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Chapter 21 Global Climate Change


Chapter 21 Global Climate Change – PowerPoint PPT presentation

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Title: Chapter 21 Global Climate Change

Chapter 21 Global Climate Change
Overview of Chapter 21
  • Introduction to Climate Change
  • Causes of Global Climate Change
  • Effects of 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
  • Greenhouse Gas
  • Gas that absorbs infrared radiation
  • Positive Feedback
  • Change in some condition triggers a response that
    intensifies the changed condition
  • Infrared Radiation
  • Radiation that has a wavelength that is longer
    than that of visible light, but shorter than that
    of radio waves
  • Greenhouse Effect
  • Increase of heat in a system where energy enters
    (often as light), is absorbed as heat, and
    released sometime later

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Natural Physical Factors Affecting Climate
  • Latitude
  • 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
  • Latitudecontinued
  • Seasons on Earth are determined by latitude and
    angle of insolation at various times throughout
    the year, and are caused by
  • Tilt of Earths axis
  • Earths revolution around the Sun
  • Parallelism of Earths axis

Seasons on Earth
Natural Physical Factors Affecting Climate
  • 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

Natural Physical Factors Affecting Climate
  • 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 sinkscalled the rainshadow

Orographic (Mountain) Effect
Natural Physical Factors Affecting Climate
  1. 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

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Natural Physical Factors Affecting Climate
  • Ocean Circulation Patterns
  • 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)

Earths Major Ocean Currents
Natural Physical Factors Affecting Climate
  • Ocean-Atmosphere Interactions
  • 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 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
  • Recorded Human Observations (only reliable for
    past 200 yrs.)
  • Ice Core Data
  • Tree Rings
  • Soil Sediments
  • Biological Fossils
  • Shells of aquatic organisms
  • Corals

Ice Core Data
  • Drilled from deep within the ground, ice cores
    can be 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

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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 climateglobal
  • 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 Milankovic
  • Variations in the Earth's eccentricity, axial
    tilt, and precession comprise the three dominant

Milankovitch Cycles Eccentricity
  • Eccentricity is, simply, the shape of 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.

Animated sequence
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Milankovitch Cycles Axial Tilt
  • Axial tilt is the inclination of the Earth's axis
    in relation to its 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!

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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
  • 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 Cyclesoverall 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
  • Evidence for Climate Change
  • 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
  • Human produced greenhouse gases are most
    plausible explanation

Introduction to Climate Change Mean Annual
Global Temperature 19602007

Causes of Climate Change
  • Greenhouse gas concentrations increasing

Causes of Climate Change
  • Increased concentration of CO2 (right)
  • Burning fossil fuels in cars, industry and homes
  • Deforestation
  • Burning of forests

Greenhouse Effect

Pollutants That Cool the Atmosphere
  • Atmospheric Aerosols
  • 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
  • Climate affected by
  • 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
  • They have limitations

Climate Models

Effects of Global Climate Change
  • Wildfire in California

Effects of Global Climate Change Melting Ice and
Rising Sea Levels
  • Sea level rise caused in 2 ways
  • Thermal Expansion
  • Melting of land ice
  • Melting has positive feedback
  • Increased melting decreases ice, which decreases
    albedo leading to further warming

Melting Ice and Rising Sea Levels

Glacier National Park
Case-In-Point Impacts in Fragile Areas
  • Eskimo Inuit live
  • traditional life
  • dictated by freezing
  • climate
  • Climate change is
  • altering their existence
  • Wildlife displaced
  • Reduced snow cover and shorter river ice seasons
  • Thawing of permafrost (right)

Effects of Global Climate Change Changing
Precipitation Patterns
  • Some areas will get more water, some areas will
    have greater droughts

Effects of Global Climate Change Effects on
  • Zooplankton in parts of California Current have
    decreased by 80 since 1951
  • Effecting entire food chain
  • Decline in krill around Antarctica
  • Species have shifted their geographic range
  • Migrating birds are returning to summer homes

Effects on Organisms Coral Reefs
  • Coral reefs can be bleached (right) due to
    increase in water temperature
  • Affects coral symbiotes and makes them more
    susceptible to diseases

Effect on Organisms Vegetation

Effect on Organisms Vegetation

Effects on Human Health
  • Increased number of heat-related illnesses and

Effects on Agriculture
  • Difficult to anticipate
  • 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 moisture-
    requiring more irrigation
  • Location (i.e. elevation and altitude) where
    certain crops can be grown may have to change

International Implications of Climate Change
  • Developed vs. Developing countries
  • Differing self-interests
  • Differing ability to meet the challenges of
    climate change

Dealing with Global Climate Change
  • Two ways to manage climate change
  • Mitigation Limiting greenhouse gas emissions to
    moderate global climate change
  • 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
  • Locate/invent alternative fuels to fossil fuels
  • Increase efficiency of cars and trucks
  • Carbon Capture and Storage
  • Plant and Maintain trees to naturally sequester

Dealing with Global Climate Change Adaptation
  • Rising sea levels and coastal populations
  • Move inland
  • Construct dikes and levees
  • Adapt to shifting agricultural zones
  • NYC sewer line

International Efforts to Reduce Greenhouse Gas
  • Kyoto Protocol
  • Legally binding
  • Provides operational rules on reducing greenhouse
  • US and Australia have not sign it - it will be
    difficult to implement without US backing