The Chemistry of Climate Change

The Science of Global Climate

“There's a lot of differing data, but as far as I can gather, over the last hundred years the temperature on this planet has gone up 1.8 degrees. Am I the only one who finds that amazingly stable? I could go back to my hotel room tonight and futz with the thermostat for three to four hours. I could not detect that difference.”

-Dennis Miller

Climate

Climate is characterized by the statistical properties of the weather over a period of time, including averages of local variables such as temperature, winds, humidity, pressure, and precipitation.

June 12, 2001

Warming Threat Requires Action Now, Scientists Say

By ANDREW C. REVKIN

In his speech on climate yesterday, President Bush said that a basic problem with the Kyoto Protocol, the proposed international pact for curtailing global warming, was that it laid out a timetable for cutting releases of heat-trapping gases before the threat posed by a buildup of those gases was clearly understood.

New York Times

Solar Radiation

h L

top of atmosphere

Earth

: zenith angle

h

Lm

m

hh

L

L

h

atmosphere gh thepath throu verticaloflength

atmosphere ethrough th

radiationsolar direct ofpath oflength

seccos

cos

m: ‘air mass’

Solar Radiation

apspagsg

tm

ttttt

eI

I

0t: attenuation coefficient

Solar Radiation

Light scattering by gases

Light absorption by particles

Light scattering by particles

Light absorption by gases

4

20

5

0

)1(10044.1

nt

ttttt

eI

I

sg

apspagsg

tm

Rayleigh Scattering

t: attenuation coefficient

Solar Radiation

Solar Radiation

extinction aerosol

40

apsp

nsp

tt

n

bt

Scattering and Absorption by Particulate Matter

‘modeled’

Solar Radiation

200 400 600 800

Wavelength (nm)

10-2

10-1

100

101

Att

enuat

ion

Coe

ffic

ient

Aerosol Extinction

Ozone Absorption

RayleighScattering

46

6

19

8

4

17

Aerosols

Clouds

31.069.01

69.0100

)41946(

Albedo

Albedo100 Units Incident

42823

45

4

3

max

5

2

/1067.515

2

1088.2

1)/exp(

12)(

KWmch

k

TemittedenergytotalF

T

kThc

hcJ

Solar Radiation

peak wavelength (nm)

Wein’s Law

Planck’s Relation

102 103 104 105

Wavelength (nm)

104

106

108

1010

1012

1014

Flu

x(W

m-2

nm

-1)

5000 K

3000 K

1000 K

500 K

300 K

100 K

1)/exp(

12)(

:)(

5

2

3

kThc

hcJ

WmJ

Solar Radiation

Flux: number of photons per second per square centimeter

200 300 400 500 600 700

Wavelength (nm)

1010

1011

1012

1013

1014

1015A

ctin

icFlu

x[p

hot

ons

cm-2

s-1nm

-1]

1)/exp(

12)(

5

2

kThc

hcJ

Solar Radiation

5800 K

2

21126

26

4828

42

42

1389

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1091.3

])5800)(1067.5][()1096.6(4[

4

4

Wm

F

W

TrP

TrFAPowerP

sun

sunsun

Solar Radiation

Radiative Power from Sun

Incident on Earth

Solar Flux

solar flux

r2

WrWmrF earthearthsun17222 104.1))(1389()(

Solar Radiation

Global energy use by population ~ 1x1013 W

1 part in 10000

2% for U.S. Urban Areas

24428

4

390)288)(1067.5(

WmKKWmF

TF

earth

earth

Solar Radiation

Earth Emission

422

42

4

4)1(

4

earthearthearthsun

earthearthearth

earth

TrrAF

TrP

TF

Radiation Balance

Fraction Absorbed

balance

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KKWm

WmT

FAT

o

earth

sunearth

19

2541067.54

1398)31.01(

4

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4/1

428

2

4/1

Radiation Balance

Actual is 290 K

Calculated T/K Actual T/K

Earth 254 290 +36

Mars 217 223 +6

Venus 227 732 +505

Temperature at the Surface of Three planets: =Tactual-Tcalculated

Greenhouse Effect

300 nm

SpeciesAbsorption Region Estimated Global Warming

H2O 2.5, 3.5, 5-7 m ~110 Wm-2

CO2 14-19 m ~50 Wm-2

CH4 3-4, 7-8.5 m ~1.7 Wm-2

O3 9-10 m ~1.3 Wm-2

Greenhouse Gases