The ozone hole is intensifying again, who is secretly destroying the ozone layer?

In recent years, the problem of “ozone hole” seems to have rarely appeared in people’s vision.

With the signing and implementation of the Montreal Protocol, the problem of ozone layer depletion is gradually improving.

However, monitoring data in recent years show that some unknown emission sources are secretly destroying the ozone layer.

The ozone layer is a thin layer of ozone-rich area in the upper atmosphere, which is an umbrella for all life on earth.

Most of the ultraviolet rays from the sun will be blocked by the ozone layer.

The ultraviolet rays that we usually carefully apply sunscreen to protect against are actually only a small part of the damage caused by ozone layer leakage.

The ozone hole is intensifying again, who is secretly destroying the ozone layer?
The ozone hole is intensifying again, who is secretly destroying the ozone layer?

In the 1970s, mankind discovered that the ozone layer was being consumed. Over Antarctica, an “ozone hole” appeared and gradually expanded.

Humans soon found the killer-chlorofluorocarbons (commonly known as freon) and other ozone-depleting substances.

This makes the world nervous. If the ozone layer is depleted, the incidence of skin cancer and other diseases will be much higher.

In 1987, 26 countries including China signed the Montreal Protocol, after which the number of parties increased to 197.

The protocol stipulates that all parties must phase out the production and use of ozone-depleting substances. After 30 years of efforts, the deterioration of the ozone layer has finally been stopped.

In 2015, NASA announced that the Antarctic ozone hole might shrink to its pre-1980s size by 2075. [1]

However, monitoring data in recent years show that the secret emission of an ozone-depleting substance is destroying the ozone layer on which we depend.

Changes in Antarctic ozone hole from 1979 to 2015. Photo credit: NASA
Changes in Antarctic ozone hole from 1979 to 2015. Photo credit: NASA

In recent years, monitoring data from all over the world show that the concentration change of trichlorofluoromethane (CFCl3, a class of ozone-depleting substances specified in the Protocol) is abnormal, which may mean the increase of its emissions.

The Protocol and its amendments stipulate that all parties should ban the production and use of trichlorofluoromethane by 2010 at the latest.

According to the data submitted by various countries to the United Nations, production activities have indeed stopped.

Countries have successively introduced alternative schemes to replace trichlorofluoromethane with substances that are less harmful or harmless to the ozone layer.

So where did these increased emissions come from?

If there is no man-made production, then the continuous release of the previous trichlorofluoromethane-containing materials should be the main emission source.

Assuming that these materials no longer increase, the release rate of trichlorofluoromethane will be slower and slower until it is lower than the natural degradation rate, and its concentration in the atmosphere will decrease rapidly.

Monitoring data also confirm this point. Before 2002, the concentration decline rate of trichlorofluoromethane gradually accelerated.

Changes in atmospheric concentration and emissions of trichlorofluoromethane.  Source: Nature[2]
Changes in atmospheric concentration and emissions of trichlorofluoromethane. Source: Nature[2]

After 2002, the production of trichlorofluoromethane has been close to zero, and thereafter the decline rate should be faster than before.

However, the actual situation is that the rate of decline has not changed.

After 2012, the rate of decline did not get faster, but only half as fast as before.

The National Oceanic Administration (NOAA) of the United States has obtained similar results in 12 monitoring points on four continents using different monitoring systems.

It can be said that this change is beyond doubt.

The degradation rate is basically unchanged, and only the increase in emissions can explain this anomaly.

Analyzing the monitoring data, scientists found that an average of 13,000 tons more were emitted each year from 2012 to 2016, an increase of 25% over the previous year.

Don’t belittle this emission. Ten thousand tons of HCFCs are enough to consume hundreds of millions of tons of ozone.

In addition, the greenhouse effect of trichlorofluoromethane is 4,750 times that of CO2.

In this regard, the annual emissions of trichlorofluoromethane in recent years have affected more than 60 million tons of CO2.

Where exactly are these sudden increases in emissions coming from?

The emission of trichlorofluoromethane is mainly divided into two parts:

  • The first is human factors, such as production and use or release from artificial materials;
  • The second is the release of natural factors, such as the ocean and other environments.

Due to the distribution of population and industry, the concentrations of pollutants in the atmosphere in the northern and southern hemispheres are generally different, which is highly correlated with anthropogenic emissions.

After 2012, the hemispheric difference in atmospheric concentrations of trichlorofluoromethane increased by 50%.

In order to eliminate the influence of natural factors such as atmospheric exchange, scientists simulated the movement of pollutants in the atmosphere.

The results show that the hemispheric difference will increase only after the increase of anthropogenic emissions, with little influence from natural factors.

Human activities are the main reason for the increase of atmospheric concentration of trichlorofluoromethane.  Source: Pixabay
Human activities are the main reason for the increase of atmospheric concentration of trichlorofluoromethane. Source: Pixabay

This confirms that the increase in emissions comes from human activities and also narrows the target to the northern hemisphere.

On the other hand, scientists have studied the monitoring data of Mauna Loa Observatory in Hawaii and found that the concentration change of trichlorofluoromethane is very consistent with some gases obviously originating from human emissions, especially some pollutants that have been confirmed to come from East Asia.

After simulating the impact of emissions from different regions on monitoring points, the reverse emission source is most likely to come from eastern Asia.

Will the release of materials increase, such as the demolition of old houses and equipment using such materials?

If so, the developed countries that first used such materials should first observe the increase in emissions.

However, data from the US National Oceanic Administration and the Global Atmospheric Experiment show that emissions from Europe and the United States have been declining [3].

Then, the only possibility is that someone in eastern Asia is secretly producing and using trichlorofluoromethane, which has been phased out for a long time.

Doubts will clear up when facts are known

To further determine the location of emission sources, scientists analyzed monitoring data from Japan’s National Environmental Research Institute in southern Korea and Okinawa, Japan.

The two monitoring points are sensitive to emissions from western Japan, the Korean Peninsula and eastern China.

The data show that East Asia’s emissions have indeed increased since 2012, confirming previous predictions.

Through model inversion, the main emission sources are Shandong and Hebei.

  • After 2012, the eastern part of China will emit an average of 13,000 tons of trichlorofluoromethane every year.
  • From 2014 to 2017, the average annual emissions will exceed 70,000 tons, accounting for 41%~64% of the global emissions increase.

Researchers believe that if some disturbing factors are excluded, the proportion may be higher in fact.

Emission distribution of trichlorofluoromethane from 2014 to 2017 simulated based on monitoring data.  Photo Source: References [4]
Emission distribution of trichlorofluoromethane from 2014 to 2017 simulated based on monitoring data. Photo Source: References [4]

The spatial distribution of the simulated emissions is inconsistent with the population density, so it is unlikely that the demolition of buildings will cause release.

The speed of building demolition and refrigerator ownership in China are also far from explaining the surge in emissions in recent years.

In addition to foreign studies, some studies in China have also pointed out, either explicitly or implicitly, that the concentration of trichlorofluoromethane in China is generally high [5].

Finally, there is only one possibility: some people are secretly producing trichlorofluoromethane, which has long been phased out. Unfortunately, they are in China.

But the Chinese government has already banned production. What is the reason why these people do not hesitate to break the law?

Find the root of the problem

Before the ban on production, trichlorofluoromethane was mainly used as foaming agent to produce polyurethane foam, a kind of heat insulation material, which is widely used in construction and refrigeration industries.

In 2015, China’s polyurethane foam output reached 4.8 million tons, accounting for more than 35% of the global output [6]. The link between the research results and the world’s largest market has focused the attention of global environmentalists on China.

In 2018, after Nature published a study on the increase in emissions of trichlorofluoromethane, the Environmental Investigation Bureau, an environmental protection organization in Washington, launched an investigation into some Chinese enterprises.

They contacted 25 enterprises that produce and sell foaming agents, and received responses from 21 of them.

Alarmingly, 18 of them said they used trichlorofluoromethane, and even some of them used all their products.

One supplier said that 70% of foaming agents in China will use trichlorofluoromethane.

In 2007, the State Environmental Protection Administration of China issued a notice stipulating that the production of ozone-depleting substances such as trichlorofluoromethane except for special uses would be completely banned by July of that year.

The government recommends the use of dichlorofluoroethane and other substances that are less harmful or harmless to the ozone layer.

However, an enterprise investigated by the Environmental Investigation Bureau said that the amount of trichlorofluoromethane used in the Chinese market is 10 times that of its substitutes.

The reason is very simple, dichlorofluoroethane is more than 15000 yuan per ton, while trichlorofluoromethane is only a few thousand yuan [7].

In recent years, with the development of China’s construction industry and the implementation of the national energy conservation and emission reduction plan, the demand for thermal insulation foam has increased rapidly.

After trichlorofluoromethane was banned, the demand for its substitutes increased significantly. However, dichlorofluoroethane is also a substance that depletes the ozone layer, with only minor harm.

The Protocol stipulates that China needs to phase out this product in 2013.

Therefore, the government gradually restricted its production and use. As a result, the market price of dichlorofluoroethane has soared.

Some enterprises do not have the ability to develop and use new materials and start to produce trichlorofluoromethane in violation of regulations.

Due to its easy production, low cost and better performance, trichlorofluoromethane is resurgent in the market.

The manufacturer showed EIA investigators the inventory of products containing trichlorofluoromethane.  Source: EIA[8]
The manufacturer showed EIA investigators the inventory of products containing trichlorofluoromethane. Source: EIA[8]

To lock the stable door after the horse is stolen

Of the 25 enterprises contacted by the Environmental Investigation Bureau, 18 said they had violated production regulations.

According to market and survey data, they estimated that the annual emissions of trichlorofluoromethane from China’s production and use exceeded 10,000 tons in 2012-2017.

This data is consistent with previous research results. According to their calculation method, China’s annual production of trichlorofluoromethane may exceed 200,000 tons in recent years.

The Ministry of Ecological Environment announced at a press conference last year: “From 2010 to the first half of 2018, the country investigated and dealt with 14 cases of illegal production of trichlorofluoromethane, destroyed about 84 tons of illegal trichlorofluoromethane and dismantled production facilities. Penalties will be imposed on 4 enterprises that illegally use trichlorofluoromethane. ” [9]

These figures are very telling.

During the EIA investigation, some enterprises said that they fully understood that their production behavior was illegal, but they would avoid detection by various means, such as someone prepared legal substitutes to avoid detection.

China has also begun to take some actions.

For example, in March this year, the Shandong provincial government awarded the first prize for scientific and technological invention to bi Yu, a professor at Shandong university of technology, in recognition of his invention of fluorine-free chlorine polyurethane foaming agent.

In recent years, the government has repeatedly stressed the need to crack down on illegal production of ozone-depleting substances to attract attention.

If the current situation is not improved in time, the efforts made by countries around the world to cooperate in protecting the ozone layer in the past decades may be threatened, and the recovery rate of the ozone layer will undoubtedly slow down.

I hope that safe and low-cost substitutes can be promoted as soon as possible, and illegal manufacturers can be punished and disciplined in a timely manner.

This is not only related to China’s international image, but also to the health of people all over the world.


  • NASA. (2015). The Antarctic Ozone Hole Will Recover.
  • Montzka, S. A., et al. (2018). An unexpected and persistent increase in global emissions of ozone-depleting CFC-11. Nature, 557(7705), 413.
  • Prinn, R. G., et al. (2018). History of chemically and radiatively important atmospheric gases from the Advanced Global Atmospheric Gases Experiment (AGAGE).
  • M. Rigby, et al. (2019). Increase in CFC-11 emissions from eastern China based on atmospheric observations. Nature.
  • Lin, Y., et al. (2019). Observations of high levels of ozone-depleting CFC-11 at a remote mountain-top site in southern China. Environmental Science & Technology Letters.
  • Market Demand Forecast and Competition Analysis of China’s Polyurethane Industry in 2017. s=/Home/Article/detail/id/539.html
  • Shao Changying. (2017). Current Situation of HCFC-141b Elimination Policy and Supervision in Shandong Province. Polyurethane Industry, B05.
  • EIA. (2018). BLOWING IT: Illegal Production and Use of Banned CFC-11 in China’s Foam Blowing Industry.
  • (2018). Ministry of Ecological Environment: Zero Tolerance for Violations Involving Ozone Depleting Substances.
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