Week 5 Stratospheric Ozone Depletion Flashcards
Describe the structure of the Earth’s atmosphere
thin layers of gases that surround the Earth.
composed of sub-layers that vary in density, gas composition, and temperature.
Troposphere
stratosphere -> where the ozone is located
mesosphere
Where is the ozone located?
90 percent of the ozone is located in the stratosphere.
although it’s only 0.003% of the atmosphere
Describe the basic chemistry of how stratospheric ozone is created and destroyed?
O2 molecules are broken down by the ultraviolet radiation from the sun into oxygen atom
These atoms join O2 molecules to become a 3 oxygen molecule. (Ozone)
3O2 + sunlight –> 2O3
What are the 3 conditions needed to enable ozone destruction?
- radiation
- very cold temperatures
- surface where ozone can be destroyed (clouds)
Where is the ozone hole?
Over Antarctica during spring in the Southern hemisphere
How is Ozone measured?
measured in dobson units, using balloon.
measuring the concentration of ozon molecules in a column of air.
<220 DU considered ozone destruction
- What do we know about the role of ozone in our atmosphere?
Ozone plays a critical role in protecting Earth from harmful UV radiation from the sun.
Aborbs 50% of UV- A
90% of UV-B
and all of UV-C radiation, protecting life on Earth.
Why is ozone disappearing?
Ozone is disappearing due to the presence of ozone-depleting substances like chlorofluorocarbons (CFCs), which break down ozone molecules in the stratosphere, particularly over Antarctica.
- What is the main goal of the Montreal Protocol, and why was it amended?
They aimed to phase out CFCs to protect the ozone layer. Every country agreed
-reduction in skin cancer cases and expected to restore the ozone layer by mid 21st century.
decreased emissions greatly, however continues to grow because cfcs still exist in the stratosphere due to long life.
What are ODSs?
Ozone depleting substances like CFCs (chlorofluorocarbons) ,
coming from refrigerants, sprays…
HFCs (hyydrofluorocarbon)
What are the control variable and planetary boundary for stratospheric ozone depletion?
Control Variable: Stratospheric ozone concentration measured in Dobson Units (DU).
Planetary Boundary: < 5% reduction from the preindustrial level of 290 DU.
What is the name of the most recent amendment for ODSs?
Kigali amendment 2016
after montreal protocol, HFCs were manufactured to replace them.
They don’t have the same ozone depleting effects but they can lead to global warming.
