Chapter 21 Global Climate Change - PowerPoint PPT Presentation

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Chapter 21 Global Climate Change


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Title: Chapter 21 Global Climate Change

Chapter 21Global Climate Change
Overview of Chapter 21
  • Introduction to Climate Change
  • Atmosphere and Weather
  • 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

Atmosphere Structure
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Atmospheric Structure
  • Troposphere
  • Lowest layer
  • Densest layer
  • Temperature decreases with altitude
  • Contains most of the water vapor and weather
  • Stratosphere
  • Second layer
  • Much less dense than troposphere
  • Temperature increases with altitude

Atmospheric Structure
  • Mesosphere
  • Coldest layer
  • Temperature increases with altitude
  • Thermosphere
  • Hottest layer
  • Temperature increases with altitude
  • Exosphere
  • Beyond Earths atmosphere merges with
    interplanetary gases

  • Atmospheric Concentrations (Constant)

Constituent Formula Concentration (ppm)
Nitrogen N2 780,840 Oxygen
O2 209,460 Argon
Ar 9340 Neon
Ne 18.18 Helium
He 5.24 Krypton Kr 1.14
Hydrogen H2 .50 Xenon Xe .09
Atmospheric Concentrations (Variable)
  • Constituent Formula Conc. ppm
  • Water Vapor H20 .1 30,000
  • Carbon Dioxide CO2 350
  • Methane CH4 1.67
  • Nitrous Oxide N2O .30
  • Carbon Monoxide CO .19
  • Ozone O3 .04
  • Ammonia NH3 .004
  • Nitrogen Dioxide NO2 .001
  • Sulfur Dioxide SO2 .001
  • Nitric Oxide NO .0005
  • Hydrogen Sulfide H2S .00005

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History of Earth Climate
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  • Milankovitch Cycles time periods of oscillations

Introduction to Climate Change-Mean Annual
Global Temperature 1960-2005
How Do We Know About Past Climate?
  • The geological record of carved mountain valleys,
    scratched bedrock, and glacial debris and
  • Recently, cores have been removed from the ice at
    Vostok Station in Antarctica.
  • The longest cores are about 2000 meters, sampling
    layers of ice deposited as early as 160,000 years
    ago. The ice trapped bubbles of air when it
    froze. The ratio of oxygen isotopes in this air
    indicates the average air temperature at the time
    the bubble was trapped in ice. The bubbles also
    trap atmospheric greenhouse gases that can be

How Do We Know?
  • Fossil plants and the distribution of pollen show
    that vegetation has changed, consistent with
    changing climate.
  • Pollen from plants, buried in shallow deposits of
    earth, indicate the distribution of vegetation
    since the last glaciations, about 20,000 years
  • Ancient Plant Distribution describes how
    vegetation has changed as the ice retreated

How Do We Know?
  • The historical record speaks to us for some 2,000
    years and there have been real quantitative
    measurements since about 1850.

Oceans and Atmosphere
  • Oceans Importance
  • Role in hydrologic cycle
  • Regulation of heat and moisture
  • Ocean currents move heat as well as water
  • Oceanic physical and biogeochemical processes are
    major regulators of natural atmospheric carbon
  • High specific heat of water heats and cools

Oceans and Atmosphere
  • 2. The Oceanic Conveyor System
  • A global system that continually exchanges
    water, heat, and salt among all of the oceans and
    between the surface layer and the deep waters

  • The exchange of heat between the ocean and
    atmopshere, as estimated from an inverse model
    (units are in W/m2). Red numbers are regions
    where the ocean undergoes net heating, and blue
    numbers indicate areas where there is net cooling
    ( indicates standard errors of the estimates)
    areas are bounded by observations along the lines
    shown. The model combines oceanic dynamics with
    global hydrographic data base. Macdonald,
    MIT-WHOI PhD Thesis, 1995

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Climate Change Terminology
  • Greenhouse Gas
  • Gas that absorbs infrared radiation
  • Ex Carbon dioxide, methane, nitrous oxide,
    chlorofluorocarbons and tropospheric ozone
  • 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

Introduction to Climate Change
  • Evidence for Climate Change
  • 11 of the 12 years between 1995 and 2006 were
    among the twelve warmest years since the
  • Phenological spring in N. hemisphere now comes 6
    days earlier
  • Warming is not due to natural causes
  • Human produced greenhouse gases are most
    plausible explanation

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
Greenhouse Effect
Greenhouse Animation
  • http//

Greenhouse Gases
  • Carbon Dioxide CO2
  • Causes of increased atmospheric CO2
  • Combustion of fossil fuels
  • Deforestation
  • Removal of other vegetation

Greenhouse Gases CO2
  • Review of carbon cycle
  • C in CO2 in atmosphere and in water is moved to
    glucose by photosynthesis
  • C in glucose is moved to CO2 by cell respiration
  • C in glucose is moved to organic molecules by
    synthesis reactions in living things
  • C in organic molecules in organisms is moved to
    fossil fuels over millions of years
  • C in limestone (CaCO3) is released slowly to CO2
    when exposed to oxygen or water

Greenhouse Gases CO2
  • Largest reservoir of carbon sedimentary rocks
  • Second largest reservoir of carbon top 300m of
    ocean (dissolved CO2), living things in ocean

Greenhouse Gases
  • Water Vapor H2O
  • Methane CH4
  • Sources fermentation, swamp gas, livestock,
    natural gas production, coal mining, landfill
    emissions, manure
  • Nitrous Oxide N2O
  • Sources agriculture, combustion of biomass,
    combustion of fossil fuels, anaerobic
    denitrificaiton, acts as a greenhouse gas and
    contributes to ozone depletion

Greenhouse Gases
  • CFCs (anthropoenic)
  • CFC chlorofluorocarbon (hydrocarbon halogenated
    specifically with Cl or F)
  • 10,000 times more efficient than CO2 in absorbing
    IR radiation
  • Uses refrigerants, industrial solvents, fire

Other Pollutants Cool the Atmosphere
  • Atmospheric Aerosols tend to cool the atmosphere
  • Both human and natural sources
  • Tiny particles that remain in troposphere for
    weeks or months
  • Contain many chemicals, but 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
  • Ocean as CO2 sink - excess CO2 is starting to
    harm ocean life

Effects of Global Climate Change- Melting Ice and
Rising Sea Levels
  • Sea level rise caused in 2 ways
  • Thermal Expansion
  • Water expands as it warms
  • Melting of land ice
  • Retreat of glacier and thinning of ice at the
  • Melting has positive feedback
  • Increased melting decreases ice, which decreases
    albedo leading to further warming

  • C\Documents and Settings\kmajka-johnston\My
    Documents\APES\climate change\methane.htm

Melting Ice and Rising Sea Levels
Case-In-Point Impacts in Fragile Areas
  • Eskimo Inuit live traditional life dictated by
    freezing climate
  • Climate change is altering their existence
  • Wildlife are smaller or 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
  • Ex Hurricanes will likely get stronger

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
  • Caused decrease in penguin populations
  • Species have shifted their geographic range
  • Migrating birds are returning to summer homes
  • Food is not available at this time

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 to which they would
    otherwise be immune

Effect on Organisms - VegetationBeech Tree Range
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 Implicationsof Climate Change
  • Developed vs. Developing countries
  • Differing self-interests
  • Differing ability to meet the challenges of
    climate change

Dealing with Global Climate Change
  • To avoid the worst of climate change, CO2 levels
    must be stabilized at 550ppm
  • 50 higher than current levels
  • Two ways to attempt to manage climate change
  • Mitigation
  • Focuses on limiting greenhouse gas emissions to
    moderate global climate change
  • Adaptation
  • Focuses on learning to live with to the
    environmental changes and societal consequences
    brought about by global climate change

Dealing with 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
  • Sequestering carbon before it is emitted
  • 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
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