1. The Radiation Budget and the Greenhouse Effect SNC2D

2. Incoming Solar Radiation The annual average of total incoming solar radiation is 342 Watts per square metre (W/m 2 ).

3. Incoming Solar Radiation This is called insolation (the actual value for any region will depend on factors like latitude).

4. Incoming Solar Radiation Approximately 30% of this is reflected back by clouds, the atmosphere, and the surface.

5. Incoming Solar Radiation Approximately 30% of the remaining radiation is absorbed by the atmosphere.

6. Incoming Solar Radiation The remainder is absorbed by and warms the surface...

7. Outgoing Thermal Radiation... and is re-emitted as infrared radiation (and thermals and water vapour).

8. Outgoing Thermal Radiation This infrared radiation can be re-absorbed by greenhouse gases in the atmosphere.

9. Greenhouse Gases This natural greenhouse effect is a good thing because it helps maintain the Earth at a temperature to support life (about 15 o C on average compared to about -20 o C).

10. Outgoing Thermal Radiation Eventually, however, almost all the energy is radiated back into space as infrared radiation.

11. The Radiation Budget The net radiation budget, the difference between incoming radiation and outgoing radiation is therefore effectively zero. Less than 1% of incoming solar energy is photosynthesized into chemical energy.

12. Greenhouse Gases However, we are taking that extra less than 1% that has been stored in the Earth (in the form of fossil fuels) and not only releasing its thermal energy but also excess greenhouse gases which absorb the outgoing radiation, putting our radiation budget out of balance.

13. Greenhouse Gases Greenhouse gases include water vapour, nitrous oxide, methane, ozone, CFCs (like freon), and...

14. Greenhouse Gases... and the very influential carbon dioxide, which has for most of human history been found at concentrations of approximately 280 ppmv (parts per million by volume) but which has climbed to over 388 ppmv as of November 2010.

15. Homework Read pg. 338 – 342 Read pg. 338 – 342 Do pg. 342 #1 – 6 Do pg. 342 #1 – 6