Download Global Climate Change

Global Climate
Change
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Introduction - Climate scale
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1 day – diurnal cycle
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Weather occurs on an hourly or daily basis
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Primary cause: Rotation of the Earth on it’s
axis
Yesterday’s weather was:
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Introduction - Climate scale
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1 year – yearly cycles
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Equinoxes and solstices.
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23.5 degree tilt of the Earth’s axis
Last year:
Earth-Sun Relations
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Introduction - Climate scale
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10 years – decadal scale
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Longer-term variabilities begin to appear
El Niño & La Niña
 Rapid climatic shifts can occur
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Last 10 years:
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El Niño & La Niña
Summary of 10 Year Time Scale (National
Climate Data Center)
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Introduction - Climate scale
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What is El Niño?
Basically, it's a giant puddle (or pod) of
heated water that sloshes across the
Pacific Ocean
 Similar to an iceberg
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Bulge on the surface
 Most of “pod” beneath the surface
 Due to difference in density
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National Geographic’s Model
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Introduction - Climate scale
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What is El Niño?
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Normal conditions in the tropical Pacific
Ocean
Surface winds move from east to west
 From high pressure in S. America to low
pressure in Australia
 Drags water westward
 Warm water pools in the western Pacific
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Introduction - Climate scale
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What is El Niño?
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Every 3 – 8 years, system reverses
Called the Southern Oscillation
 Trade winds weaken or reverse
 Warm water migrates from Australia to S.
America
 Arrives in time for Christmas – Corriente del

Niño
El Niño and La Niña
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Introduction - Climate scale
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ENSO - El Niño-Southern Oscillation
Typically lasts 1 year
 May last up to 3
 In multi-year events, first year not as
affected
 Affects both hemispheres
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Introduction - Climate scale
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Recognizing an El Niño
Sea Surface Temperatures (SST)
 Normal: 6-8° C warmer in the western
tropical Pacific than in the eastern tropical
Pacific
 Check SST to see if in “normal” range
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Introduction - Climate scale
La Niña
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Return to “normal” conditions from an El Niño
strong
Produces:
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Strong currents
Powerful upwelling
Chilly and stormy conditions along S. American coast
Eastern Pacific cools rapidly, Western Pacific
warms rapidly
Renewed Trade Wind activity spreads the cooler
eastern Pacific waters westward
El Niño & La Niña Regional Impacts
Does ENSO Impact Hurricane
Frequency?
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Introduction - Climate scale
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100 years – Centennial scale
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Paleoclimatic data to track solar and ocean
variability
Large scale climatic changes and variability
 Pacific Decadal Oscillation (PDO) & North
Atlantic Oscillation (NAO)
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Introduction - Climate scale
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100 years – Centennial scale
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Last 100 years:
Human population and CO2 levels rose
exponentially
 Climate related events severely impacts human
populations
 Summary of 100 Year Time Scale
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Occurs every 15 – 20 and 50 – 70 years
Coincides with ENSO
The Past 100 Years: The 20th Century's
Human Climate Conundrum
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Introduction - Climate scale
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1,000 years
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Variability in
Carbon cycles on land and sea
 Thermohaline current
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Last 1,000 years
Europe’s “Little Ice Age”
 Large Volcanic Eruptions
 Multi-decadal droughts
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Thermohaline Circulation
Millennial Temperature
Reconstruction
National Ice Core Laboratory (http://nicl.usgs.gov/proc.htm )
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Introduction - Climate scale
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10,000 years
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Natural cycles begin to appear
Those not influenced by humans
 Use Paleoclimatic data
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Introduction - Climate scale
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10,000 years
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Last 10,000 years
End of last Ice Age
 Melting of polar ice caps and glaciers
 Rising sea level
 Formation of the Black Sea, Pleistocene Lakes
in Western U.S.
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Did the influx of freshwater 8,200 years ago from large
lakes in what is now northern Canada help trigger the
coldest climate event in the Earth's climate system in the
past 10,000 years?
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Introduction - Climate scale
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100,000 years
Extreme long term trends
 Milankovitch cycles
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Last 100,000 years
Last Ice Age cycle 60,000 to 20,000 ybp
 Ice Age Cycles began ~2.6 myo to present
 Decline of the Neanderthal, rise of Homo
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sapiens
Causes of Global Climate
Change
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Global Cooling
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Volcanic Eruptions
Tambora, Indonesia – 1815 “year without a
summer”
 Mount Toba, present day Sumatra - 73,000
years ago accelerated glaciation

Causes of Global Climate Change
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Milankovitch cycles
Eccentricity – 100,000 to 400,000 year
periods
 Obliquity – every 41,000 years
 Processional of equinoxes – every
23,000 years

Eccentricity: The Shape of the
Earth’s Orbit
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Shape of Earth’s orbit changes from
circular to elliptical over 100,000 years.
More circular: stable climate
 More elliptical: strong climate variations
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Eccentricity
t
warmer
cooler
Obliquity: Tilt of Earth’s Axis
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The degree to which the axis tilts varies
from 21.5͍° to 23.5° over 41,000 years
More tilt: poles receive more sunlight
 Less tilt: poles receive less sunlight
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Obliquity
Precession of the equinoxes
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As the Earth spins, it
wobbles a bit

N Pole currently points
towards Polaris (the
North Star) but shifts to
point towards Vega over
23,000 years
Precession of
the equinoxes
Causes of Global Climate Change
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Global Cooling
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Changes in ocean circulation
Changes to Thermohaline current
 Position of the continents
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THE GLOBAL OCEAN CONVEYOR—The global ocean circulation system, often
called the Ocean Conveyor, transports heat throughout the planet. White sections
represent warm surface currents. Purple sections represent deep cold
currents. (Illustration by Jayne Doucette, WHOI)
DRAMATIC CHANGES IN THE NORTH ATLANTIC—Subpolar seas bordering the North
Atlantic have become noticeably less salty since the mid-1960s, especially in the last decade.
This is the largest and most dramatic oceanic change ever measured in the era of modern
instruments. This has resulted in a freshening of the deep ocean in the North Atlantic, which
in the past disrupted the Ocean Conveyor and caused abrupt climate changes. (B. Dickson,
et. al., in Nature, April 2002)
DRAMATIC CHANGES IN THE NORTH ATLANTIC—Subpolar seas bordering the
North Atlantic (top) have become noticeably less salty since the mid-1960s, especially
in the last decade (bottom). This is the largest and most dramatic oceanic change ever
measured in the era of modern instruments. This has resulted in a freshening of the
deep ocean in the North Atlantic, which in the past disrupted the Ocean Conveyor and
caused abrupt climate changes. (B. Dickson, et. al., in Nature, April 2002)
A LONG RECORD OF
ABRUPT CLIMATE
CHANGES
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The Younger Dryas
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about 12,700 years ago, average
temperatures in the North Atlantic region
abruptly plummeted nearly 5°C and
remained that way for 1,300 years before
rapidly warming again.
A LONG RECORD OF
ABRUPT CLIMATE
CHANGES
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The 8,200-Year Event
A similar abrupt cooling occurred 8,200
years ago.
 It was not so severe and lasted only about
a century.
 But if a similar cooling event occurred
today, it would be catastrophic.
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A LONG RECORD OF
ABRUPT CLIMATE
CHANGES
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The Medieval Period
An abrupt warming took place about 1,000
years ago.
 It was not nearly so dramatic as past
events, but it nevertheless allowed the
Norse to establish settlements in
Greenland.
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A LONG RECORD OF
ABRUPT CLIMATE
CHANGES
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The Little Ice Age
The Norse abandoned their Greenland
settlements when the climate turned
abruptly colder 700 years ago.
 Between 1300 and 1850, severe winters
had profound agricultural, economic, and
political impacts in Europe.

What Happens if the Conveyor
Shuts Down?
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Scenario 1: Conveyor slows down within
next two decades.
Such a scenario could quickly and markedly
cool the North Atlantic region, causing
disruptions in global economic activity.
 These disruptions may be exacerbated
because the climate changes occur in a
direction opposite to what is commonly
expected, and they occur at a pace that
makes adaptation difficult.

Source: Abrupt Climate Change: Should We Be Worried? By Robert B. Gagosian <http://www.whoi.edu/institutes/occi/viewArticle.do?id=9986>
What Happens if the Conveyor
Shuts Down?
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Scenario 2: Conveyor slows down a century
from now.
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In such a scenario, cooling of the North Atlantic
region may partially or totally offset the major
effects of global warming in this region.
Thus, the climate of the North Atlantic region may
rapidly return to one that more resembles
today’s—even as other parts of the world,
particularly less-developed regions, experience the
unmitigated brunt of global warming.
If the Conveyor subsequently turns on again, the
“deferred” warming may be delivered in a decade
Source: Abrupt Climate Change: Should We Be Worried? By Robert B. Gagosian <http://www.whoi.edu/institutes/occi/viewArticle.do?id=9986>
Effects of Global Cooling

Temperatures
Europe and North America ~20°C colder
than present
 Tropical regions ~ 2°C colder than present
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Development of ice caps
Lowers sea levels
 Causes land bridges to form
 Changes to flora and fauna
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Effects of Changes in Sea Level Across Beringia
Sea Level at LGM
~10,000 ybp
~12,000 ybp
Present
Last Glacial Maximum
Today
Causes of Global Climate Change

Global Warming

Sunlight received by the Earth may be
reflected by either the atmosphere or the
surface.
Some of the light is absorbed by the Earth and
re-emitted as infrared energy (heat).
 Gases prevent some of this heat from escaping
to space thereby causing the Earth to grow
warmer.
 Global temperatures are 0.6ºC higher than 100
years ago

Temperatures of the northern
hemisphere for the past 1000 years.
Globally-averaged surface
temperatures
Causes of Global Climate Change
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Global Warming
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Gases that cause the global warming
(greenhouse effect)
Carbon dioxide (CO2)
 Methane
 Chlorofluorocarbons

Effects of Global Warming

The impact on the Earth is uncertain
Scientists are unable to precisely model the
nature of this process
 General atmospheric warming due to
human pollution is highly probable
 Polar ice caps may partially melt raising
sea level
 Some parts of the land may receive less
rain while others receive more

Lands Vulnerable to Sea Level Rise On the Gulf Coast
Table 3
AMOUNTS OF LOW LAND IMPLIED BY VARIOUS MAP DATA SETS 1
(square kilometers)
State
Elevation between 0 and 1.5 meters Elevation between 1.5 and 3.5 meters
District of Columbia
1.5
4
Pennsylvania
2.5
2.5
New Hampshire
42.4
20
Connecticut
63
48.6
Rhode Island
121.9
61.7
Mississippi
173.2
824.1
Alabama
194.7
354.6
New York
239.9
265.8
Massachusetts
364.7
375
Maine
382.9
176.1
Delaware
387.8
172
Virginia
968.5
1,041.40
New Jersey
1,083.00
637.8
Maryland
1,547.10
806.1
Georgia
1,742.60
1,078.30
South Carolina
2,333.70
2,401.70
Texas
5,177.70
4,213.20
North Carolina
5,835.90
3,864.60
Florida
12,250.80
12,742.90
Louisiana
24,724.70
4,345.20
Total
57,638.60
33,435.70
Effects of Global Warming

Some Solutions To The Global Warming
Problem
Use Energy More Efficiently
 Develop Alternate Energy Sources

Effects of Global Warming

Some Solutions To The Global Warming
Problem

Other Strategies
Improve public transit to reduce automobile
use
 Reverse deforestation
 Rapidly terminate the world-wide use of
chlorofluorocarbons
 Modify your life style so as to minimize impact
on the environment

Effects of Global Warming

Serious Concerns
The developed countries achieved their
wealth on fossil fuels. How can we deny
developing nations these same benefits?
 Deforestation is a short-term benefit to the
logging industry and farmers around the
world. How can we prevent them from
making a living?

Effects of Global Warming

Serious Concerns

Many poor coastal countries will suffer
greatly from a sea level rise and yet they
produce very little carbon pollution. What
obligations do the rich countries have to
those who will suffer because of the
pollution of others?
Past Civilizations & Climate
Change

Maya
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Three time periods
Preclassic Period from 2000 BC to 250 A.D.,
 Classic Period from 250 A.D. to 900 A.D.,
 Postclassic Period from 900 A.D. to the time of
Spanish Conquest beginning in 1524 A.D..

Source: http://www.ncdc.noaa.gov/paleo/slides/slideset/12/
Past Civilizations & Climate
Change
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Maya
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Classic Period from 250 A.D. to 900 A.D.,
Culture flourished 600 – 800 A.D.
 Collapse occurred between 800 and 900 A.D..

Past Civilizations & Climate
Change
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Maya

Symptoms of the collapse included:
rapid depopulation of the countryside and
ceremonial centers in 50 to 100 years
 abandonment of administrative and residential
structures
 cessation of:

– building construction, carving of sculptured
monuments, manufacture of pottery, stonework, jade
carvings, Classic calendrical (long count) and writing
systems.
Past Civilizations & Climate
Change
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Maya

Proposed causes of the Collapse (Natural):
soil exhaustion due to slash-and-burn agriculture
 water loss and erosion of topsoil evident by
increased sedimentation in lakes
 natural disasters (earthquakes, hurricanes)
 climatic change
 disease
 insect infestations
 overpopulation

Past Civilizations & Climate
Change
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Maya

Proposed causes of the Collapse
(sociopolitical):
peasant revolts resulting in the overthrowing of
the elite class
 inter-site warfare between Maya city-states
 invasions by peoples from outside the Maya
civilization
 failure of centralized political authority.

Past Civilizations & Climate
Change

Mesopotamia
Akkadian empire established between the
Tigris & Euphrates Rivers around 2300 B.C.
 Society collapsed +/- 150 years later

Abandonment of agricultural plains in the north
 Mass migration to more arid lands to the south

Source: http://www.ldeo.columbia.edu/res/pi/arch/examples.shtml
Past Civilizations & Climate
Change

Mesopotamia

World climate records abrupt climate
change around the same time

Cool & drought conditions for next 200 – 300
years
Source: http://www.ldeo.columbia.edu/res/pi/arch/examples.shtml
Map of the Akkadian empire
(source: http://research.yale.edu/leilan/akkadian/)
Past Civilizations & Climate
Change

Others
Akkadian empire (Mesopotamia)
 Teotihuacán
 Roanoke

Modern Civilizations & Climate
Change

Where will the people go if . . .
Sea level rises?
 Climate regimes shift?
 Animals/fish/etc. become extinct or
migrate elsewhere?

“Whatever befalls the Earth befalls the sons
of the Earth. Man did not weave the web of
life; he is merely a strand in it. Whatever he
does to the web, he does to himself.
Contaminate your bed, and you will one night
suffocate in your own waste.”
Chief Seattle
1785 - 1866
~ End ~