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!

License to Krill II

Last week, I looked at the impact of a whaling ban on krill population and penguin populations. This post will discuss natural causes of changes in krill population that humans have no (direct or indirect) impact on. Like last week I will continue my focus on the West Antarctic Peninsula (WAP).

Figure 1 shows the change in winter sea ice extent from 1980 and 2010 and it is evident that there has been a reduction in winter sea ice extent during the period.

Figure 1. Winter sea ice extent in 1980 and 2010. Adapted from: Lenfest Ocean Program, (2011)

What is causing reduced sea ice extent?

Trivelpiece et al. (2011) and Vaughan et al. (2003) argue that this region has experienced a 5-6^oC increase in mean winter air temperatures in the past 50 years and this is resulting in decreased winter sea ice extent. Figure 2 shows a gradual increase in mean winter temperatures from 1950 to 2000. The grey region is of particular interest because it shows a warming trend from 1980 to 2001.

Figure 2. Mean winter temperatures at the Faraday Station. Adapted from: Lenfest Ocean Program, (2011)

By comparing figure 2 with figure 1, it is possible to correlate an increase in mean temperatures with reduced sea ice extent. However there are also other factors affecting sea ice extent.

Atmospheric and oceanic temperatures are changing in the WAP region due to changes in the El Niño Southern Oscillation (ENSO). This is reducing sea ice extent. El Niño is a weather event that occurs in the Pacific when there are weaker trade winds and this alters the climate in the surrounding regions, notably South America and Australia. During El Niño, warm water that would normally be in the West Pacific flows to the East Pacific and atmospheric pressure falls. South America experiences unusually wetter climate while regions near Australia experience more drought-like conditions. La Niña, on the other hand, is the opposite effect where atmospheric pressure increases, trade winds blow more intensely and cold water flows to the west Pacific.

Shevenell et al. (2011) explain that during La Niña events, there are higher sea surface temperatures in the WAP and this reduces sea ice extent. The reason for this is that there is high pressure in the Bellingshausen Sea (see figure 3) which brings warm air towards Antarctica, causing reduced sea ice extent. Furthermore, north easterly winds dominate which Harangozo (2006) and Quetin et al. (2007) find is negatively correlated with sea ice extent (strong north easterly winds lead to reduced sea ice extent) because it does not provide good conditions for ice formation. Furthermore, Shevenell et al. (2011) mention that there are positive feedbacks that enhance this effect, which can explain how winter sea ice extent falls even when there is no La Niña event. 

Figure 3: Bellingshausen Sea in West Antarctica. Adapted from The Encyclopedia of Earth

Sea Ice Extent and Krill Population

You must be wondering how sea ice extent is related to krill population. One way sea ice helps the krill population is through providing a habitat for microbial communities that young krill use as a source of food (Quetin et al. 2007). This improves their chance of survival and helps increase the krill population in the summer (ibid). Additionally, high sea ice extent and duration is positively correlated with reproductive success of krill (Loeb et al. 1997). The fact that winter sea ice extent is reducing means that there will be a smaller krill population surviving to the summer without the microbial communities to feed on. Hence, krill population will decline in the long term if La Niña events are frequent. Even under normal conditions when there is no La Niña event, there could be lagged responses in the system as it gets used to the normal climatic conditions. This can result in long term variability in krill populations. 

Hopefully in this post I have shown that krill populations are not solely affected by human actions. Natural climate variability is often under-stated in the media and in literature about wildlife. Today, I have highlighted how complex it is to try and understand how humans and natural variability affect Antarctica. 

This post has helped level the playing field, so the updated scores are now negative impacts 4, positive/ natural impacts, 3. Next week, I will move on to the effects of plastics on Antarctic seals. There are no surprises as to which way the scores will lean next week...

Natural Climate Variability and The Arctic Oscillation

Last week, I posted about the Larsen B ice shelf, proposing that its break up may have been human induced. There is a lot of uncertainty about climate change at the moment. In my very first post, I highlighted this issue explaining that it can leave you feeling confused about what is actually happening! Some researchers believe that the Larsen B ice shelf collapsed because of greenhouse gases, while other researchers, primarily climate change sceptics, believe that natural climate variability is actually contributing to the climate in Antarctica. This post is going to present their arguments. 

The Arctic Oscillation

Antarctica experiences changes in climate due to natural climate variability. One example of this is the Arctic Oscillation. The Arctic Oscillation fluctuates between a positive and a negative state, as shown in Figure 1. When in a positive state, the Arctic experiences unusually low atmospheric pressure and a warmer climate (Bjornaes and Pal, 2012, 'The State of the Poles', p.19). Furthermore, the jet stream blows strongly from west to east. When in a negative state, the Arctic experiences high pressure and the jet stream is weaker. 

Figure 1. Arctic Oscillation. Adapted from Bjornaes and Pal (2012, 'The State Of The Poles': p.19). 

The Arctic Oscillation affects the climate in Antarctica. A study by Chylek et al. (2010) investigated the effect of the Arctic Oscillation on the Antarctic climate and found that when the Arctic warms, Antarctica cools and vice versa. Additionally, Brunier and Brook (2001) observed this “bipolar see-saw pattern” from ice core records dating back to the last glacial period, demonstrating that this phenomenon is independent of human impacts. Figure 2 is a graph that illustrates the bipolar see-saw pattern, plotting temperatures against time. It is evident that as temperatures in the Arctic fall, in Antarctica they rise, despite emissions and other anthropogenic interferences with climate change.

Figure 2. Bipolar Seasaw Pattern. Source: Chylek et al. (2010).

Arctic (blue) and Antarctic (red) temperature time series smoothed by a 11 year running average (thin lines) or 17 year running average (thick lines)

Larsen B 

The bottom right of figure 1 shows a time series of the patterns of negative and positive oscillation indexes. The circled year represents the year 2002, the same year that the Larsen B ice shelf collapsed. The figure shows that the Arctic Oscillation Index (a measure of the magnitude of the Arctic Oscillation phenomenon) was negative that year, demonstrating that when the Arctic cooled, Antarctica warmed. It can be argued that this warming accelerated the melting of ice during the summer months which led to the break-down of the Larsen B ice shelf. In fact, Domack et al. (2005) conducted a study to determine the stability of the Larsen B ice shelf during the Holocene and found that the ice shelf had been thinning throughout the Holocene, i.e. throughout the past 11,500 years! This is evidence against human induced warming affecting the Antarctic right? 

How does the Arctic Oscillation work? 

In this description, I will explain how the oscillation leads to a warmer Arctic. A similar mechanism operates in the opposite direction to explain Antarctic warming as well. Described by Chylek et al.(2010), winds over the Southern Ocean are drawn to the surface by wind stress. This water is heated by the sun and the Atlantic surface current transports it away from Antarctica. As the water warms more, it travels towards the Arctic leaving Antarctica deficient in heat. The more efficient this transport, the greater the warming. This demonstrates the importance of the role of ocean currents in natural climate variability.

Conclusions

Arctic Oscillation and the work done by the researchers mentioned above are just one of many scientific models and explanations for the Larsen B ice shelf collapse and for climate in Antarctica. If studying Economics and geography at UCL has taught me anything, its that the world is full of uncertainties. Researchers aiming to devise what is human induced and what isn't in our planet will always end up with different explanations because Earth is complex. 

My personal view regarding this matter is that natural causes are not strong enough to determine what caused the Larsen B ice shelf to disintegrate. Although evidence presented suggests that Arctic Oscillation impacts the climate in Antarctica, uncertainty lies in the magnitude of the positive feedback systems between Antarctic waters and heating from the sun. There is also uncertainty in the strength of the transportation of these waters. To me, it seems unlikely that early humans at the start of the Holocene caused enough warming to contribute to the thinning of the Larsen B ice shelf, as illustrated by figure 3 in my post last week. 

That's all today! The score so far is 1-1. Next time, I will explore how tourism has affected Antarctica, thank you for reading!