Chapter 13 Earths Atmosphere and Climate

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Chapter 13 Earths Atmosphere and Climate
Big Question Global Warming Is Happening What
Part Do We Play?
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Case StudyGlobal Warming and the Polar Bears of
Hudson Bay
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Is the Global Temperature Rising?

• Yes, and it is rising globally
• Has the temperature risen steadily?

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• In the last 100 years, the global average annual
  temperature has risen approximately 0.6C
• It has also gotten warmer faster
• The overall picture supports the view that global
  warming is occurring

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What Causes Climate Change and What Is Making It
Get Warmer?

• Studies of ice cores show Earths surface
  temperature has varied over time

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• The answer lies in the Earths energy balance
  between the amount of energy coming in from the
  sun and the amount of energy radiated out by the
  Earth

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• Albedo the percentage of light received by a
  surface that is reflected and scattered

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• Energy takes a complex path from Earths surface
  to space
• The warmer an object, the more energy it radiates

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Variation in the Suns Energy May Be A Reason for
Climate Changes

• The suns energy seems to have varied over the
  ages
• The Little Ice Age lasted from about 1450 to 1850

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Milankovich Cycles Another Possible Explanation

• Some temperature cycles stem from Earths wobble
  in an elliptical orbit.

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Volcanoes Can Alter Climate

• Volcanic eruptions cool the climate in two ways
• - Atmospheric dust reflects sunlight back
  into
• space
• - Smaller dust particles provide water
  condensing
• surfaces, forming clouds

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Dust from Our Own Activities Also Cools the
Climate

• Aerosol pollution particles reduce amount of
  sunlight reaching Earth
• Emissions have reduced global warming

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Variations in Ocean Currents May Affect the
Climate

• Ocean currents and prevailing winds warm or cool
  our planet
• The Gulf Stream a major ocean circulation
  affecting climate

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El Niño A Climate Phenomenon Linked to Ocean
Currents

• A climate change linked to variations in ocean
  currents is the Southern Oscillation
• Upwellings cool surface water and support bird
  and fish populations

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• El Niño occurs when upwellings slow or cease

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• El Niño is important for two reasons
• It is a global event
• It is likely to become more common and more
  intense
• The initial cause of El Niño is unknown

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The Greenhouse Effect, and How It Warms Earths
Surface

• Earths surface temperature determined by four
  main factors
• 1. Amount of sunlight Earth receives
• 2. Amount of sunlight Earth reflects
• 3. Retention of heat by atmosphere
• 4. Evaporation and condensation of water
  vapor

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• Playing Ping-Pong with infrared rays
• - Suns energy reaches Earth
• - Earths surface reflects energy back to
• atmosphere
• - Gases in Earths atmosphere send it back
• again

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• Greenhouse gases are particularly good at
  absorbing infrared radiation
• Include water vapor, carbon dioxide, methane,
  nitrogen oxides, ozone and chlorofluorocarbons
  (CFCs)
• Greenhouse gases trap heat much as panes of glass
  do in a greenhouse
• A small amount of gas has a big effect on
  temperature

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• Gases produce a greenhouse effect on other
  planets too

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Greenhouse Gases Are Increasing

• We are part of the reason
• Carbon dioxide has been increasing in the
  atmosphere for some time

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• First suggested early in the 19th century
• 1957 an observatory established on Mauna Loa
  Volcano, Hawaii
• Scientists now can estimate the carbon dioxide
  concentration in ancient atmosphere
• - Measure concentration in air bubbles
• trapped in polar ice sheets

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• People add to atmospheric carbon dioxide by
• - Burning fossil fuels and wood
• - Major changes in land use, i.e. cutting
• down forests and removing prairies

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Methane

• Concentration more than doubled in the past 200
  years
• People can add to atmospheric methane by
• - Increasing habitats where
  methane-producing
• bacteria live
• - Increasing number of domesticated
  ruminants
• (cows, etc.)
• - Processing and burning fossil fuels
• - Destroying wetlands (releases stored
  methane)
• - Increasing the size of landfills and
  stored
• organic matter

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Chlorofluorocarbons (CFCs)

• Once thought harmless
• Increasing in atmosphere about 5 per year
• Use as propellants banned in the U.S. in 1978
• Montreal Protocol of 1987 was an international
  agreement to reduce and eventually eliminate
  production of CFCs

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Nitrous Oxide

• increasing in the atmosphere and likely
  contributes as much as 5 of the anthropogenic
  greenhouse effect

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Ozone

• Is a contributing greenhouse gas, but has been
  difficult to determine percentage of greenhouse
  effect due to ozone

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Would It Really Be So SeriousIf Earth Warmed Up
a Bit?

• Changes in the atmosphere affect living things
  and habitats
• Steps to forecasting effects
• 1. Forecast changes in climate and physical
• conditions of the oceans and land
  surfaces
• 2. Forecast species and ecosystems response

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• Computer models are the major scientific tool in
  step one
• Model results global warming will increase
  Earths surface temperature by 1.5 to 4.5C from
  1990 to 2100

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• Forecasts suggest that temperatures are rising

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Florida with a 20 ft. rise in sea level.
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If all the ice caps melted 170 ft rise.
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The Effects of a Rising Sea Level

• Risen naturally since last ice age
• Increases damage from major storms

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Global Warming Affects on World Climate

• Glaciers are melting and ice caps are shrinking,
  impacting terrestrial water supplies, power
  generation, and agriculture

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Global Warming Affects on World Climate

• Change frequency and intensity of storms
• Other climate changes
• - i.e. wetter winters, hotter and drier
• summers, and increased droughts
• Super high priced insurance.

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Agriculture

• May seriously affect worlds food supply
• Longer growing seasons in some areas
• The best agricultural areas may no longer be in
  North America
• Winter snowpacks will store less water

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Lowering of Water Tables and Reservoirs

• Could cause serious water supply shortages
• Water use in some regions is already unsustainable

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Biological and Ecological Changes

• Biosphere changes due to damaged ecosystems
• Spring arrives up to two weeks earlier
• Early spring stresses some species
• Some species are changing their geographic ranges
• - i.e. Sachem skipper butterflies expanding
  range

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• Many species moving northward

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Species Migration SpreadsDiseases

• Example Changing range of disease carrying
  mosquitoes

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• West Nile virus is an example of global
• warming spreading disease
• - Mild winters preserve more mosquitoes
• in still water locations
• - Dry springs increase surface-water site
• mosquito and bird concentrations
• - Mosquitoes with virus bite uninfected
• birds
• - Infected birds are bitten by uninfected
• mosquitoes, passing the virus to them
• - Hot, wet summers cause mosquito population
• to mature and grow rapidly

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Endangered Species

• What will happen to species that can not migrate
  nor adapt?
• Case Study Kirtlands warbler
• - an endangered-species success story

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• Kirtlands warblers require a very specific
  habitat
• nest only in young jack-pine woodlands
• To save these birds, 38,000 acres were set aside
  in Michigan

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• computer simulation shows that jack pine will not
  be able to grow there in global warming climates

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Slowing the Temperature Rise

• Reduce production and release of greenhouse gases
• Find ways to sequester (store) greenhouse gases
• Actively cool the climate

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Mitigating Global Warming

• Toronto 1988 scientists recommended a 20
  reduction in carbon dioxide emissions by 2005
• Earth Summit 1992 Blueprint for reducing global
  emissions
• Kyoto 1997 Legally binding emission limits
• We have run out of excuses

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Mitigating Global Warming

• 1997, 160 nations signed the Kyoto Protocol
  treaty to roll back CO2, methane, and nitrous
  oxide emissions to 5 below 1990 levels by 2012
• Who signed all European Nations, Japan, Russia,
  but NOT THE U.S.!
• U.S. energy plan to burn more coal, drill for
  oil in the Arctic National Wildlife Refuge, and
  build more nuclear plants.
• What is being done in the United States?
• Why is the Kyoto Accord so important?

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Alleviating the Effects of Global Warming

• Move species to new habitats
• Establish new nature preserves
• Establish wildlife corridors
• Develop new strains of improved-yield crops
• Learn to live with the changes