Earth : Atmosphere
Lecture 18
Increase in Atmospheric Oxygen
The amount of oxygen in the atmosphere has evolved with time.
Outgassing  losing H & He, N2 remain  increased O2 & decrease of CO2
Comparing Atmosphere
Structure of Earth Atmosphere
 Like the interior, the atmosphere has a layered structure.
Layered Structure
Greenhouse effect
Greenhouse effect
Moderate Greenhouse effect is good!
 Without the modest greenhouse effect
on the Earth, the average global
temperature of the Earth would be
-2°F
 With the right amount of greenhouse
gas, Earth’s average temperature is
58°F
Human and the Earth
World Population Growth Through History
12
Prediction
11
2100
9
Old
Stone
7 Age
Billions
8
New Stone Age
Bronze
Age
Iron
Age
6
Modern
Age
Middle
Ages
2000
5
4
1975
3
1950
2
1
Black Death —The Plague
1+ million 7000 6000 5000
years
B.C. B.C. B.C.
4000
B.C.
Exponential Growth
10
1900
1800
3000 2000 1000 A.D. A.D. A.D. A.D. A.D. A.D.
B.C. B.C. B.C.
1 1000 2000 3000 4000 5000
Source: Population Reference Bureau; and United Nations, World Population Projections to 2100 (1998).
Just how many of us are there?
Paul MacCready, designer of the first solar-powered aircraft, has estimated the total
weight of all terrestrial and avian vertebrates.
 When agriculture began, we humans and our pets and livestock together accounted
for less than 0.1% of the total.
 Today, we and our domesticated animals account for 98% of the total
Tokyo Water Park Slogan
“Welcome to breathtaking Tokyo Water
Park where you can wash away the
pressure and stress of the overcrowded
city and relax with your friends in the
smoothing enjoyment of sun, fun and
splashing."
Summer Beach in Busan, Korea
With its huge and still growing population
and rapidly growing per capita use of
resources, China is a disaster not only for
China’s own environment, but for the world
as a whole.
Just a few specific examples:
• Endless construction of coal burning power plants
• Destruction of the world’s rainforests to supply China with food and other
resources
• Massacre of 100 million sharks a year for shark’s fin soup
• Funding of numerous environmentally and socially destructive dams worldwide
Did something change here?
Logarithmic plot  straight line in this
plot is exponential behavior
slope indicates growth rate
1%/yr
0.035% per year
A closer look at recent trends…
green (oil) revolution
1.9%/yr
(pesticides, irrigation, fertilizers…)
industrial revolution
0.8%/yr
1950
1865
0.4%/yr
Human Impacts on the Earth!
Deforestation : Amazon
Global Warming
Doesn’t everyone already know about Global Warming?
GALLUP annual poll
global warming is generally exaggerated?
392.40 ppm
Venus and Earth
Venus
Earth
 0.7 Astronomical Unit
 0.95 Rearth
 Rocky planet
 Geological activity
 Thick atmosphere
 1.0 Astronomical Unit (AU)
 1.0 Rearth
 Rocky planet
 Geological activity
 Thick atmosphere
 900°F
200,000 more CO2 in atmo
 57°F
Venus was like a tropical paradise (~80°F) before
Either through “Dry” or “Wet” runaway greenhouse effect, Venus lost all her
water and CO2 had to be remained in the atmosphere
Dry effect
Wet effect
Temp was high enough initially so
that there was no water
condensation
no CO2 dissolution
accumulated outgassed CO2
warmer temp
more evaporation of water
H2O broken by solar UV
higher CO2 and hotter temp
More net evaporation than
precipitation
ocean gradually vanished
higher T caused rocks to release
stored carbon
more H2O in the atmosphere
causing even stronger greenhouse
H2O broken by solar UV
dry, barren, hot planet
Can Earth follow the same footsteps of Venus
YES!
 “Wet” runaway greenhouse effect on Earth would require that the majority of the
oceans around the world would evaporate more water than precipitate  critical
temperature is about 80F
 By 2100, average global temperature can rise ~70F which is dangerously close to the
critical point.
 The only thing that has prevented Earth from being another Venus was the CO2
cycle which is a slow, yet very delicate process.
 If this process were ever to start, there is not way to stop it
Localized Runaway Greenhouse effect
 Pacific ocean to the NE of Australia exhibited a runaway effect (May 2002)
 This location was warm enough year round to continually evaporate more water
vapor than precipitated back to it.
 Luckily, this is only a localized effect and surrounding ocean compensate for it. But,
this may be an example tells us that we are uncomfortably close to the entire
planetary runaway effect.
Should we take a risk with the tipping point?
Dr. Martin Luther King, Jr.
"Unlike the plagues of the dark ages or contemporary
diseases we do not yet understand, the modern plague of
overpopulation is soluble by means we have discovered and
with resources we possess. What is lacking is not sufficient
knowledge of the solution, but universal consciousness of the
gravity of the problem and the education of the billions who
are its victims.”
Acceptance Speech: Margaret Sanger Award in Human Rights, 1966
As educated people and citizens, we have responsibilities
to remind the public.
In summary…
Important Concepts
Important Terms
 Earth’s Atmosphere
 Greenhouse effect
 Runaway greenhouse effect
 Exponential growth
• runaway greenhouse effect
 Global warming
 Similarity b/w Venus & Earth
Chapter/sections covered in this lecture : sections 9-5 through 9-7