Over AntarcticaThe ozone layer is empty(ozone depletion) has attracted widespread attention at the social level. In recent years, however, little has been said about the hole in the ozone layer. Is it because human beings have become numb in the face of disasters?Of course not, on January 9 this year, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) vividly explained to us what it means to "make a fortune in silence", and they released an exciting piece of good news:
The TCO (total ozone column) in the Antarctic is expected to return to 1980 levels around 2066, the Arctic TCO to 1980 levels around 2045, and the near-global average (60°N 60°S) to 1980 levels around 2040.
It's like the ozone hole saying, "I'm going to shrink quietly and surprise everyone." ”
Changes in the extent of the maximum ozone hole from 1979 to 2019).
This is a historic moment for humanity to solve this major climate crisis for the survival of human civilization for the first time through global efforts.
What is the ozone layer?Why is the ozone hole so important?How did humans repair the hole in the ozone layer?In this way, the problems that we only knew but did not understand in the past will be explained clearly at once today.
Changes in the ozone hole from 1960 to 2100).
What is the ozone layer?
The Earth's atmosphere is extremely thick, totaling several thousand kilometers, and can be easily divided into troposphere (0 10 20 km), stratosphere (10 20 50 km), mesosphere (50 85 km), thermosphere (85 800 km) and fugitive layer (800 3000 km) from bottom to top.
The troposphere is the part of the atmosphere closest to the surface of the earth, which contains almost the entire biosphere and is the environment in which we humans and other organisms liveAt the same time, it is also the densest atmospheric layer, with a total mass of about 75% of the total mass of the atmosphere. The temperature of the troposphere mainly comes from the surface, showing a situation of hot at the bottom and cold at the top, and the convective movement up and down is very active, hence the name troposphere.
The stratosphere begins at an altitude of about 10-15 kilometers (km) above the Earth's surface and extends to an altitude of about 50 km. Unlike the troposphere, the stratosphere is cold and hot, so the air flow in this layer is very stable. The stratospheric advection characteristics make it very suitable for aircraft operation, so most civil aircraft have a level flight phase at the bottom of the stratosphere.
The reason for the stratosphere's nature is related to the ozone layer, the protagonist of our article. Most ozone (about 90%) is found in the stratosphere, with the highest ozone concentrations occurring at an altitude of about 15 to 35 kilometers above sea level, often referred to as the "ozone layer". The ozone layer is able to absorb most of the heat from ultraviolet rays, heating the upper stratosphere, thus causing the stratosphere.
As for the mesosphere, thermosphere and fugitive layer, they are too far away from our human beings and have become the research category of space science in scientific research.
The ozone layer refers to the layer in the stratosphere with a high concentration of ozone, the peak of which occurs at an altitude of about 20 25 km. Although the ozone layer is called a layer, its abundance is still relatively low, and even in the regions with the highest concentration of the ozone layer, there are only a few thousand ozone molecules per billion air molecules. If we bring all the ozone molecules in the atmosphere to the surface of the earth and form a pure ozone layer that covers the entire planet, the average thickness of the resulting layer is about 3 millimeters.
But even this thin 3 millimeters plays a vital role in protecting life on Earth.
ozone in the atmosphere).
The role of the ozone layer.
The structure of the ozone molecule makes it extremely absorbent of ultraviolet light, which can convert the energy of most ultraviolet photons into heat and dissipate it
This characteristic makes most of the ultraviolet rays harmful to living organisms blocked by the ozone layer, and the huge energy is converted into the basic heat energy of heating above the stratosphere, so that the stratosphere can stably carry aircraft flights, and lay the foundation for the normal operation of surface organisms and weather systems.
At the same time, ultraviolet rays are also the main cause of the ozone layer;Oxygen at the top of the stratopause forms ozone under the action of short-wave ultraviolet (UVC) rays
The process of stratospheric ozone production).
In addition, certain natural activities deplete ozone;Such as volcanic activity, etc. The eruption of the Tonga volcano in January 2022 caused a 5% reduction in total stratospheric ozone over the Southwest Pacific and Indian Oceans in just one weekOn September 16 this year, monitoring data from the European Space Agency showed that the area of the Antarctic ozone hole reached 26 million square kilometers, close to the largest in history.
Over time, different natural activities and atmospheric chemistry have kept the ozone concentration in the atmosphere within a relatively stable rangeBut in recent decades, things seem to have changed.
The crisis of the ozone layer.
In the early 20th century, with the help of the Carnot cycle principle, an effective method of refrigeration was discovered, that is, by compressing and liquefiing gas, and then relying on the evaporation of the gas to absorb heat.
However, in early refrigeration plants, most of them used cheap and easily liquefied gases, such as sulphur dioxide (SO2) or ammonia (NH3). For example, SO2 can be at -10 or 2Liquefies at 5 atm, while NH3 liquefies at -33 or 9 atm.
Refrigeration equipment brings comfort and convenience to people's lives, but it also sows the seeds of disaster.
Both SO2 and NH3 are extremely irritating and toxic gases. In 1929, a large refrigerator used in a hospital in Ohio, USA, suffered a serious ammonia leak, killing more than 100 people.
The bitter lesson forced people to actively look for alternatives to these toxic gases, and soon, a very "excellent" alternative was discovered.
After studying the elements, the American inventor Thomas Millich found a substance: difluorodichloromethane (CF2Cl2), which is a boiling point -298 is a colorless, non-toxic, non-corrosive and non-pungent odor gas, and the gas does not contain element H and cannot be burned, and is considered an almost "perfect" refrigerant. In 1931, the American company DuPont began large-scale industrial production of this compound, trade name"Freon".(In today's numbering system, the compound is R12) and Freon has replaced almost all the previous refrigerants in just over ten years after its inception due to its stable, safe and efficient advantages, and has become popular in thousands of households. However, it is precisely this perceived near-"perfect" that has caused huge scars on the earth.
In 1924, the ozone spectrometer was introduced, and human beings began to regularly observe the ozone content in the atmosphere, and during this time, under the leadership of British meteorologist Gordon Dobson, the United States, Egypt, India, the Soviet Union, New Zealand, and the Spitsbergen Islands (Arctic) successively established observation points of ozone concentration, which opened the prelude to human research on the ozone layer.
In 1957, shortly after World War II, the Royal Society's expedition team built the Halle Research Station on the Brent Ice Shelf in Antarctica to conduct long-term observations of the atmosphere in Antarctica.
In 1974, American scientists Mario Molina and Sherwood Rowland proposed:The levels of chlorofluorocarbons (CFCs) in the environment are steadily increasing, and the large number of chlorine atoms produced by photolysis in the stratosphere can destroy the ozone layer in the atmosphere；Here's how this process works:
Obviously, the chlorine radicals in this reaction process are catalysts that can destroy the atmospheric ozone layer with great efficiency and continue to act in the atmosphere for decades, and the total reaction is roughly as follows:
(Note: Brominated hydrocarbons have a similar reaction, roughly as follows:.)
Although it looks basically the same as the chlorine catalytic process, the total reaction is:
It can be seen that although bromine and chlorine look about the same, there are still certain differences, and the catalytic reactions of the two are essentially different).
Ozone Destruction Cycle 1).
They mentioned that if HCFC production continued at the current annual rate of 10 per cent, the ozone content in the atmosphere would be reduced by 5.7 per cent over 20 years and by 30.50 per cent over 75 years.
The "difluorodichloromethane" mentioned above is a type of HCFC;It should be noted that the substances that are depleting to the ozone layer are not only HCFCs, but also halons such as difluorodichlorobromomethane, trifluorobromomethane and some other substances.
In the 70s, the chlorofluorocarbon industry in the United States was worth more than $8 billion, directly or indirectly supplying 1.4 million jobs, so the chemical giants did not care about this research result. Plans to reduce or ban HCFCs have been significantly hampered and cannot be implemented.
Ten years later, in 1985, scientists at the British Antarctic Survey made an astonishing discovery.
They analysed a large number of ozone observations from the Halley Research Station since 1956 and found that between 1977 and 1984, the amount of ozone in the atmosphere of Halley Bay, Antarctica, decreased by more than 40 percent in the spring (September to November). This study was quickly confirmed by the scientific community, and after the study it was discovered:The ozone depletion in the upper atmosphere is even more terrifying, and there is a huge "ozone hole" in the sky above the Antarctic continent...
This measured data, far more than a decade ago, shook the world and confirmed that chlorofluorocarbons (CFCs) have a tremendous lethal effect on the ozone layer;For a time, atmospheric ozonomics and dynamics became a research boom, and countless theories and observations proved this terrible situation, and society's attitude towards chlorofluorocarbons and other substances changed abruptly.
Redemption - "Nuwa Mends the Sky" action.
As the international community recognized the imminent crisis of the ozone layer, the catastrophe finally took a turn for the worse. On March 22, 1985, the international community signed the Vienna Convention for the Protection of the Ozone Layer, proclaiming a magnificent plan to save the planet. Two years later, on September 16, 1987, at the meeting in Montreal, the Montreal Protocol on Substances that Deplete the Ozone Layer was launchedOperation Mending the Heavens".
These two historic documents vowed to strengthen the control of ozone-depleting substances (ODS). The list of States Parties brings together the world's major industrial countries, such as the United States, the Soviet Union, Germany, etc. China also acceded to the two conventions in 1989 and 1991 respectively, and stood at the forefront of this war.
These agreements have not only led industrialized countries to reform their refrigeration systems, but also to the adoption of greener technologies in developing countries. Hazardous substances that were once widely used in the refrigeration, fire extinguishing and cleaning sectors are gradually being withdrawn from the market.
Now, we can comfortably say that the substances that used to harm the ozone layer in the past, such as fire extinguishing agents such as refrigerants such as R12, and even carbon tetrachloride (CCL4), which was familiar in high school, are no longer manufactured and used, and they are replaced by more environmentally friendly refrigerants and fire extinguishing agents, such as R134A (CH2FCF3), R32 (CH2F2), HFC-227EA (C3F7H) and Novec 1230 (C6F12O). These new materials have virtually no damage to the ozone layer.
This history teaches us that when people come together and work towards a common goal, we have the power to overcome environmental challenges, protect our planet, and create a more sustainable future. It also reminds us that each of us has a responsibility to remain committed to protecting our environment to ensure the sustainability of our planet.
Climate effects of the ozone hole in the layer.
As we all know, the function of the ozone layer is mainly to block high-energy ultraviolet radiation from the sun and the universe, and to provide a good environment for low-ultraviolet radiation for life on earth. Is that what the ozone layer does to that?
With the gradual development of atmospheric science, mankind has gradually recognized the deeper effects of the ozone layer, more preciselyIt is the influence of the chemical composition of the stratosphere on the climate
Despite increasing global warming, not exactly everywhere on the planet is heating up. As mentioned earlier, the ozone layer is mainly found in the stratosphere at an altitude of 20 to 50 km. However, what is remarkable is that;Between 1960 and 2020, the temperature here was around 0The speed of 6 is slowly decreasing.
Ozone's role in the atmosphere is to help maintain the temperature balance of the atmosphere, but if it decreases, it can affect the way the atmosphere moves, especially in the Antarctic region, and could have important effects on the Earth's climate and climate patterns.
When ultraviolet radiation emitted by the sun enters the atmosphere, ozone converts this high-energy radiation into heat. This helps protect the atmosphere from excessive ultraviolet rays that could be harmful to living organisms and the environment. Therefore, if ozone decreases, the stratosphere (a portion of the atmosphere) in the atmosphere cannot absorb enough heat, causing the temperature of the atmosphere to drop. This is especially true in Antarctica, the Antarctic region of the Earth.
At the same time, there is a significant temperature difference between the Earth's South Pole and the equatorial region. The equatorial region is generally hotter, while the South Pole is colder. This results in a flow of air from above to the Antarctic region, which forms a westerly wind belt around the Earth due to the Earth's rotation and the Coriolis force, which is the area where the air currents at high altitude flow from west to east.
The westerly wind belt exists not only in the troposphere, but also in the stratosphere. Its presence greatly weakens the flow of air between the Stratosphere and other regions in AntarcticaAs ODS continues to enter the Antarctic through various routes, the ozone depletion is not replenished, and an "ozone hole" is formed over the Antarctic.
With the continuous expansion of the ozone hole over Antarctica, the temperature of the stratosphere in this region gradually decreases, which increases the temperature difference between the upper Antarctic and the equatorial upper air, and the circum-Antarctic westerly wind belt and polar vortex will be strengthenedSo what are the implications of this?
The energy of the wind affects the flow of seawater. A strong westerly wind belt will accelerate the flow velocity of the Antarctic current around the pole, and at the same time, through stronger Ekman transport, a large amount of polar surface seawater will be transported to the north, causing the warm sea water in the polar bottom to move upward, warming the surface of the Antarctic Ocean and reducing Antarctic sea ice.
At the same time, we need to know that the energy of ultraviolet radiation, which cannot be stopped by the stratosphere, does not disappear in a vacuum, but it rushes to the surface, heats the troposphere, and further affects our weather system and atmospheric flow.
However, the effects of the ozone hole are only one of many factors affecting the atmosphere and ocean systems, and are too theoretical to prove. For example, between 2010 and 2015, the sea ice in Antarctica increased from about 2.5 million square kilometers to about 3.6 million square kilometers, and last year it reached 1.92 million square kilometers.
At present, we are not able to accurately model the weather system, so we have not been able to confirm the impact of the ozone hole, but we are finally seeing the dawn of victory in this war.
According to the research of American meteorologist Antara Banerjee and others, it can be confirmed that the effective implementation of the above two conventions has basically stopped the changes in atmospheric circulation caused by the Antarctic ozone hole, and the atmospheric changes caused by the depletion of the ozone layer will gradually recover.
Unity, perpetuating the flame of civilization, so to speakThe solution to the problem of the ozone layer is not the work of gods and saviors, but the fact that each of us has become a "Nuwa" to mend the heavens, to atone for our previous mistakes, and to change in order to live in harmony with nature。It is hoped that in the distant future, human beings will be able to overcome dangers, live in friendship with nature, unite as one, and sustain civilization.
*The content represents the author's views only.
It does not represent the position of the Institute of Geology and Geosciences of the Chinese Academy of Sciences.
If you need it, please contact the original***