1. Albedo and Energy Balance
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2. Solar Constant: The power of the Sun at the point it reaches the top of Earth’s atmosphere
After it enters the atmosphere…
Absorbed and scattered by the gases in the atmosphere
Absorbed and/or reflected by the clouds
Reflects off Earth’s surface
Is absorbed by Earth’s surface
What happens to the radiant energy from the sun when it enters Earth’s atmosphere?

3. Let’s focus on the light that is reflected—off the clouds or off any part of the Earth’s surface
Albedo (a)
𝒂= 𝒆𝒏𝒆𝒓𝒈𝒚 𝒓𝒆𝒇𝒍𝒆𝒄𝒕𝒆𝒅 𝒃𝒚 𝒂 𝒈𝒊𝒗𝒆𝒏 𝒔𝒖𝒓𝒇𝒂𝒄𝒆 𝒊𝒏 𝒂 𝒈𝒊𝒗𝒆𝒏 𝒕𝒊𝒎𝒆 𝒕𝒐𝒕𝒂𝒍 𝒆𝒏𝒆𝒓𝒈𝒚 𝒊𝒏𝒄𝒊𝒅𝒆𝒏𝒕 𝒐𝒏 𝒕𝒉𝒆 𝒔𝒖𝒓𝒇𝒂𝒄𝒆 𝒊𝒏 𝒕𝒉𝒆 𝒔𝒂𝒎𝒆 𝒕𝒊𝒎𝒆
If a surface does not reflect any light, its Albedo = 0
If 100% of incident light is reflected, albedo = 1
Albedo

4. Approximate albedo values for different surfaces of the Earth:
Average Albedo of the Earth: a = 0.35
Is this a constant value? If not, on what might the value depend?
Albedo of the earth

5. Factors affecting Albedo
Seasons
Ice and Snow covering ground
Leaves on trees…or not
Amount of cloud cover
Type of clouds
Type of terrain getting sunlight at different points of the rotation
Factors affecting Albedo

6. Connections… Snow on the ground and cold air temps?
Snow stays around a while
Snow on the ground…but has a light covering of dirt?
Dirt/soil has a lower albedo, so absorbs energy more than snow
When it gives off its radiation, it contributes to the latent heat the snow needs to gain to melt
Connections…

7. Gases in the atmosphere “trap” radiation (heat) in the atmosphere and direct it back toward Earth’s surface
Some greenhouse gases:
Water vapor
Methane (CH4)
Nitrous oxide (N2O)
Carbon dioxide (CO2)
Ozone (O3)
Nitrogen dioxide (NO2)
Greenhouse gases make up approximately 1% or so of the composition of the atmosphere
Greenhouse Effect

8. Natural Greenhouse Effect
Some amount of the greenhouse effect is necessary for our atmosphere to maintain a life-sustaining temperature balance
Quantified as the effect that can be attributed to a naturally-occurring level of the greenhouse gases in the atmosphere
Natural Greenhouse Effect

9. Enhanced greenhouse effect
A result of the increased concentration of some or all of the greenhouse gases
Enhanced greenhouse effect

10. We know that black bodies emit light over a full spectrum of wavelengths
When that continuous spectrum of light passes through a cooler body of gas (i.e. our atmosphere), certain wavelengths get absorbed, depending on the chemical composition of the gas
Absorption Spectrum

11. Connection between wavelength and frequency
We can connect the frequency of the light absorbed or transmitted with its wavelength through the following relationship:
𝒄=𝒇𝝀
Where:
c = speed of light in a vacuum = 3.00 x 108 m·s-1
f = frequency of light (in Hz (Hertz))
l = wavelength of light (in meters, m)
Connection between wavelength and frequency

12. Gases in our atmosphere: Transmittance of light

13. Homework for Monday—entrance question, written in your warm-up journal:
Do a little research and thinking regarding the following:
What human or physical events or actions contribute to the enhanced greenhouse effect? (be prepared to cite your source!)
What do YOU do that may be contributing a little to the enhanced greenhouse effect? (just think and reflect on that one—I won’t ask you to share out if you don’t want to)
What could we, as a school/community/society, do to help minimize our contributions to the enhanced greenhouse effect?
Homework for Monday

14. Earth’s energy Balance
From your textbook—an example of what happens to the energy that the Earth receives from the Sun, and how the Earth radiates thermal energy back into space
(no, the world is not truly flat…don’t go there.)
Your textbook states “Study this carefully”…so you should be able to recreate this diagram
Earth’s energy Balance

15. Some things to consider…
Read pages
What are some known and probable causes of global warming (the Climate Crisis)?
What are some known and probable effects of global warming?
What could you do to model one of these ideas in order to provide evidence regarding the cause and/or effect of global warming?
Some things to consider…