Earth

1
Earths Environment, Climate Change, and Human
Impacts
2
The Earths Energy Budget
3
Return to Physics

• Energy is transferred by
• Conduction. Faster molecules bump into slower
  molecules. Heating a skillet on the stove.
• Convection. Energy is transferred with the
  material. Boiling pot of soup.
• Latent heat. Energy is lost or absorbed when
  changing states (e.g., energy required to
  evaporate water).
• Radiation. Heat from Sun reaching Earth.

4

• Radiation Basic Concepts
• All matter radiates energy.
• Radiant energy travels in the form of
  electromagnetic waves.
• These waves do not require molecules to
  propagate.
• Different types of radiation are characterized
  by different wavelengths
• AM radio waves 100 meters
• Microwaves 1 mm
• Infrared 10-6 meters (1 micrometer (µm) 10-6
  meters)
• Visible light 5 x 10-7 meters
• UV 1 x 10-7 meters

5
Electromagnetic Spectrum of the Sun
6

• Radiation Basic Law
• Stefan Boltzman law
• E ? T4
• E is energy in Watts/m2
• T is temperature.
• ? is a constant.
• As T increases, E increases by a power of 4.
• If T doubles, E increases by 16 times!

7
Spectrum of the Sun vs. Spectrum of the Earth
8

• If the Earth always radiates energy, why doesnt
  it cool?
• It is in a state of radiative equilibrium.
  Incoming radiation is balanced by outgoing
  radiation.
• Radiative equilibrium predicts surface
  temperature of approximately 255 K (approximately
  -18C).
• But, the Earths observed average surface
  temperature is 288 K (approximately 15C).
• Why the difference? The answer lies in an
  understanding of absorption, reflection,
  transmission of radiation.

9
Absorption
Day

• Objects that are good absorbers are also good
  emitters.
• Consider an asphalt road.
• During the day the asphalt absorbs solar
  radiation and warms.
• At night the asphalt emits infrared radiation and
  cools relative to its surroundings.

Warm
Asphalt Road (warms due to solar radiation)
Night
Cool
Asphalt Road (cools by IR radiation)
10
Albedo

• Albedo the ratio of reflected radiation to
  incident radiation.
• Surface albedo varies
• Spatially
• Temporally
• Earths average albedo is 31.

11
With Greenhouse Effect
Fig. 23.6
12
The Greenhouse Effect
13
The Greenhouse Effect

• A global warming effect in which the atmosphere
  of a planet traps heat and maintains the surface
  of the planet at a higher temperature than if
  there were no atmosphere.
• Has existed throughout Earths history.
• TMJ.

14
Composition of the Atmosphere

• Atmosphere
• Nitrogen (78)
• Oxygen (21)
• Minor constituents Argon, carbon dioxide, water
  vapor, ozone
• Major greenhouse gases
• Water vapor
• Carbon dioxide

15
The future of climate change is difficult to
predict.

• What do we know?

16
What do we know?

• Temperature and carbon dioxide are highly
  correlated.

Fig. 23.7
17
What do we know?

• Temperature and carbon dioxide have been
  increasing since the Industrial Revolution.

Fig. 23.8
18
What do we know?

• Compared to the last 1000 years, temperatures and
  carbon dioxide levels have been higher in the
  last century.

Fig. 23.8
19
What do we think we know?

• We think we know how carbon is cycled through
  various Earth reservoirs.

Fig. 23.11
20
How do we figure out whats going to happen?

• Computer models.
• Supercomputers.
• General Circulation Models (GCMs) encompass
  various parts of the Earth system (atmosphere,
  oceans, etc.).
• Very complex.

Fig. 23.2
21
Why do we have difficulties with predictions?

• Positive and negative feedbacks complicate
  climate change predictions.
• Positive feedback A change in one component is
  enhanced by changes in another component.
• Negative feedback Change in one component
  counteracts a change in another component.

22
Feedbacks

• Water vapor feedback Positive.
• Increasing temperature increases amount of water
  vapor in atmosphere. Water is a greenhouse gas,
  so this increases surface temperature, which in
  turn increases evaporation, etc.

23
Feedbacks

• Albedo feedback Positive.
• Increasing temperature decreases snow and ice,
  which decreases albedo. Decreased albedo means
  more absorbed energy, which means increasing
  temperature.

24
Feedbacks

• Radiation feedback Negative.
• An increase in energy reaching the Earths
  surface causes an increase in the temperature of
  the Earth, and therefore the amount of heat the
  Earth reradiates back out.

25
Feedbacks

• Plant growth feedback Negative.
• More carbon dioxide means more plant growth,
  which means more use of carbon dioxide in
  photosynthesis.

26
So, could we add Fe to fertilize ocean thus
ameliorate greenhouse CO2 build-up? 1. Will it
work? 2. What are the ecological consequences?
 Just Add Iron ABCnews.com, Amanda Onion
10/11/00   How algae may slow warming By Gareth
Cook, Boston Globe Staff, 10/12/2000   Helping
ocean algae could beat greenhouse effect
LONDON (Reuters), WIRE10/11/2000 Global
Warming NPR Morning Edition- John Nielsen,
10/11/00 Iron-Fed Plankton Absorbs Greenhouse
Gases By ANDREW C. REVKIN, NY Times,
0/12/00   Iron May Increase Gas - Eating
Algae By THE ASSOCIATED PRESS, 10/11/00
Oct. 2000
27
Why else do we have trouble predicting climate
change?

• Systems are
• COMPLEX!

28
So what do you do if you want to learn more about
this?
29
 Department Course Number Course Name Semester Units
 MAC  2311 Calculus with Analytics Geometry I  4
 MAC  2312 Calculus with Analytic Geometry II    4
 CHM  1045 General Chemistry I    3
 CHM  1045L General Chemistry I Laboratory  1 
 CHM  1046 General Chemistry II  3
 CHM  1046L General Chemistry II Laboratory  2
PHY  2048C General Physics A and Laboratory    5
PHY  2049C General Physics B and Laboratory  5
 GLY  2010C Physical Geology  4
 GLY  2100 Historical Geology  3
 GLY  2100L Historical Geology Laboratory  1
 GLY  3200C Mineralogy and Crystallography  3
 GLY  3220C Optical Mineralogy 2
 GLY  3310C Igneous and Metamorphic Petrology  3
 GLY  3340C Sedimentary Petrography  2
 GLY  3400C Structural Geology  4
 GLY  3600C Paleontology  4
 GLY  4511 Principles of Stratigraphy  3
 GLY  4750 Geological Field Methods  1
 GLY   4751 Field Course  6
 GLY  4XXX Geological Elective  2