Pillalamarri Srikrishnarka
Dielectica traverses through the literature on this topic – and summarizes as they appear.
Key words: Chlorofluorocarbons (CFC), Montreal treaty, Global warming, Greenhouse
Chennai, India: Before directly going into the Montreal protocol, let’s travel back in time where we have read that the earth’s surface is protected from the harmful UV radiations coming from the sun. It’s a thin layer of ozone (O3) that is formed when a nascent oxygen species react with oxygen forming a particularly dense molecule that is highly efficient in absorbing the UV radiations. Typically present at 25 km from the earth’s surface and protecting us from skin cancer. Thinning of this protective layer was observed by Farman, Gardiner and Shanklin in 1985 over the Halley and Faraday stations in Antarctica [1]. There was about ~16 % decrease in the overall density of the O3 layer and it has been raised a serious concern. Upon further investigation into what led to this decrease, they understood the chlorofluorocarbons (CFCs) are the main culprits. These CFCs were commonly present in propellants, as coolants in refrigerators and also for aerosolizing paint and scent. The global body met in 1987 in Montreal and signed a treaty to phase out the manufacture and sale of CFC-based gadgets by 2010. This has been a success story, where a collective work led to an overall decrease in the CFC consumption and there has been a significant O3-hole coverage. However, due to the high lifetime (~ 50 years) of the CFCs, the atmosphere can fully recover only by 2050.
Now, let us consider a scenario wherein if there was no Montreal treaty and we continued the rampant usage of CFCs coupled with the increased consumption of fossil fuels, which caused an increase in the overall concentration of greenhouse gases in the atmosphere. Recently, a paper was published where the scientists have simulated a scenario that deals with the above question, the outcome is rather warming (pun aside). In their simulation, they have considered 3 scenarios; the first one, where the simulation follows the present time(with no control over the production of CO2 and the other greenhouse gases, but there is a ban on CFCs), the second one where the ozone layer was fixed in 1960 but no control over the production of CO2, and other greenhouse gases and the third is where there was no Montreal treaty and there is rampant usage of CFCs. The simulation was based on past historical data and predictions till 2100. Let’s look into their extreme scenario where there was no control over the production and consumption of the CFCs.
In figure 1a, we see the depletion in the ozone layer from the year of 2000 in both scenarios 1 and 3.However, there was a significant decrease after 2040 in the case of third scenario, where there was no Montreal treaty. Overall ~70 % decrease in the ozone layer was projected at the end of this century.
They observed an increase in the production of greenhouse gases till 2075, however, thisrise was decelerated in all of their simulations. What does this lead to? There was a steady rise in the temperature of the earth due to global warming. With the absence of the ozone layer by the end of the century, they observed an increased temperature by 6 k compared to that of 3.3 k. This increased temperature surely impacts everyone on the planet. Plants are the major source for carbon fixation, i.e., they inhale CO2, convert them into energy and release O2 into the atmosphere. What happens to this conversion when there is abundant UV radiation in the absence of the protective ozone layer? For every 10% increase in UV radiation, they observed a 3% reduction in the fixation. We might feel 3% is so minuscule and should it matter? Because of the poor carbon fixation, by the end of the century, the CO2 concentration doubled from 400 ppm to ~900 ppm. This news not only predicts the grim future if we don’t take care of our environment, but also the importance of the Montreal treaty which will save our planet.
The Montreal treaty is a success story, we need to remind ourselves that we all must towards the collective good over individual greed and make this world a better place for the future generation. All the governing bodies must meet regularly and implement the Paris Accords at the individual level, so that we can reduce global warming to less than 1.5 oC.
Source:
[1] PaulJ.Young et al.Nature,2021, 596, 384–388.
https://www.nature.com/articles/s41586-021-03737-3