This presentation was given to discuss radiometric quantities.

REVIEW: Read this nice website on blackbody radiation.

We will briefly review Snell's law:
In brief, Snell's law refers to the behavior of waves at an interface. It is a necessary condition for waves to be continuous at interfaces, as illustrated.

Topics this week include

1. Practical calculation of the emission from a human body, and the energetics involved.
How much food energy do I need to eat to replace the IR energy I lost?

2. Practice with calculations of radiation transfer in the IR:
What is the spectrum of radiation in an opaque container where the walls have emissivity less than 1?
We find that the spectrum is that of a perfect blackbody as along as the walls have reflectivity less than 1.
Two options exist for radiation in an enclosure: the walls reflect, or absorb radiation.
reflectivity + absorptivity = 1. Absorptivity=emissivity, so emissivity = 1 - reflectivity.

3. Greenhouse gases are a very GOOD thing in our atmosphere, because they make the surface temperature much warmer than it would be otherwise.
Too much of a good thing gives us a fever though. First we discuss the Earth and Sun from the perspective of a man on the moon that just watches the radiation balance.
Then we need to ask the man/woman/child on the Earth for some perspective -- What does the atmosphere do to make the Earth hospitable?
The Earth is really not like a greenhouse. The greenhouse, like the Earth's atmosphere, lets in sunlight to its interior.
The greenhouse walls and roof keep the heat in, but all manner of convection happens in the atmosphere in response to the solar radiation.
Infrared active gases heat the Earth's surface yet more,
while in the IR, the greenhouse interior is very likely characterized as a blackbody at the temperature of the interior.
The bottom line from this section is that it is very clear that reducing the IR transmissivity of the atmosphere by introducing more infrared active gas to the atmosphere
is certainly going to warm the surface. So what happens next? What are the responses to this from the clouds, water vapor, ocean currents --- certainly more entropy production.

HOMEWORK ESSAY PROBLEM TO SUMMARIZE CHAPTER 1:
On a scale of 1 to 10, with 10 being most significant, rate the importance of what we are doing to the atmosphere by the introduction of new infrared
active gases against the things that happen naturally in climate, like solar output changes and sun orbital parameter changes, plate tectonics, volcanic emissions, extraterrestrial impacts of large objects with the Earth such as comets, and incidental eruptions of melted methane ice, and mention other comparable geophysical events that you might know of, but are not listed here.
In doing this rating, make it relevant to two time scales. This first time scale is
a human life time, 100 years, and the second time scale is 1,000,000 years, roughly time enough for 20,000 generations of people that live 50 years each.
How is your rating impacted by your need to move around in cars, to keep warm, to cook things, to make things, to grow things?

Explain your rating.

Bonus points:
1. Discuss how we might do things differently, and back these thoughts up with solid numbers and a discussion of the tradeoffs
(solar power, windmills, CO2 sequester, nuclear power, fuel efficiency, trends in energy use worldwide, stay at home, etc)
2. Discuss what you think will happen to the Earth's climate in the next 1,000 years, based on available literature, and your intuition.
If history is any guide for the future, do we have a comparable time in the past Earth's history to look at to help us understand our future?