The Stratospheric Ozone Problem

First, what is the ozone problem? About 2 billion years ago Life on Earth was entirely single-celled organisms living in the oceans when one type of bacteria (Cyano) began emitting Oxygen to the atmosphere. The oxygen changed the entire biosphere such that Oxygen-emitting plants could develop.

When diatomic Oxygen (O 2 ) is impacted by solar radiation, it splits into two Oxygen atoms. These each combine with O 2 molecules to form O 3, called Ozone.

The ozone is mainly in the stratosphere because that’s where there is a balance between the amount of Oxygen and the amount of UV radiation The Ozone absorbs UV radiation. Once the protective Ozone layer was established, biological organisms could live outside the ocean.

Ozone depletion in the stratosphere threatened to eliminate our protective layer, allowing more high-energy radiation to get through.

Ozone depletion is concentrated over the Antarctic but can be found over the Arctic as well. The effect was predicted by Rowland and Molina in 1974.

Rowland and Molina were not only vindicated, they were honored.

Has the Montreal Protocol worked? Show animations from nasa.gov/

2013: From The “hole” is the area below 220 DU, around 24 million square km.

2000: The maximum size is 30 million square kilometers. This is as big as it got.

From The minimum for 2013 was 160 DU on Sept 29.

In 2000 the minimum was 89 DU on Sept 29

The all-time minimum in Ozone was 73 DU, recorded on Oct 10, 1994.

Have we “turned the corner” on Ozone depletion?

The updated data from Halley Bay balloons now agrees with satellite observations and Ozone is on the rebound!

How was it done? EPA lists acceptable substitute chemicals for CFCs. Mostly these are more chemically active versions with similar chemical makeups.

The substitutes for cleaning computer chips and other materials are more diverse

HCFCs are also Ozone Depleting Substances and are now being phased out by international treaty.

An important component to the effort is public awareness of the risk. From

People also now protect their skin like in the video – not by donning suits of armor but by using sunscreen (also called sunblock) Sunscreen works by blocking and absorbing UV rays through a combination of physical and chemical particles. Physical particles, such as zinc oxide and titanium dioxide, are used to reflect UV radiation from the skin. At the same time, complex chemical ingredients in sunscreen react with radiation before it penetrates the skin, absorbing the rays and releasing the energy as heat. Text from

Even the Ozone layer can’t protect us from all Ozone. UV-A rays are not stopped at all! Sunscreen that is labeled UV-A and UV-B helps block both but nothing is perfect. If you insist on tanning, you will pay a price later in life in wrinkles and possibly cancer.

Without the Montreal Protocol, the world would have become very dangerous within the next 50 years. Computer simulation by atmospheric chemists from NASA’s Goddard Space Flight Center, the Johns Hopkins University, and the Netherlands Environmental Assessment Agency, reported at

So, we’re actually in danger now and probably will be until the middle of this century.

There are skeptics about Ozone depletion

We must also be skeptical of the skeptics. Scientists question everything. What are his credentials to be questioning trained atmospheric chemists like Rowland and Molina?

But some skeptics are reputable scientists. Question everything, even your own conclusions!

Next: Class discussion. CFC’s were an invention of the chemical industry. They seemed to be entirely beneficial with no drawbacks. But further study by Rowland and Molina showed a big drawback – namely the end of life on Earth as we know it. Science can produce dangerous results (nuclear bombs, deadly viruses, clones, Frankenstein monsters, Ozone-depleting chemicals, etc.). These results are undesirable and should be avoided. Should the government act as a safeguard to prevent scientists from doing research that will lead to such dangers to the human race? Which government? Should it be governmental? How should such a review board decide who does what research? How would such decisions be enforced?