Physics of the Atmosphere

Global Warming

The sun Emits Light that radiates through space and warms the Earth

Blackbody Curve

The sun emits most of its light as visible light

Absorbed radiation heats up the Earth and it radiates as a blackbody at a lower temperature

Molecules

Combination of atoms; most in the atmosphere contain only a few atoms (e.g. CO2, O2)

Molecules are held together by an attractive electrical force. If they get too close to each other, the atoms start to repel. The net result gives something that behaves like a spring

Emission and Absorption of Electromagnetic Radiation by Molecules

Emission:Because of the spring-like forces between atoms in a molecule, they can vibrate and vibrating charges emit electromagnetic radiation. For most molecules this radiation is in the infrared part of the electromagnetic spectrum

Absorption:If electromagnetic radiation of the right wavelength passes near the molecule, it can “resonate” and the molecule can absorb the radiation. For many molecules, this is also in the infrared part of the electromagnetic spectrum

Light

Light

Composition of the Atmosphere

Major :

N2 78.084%O2 20.946%Ar 00.934%

99.964%

Some Trace Gases (in ppm)

CO2 350H2O 20-20,000Ne 12He 5NO2 2CH4 2

Greenhouse gases

Albedo:Snow and clouds have high albedo; dark earth has low albedo

Solar constant:increased by about 30% during the lifetime of Sun

Atmospheric Concentrations of CO2Mauna Loa, Hawaii 1959-1992

Source: Trends’93 A Compendium of Data on Global Change, Oak Ridge National Laboratory, Publication no. ORNL/CDIAC-65. Mauna Loa data from C.D. Keeling and T. Whorf

290

300

310

320

330

340

350

360

1959

1963

1967

1971

1975

1979

1983

1987

1991

Years

Ann

ual C

once

ntra

tions

of C

O2

Z(p

pmv)

8

0

1000

2000

3000

4000

5000

6000

United St

ates

People'

s Rep

. Of C

hina Russia

Japan

Germany

India

United

Kingdom

Canada

Mexico

South A

frica

CO2 Emissions From Fossil Fuel Combustion: 1996

Source: CO2 Emissions from Fuel Combustion 1971 - 1996, International Energy Agency, page II.4-5, 1998 Edition

Mill

ion

Tonn

es o

f CO

2

0

5

10

15

20

25

United Stat

esCan

ada

German

yRussi

a

United K

ingdom

Japan

South A

frica

Mex

ico

People'

s Rep

. Of C

hina

India

Mill

ion

Tonn

es o

f CO

2

CO2 Emissions Per Person: 1996

1.9% 5.8%

10.0%

82.3%

1.9% 5.8%

10.0%

82.3%

Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 - 1996. U.S. EPA publication #236-R-98-006

Carbon Dioxide

Hydroflourocarbons (HFCs), perflourocarbons (PFCs), and Sulfur hexaflouride (SF6)

Nitrous Oxide

Methane

Global Warming is a complicated problem

There are many complicated affects that work together

e.g. Increased CO2 causes planet to warm which causes more water vapor to form. Water vapor is also a greenhouse gas which will cause more warming (positive feedback)

Increased CO2 causes planet to warm which causes more water vapor to form. This causes more clouds which increases the amount of sunlight reflected away from the Earth (increases the albedo) which would cause the planet to cool.

Actions of the US on Global Warming

•Developing countries are not included•Cost is too great – wait until science is more precise•Warmer temperatures are not necessarily bad•Too many uncertainties in science

-Climate models have “fudge” factors-Global climate models don’t agree with each other-Evidence for connection of solar cycle and warming-Discrepancies between surface and atmospheric temperature data