Montreal Protocol: How the world can save the ozone layer

The ozone layer protects humans, animals and plants from harmful ultraviolet rays, although it has been patient for decades. Why is protecting them still a success story – and what needs to happen?

September 1987: Representatives of 24 countries met in Montreal, Canada. They want to address one of the most pressing environmental problems of the 1980s: the destruction of the ozone layer by chemicals. On September 16, they signed a historic agreement, the Montreal Protocol. In this agreement, they commit to producing and consuming fewer ozone-depleting substances.

“Unique document”

More than 35 years later, the Montreal Protocol became the first agreement in the history of the United Nations to be ratified by all member states. “It’s quite crazy when you think about it that the whole world said: ‘We believe in it.’ We are convinced that this is right and important, and we signed up to it,” says Birgit Hassler. She and her colleague Hella Garni conduct research at the DLR Institute for Atmospheric Physics in Oberpfaffenhofen.

The anniversary of the Montreal Protocol on September 16 is now International Day for the Preservation of the Ozone Layer. For Hassler, the agreement is a “unique document.” Accordingly, it is always good to remember it and be able to say that the impact of the global treaty is clearly visible.

The Montreal Protocol – a scientific success story? “You can say that generally,” Garney asserts. “We understand what affects the ozone layer, the chemistry behind it, the physics behind it, the dynamics behind it,” Hassler says. “We know what affects, we understand it, and we can also say we acted that way.” “We have removed the main influencing factors for that, namely CFCs.”

The first ozone hole and its consequences

Hasler is talking about chlorofluorocarbons, or CFCs for short. In the past, these gases were often used as coolants or propellants for spray cans. The problem: CFCs are “very long-lasting,” Hassler says. They remain in the atmosphere for decades and cause depletion of the ozone layer that surrounds the Earth and protects it from the sun’s ultraviolet rays.

This occurred with particular force over Antarctica. A British research team discovered a site there in 1985 where ozone levels were below 220 Dobson units – 130 units below normal. Therefore, the thickness of the protective layer was less than 2.2 mm, which meant that more harmful UV rays could reach the ground.

News of the Antarctic ozone hole caused a sensation, including in the scientific community. Hassler says it was already known in the 1970s what chemical processes could be used to break down ozone. After the hole was discovered, it was also measured and the problem was scientifically proven.

Maximum CFC levels in the 1990s

The reaction of decision-makers around the world was: By adopting the 1987 Montreal Protocol, signatory states initially committed themselves to gradually reducing the production and consumption of CFCs and halons. In the years that followed, protections were further tightened. Other substances that were supposed to replace CFCs were included in the protocol.

Although measures began years ago, the concentration of CFCs in the upper atmosphere peaked in the mid-to-late 1990s, according to Hassler: “It took from the signing of the Montreal Protocol for CFCs to enter the atmosphere.” The global stratosphere, that is, the global stratosphere.” to the upper layers of the atmosphere, and is distributed.”

The ozone layer is slowly recovering

Garney explains that a decline in values ​​has been observed there since around 2000. However, natural degradation processes take a long time: “That is why the recovery of the ozone layer is relatively slow.” It could take until 2066 for the ozone layer to fully recover, according to a report published by the World Meteorological Organization and the United Nations Environment Program in early 2023.

Hassler and Garney are co-authors of the report. Hassler says the numbers come from model simulations. It indicates when the ozone layer would have returned to its 1980 state. There are uncertainties in the modeling process, but statistically it can be seen that the ozone layer is recovering in many places.

Garney adds that general statements are not possible due to natural fluctuations in the atmosphere, which affect the depletion of the ozone layer, and which are similar to temperature fluctuations on Earth. There are still years with large ozone holes.

One positive piece of news in the report, Hassler says, is that “over the past four years, more evidence has been found that the Montreal Protocol actually works.”

Switching to “naturals” as the next step?

Katja Bekken of the Federal Environment Agency also assesses the phase-out of substances such as CFCs and their climate-harming successors as a “really positive development at the international level.” Ozone-depleting gases have been virtually eliminated from production and consumption since the Convention entered into force.

Pekin believes that more work is needed, among other things, in switching to substances that are not chemical but natural, for example carbon dioxide: “We have taken a lot of steps and now partly end up using halogenated substances, which do not exist.” “And it still exists.” The ozone layer is not only harmful to the climate, nor does it have a high global warming potential, but its decomposition products cause major problems.

Politics always lags behind in finding internationally acceptable solutions. “We have to get everyone together at the table and that takes time,” Bacon said.

“Keep checking and searching.”

The Convention for the Protection of the Ozone Layer shows what could happen if this worked. “It’s always nice to say: The Montreal Protocol has been signed by everyone and it really helps,” says Hassler.

But: It is necessary to continue to monitor the situation, as Garney emphasizes: “I think it is an important statement that – even though the problem seems to have been solved – you still have to keep checking and seeing if what happens next will happen as one expects. “Both from the political side or from the scientific side.”