Group members preparing summary: Greg Cillo, Rusty Krevenz, Kardell.Summary Section:
This unit discussed Man-made chemicals and CFCs and how they react to destroy Ozone. The Ozone level is in the stratoshpere, and protect the earth from the harmful ultra-violet radiation. The CFCs react with the UV radiation to break down ozone. The primary chemical in the CFCs that do this is Cl. Since the CFCs are very stable they can make it slowly to the Stratosphere. The reaction to break Ozone becomes a repetitive process, with Cl reacting over and over with Ozone and UV radiation. This process produces more Cl molecules. Then the process repeats itself. One Cl atom can destroy 100,000 molecules of ozone. The destruction of Ozone finally stops when Chlorine Nitrate reacts with Cl atoms. In the early spring the Chlorine Nitrate is still stuck to the earth surface, this is why the Cl reacts and destroys Ozone at this time. The Chlorine Nitrate then goes up into the stratosphere as the earth warms up more. Most of the destruction of Ozone comes from Cl produced from factories and CFCs, not from the Cl found in salt or seawater. CFCs have a very long life time. Ozone levels have dropped in a 30 yr period from 300 dobsen units to less then 200 dobsen units. In someplaces they have decreased signifantly to zero. The destruction of ozone occurs mostly over the poles of the earth. The big reason is that the lack of incoming radiation in the winter, which causes very cold temperatures to form, causes ice nuclei to form. This is what causes the Cl to be released from the CFCs. This is the reason ozone decreases the most in the late winter or early spring. It is possible to reduce the effects of ozone destruction by putting in a hydrogen atom into the structure of the CFCs. Also, if we put no new CFCs into the ozone the ozone level could return to the original levels of ozone in 65 years.
Lecture Summary:
In Lecture we discussed how the scientist didn't know what was wrong at first when tehy discovered the hole. They thought it was an error in their data. We also discussed why the ozone only decreases in late winter. As the sun first comes over the horizon the first UV light causes the Cl molecules to go up from the surface and break up the Ozone. Later in the spring as the temperatures warm up more, the chlorine nitrate atoms go up from the surface and reacts with Cl molecules to stop the destruction of Ozone. We also discussed in lecture why the Ozone hole is over the South pole instead of the north pole. The reason is their is more land in the Northern Hemisphere and less in the southern hemisphere. This causes more mixing of the air. As a result the northpole doesn't get as cold as the south pole. Also the south pole is over land and the north pole is not. So this also causes an ozone hole over the south pole.
Dialog Summary:
A student posed a question whether the destruction of ozone poses a threat to Global warming. A student responded that there would be a 4 degree increase without ozone blocking out UV rays. Anothe student discussed a better reason for the ozone hole over the south pole instead of the north pole. He said it is due to the lack of large land masses and more ocean area around the south pole. The wind around the south pole is less distrubed which leads to more of a closed circulation. As a result the heat is constantly escaping. That is why it is colder in Antarctica then in the North pole. The north pole doesn't have a closed circulation, so this lessons the chance of the north pole getting as cold as Antartica.