Announcements
•The last Dark Sky Observing Night is tonight.
Starts at 7:30pm at the APSU Observatory on
“The Farm”. Try to arrive a little early so your
lights don’t interfere with the observing in
progress.
•Since there is a high chance tonight will be
cancelled, we will try again tomorrow night
(Tuesday). There is also a Dark Sky Alternative
posted in www.apsu.edu/astronomy/dark-skyobserving-night
The Greenhouse Effect
Lecture-Tutorial
The greenhouse gasses are mostly CO2 and H2O but CH4
and a few others also contribute
iClicker Question
The main reason Earth’s average
temperature is not below 0°C is because
a) volcanoes heat the atmosphere.
b) solar radiation alone is enough.
c) the greenhouse effect warms the
ground above what it would
otherwise be.
d) continental drift and tectonics adds
heat to the atmosphere.
Another iClicker Question
The greenhouse effect is caused mostly by
a) the aurora borealis.
b) pesticides.
c) depletion of the ozone layer by
manmade CFC’s.
d) carbon dioxide and water vapor in the
atmosphere
One More iClicker Question
The Earth’s surface absorbs energy
from sunlight and then radiates the
same amount of energy back into space.
The best proof for this fact is that the
average annual surface temperature on
Earth is
a) warming rapidly.
b) not changing much.
c) cooling rapidly.
d) fluctuating wildly.
Earth’s
Atmosphere
is layered
like an
onion
The layers are due to
how the temperature
changes with altitude.
Mars and Venus don’t
show the same kind
of layering.
The way temperature changes
is due to energy transport
In the troposphere
convection is driven by
heat from the ground
In the stratosphere and
thermosphere energy is
absorbed directly from the sun
Just as in the interior of the
planets, convection is
important to atmospheres
Rotation and the Coriolis effect are
also important
Magnetic fields are also very
important to atmospheres
Earth’s relatively strong magnetic field protects our
atmosphere from erosion by the solar wind
The weak or non-existent
magnetic fields of Venus and
Mars lead to strong erosion by
the solar winds
iClicker Question
ClassAction website
Terrestrial Planets module
Magnetic Fields and
Atmospheres
Another iClicker Question
If its mass was closer to that of
Earth and Venus, Mars might
a) still have an active interior.
b) have a thick atmosphere.
c) have abundant liquid water and
larger ice caps.
d) have a strong magnetic field.
e) All of the above.
Is mankind changing Earth’s
atmosphere?
Man?
Each spring in Antarctica a hole
develops in the ozone layer
Ozone depletion is caused by
CFC’s
CFC’s are Chlorofluorocarbon molecules which are
man made compounds. They do not occur naturally
The solution: stop using CFC’s
The 1987 Montreal Treaty gradually reduces the
production and consumption of CFC’s worldwide
Is the Ozone Hole getting
worse or better?
Our actions have led to an
increase in the level of a
number of greenhouse gases
Unfortunately,
we can’t stop
producing
these gases
as easily as
we stopped
producing
CFC’s
Deforestation has a major
impact Earth’s atmosphere
Deforestation removes the
trees that remove CO2
The cut trees are
usually burned which
adds more CO2 to the
atmosphere
There is a direct relationship
between the level of CO2 and the
global average temperature
One model
of where it
will get hot
in the future
based on
increases in
CO2 levels
All models predict that it will
get warmer
We are performing an experiment
on our atmosphere. What the
outcome will be we don’t yet know