Ozone, a crucial atmospheric layer shielding our planet from the sun's harmful radiation, faced a grave threat when a hole was discovered. Surprisingly, this global climate concern is seldom discussed nowadays. But why has it faded from public attention? And how did this ominous hole form in the first place? To find answers, watch Dhruv Rathee's enlightening video!
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00:00Namaskar, friends.
00:01In October 1982,
00:03in a research station amidst the snowstorms in Antarctica,
00:07scientist Joseph Farman was taking some measurements.
00:11He was measuring the amount of ozone present in the Earth's atmosphere
00:14by using a machine.
00:16Suddenly, the machine gives a reading which is very strange.
00:19According to the machine, the amount of ozone in the atmosphere
00:22has decreased by 40% compared to normal.
00:25Joseph is not surprised to see this.
00:27He thinks, how can such a strange number, ozone levels,
00:30decrease by 40%?
00:31There must be something wrong with this machine.
00:33The machine is not working properly.
00:34It's very old, by the way.
00:36He also thinks that if the amount of ozone had really decreased so much,
00:39then surely NASA's thousands of satellites would have caught it.
00:43So he packs his stuff and goes back home.
00:46The next year, in October 1983, he comes again.
00:49This time, he brings a new machine with him
00:52and again takes measurements.
00:54According to the reading this time,
00:56the amount of ozone has decreased even more
00:58compared to last year.
01:00He thinks there is something wrong here.
01:02There is no such unbelievable reading possible.
01:04But again he thinks that if there was a problem,
01:07then surely NASA's huge agencies would have been able to find it.
01:10So again he packs his stuff and goes home.
01:13Another year later, in October 1984,
01:17when he comes back to do his work,
01:19he decides that this time he will take the reading
01:22to some other research station.
01:24About a thousand miles away from his original research station,
01:26he sets up the machine again for reading
01:29and takes measurements.
01:31He finds out that the amount of ozone has decreased even more.
01:34Here he realizes that this is an emergency situation.
01:38He brings his evidence to NASA
01:40and soon the world finds out
01:42about the ozone hole in Antarctica.
01:46Surprisingly, this ozone hole
01:48was growing very fast year after year.
01:52NASA's scientists had overlooked it.
01:54When they went back to look at their satellite data,
01:57they saw some such photos.
01:59In the year 1979, it was completely normal.
02:01In 1980 and 1981,
02:03a little bit of blue started to appear.
02:05In 1982, a proper hole started to appear.
02:08In 1983, this hole got bigger.
02:10And in the next year, 1984,
02:12this hole had become so big.
02:14The whole world is shocked by this news.
02:16If the ozone continues to decrease in this way,
02:19then this is going to be a terrible event.
02:21All the plants, animals,
02:23and humans on earth are in danger.
02:26If the ozone is over,
02:28then life on earth will be over.
02:30And the rate at which this hole was growing,
02:32it was being predicted that
02:34by the year 2050,
02:36the ozone layer would be completely over.
02:38Every October, a hole appears
02:40in the ozone layer over the South Pole.
02:42The hole in the ozone shield
02:44is the size of the continental United States.
02:46The protective ozone layer
02:48is being threatened as never before.
02:50We are all at risk.
02:51Ozone depletion is not a natural thing.
02:53It stems from human emissions
02:55of chemicals called chlorofluorocarbons
02:57or CFCs.
03:01Before we move ahead in the story,
03:03let's understand the ozone layer.
03:05Ozone is a gas
03:07as you must have studied in school.
03:09Its chemical formula is O3
03:11while the chemical formula of oxygen is O2.
03:13A molecule of ozone
03:15is made up of 3 oxygen atoms.
03:17Approximately 600 million years ago,
03:19an ozone layer was formed on earth.
03:21There is a zone in the atmosphere
03:23of the earth
03:25which is 15-35 km above the surface.
03:2790% of the ozone on earth
03:29is found in this area.
03:3132 km above the surface,
03:33the highest concentration of ozone
03:35is found which is
03:370.0015%.
03:39It's not a big number.
03:41This gas is actually found
03:43in a very small amount in the atmosphere.
03:45This small amount is very important
03:47for the earth.
03:49Ozone is actually made up of oxygen
03:51when the ultraviolet radiation of the sun
03:53collides with the molecule of oxygen.
03:55There is a very simple chemical reaction here.
03:57Because of the ultraviolet radiation,
03:59the molecule of oxygen
04:01splits the atoms of oxygen.
04:03When these separated atoms
04:05mix with the molecules of oxygen,
04:07ozone is formed.
04:09O2 plus O equals to O3.
04:11There is a constant cycle here
04:13where the molecule of ozone
04:15collides with an atom of oxygen
04:17and oxygen is formed again.
04:19A cycle of these two reactions
04:21continues and this cycle is
04:23called the Chapman Cycle.
04:25It's named after the scientist Sidney Chapman
04:27who explained this chemical reaction
04:29for the first time
04:31in May 1929.
04:33This reaction is called photodissociation
04:35or photolysis.
04:37Photo means light and dissociation means
04:39split up.
04:42Ozone layer is mainly known
04:44to protect us from the harmful ultraviolet
04:46or UV radiation of the sun.
04:48UV rays can cause sunburns,
04:50weaken our immune system,
04:52cause cataracts
04:54and cause skin and eye cancer.
04:56Now you might be thinking
04:58that if the job of ozone
05:00is to protect us from UV rays,
05:02then why do we apply sunscreen
05:04to protect ourselves from UV rays?
05:06The reason behind this is very interesting.
05:08Almost every wavelength of radiation
05:10emanates from the sun.
05:12Almost every kind of rays
05:14emanate from the sun in the electromagnetic spectrum.
05:16Whether it's visible light
05:18which is between 380-700 nm
05:20or UV rays,
05:22gamma rays or X-rays.
05:24These three rays are in the harmful category
05:26because they are ionizing
05:28and their long-term exposure
05:30is very harmful for humans.
05:32They can tear our body apart
05:34and go inside and change our DNA.
05:36Now even in the ultraviolet range,
05:38there are three categories of UV rays.
05:40UVA, which is the wavelength of 315-400 nm.
05:42UVB, which is the wavelength of 280-315 nm.
05:44And UVC, which is the wavelength of 100-280 nm.
05:46UVC's wavelength is the smallest
05:48so it is the most dangerous.
05:50Then UVB and then UVA.
05:52Now our ozone layer
05:54mainly stops X-rays, gamma rays
05:56and UVC radiation
05:58from reaching the earth.
06:00UVB radiation
06:02is only partially absorbed
06:04by our ozone layer.
06:06And UVA is almost
06:08not absorbed at all.
06:10It passes through the ozone layer.
06:12That's why the sunscreens
06:14protect us from UVA and the remaining
06:16UVB radiation.
06:18Most of the sunscreens
06:20only protect you from UVB radiation.
06:22That's why it is said to always buy
06:24a broad-spectrum sunscreen.
06:26A sunscreen that protects you from both
06:28UVA and UVB radiation.
06:30In the collection and analysis
06:32of UV radiation data,
06:34scientists were able to find
06:36the harmful effects of
06:38a particular wavelength on our skin.
06:40This data analysis was used
06:42by different companies
06:44in the formulation of sunscreens.
06:46To find out
06:48which ingredients
06:50provide the best protection
06:52from UVB radiation.
06:54When we talk about the end of the ozone layer,
06:56you can understand how much
06:58the risk increases.
07:00Because UVC radiation can also reach the earth.
07:02And the rest of the harmful rays can also reach the earth.
07:04This is the reason, friends,
07:06that before the ozone layer was formed on earth,
07:08600 million years ago,
07:10the life that existed at that time
07:12was so much inside the ocean
07:14that harmful radiation could not reach there.
07:16But photosynthesis is still possible.
07:18When life came out of the water
07:20and came to the earth due to evolution,
07:22the credit for this also goes to the ozone layer.
07:24After the arrival of ozone,
07:26many complex multicellular organisms
07:28were able to live on the sea
07:30There they got more exposure to sunlight
07:32and gradually
07:34they were able to come to the earth.
07:36I have talked about this in detail in the evolution video.
07:38Before the ozone layer was formed,
07:40there was nothing to protect the earth from harmful radiation.
07:42And after its formation,
07:44only 50-60 million years later,
07:46we saw diversification in life.
07:48Now all this happened millions of years ago.
07:50But humans learned
07:52about all these things
07:54only 200 years ago.
07:56In March 1839,
07:58a scientist in the city of Basel,
08:00Christian Schönbein,
08:02was experimenting on the electrolysis of water.
08:04By using electricity,
08:06he was separating water into oxygen and hydrogen.
08:08While doing these experiments,
08:10he noticed a strange smell.
08:12This smell was coming from a gas.
08:14And when he isolated this gas,
08:16he named this gas
08:18Ozone.
08:20The word Ozone actually comes from the Greek verb
08:22Ozyme,
08:24which means to smell.
08:26When the smell was coming,
08:28he named this gas Smell.
08:3026 years later, in 1865,
08:32it was discovered that
08:34the molecule of ozone is made up of 3 oxygen atoms.
08:36Later on, scientists also discovered
08:38that harmful radiations
08:40get blocked out by ozone.
08:42This gas turns into a dark blue liquid
08:44at a temperature of
08:46minus 112 degrees Celsius.
08:48And at minus 193 degrees Celsius,
08:50it becomes a solid.
08:52A solid of a deep purple colour.
08:54It is also known that
08:56the exposure of this gas is actually
08:58toxic for humans.
09:00While living in the atmosphere,
09:02this gas is protecting us.
09:04But if it stays with us on the ground,
09:06it is harmful for us.
09:08If we talk about the smell,
09:10it is similar to when you
09:12go to an electrical equipment
09:14and the smell you get during sparks.
09:16Or when there is a lot of electricity
09:18and the smell of soil.
09:20Some people find this smell sweet and fresh.
09:22Others find this smell metallic
09:24and like bleach.
09:26In 1921,
09:28a British geophysicist,
09:30G.M.B. Dobson,
09:32made a machine through which
09:34the concentration of ozone
09:36can be measured in the atmosphere.
09:38This machine is called
09:40Dobson Spectrophotometer.
09:42It is the standard device
09:44that we use to measure
09:46ozone in the atmosphere
09:48while sitting on the ground.
09:50In fact, the concentration of ozone
09:52is measured in Dobson Units.
09:54The units are named after Dobson.
09:56The normal thickness of the ozone layer
09:58is 3-5 mm,
10:00which is 300-500 Dobson Units.
10:02After 8 years of making the Dobson machine,
10:04Sidney Chapman made the equations
10:06for the formation of ozone
10:08and brought the Chapman Cycle to the world.
10:10The ozone on the ground
10:12is harmful for humans.
10:14It is called Bad Ozone.
10:16When scientists like
10:18Einstein were working with ozone,
10:20they used to have chest pain
10:22and difficulty in breathing.
10:24They also observed that
10:26small animals in an ozonized environment
10:28used to die.
10:30Today, bad ozone
10:32is increasing due to the use of fossil fuels.
10:34Specifically, Nitrogen Oxides,
10:36NOXs,
10:38like Nitrogen Dioxide,
10:40when they are released by burning coal
10:42or the exhaust of a car,
10:44ozone is formed at the surface level.
10:46Due to heat and UV rays,
10:48the Nitrogen Dioxide
10:50splits into Nitrogen Oxide
10:52and an Oxygen atom.
10:54This Oxygen atom then reacts
10:56with the Oxygen molecule to form ozone.
10:58Besides Nitrogen Oxides,
11:00VOCs are also responsible.
11:02Like Benzene,
11:04which comes from the combustion of gasoline.
11:06Sometimes, it evaporates in paints
11:08which are applied to the walls
11:10or in nail polish removers.
11:12It depends on the weather conditions
11:14how much bad ozone will form.
11:16In the months of summer,
11:18it forms more when there is more UV radiation
11:20and more heat is present.
11:22On the other hand, when it rains
11:24and there is high humidity,
11:26less ozone is formed.
11:28This is why ozone is also considered
11:30as an air pollutant.
11:32Look at this article from 2023.
11:34Ozone emerges as lead air pollutant
11:36in Delhi.
11:38Often, we focus more on air pollutants
11:40like PM2.5, Carbon Monoxide
11:42and ignore ozone.
11:44Some of you may think
11:46that this is not a good thing.
11:48That a lot of ozone is produced on the ground
11:50and there is an ozone hole on the top.
11:52The ground ozone will mix with the top
11:54and the ozone hole will close.
11:56This is beneficial for us.
11:58But unfortunately, this does not happen.
12:00The first reason is that the ozone
12:02does not mix with the top.
12:04The second reason is that the concentration
12:06on the ground is harmful for us.
12:08It is still a very low concentration
12:10compared to the concentration
12:12we need in the atmosphere to form the ozone layer.
12:14And as you saw from different chemical reactions,
12:16ozone is also a very reactive gas.
12:18So we cannot even transport it
12:20so easily to the top.
12:22Now the question is that if
12:24ozone is forming so much because of humans,
12:26then how did the ozone hole problem arise?
12:28It's about the 1950s-60s.
12:30There were a lot of research stations
12:32in Antarctica.
12:34They were made to study space,
12:36the earth and the weather.
12:38And some of these research stations
12:40were actually monitoring the ozone layer.
12:42Specifically, there was an American station
12:44in Antarctica from 1961
12:46where a Dobson spectrophotometer
12:48was installed.
12:50In August 1964, for the first time,
12:52satellites were used to measure
12:54the ozone concentration.
12:56These were NASA's Nimbus program
12:58weather satellites.
13:00In the 1970s, NASA was worried
13:02that all the spacecrafts
13:04that were sent to the moon
13:06might get disturbed by the ozone layer.
13:08They were worried that the spacecrafts
13:10might have a negative impact on the ozone layer.
13:12Fortunately, the spacecrafts
13:14didn't have any negative impact.
13:16But the negative impact was caused
13:18by some small daily life things.
13:20A chemical that was in your
13:22hairspray bottle,
13:24in the can of shaving cream
13:26and was used as a solvent in the fridge.
13:28The category of this chemical
13:30is called chlorofluorocarbons
13:32or CFCs.
13:34In June 1974,
13:36a controversial scientific paper was published
13:38by these three scientists who won the Nobel Prize.
13:40In this scientific paper,
13:42they showed how due to CFCs,
13:44the ozone in the atmosphere
13:46is getting destroyed.
13:48These scientists warned that
13:50CFCs have a lifespan of 40-150 years.
13:52And they have the potential
13:54to completely destroy the ozone layer.
13:56These scientists made a lot of fun
13:58after this paper came out.
14:00Some people didn't believe it at all.
14:02They said, what nonsense is this?
14:04It's not like that.
14:06By that time, CFCs had become
14:08very common chemicals.
14:10They were being used in a lot of
14:12manufacturing applications.
14:14The advantage of CFCs was that
14:16they were very stable on the earth.
14:18But the problem was that
14:20when they collided with the sun's radiation
14:22in the atmosphere,
14:24they released chlorine.
14:26And after the release of chlorine gas,
14:28there was a very dangerous reaction.
14:30Look at this reaction.
14:32Chlorine gas reacts with the ozone
14:34and produces Oxygen
14:36and Chlorine Monoxide.
14:38As I told you in the Chapman Cycle,
14:40a cyclic reaction was already happening.
14:42Oxygen's individual atoms were present
14:44in the atmosphere.
14:46Chlorine Monoxide reacts with
14:48Oxygen's atoms and produces
14:50Oxygen and Chlorine again.
14:52Do you understand the meaning of these two reactions?
14:54Chlorine reacts with ozone
14:56and after the second reaction,
14:58Chlorine is released again
15:00and Oxygen is released.
15:02The Chlorine that is released again
15:04can react with Ozone again
15:06and Ozone will be eliminated
15:08and more Chlorine will be produced.
15:10This has become a very dangerous loop.
15:12One Chlorine atom can
15:14eliminate thousands of ozone molecules.
15:16Later, some scientists
15:18did experiments to find out the truth
15:20of this scientific paper.
15:22It was found that it was true.
15:24Each Chlorine atom present in these CFCs
15:26is having a major impact on the ozone layer.
15:28But the scientists still estimated
15:30that if things continue like this,
15:32then due to CFCs,
15:342-4% ozone layer will be eliminated
15:36by the year 2099.
15:38This was the theoretical prediction
15:40of the scientists.
15:42So people didn't worry much.
15:44Now let's come to the story of Joseph Farman
15:46which I told you in the beginning of the video.
15:48In a research station in Antarctica,
15:50Joseph Farman
15:52goes there every year
15:54and used to check and measure
15:56the ozone level.
15:58Suddenly, in 1982, his reading showed
16:00that 1 third of the ozone layer
16:02has been eliminated in Antarctica.
16:04This reading was unbelievable
16:06because the scientists estimated
16:08that only 2-3% of the ozone layer
16:10will be eliminated.
16:12That's why he thought that
16:14his machine must have broken down.
16:16So next year, he brought a new machine
16:18and again showed the same reading.
16:20Then he thought that there must be a problem
16:22and went to Antarctica.
16:24Again, he found out the same thing.
16:26When he told NASA,
16:28NASA's scientists measured it,
16:30we saw these horrific images.
16:32It showed us that in every year,
16:34the ozone hole is increasing rapidly.
16:36All the theoretical predictions
16:38that the scientists had made
16:40were completely wrong.
16:42Actually, the situation was very dangerous.
16:44In August 1985,
16:46the world was shown the first map
16:48of the ozone hole
16:50on Antarctica.
16:52The measurements on this map
16:54are written in Dobson units.
16:56As I said, 300-500 units
16:58was the normal measurement
17:00of the ozone layer thickness.
17:02But in the middle of the ozone hole,
17:04you can see that these measurements
17:06had fallen below 200 Dobson units.
17:08In some places,
17:10almost 150 Dobson units were touching.
17:12Every October, a hole appears
17:14in the ozone layer over the South Pole.
17:16What worries scientists most is
17:18to ensure what causes the hole.
17:20Now that you have understood
17:22the entire scientific background,
17:24you can know that the ozone hole
17:26is actually not a hole.
17:28It is a metaphorical way of saying
17:30that the ozone layer has become
17:32very thin.
17:34The thing we call the ozone hole
17:36is actually the ozone layer
17:38whose thickness
17:40has reduced by 1 third.
17:42In 1977,
17:44250 Dobson units were measured
17:46and in 1984,
17:48160 Dobson units
17:50were measured.
17:52It was obvious that
17:54we needed to take action immediately.
17:56But there was still a question
17:58in the minds of scientists.
18:00Why is the ozone hole
18:02forming above Antarctica?
18:04There are many reasons behind this.
18:06First, the air that goes up
18:08converges towards the North and South Poles.
18:10So the ozone layer was not only
18:12seen above Antarctica
18:14but also above the North Pole.
18:16But in Antarctica,
18:18it was seen even more.
18:20The reason behind this is the
18:22Polar Stratospheric Clouds.
18:24These are a type of clouds
18:26that are seen above Antarctica.
18:28The droplets of these clouds
18:30are a mixture of nitric and sulfuric acids.
18:32Chemicals like chlorine and bromine
18:34react on the surface of these droplets
18:36to break the ozone.
18:38These clouds only form at a temperature
18:40of minus 78 degrees Celsius.
18:42The temperature increases
18:44and the cold conditions
18:46are not so severe in the Arctic.
18:48They are mostly above Antarctica.
18:50That's why the ozone layer
18:52is seen the most here.
18:54In the stratosphere part of the atmosphere,
18:56the air is not so cold.
18:58At the starting point,
19:00the average temperature is minus 51 degrees Celsius.
19:02And at the top,
19:04the average temperature is minus 15 degrees Celsius.
19:06The temperature increases
19:08when the height increases.
19:10That's why Antarctica was most vulnerable
19:12to this threat.
19:14But the good news in this story is
19:16that the politicians immediately
19:18take action.
19:20After this finding in 1985,
19:22in 1986,
19:24the United Nations starts
19:26negotiations.
19:28A treaty is started
19:30to ban CFCs all over the world.
19:32In 1987,
19:34a Montreal Protocol is made
19:36which comes into force in 1989.
19:38Later, in the history of the world,
19:40the first United Nations treaty
19:42is made which is signed
19:44by every country in the world.
19:46All 198 member countries
19:48of the United Nations
19:50ratify this treaty.
19:52Because of this, CFCs are replaced
19:54by HFCs,
19:56Hydrofluorocarbons,
19:58which don't have a bad effect on the ozone layer.
20:00In the 1990s,
20:02action is taken by the countries
20:04to reduce the use of CFCs.
20:06Still, in the year 2000,
20:08the largest ozone hole is seen
20:10which was almost 30 million km2.
20:12This is because
20:14there is a delay in taking action
20:16and its impact.
20:18But the positive results start to be seen
20:20soon after this.
20:22CFC consumption was 800,000 metric tons
20:24in the 1980s, all over the world.
20:26In 2014, it fell down
20:28to only 156 metric tons.
20:3299% CFCs
20:34are eliminated by all the countries
20:36of the world.
20:38This is the biggest achievement
20:40in the history of humanity.
20:42Within 5-10 years,
20:44the problem was identified
20:46and all the countries of the world
20:48started taking action on its solution.
20:50And today, we can see the result.
20:52The ozone hole is getting smaller.
20:54As per the report of the United Nations
20:56released in January 2023,
20:58in the next 40 years,
21:00things will be back to normal
21:02and the ozone hole will be completely eliminated.
21:04They have projected
21:06that by the year 2040,
21:08the ozone layer will come back
21:10to the level of 1980.
21:12By the year 2045,
21:14the ozone hole above the Arctic
21:16will be completely eliminated.
21:18Our ozone layer will be fully recovered.
21:20And above Antarctica,
21:22our ozone layer will be fully recovered
21:24in the year 2066.
21:26Two years ago, another study was done
21:28which found that
21:30due to climate change,
21:32the effects of climate change
21:34are under control.
21:36If CFCs were still used,
21:38the global temperature
21:40would have increased
21:42from 2.5°C to 1999.
21:44In the year 2016,
21:46hydrofluorocarbons,
21:48HFCs were also included
21:50in the list of controlled substances.
21:52In the next 30 years,
21:54HFCs are also being phased out.
21:56This is because HFCs
21:58are 1000 times more effective
22:00than carbon dioxide in heat-trapping.
22:02So even though HFCs
22:04don't have a negative effect on the ozone hole,
22:06they have a negative effect on climate change.
22:08From this entire story,
22:10we learn a very important lesson.
22:12If governments and people
22:14from all over the world
22:16fight about the problems of the world,
22:18their solution can be found very soon.
22:20The next biggest problem
22:22that the world is facing
22:24is climate change.
22:26Again, all people and governments
22:28need to take united action
22:30to deal with this problem.
22:32What is your opinion on this?
22:34Tell us in the comments below.
22:36If you liked this video,
22:38you can click here to watch
22:40the video on cloud seeding
22:42which I explained about
22:44the technology of artificial rain and cloud seeding.
22:46Thank you very much!
22:56You