Transcript Chapter 21: Global Climate Change (2013)

Chapter 21
Global Climate Change
Overview of Chapter 21
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Introduction to Climate Change
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Effects of Climate Change
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Causes of Global Climate Change
Melting Ice and Rising Sea Level
Changes in Precipitation Patterns
Effects on Organisms
Effects on Human Health
Effects on Agriculture
Dealing with Global Climate Change
Climate Change Terminology
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Greenhouse Gas
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Positive Feedback
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Change in some condition triggers a response that
intensifies the changed condition
Infrared Radiation
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Gas that absorbs infrared radiation
Radiation that has a wavelength that is longer than that
of visible light, but shorter than that of radio waves
Greenhouse Effect
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Increase of heat in a system where energy enters
(often as light), is absorbed as heat, and released
sometime later
Natural Physical Factors Affecting Climate:
1. Latitude:
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near equator is warm, near poles is cold, because at
equator the Sun strikes Earth at a higher angle of
insolation, at poles Sun strikes Earth at a lower angle
of insolation
Natural Physical Factors Affecting Climate:
1. Latitude…continued:
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Seasons on Earth are determined by latitude and
angle of insolation at various times throughout the
year, and are caused by:
• Tilt of Earth’s axis
• Earth’s revolution around the Sun
• Parallelism of Earth’s axis
Seasons on Earth…
Natural Physical Factors Affecting Climate:
2. Proximity to a large body of water (ocean or
large lake):
• Water has a high specific heat, so the
ocean does NOT heat up or cool down
easily, and therefore helps to regulate
temperatures of nearby coastal areas
Natural Physical Factors Affecting Climate:
3. Nearness to mountains:
• Higher elevations have colder avg.
temperatures, longer snowpack, etc.
• Orographic effect: (rainshadow)
– Windward side of mountains force air to rise,
expand, cool, and cause water vapor to condense,
forming clouds and abundant rainfall
– Leeward side of mountains experience dry
conditions as air sinks…called the “rainshadow”
side.
Orographic (Mountain) Effect:
Natural Physical Factors Affecting Climate:
4. Wind Circulation Patterns –
caused by unequal heating
of the Earth, which creates
different temperature
zones, which creates
different pressure belts,
which forces the major
wind belts to occur, which
determines major weather
and climate patterns
Natural Physical Factors Affecting Climate:
5. Ocean Circulation Patterns:
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Prevailing wind belts create mass movements of
ocean water (currents)
Circular ocean currents are called “gyres”
Ocean currents are also influenced by the Coriolis
effect, and tend to circulate clockwise in the N.
hemisphere, and counterclockwise in the S.
hemisphere
Ocean currents are forced to move around major
landmasses (continents and islands)
Earth’s Major Ocean Currents
Natural Physical Factors Affecting Climate:
6. Ocean-Atmosphere Interactions
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Ocean interacts with the atmosphere to
dramatically influence climate patterns worldwide
El Nino & La Nina can impact global climate in any
given year
Long-Term Natural Factors Affecting
Climate
• Paleoclimatology – the study of climate changes over
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the history of the Earth
A variety of techniques and inferences are used to
measure or infer atmospheric gas content,
temperatures, dust particles, life forms, etc.
Methods Used to Determine Past Climate:
1. Recorded Human Observations (only reliable for past 200
yrs.)
2. Ice Core Data
3. Tree Rings
4. Soil Sediments
5. Biological Fossils
– Shells of aquatic organisms
– Corals
Ice Core Data:
• Drilled from deep within the ground, ice cores can be
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used to measure increases and/or decreases in
snowfall over time as well as changes in atmospheric
gases as seen in trapped air bubbles, dust, and
oxygen isotopes.
Scientists drilling in the Greenland ice sheet have been
able to piece together a climate record dating back
approximately 110,000 years
Antarctic ice samples have yielded information as far
back as 750,000 years.
Ice cores can provide vast amounts of information,
including an annual record of temperature,
precipitation, atmospheric composition, volcanic
activity, and even wind patterns.
Ice Core Data:
• Specifically, CO2 and CH4 concentrations can be
analyzed and used to infer past temperatures.
• Thickness of ice layers also reflects
temperature and precipitation in the past.
• Atmospheric dust particles can also be analyzed
from ice cores.
Vostok
Ice
Core
Data:
Long-term natural influences on
climate…global changes
• There are several LONG-TERM changes that
have influenced climate in a cyclic manner.
• Milankovitch Cycles are the collective effect of
changes in the Earth's movements upon its
climate, named after Serbian civil engineer and
mathematician Milutin Milanković
• Variations in the Earth's eccentricity, axial tilt,
and precession comprise the three dominant
cycles
Milankovitch Cycles: Eccentricity
• Eccentricity is, simply, the shape of
Animated sequence
the Earth's orbit around the Sun.
• This constantly fluctuating, orbital
shape ranges between more and
less elliptical (0 to 5% ellipticity)
on a cycle of about 100,000
years.
• These oscillations, from more
elliptic to less elliptic, are of prime
importance to glaciation in that it
alters the distance from the Earth
to the Sun, thus changing the
distance the Sun's short wave
radiation must travel to reach
Earth, subsequently reducing or
increasing the amount of radiation
received at the Earth's surface in
different seasons.
Milankovitch Cycles: Axial Tilt
• Axial tilt is the inclination of the Earth's axis in relation to its
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plane of orbit around the Sun.
Oscillations in the degree of Earth's axial tilt occur on a
periodicity of 41,000 years from 21.5 to 24.5 degrees.
A larger tilt will result in warmer summers and colder winters!
Milankovitch Cycles: Precession (wobble)
• Precession is the Earth's slow wobble as it spins
on axis. This wobbling of the Earth on its axis
can be likened to a top running down, and
beginning to wobble back and forth on its axis.
• The precession of Earth wobbles from pointing
at Polaris (North Star) to pointing at the star
Vega.
• When this shift to the axis pointing at Vega
occurs, Vega would then be considered the
North Star. This top-like wobble, or precession,
has a periodicity of about 23,000 years.
Milankovitch Cycles: Precession (wobble)
Animated sequence
Milankovitch Cycles…overall effect:
Current Observations of Climate
• Today, a wide variety of instruments has been
deployed to continuously measure a large
number of climate factors including:
– Air temperature
– Sea surface temperature
– Greenhouse Trace Gas concentrations (CO2, CH4,
O3, NO, NO2, etc.
– Response of plants (budding times, size, etc.)
– Response of animals (changes in range, timing of
reproduction, etc.)
Introduction to Climate Change
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Evidence for Climate Change
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14 warmest years since mid-1800s have
occurred since 1990
Phenological spring in N. hemisphere now
begins 6 days earlier
Warming is not due to natural causes
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Human produced greenhouse gases are most
plausible explanation
Introduction to Climate Change:
Mean Annual Global
Temperature 1960–2007
Causes of Climate Change
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Greenhouse gas concentrations increasing
Causes of Climate Change
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Increased
concentration of CO2
(right)
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Burning fossil fuels in
cars, industry and
homes
Deforestation
Burning of forests
Greenhouse Effect
Pollutants That Cool the
Atmosphere
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Atmospheric Aerosols
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Both human and natural sources
Tiny particles that remain in troposphere for
weeks or months
Often contain sulfur
Complicates models of climate change
Climate Models
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Climate affected by:
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winds, clouds, ocean currents, and albedo
Used to explore past climate events
Advanced models can project future
warming events
Models are only as good as the data and
law used to program them
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They have limitations
Climate Models
Effects of Global Climate Change
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Wildfire in California
Effects of Global Climate Change:
Melting Ice and Rising Sea Levels
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Sea level rise caused in 2 ways
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Thermal Expansion
Melting of land ice
Melting has positive feedback
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Increased melting decreases ice, which
decreases albedo leading to further warming
Melting Ice and Rising Sea Levels
1957
1998
Glacier National Park
Case-In-Point Impacts in Fragile
Areas
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Eskimo Inuit live
traditional life
dictated by freezing
climate
Climate change is
altering their existence
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Wildlife displaced
Reduced snow cover and shorter river ice
seasons
Thawing of permafrost (right)
Effects of Global Climate Change:
Changing Precipitation Patterns
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Some areas will get more water, some
areas will have greater droughts
Effects of Global Climate Change:
Effects on Organisms
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Zooplankton in parts of California Current
have decreased by 80% since 1951
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Effecting entire food chain
Decline in krill around Antarctica
Species have shifted their geographic
range
Migrating birds are returning to summer
homes earlier
Effects on Organisms: Coral Reefs
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Coral reefs can be bleached (right) due to
increase in water temperature
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Affects coral symbiotes and makes them more
susceptible to diseases
Effect on Organisms: Vegetation
Effect on Organisms: Vegetation
Effects on Human Health
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Increased number of heat-related illnesses
and deaths
Effects on Agriculture
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Difficult to anticipate
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Productivity will increase in some areas and decrease
in others
Rise in sea level will inundate flood plains and
river valleys (lush farmland)
Effect on pests is unknown
Warmer temperatures will decrease soil moisturerequiring more irrigation
Location (i.e. elevation and altitude) where
certain crops can be grown may have to change
International Implications of
Climate Change
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Developed vs.
Developing
countries
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Differing selfinterests
Differing ability
to meet the
challenges of
climate change
Dealing with Global Climate
Change
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Two ways to manage climate change
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Mitigation: Limiting greenhouse gas emissions
to moderate global climate change
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Adaptation: Learning to live with
environmental changes and societal
consequences brought about by global
climate change
Relationship Between Mitigation
and Adaptation
Dealing with Global Climate
Change: Mitigation
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Locate/invent alternative fuels to fossil
fuels
Increase efficiency of cars and trucks
Carbon Capture and Storage
Plant and Maintain trees to naturally
sequester carbon
Dealing with Global Climate
Change: Adaptation
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Rising sea levels and coastal populations
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Move inland
Construct dikes and levees
Adapt to shifting agricultural zones
NYC sewer line
International Efforts to Reduce
Greenhouse Gas Emission
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Kyoto Protocol
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Legally binding
Provides operational rules on reducing
greenhouse gases
US and Australia have not sign it - it will be
difficult to implement without US backing