance, it has been observed that marine phytoplankton and diatoms have experienced DNA damage due to greater UV exposure (Buma et al. 2001). Furthermore, Smith et al. (1992) discovered that, in the Bellingshausen Sea (for a map of its location, see this post), a greater concentration of UV radiation is hindering photosynthesis which in turn is preventing the growth of phytoplankton. These findings illustrate how the marine ecosystem is negatively affected by the hole in the ozone layer. More specifically, phytoplankton is affected negatively. The importance of phytoplankton is illustrated by the food chain from my post from 29 November. Krill and penguins feed on phytoplankton. This shows how ozone depletion affects the food chain and therefore causes a change in the marine ecology of Antarctica. Additionally, this highlights that although ozone depletion happens in the stratosphere, there are indirect terrestrial effects observed as well.

Figure 2. Marine phytoplankton

I shall end this post with a short video to summarise the hole in the ozone layer, i.e. the key findings, the mechanism, the treaty…etc. It is presented by Shanklin, who co-discovered the hole in the ozone layer.

Next week, I will explore the subsequent regulation that followed from this discovery and its success at restoring the ozone layer. The updated score is 7-4, negative impacts seem to be taking the lead!