Global WarmingGlobal WarmingIs Human-Induced Climate Change

Going To Destroy The World?

Ok… that’s a bit dramatic. But, good questions are:

1) What is the evidence for recent climate change?2) Do we need to worry about it – what are the consequences?3) What can we do about it?

Data and diagrams from Richard Deem, Michael Mann, Lee Kump and the Intergovermental Panel on Climate Change

History of Earth’s Atmosphere/Climate

History of Earth’s Atmosphere/Climate

• Earth formed ~4.6 billion years ago• Originally very hot, probably molten, early

impact forming the moon• Any early atmosphere removed by initiation

of sun’s fusion reactions and solar wind• Granitic crust and liquid water was present

by ~4.3 billion years ago (zircon dating)• However, much of Earth’s early history was

erased during late heavy bombardment (~3.9 billion years ago)

• First life appeared by ~3.8 Ga

• Photosynthesis began 3.5-2.5 Ga, clear evidence for significant oxygen in the atmosphere by 2.0 Ga• Photosynthesis introduced oxygen and

removed carbon dioxide and methane (greenhouse gases)

• Earth began current cycles of glacial and interglacial periods ~3 Ma

History of Earth’s Atmosphere/Climate

History of Earth’s Atmosphere/Climate

Sun

Earth’s TemperatureEarth’s Temperature

Solar EnergySolar Energy

Solar EnergySolar Energy

Sun

Earth’s TemperatureEarth’s Temperature

Solar

Energy

Solar

Energy

RadiativeCooling

RadiativeCooling

Sun

Earth’s TemperatureEarth’s Temperature

Solar

Energy

Solar

Energy

RadiativeCooling

RadiativeCooling

Sun

Earth’s TemperatureEarth’s Temperature

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% CO2

• 3% N2

• Water & sulfuric acid clouds

• Temperature:860°F (hotter than Mercury which is nearest to the sun)

Venus

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 Atmospheric CO2 Levels?Future Atmospheric CO2 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

• Really is symbolic only, since such levels of reduction will likely not significantly impact global warming

-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

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

2007 Temperature Changes Compared to 1951-1980

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 over ~1,500 years• Mostly due to changes in thermohaline

circulation system of the ocean

Temperature History of the EarthTemperature History of the Earth

• For the past 3 Ma, the Earth has been experiencing ~100 ka cycles of glaciation followed by ~10 ka interglacial periods

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

Orbital Parameters & Earth’s ClimateOrbital Parameters & Earth’s Climate

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

Eccentricity(100 ka)

Temperature

Obliquity(41 ka)

Precession(22 ka)

Temperature History of the EarthTemperature History of the Earth

• For the past 3 Ma the earth has been experiencing ~100 ka cycles of glaciation followed by ~10 ka interglacial periods

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

“Hockey Stick” Controversey“Hockey Stick” Controversey

1000 1200 1400 1600 1800 2000-0.8

Year

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-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

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: Primarily Impacts the Northern Hemisphere and Land Masses

Consequences of Global Warming: Primarily Impacts the Northern Hemisphere and Land Masses

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-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

2007 Temperature Changes Compared to 1951-1980

2007 Temperature Changes Compared to 1951-1980

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

Consqeuences of Global Warming: Ice Sheets Melting?

Consqeuences of Global Warming: Ice Sheets Melting?

• GRACE (gravity measured by satellite) found melting in 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)

• And - Glaciers are retreating

all over the world.

Consqeuences of Global Warming: Rise in Sea Levels?

Consqeuences of Global Warming: 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 probably unrealistic

Consqeuences of Global Warming: How Much Temperature Increase?Consqeuences of Global Warming: 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

• Summary – most studies suggest ~4°C over the next century

Potential Worldwide Precipitation Changes

Potential Worldwide Precipitation Changes

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

Mitigation of Global Warming?Mitigation of Global Warming?

• Conservation• Reduce energy needs• Recycling

• Alternate energy sources• Nuclear• Wind• Geothermal• Hydroelectric• Solar• Fusion?

ConclusionsConclusions• Global warming is happening• Most warming is probably the result of

human activities – but this is still under debate

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

• The costs to mitigate global warming will be high – are they worthwhile?

• Extra slides 2010 beyond this point

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

Main Ocean CurrentsMain Ocean Currents

Adapted from IPCC SYR Figure 4-2

YoungerDryas

YoungerDryas

Younger Dryas Event – Greenland DataYounger Dryas Event – Greenland Data

-55-55

-50-50

-45-45

-40-40

-35-35

-30-30

-25-25

05101520Age (ka)

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

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?

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-1.0

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-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”

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 (Ka)Time (Ka)

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