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U4735x Environmental Science for Decision Makers

Lecture 19: The primary control of our climate is the sun and our distance from it.

James D. Hays

Take away ideas and understandings:

1. Understand the conservation of energy law. It is important to this week's work and the course as a whole.
2. Solar energy and gravitational energy are the ultimate sources of energy to power all climate subsystem processes.
3. Understand black body radiation.
4. The relationship between the absolute temperature of a black body and the energy flux it radiates.
5. The relationship between the wave length of the maximum energy output of a black body and its absolute temperature.
6. You should know why the intensity of a light dims as you move away from it.
7. You should be able to use these relatively simple relationsips to calculate the effective temperature of the Earth or any other planet if you know the temperature of the sun and the distance of the planet from it.
8. You should know why the Earth is warmer at the equator than it is at the ploles.
9. You should know, in a qualitative way, why the energy of a beam of electromagnetic energy is proportional to its frequency and why this is important.

I. What is climate?

Important characteristics of all the planets are controlled by their climates.


1. Local climate - long term average of local weather.
2. Global climate - long term average of global weather.
3. How can we understand the Earth's climate?

II. Solar energy

A. What is energy? - (notes on energy, work, and power)

B. Electromagnetic radiation

1. Generation
2. Waves (Figure 2)
3. Spectrum

C. Black Body Radiation

1. Spectrum
2. Intensity dependent on T
3. Frequency dependent on T
4. Relation of intensity to distance

D. Calculation of Earth's effective temperature

Text by James D. Hays