Earth : Atmosphere

Lecture 18

2.2 billion years o

ld

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

A.D.2000

A.D.1000

A.D.1

1000B.C.

2000B.C.

3000B.C.

4000B.C.

5000B.C.

6000B.C.

7000B.C.

1+ million years

8

7

6

5

2

1

4

3

OldStoneAge New Stone Age

BronzeAge

IronAge

MiddleAges

ModernAge

Black Death — The Plague

9

10

11

12

A.D.3000

A.D.4000

A.D.5000

18001900

1950

1975

2000

2100Prediction

Billi

ons

Source: Population Reference Bureau; and United Nations, World Population Projections to 2100 (1998).

World Population Growth Through History

Expo

nenti

al G

row

th

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.

• 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 world-

wide

Just a few specific examples:

Did something change here?

Logarithmic plot straight line in thisplot is exponential behavior

slope indicates growth rate

0.035% per year

1%/yr

A closer look at recent trends…

0.4%/yr

0.8%/yr

1.9%/yr

1865

1950

industrial revolution

green (oil) revolution(pesticides, irrigation, fertilizers…)

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

Venus0.7 Astronomical Unit0.95 Rearth

Rocky planetGeological activityThick atmosphere

900°F200,000 more CO2 in atmo

Earth1.0 Astronomical Unit (AU)1.0 Rearth

Rocky planetGeological activityThick atmosphere

57°F

Venus was like a tropical paradise (~80°F) before

Dry effect

Temp was high enough initially so that there was no water condensation

no CO2 dissolutionaccumulated outgassed CO2

warmer tempmore evaporation of waterH2O broken by solar UVhigher CO2 and hotter temp

Wet effect

More net evaporation than precipitation

ocean gradually vanishedhigher T caused rocks to release

stored carbonmore H2O in the atmosphere

causing even stronger greenhouseH2O broken by solar UVdry, barren, hot planet

Either through “Dry” or “Wet” runaway greenhouse effect, Venus lost all her water and CO2 had to be remained in the atmosphere

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 ConceptsEarth’s AtmosphereGreenhouse effect• runaway greenhouse effect

Global warmingSimilarity b/w Venus & Earth

Important TermsRunaway greenhouse effectExponential growth

Chapter/sections covered in this lecture : sections 9-5 through 9-7