Climate Change

Advanced Placement ConferenceAugusta, ME

October 30, 2009

2

Disparity in location

Sun

Earth’s Temperature

Solar

Energy

Solar

Energy

Solar

Energy

Solar

Energy

Sun

Earth’s Temperature

Solar

Energy

Solar

Energy

RadiativeCooling

RadiativeCooling

Sun

Earth’s Temperature

Solar

Energy

Solar

EnergyRadiativeCooling

RadiativeCooling

Sun

Earth’s Temperature

Solar

Energy

Solar

Energy

RadiativeCooling

RadiativeCooling

Greenhouse EffectSun

8

Energy Budget(incoming)

9

Surface Energy Balance

10

Atmosphere Energy Balance

• Certain molecules within the atmosphere absorb some of the radiation emitted by the surface. This raises their temperature–Asymmetry – mass – bond strength

• Once the energy is absorbed, it is re-radiated in all directions, some of it returns to the surface

• This return of heat energy to the surface, increases its temperature by ~ 15oC

11

Greenhouse Gases

Earth’s Atmospheric GasesNitrogen (N2)

Oxygen (O2)

Water (H2O)

Carbon Dioxide (CO2)

>99%

Methane (CH4)

<1%

Non-Greenhouse

Gases

GreenhouseGases

Argon (Ar)

Sun Runaway Greenhouse Effect

• 97% carbon dioxide• 3% nitrogen• Water & sulfuric acid

clouds• Temperature:

860°FVenus

• Water vapor is strong absorber of infrared radiation, but not at all frequencies

• Infrared radiation at particular frequencies is “invisible” to water vapor.

• These are the water vapor windows and radiation emitted at these frequencies escapes freely into space (Most important is the 10µ m window)

• Unless a different atmospheric molecule can absorb these radiations and partially “close” the water-vapor window

14

The Water-Vapor Window

15

Closing the Window

170

220

270

320

370

420

200000400000600000Time (YBP)

CO2 (

ppm

)

Vostok Ice CoreDome Concordia

Carbon Dioxide Levels

0

Muana Loa ReadingsCO2 Levels Since 1958

310330350370

10203040

CO2 (

ppm

)

0

Worldwide Carbon EmissionsCa

rbon

(109 m

etric

tons

)

0

1

2

3

4

5

6

7

8

1750 1800 1850 1900 1950 2000Year

Liquid fuelLiquid fuelTotalTotal

Gas fuelGas fuelSolid fuelSolid fuel

Variable & Increasing Gases

Figure 1.3Nitrogen and oxygen concentrations experience little change, but carbon dioxide, methane, nitrous oxides, and chlorofluorocarbons are greenhouse gases experiencing discernable increases in concentration. CO2 has risen more than 18% since 1958. Fossil fuels are the biggest problem!

Temperature History of the Earth

• For the past 3 million years, the earth has been experiencing ~100,000 year cycles of glaciation followed by ~10,000 year interglacial periods

• These climate periods are largely the result of cycles in the earth’s orbit – precession, obliquity, and eccentricity

Orbital Parameters: Precession

PerihelionApehelion

Orbital Parameters: Obliquity22.5°24.5°

Orbital Parameters: Eccentricity

PerihelionApehelionApehelion

Minimum: 0.005Minimum: 0.005

Maximum: 0.061Maximum: 0.061

Not to scale!Not to scale!To Scale!To Scale!

Orbital Parameters & Earth’s Climate

Age (kya)1000900 800 700 600 500 400 300 200 100 0

Eccentricity(100 ky)

Temperature

Obliquity(41 ky)

Precession(22 ky)

YoungerDryas

YoungerDryas

Younger Dryas Event

-55-55

-50-50

-45-45

-40-40

-35-35

-30-30

-25-25

05101520Age (kya)

Tem

pera

ture

(°C)

Tem

pera

ture

(°C)

0.050.05

0.100.10

0.150.15

0.200.20

0.250.25

0.300.30

0.350.35

Snow

Acc

umul

ation

(m/y

r)Sn

ow A

ccum

ulati

on (m

/yr)

Little Ice AgeLittle Ice AgeIce Age

Medieval WarmMedieval Warm