Why should we be concerned about Global Warming? Why should we be concerned about Global Warming?

Why should we be concerned about Global Warming?

“Why should we be concerned about Global Warming?”

• Many people consider that Global Warming is the greatest environmental threat of the 21st Century.

• However, during the 80s and early 90s scientists argued about the causes and effects of global warming.

• In the late 1990s scientists reached a consensus that global warming was a cause for concern.

• So, why should you be concerned about global warming?

IntroductionIntroduction

• Is the world getting warmer?

• If so, are the actions of mankind to blame for earth’s temperature increases?

• What can/should be done about these issues?

• Are the potential resolutions worth the cost to implement them?

History of Earth’s ClimateHistory of Earth’s Climate

• Earth formed ~4.6 billion years ago• Originally very hot• Sun’s energy output only 70% of

present• Liquid water present ~4.3 billion years

ago (zircon dating)• Much of earth’s early history erased

during late heavy bombardment (~3.9 billion years ago)

History of Earth’s ClimateHistory of Earth’s Climate

• Life appeared ~3.8 billion years ago• Photosynthesis began 3.5-2.5 billion

years ago Produced oxygen and removed carbon

dioxide and methane (greenhouse gases) Earth went through periods of cooling

(“Snowball Earth”) and warming

• Earth began cycles of glacial and interglacial periods ~3 million years ago

Sun

Earth’s TemperatureEarth’s Temperature

Solar

Energy

Solar

Energy

Solar

Energy

Solar

Energy

Sun


Solar

Energy

Solar

Energy

RadiativeCooling

RadiativeCooling

Sun


Solar

Energy

Solar

Energy

RadiativeCooling

RadiativeCooling

Sun


Solar

Energy

Solar

Energy

RadiativeCooling

RadiativeCooling

Greenhouse EffectGreenhouse EffectSun

Earth’s Atmospheric GasesEarth’s Atmospheric Gases

Nitrogen (N2)

Oxygen (O2)

Water (H2O)

Carbon Dioxide (CO2)

99%

Methane (CH4)

1%

Non-Greenhouse

Gases

GreenhouseGases

Sun Runaway Greenhouse EffectRunaway Greenhouse Effect

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

acid clouds• Temperature:

860°F

Venus

Carbon Dioxide

170

220

270

320

370

420

200000400000600000Time (YBP)

CO

2 (p

pm

)

Vostok Ice CoreDome Concordia

Carbon Dioxide LevelsCarbon Dioxide Levels

0

Muana Loa ReadingsCO2 Levels Since 1958

310330350370

10203040

CO

2 (

pp

m)

0

Worldwide Carbon EmissionsWorldwide Carbon EmissionsC

arb

on

(10

9 m

etri

c to

ns)

0

1

2

3

4

5

6

7

8

1750 1800 1850 1900 1950 2000Year

Liquid fuelLiquid fuelTotalTotal

Gas fuelGas fuelSolid fuelSolid fuel

Annual Carbon EmissionsAnnual Carbon Emissions

Annual carbon emissionsAtmospheric CO2

Atmospheric CO2 average

1955 1965 1975 1985 1995 20050

4

6

8

2

Year

Car

bo

n (

109

met

ric

ton

s)

Future Carbon Dioxide LevelsFuture Carbon Dioxide Levels

• Increasing CO2 emissions, especially in China and developing countries

• Likely to double within 150 years: Increased coal usage Increased natural gas usage Decreased petroleum usage (increased

cost and decreasing supply)

Kyoto ProtocolKyoto Protocol

• Adopted in 1997

• Cut CO2 emissions by 5% from 1990 levels for 2008-2012

• Symbolic only, since cuts will not significantly impact global warming

Past Temperatures

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1880 1900 1920 1940 1960 1980 2000Year

M

ean

Tem

per

atu

re (

°C)

Recorded Worldwide Temperatures

Recorded Worldwide Temperatures

FlatDecreasing

Winter Temperatures

10

11

12

13

14

15

16

17

1880 1900 1920 1940 1960 1980 2000

Year

Summer Temperatures

18

19

20

21

22

23

24

25

1880 1900 1920 1940 1960 1980 2000

Year

Annual Temperatures

15

16

17

18

19

20

21

22

1880 1900 1920 1940 1960 1980 2000

Year

Tem

per

atu

re (

°C)

Historic Los Angeles Temperatures

Historic Los Angeles Temperatures

-3 -2.5 -1.5 -1 -.5 -.1 .1 .5 1 1.5 2.5 3.4

2007 Temperature Changes Compared to 1951-1980


Past Temperatures MeasurementPast Temperatures Measurement

• Proxy – a method that approximates a particular measurement (e.g., temperature) Ice cores Pollen records Plant macrofossils Sr/Ca isotope data Oxygen isotopes from speleothem calcite

(stalactites and stalagmites)

Temperature History of the EarthTemperature History of the Earth• Little ice age (1400-1840) – 1°C cooler • Medieval warm period (800-1300) – 1°C

warmer than today• Cool/warm cycles occur ~1,500 years• Affect mostly Northeastern U.S. and North

Atlantic• Mostly due to changes in thermohaline

circulation • Dramatic shutdown of thermohaline

circulation occurred 8,200 years ago as a large lake in Canada flooded the North Atlantic

Main Ocean CurrentsMain Ocean Currents

Adapted from IPCC SYR Figure 4-2

Temperature History of the EarthTemperature History of the Earth

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

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

Orbital Parameters: PrecessionOrbital Parameters: Precession

PerihelionApehelion

Orbital Parameters: ObliquityOrbital Parameters: Obliquity22.5°24.5°

Orbital Parameters: EccentricityOrbital 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 ClimateOrbital 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)


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

• Last ice age began to thaw 15,000 years ago, but was interrupted by the “Younger Dryas” event 12,900 years ago

YoungerDryas

YoungerDryas

Younger Dryas EventYounger Dryas Event

-55-55

-50-50

-45-45

-40-40

-35-35

-30-30

-25-25

05101520Age (kya)

Tem

per

atu

re (

°C)

Tem

per

atu

re (

°C)

0.050.05

0.100.10

0.150.15

0.200.20

0.250.25

0.300.30

0.350.35

Sn

ow

Acc

um

ula

tio

n (

m/y

r)S

no

w A

ccu

mu

lati

on

(m

/yr)

Little Ice AgeLittle Ice AgeIce Age

Medieval WarmMedieval Warm

Younger Dryas EventYounger Dryas Event

-44-44-43-43-42-42

-41-41-40-40-39-39-38-38-37-37

-36-36-35-35-34-34

18O

(G

reen

lan

d)

18O

(G

reen

lan

d)

-8.0-8.0

-7.5-7.5

-7.0-7.0

-6.5-6.5

-6.0-6.0

-5.5-5.5

-5.0-5.0

-4.5-4.5

-4.0-4.010111213141516

18O

(C

hin

a)18

O (

Ch

ina)

YoungerDryas

YoungerDryas

Age (kya)


Middle Pliocene (3.15 to 2.85 million ya)

• Temperatures: 2°C higher than today. 20°C higher at high latitudes 1°C higher at the Equator

• Sea levels were 100 ft higher

• Causes CO2 levels that were 100 ppm higher

Increased thermohaline circulation


Eocene (41 million years ago)

• Opening of the Drake Passage (between South America and Antarctica).

• Increased ocean current exchange Strong global cooling First permanent glaciation of Antarctica

~34 million years ago


Paleocene Thermal Maximum (55 mya)

• Sea surface temperatures rose 5-8°C

• Causes Increased volcanism Rapid release of methane from the oceans


Mid-Cretaceous (120-90 mya)

• Much warmer

• Breadfruit trees grew in Greenland

• Causes Different ocean currents (continental

arrangement) higher CO2 levels (at least 2 to 4 times

higher than today, up to 1200 ppm)

Recent Temperature Changes

“Hockey Stick” Controversey“Hockey Stick” Controversey

1000 1200 1400 1600 1800 2000-0.8

Year

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Tem

per

atu

re C

han

ge

(°C

)

Direct temperature measurementsMann et al. 1999

Mann et al. 1999Esper et al. 2002

800 1000 1200 1400 1600 1800-2

-1

0

1

2

Tem

per

atu

re C

han

ge

(°C

)

2000Year

Is the Hockey Stick Correct?Is the Hockey Stick Correct?

Is the Hockey Stick Correct?Is the Hockey Stick Correct?

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0 400 800 1200 1600 2000Year

Tem

per

atu

re C

han

ge

(°C

)

Mann et al. 1999Esper et al. 2002Moberg et al. 2005Mann et al. 2008

U.S. National Academy of Sciences: June 2006

U.S. National Academy of Sciences: June 2006

1000 1200 1400 1600 1800 2000-0.8

Year

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Tem

per

atu

re C

han

ge

(°C

)

“high level of confidence”“2:1 chance of being right”

-1.0

-0.5

0.0

0.5

1.0

1.5

1980 1990 2000Year

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1980 1990 2000Year

Tem

per

atu

re C

gan

ge

(°C

)

Atmospheric TemperaturesAtmospheric TemperaturesTroposphere Stratosphere

170170

220220

270270

320320

370370

00200000200000400000400000600000600000Time (YBP)Time (YBP)

CO

2 (p

pm

) A

nta

rcti

ca

CO

2 (p

pm

) A

nta

rcti

ca

2525262627272828292930303131

SS

T (

°C)

Tro

pic

al P

acif

icS

ST

(°C

) T

rop

ical

Pac

ific

CO2 Concentration Vs. TemperatureCO2 Concentration Vs. Temperature

Consequences of Global Warming

Global Warming Primarily Impacts the Northern Hemisphere

Global Warming Primarily Impacts the Northern Hemisphere

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1920 1960 2000Year

Tem

pera

ture

Cha

nge

(°C

)

1920 1960 2000Year

Northern vs. Southern Latitude Land vs. Ocean

Northern HemisphereSouthern Hemisphere

LandOcean



-3 -2.5 -1.5 -1 -.5 -.1 .1 .5 1 1.5 2.5 3.4

Ice Sheets Melting?Ice Sheets Melting?

• GRACE (gravity measured by satellite) found melting of Antarctica equivalent to sea level rise of 0.4 mm/year (2 in/century)

• Zwally, 2005 (satellite radar altimetry) confirmed Antarctica melting Greenland ice melting on

exterior, accumulating inland(higher precipitation)

Melting Glaciers – Mt. KilimanjaroMelting Glaciers – Mt. Kilimanjaro

1000

800

600

400

200

0

-200

-400

-6002003 2004 2005

Ice

Mas

s (k

m3 )

Year

Changes in Antarctica Ice Mass Changes in Antarctica Ice Mass

Rise in Sea Levels?Rise in Sea Levels?

• Present rate is 1.8 ± 0.3 mm/yr (7.4 in/century)

• Accelerating at a rate of 0.013 ± 0.006 mm/yr2

• If acceleration continues, could result in 12 in/century sea level rise

• Scenarios claiming 1 meter or more rise are unrealistic

Changing Sea LevelsChanging Sea Levels

1700 1750 1800 1850 1900 1950 2000-20

-10

0

10

20

Rel

ativ

e S

ea L

evel

(cm

)

Adapted from IPCC SYR Figure 2-5

Amsterdam, NetherlandsBrest, FranceSwinoujscie, Poland

Glo

bal T

emp

erature C

han

ge

Time (KYBP)Time (KYBP)

Sea

Lev

el (

m)

Sea

Lev

el (

m)

2020

00

-20-20

-40-40

-60-60

-80-80

-100-100

-120-120

Sea Levels for 450,000 YearsSea Levels for 450,000 Years

450450 400400 350350 300300 250250 200200 150150 100100 5050 002525

2626

2727

2828

2929

3030

3131

SS

T (

°C)

Tro

pic

al P

acif

icS

ST

(°C

) T

rop

ical

Pac

ific

Increase in Hurricanes?Increase in Hurricanes?

• Two studies showed the total number of hurricanes has not changed

• However, the intensity of hurricanes has increased (more category 4 and 5 hurricanes and cyclones)

• Probably due to higher sea surface temperatures (more energy)

• Difficult to know if this trend will continue

• Two studies showed the total number of hurricanes has not changed

• However, the intensity of hurricanes has increased (more category 4 and 5 hurricanes and cyclones)

• Probably due to higher sea surface temperatures (more energy)

• Difficult to know if this trend will continue

18601860 18801880 19001900 19201920 19401940 19601960 19801980 20002000 2020202000

55

1010

1515

Data UnreliableData Unreliable

Scaled August-OctoberSea-Surface TemperatureAdjusted Atlantic StormPower Dissipation Index

Scaled August-OctoberSea-Surface TemperatureAdjusted Atlantic StormPower Dissipation Index

SS

T/S

PD

I (m

eter

s3 /se

c2 )S

ST

/SP

DI (

met

ers3 /

sec2 )

How Much Temperature Increase?

How Much Temperature Increase?

• Some models propose up to 9°C increase this century

• Two studies put the minimum at 1.5°C and maximum at 4.5°C or 6.2°C

• Another study puts the minimum at 2.5°C

Wildlife EffectsWildlife Effects

• Polar Bears Require pack ice to live Might eventually go extinct in the wild

• Sea turtles Breed on the same islands as

their birth Could go extinct on some islands

as beaches are flooded

• Other species may go extinct as rainfall patterns change throughout the world

• Polar Bears Require pack ice to live Might eventually go extinct in the wild

• Sea turtles Breed on the same islands as

their birth Could go extinct on some islands

as beaches are flooded

• Other species may go extinct as rainfall patterns change throughout the world

Effect on HumansEffect on Humans

• Fewer deaths from cold, more from heat

• Decreased thermohaline circulation Cooler temperatures in North Atlantic

• CO2 fertilization effect

• Precipitation changes Droughts and famine (some areas) Expanded arable land in Canada, Soviet Union

Potential Worldwide Precipitation Changes

Potential Worldwide Precipitation Changes

-50 -20 -10 -5 5 10 20 50

Drought in AfricaDrought in Africa

Lake FaguibineLake Faguibine Lake ChadLake Chad

Cost to Stabilize CO2 Concentrations

Cost to Stabilize CO2 Concentrations

450 550 650 750

18001600140012001000

800600400200

0

Carbon Dioxide (ppm)

Co

st (

Tri

llon

s U

.S. D

olla

rs)

Possible Solutions to Global Warming

Mitigation of Global WarmingMitigation of Global Warming

• Conservation Reduce energy needs Recycling

• Alternate energy sources Nuclear Wind Geothermal Hydroelectric Solar Fusion?

http://upload.wikimedia.org/wikipedia/commons/4/44/Recycle001.svg

Storage of CO2 in Geological FormationsStorage of CO2 in Geological Formations

1. Depleted oil and gas reservoirs

2. CO2 in enhanced oil and gas recovery3. Deep saline formations – (a) offshore (b) onshore

4. CO2 in enhanced coal bed methane recovery

1. Depleted oil and gas reservoirs

2. CO2 in enhanced oil and gas recovery3. Deep saline formations – (a) offshore (b) onshore

4. CO2 in enhanced coal bed methane recovery

Adapted from IPCC SRCCS Figure TS-7

3a3a22

3b3b 11 44

ConclusionsConclusions

• Global warming is happening

• Most warming is probably the result of human activities

• There will be positive and negative (mostly) repercussions from global warming

• The costs to mitigate global warming will be high – better spent elsewhere?

Documents

Why should we be concerned about Global Warming? Why should we be concerned about Global Warming?