Stratospheric Ozone. Stratosphere is about 10,000 m to 49,000 m Temperatures about -50 o C until 30,000 m and then increase to about 23 o C. Increase due to absorption of UV by ozone/oxygen. Ozone protects earth surface from UV rays. Ozone Formation/Destruction in the Stratosphere.
Short-wave UV light in stratosphere breaks down CFCs and chlorine is released
Much of the chlorine reacts to form HCl or other compounds that do not react with ozone
Cl + O3 ClO + O2
ClO + O Cl + O2
ClO + ClO Cl2O2 Cl2 + O2
Cl2 can photodissociate to form more chlorine atomsHow do CFCs affect ozone?
Methane – production of coal, gas and oil. Decomposition of wastes at landfills. Raising livestock.
Nitrous oxide – industrial and agricultural activites.
CFCs, HFCs, sulfur hexafluoride – generated in industrial processes.
Water vapor, ozone.What are greenhouse gases?
Global Warming Potential: a number that refers to the amount of global warming caused by a substance
The GWP is the ratio of the warming caused by a substance to the warming caused by a similar mass of carbon dioxide. Thus, the GWP of CO2 is defined to be 1.0 . Methane is 21. Nitrous Oxide (N2O) is 310. CFC-12 has a GWP of 8,500, while CFC-11 has a GWP of 5,000. Various HCFCs and HFCs have GWPs ranging from 93 to 12,100. SF6 is 23,900. Water, a substitute in numerous end-uses, has a GWP of 0.
Severe shifts in agriculture due to extreme weather, extended droughts and flooding. For example, glaciers have disappeared in Northern India, severely affecting the region where farmers rely on melting of glaciers for irrigation.