Homework 1 Key
1) The greenhouse effect is the mechanism whereby the gases in the atmosphere absorb
infrared radiation emitted by the planet's surface, re-radiating some of the energy back
toward the surface. The greenhouse effect allows the planet's surface temperature to be
greater than the plant's effective radiating temperature. Global warming refers to the
increase in surface temperature that has been observed at the Earth's surface over the past
~150 years. It is widely believed that an enhancement of the greenhouse effect through
anthropogenic emission of IR-absorbing gases (greenhouse gases) is the primary cause of
global warming.
2) Weather occurs on a timescale of days to a month. Climate refers to the statistics of
weather over longer periods of time, decades to centuries. Changes in the weather can be
predicted with relatively high skill for up to a week; our ability to predict changes in the
climate is highly uncertain.
If climate warms, the distribution of weather will be affected. Possible examples include:
more frequent warm days, “hotter” or more extreme warm days, less frequent cold days,
less or more rain, less snow, less or more clouds.
3) Questions of Origin deal with the source of knowledge. Questions of Validity deal
with the accuracy of knowledge, i.e., whether or not knowledge agrees with
experimentation and observation. In terms of Fig. 1.4, an example of a question of origin
would be “Who made the graph?” or “Who recorded the thermometer data?” A question
of validity would be “Would another set of temperature observations confirm or disprove
the trend?” or “Would future temperature observations continue the display trend?”
4) a) T-->C-->A Negative Feedback; Stable Equilibrium
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b) T--oC-->A Positive Feedback; Unstable Equilibrium
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c) T-->C--oA Positive Feedback; Unstable Equilibrium
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d) T--oC--oA Negative Feedback; Stable Equilibrium
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5) a) E(in) = S(1-A)
Venus = 528.6 W/m2
Earth = 959 W/m2
Mars = 462.54 W/m2
b) Te = ( E(in)/ 4^.25
Venus = 219.7 K
Earth = 255 K
Mars = 212.5 K
c) Tg = Ts-Te
Venus = 503.3 K
Earth = 33 K
Mars = 5.5 K
6)a) Albedo – The ratio of the reflected energy to the incident energy (the total energy
that “falls on” the surface) for a given surface. Changes in albedo are important for
climate, as it determines how much energy the planet can absorb.
b) Positive Feedback Loop – A system where a small disturbance will be amplified. The
system's response will be greater than the “initial response” (i.e., the response exhibited
by a similar system with no feedback).
c) Infrared Radiation – Radiation with a wavelength longer than visible light, between 0.7
and 1000 m. This is the primary form of energy emitted from the Earth's surface.
d) Unstable Equilibrium – A state in which the system will remain if left undisturbed, but
slight disturbances will amplify throughout the system, ultimately carrying the system to
a new, stable state.