Human effects
Ozone (O3)
- Formed by UV high in atmosphere
- Blocks UV
- which is harmful to life on earth (skin cancer, death)
- CFC’s were destroying it
- growing Ozone hole near S. pole
- Worldwide treaty limits CFC’s (refrigerators, etc.)
Greenhouse effect -- CO2
- Transparent to solar radiation
- visible light near 500 nm
- opaque to infrared radiation
- Earth’s emission peaks at 10,000 nm (i.e. 300 K)
- Acts like “blanket” to trap heat
- T increased at Earth’s surface TA 58
- presently, ?T ~ +20o C -- which is good!