Global Warming and the Greenhouse Effect

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Global Warming and the Greenhouse Effect

• 3rd-Order climate changes

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Recap

• 1st-order climate changes
• Driven by plate tectonics
• 300-m.y. cycle
• 12-20 degree C changes
• 2nd-order changes
• Driven by Earths orbital variations
• 20 k.y. to 400 k.y. cycle
• 5-12 degree C changes

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Climate cycle diagram
1st 2nd 3rd (little squiggles
1st order alone
1st 2nd together
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3rd-order changes

• Years to centuries in length
• gt1 to 5 degree C temperature changes
• Happening CONCURRENTLY with 2nd and 1st order
  changes
• Example the Greenhouse effect

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What is the Greenhouse effect?

• Catastrophic climate change caused by human
  activity
• Industrialization Consumerism
• Burning fossil fuels releases greenhouse gases,
  which heat the planet
• Ozone depletion is related
• The ozone hole is real!
• Ozone filters harmful UV light

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Popular visions of greenhouse world

• Global average temperatures increase by up to 5
  degrees C
• Current global average 59 F
• El Paso average high temp. for June 95 F
• For Tucson, ave. high temp. for June 100.2
• What if these numbers were to increase by 9 F?
• Widespread drought and desertification
• Much farmland rendered unproductive

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Popular vision, continued

• Global sea level rise
• ExampleHouston
• Elevation rises 1 ft for every mile inland
• If sea level rose 1 ft, then the mile closest to
  the coast is submerged

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Popular vision summary

• Greatest refugee crisis in human history
• Flooded cities
• Drought
• Land made unproductive
• Health effects from increased UV exposures
• This is the popular (as in Pop) vision
• Does the science support this?

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How does the Greenhouse effect work?

• What is a greenhouse?
• A glass house used to grow tropical plants in
  non-tropical areas
• So is the Effect like putting the Earth in a
  glass house?
• NO!
• Why not?

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Greenhouse

• A glass house works because it allows the air
  inside to heat up, BUT
• That air does NOT mix with the cooler air outside
• This is not how the atmosphere heats
• So it shouldnt really be called the Greenhouse
  effect at all!

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How it works 1

• Insolation comes in
• The energy excites electrons in the gas
  molecule
• The molecule re-radiates the energy back out
• This adds heat to the atmosphere
• Not the same as a glass house!

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How it works 2

• The more greenhouse gases there are, the more the
  atmosphere will be warmed
• Greenhouse gases are
• Carbon dioxide CO2
• Nitrous Oxide N2O
• Methane NH4
• Chlorofluorocarbons CFCs
• Do not occur naturally
• Water vapor (clouds!)

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How it works 3

• CO2 is a big player and occurs naturally
• How CO2 is added to the atmosphere
• Exchange between atmosphere seawater
• Animal respiration
• Burning fossil fuels
• Volcanism
• How CO2 is removed from atmosphere
• Exchange between atmosphere seawater
• Photosynthesis
• Formation of carbonate rocks (limestones) in
  oceans

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Equivalent Carbon Dioxide

• Not all greenhouse gases heat the atmosphere the
  same amount
• Combine all the greenhouse gases
• For simplicity
• Example
• If you need 1L of CO2 to increase temp in a
  parcel of air 1 degree
• You would only need 1 mL of CFCs to do the same

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Equivalent CO2
NH4
CO2
N2O
CFC
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Assessing global warming

• If global equivalent CO2 levels increase,
• Then global temperature should increase
• We can predict how much temps. increase
• We compare our predictions with observations
• We make policy (about fossil fuels) based on this
  science

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Lets look at the data

• But first
• A statistics lesson
• What are charts and graphs telling us?
• A comparison of X with Y
• Look for relationships
• Determine correlation or causation
• Example
• A graph of Science vs. Fun
• A graph of Liberal Arts vs. Fun

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Science (X) vs. Fun (Y)

• When Science increases, Fun also does
• The data points seem to line up.
• The process of fitting a line to the points is
  called regression analysis
• When regression line and points match, this is a
  GOOD FIT

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Liberal Arts vs. Fun

• When LA increases, cant tell if fun does
• Points dont fit well to a regression line
• This is a BAD FIT
• A weak trend? Which way?
• What would happen if you only saw the regression
  line?
• You would change your major to Science

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Actual CO2 Levels

• Good fit?
• Why the increase between 1750 and 1850?
• Industrial Revolution
• Why the drop around 1930?
• Great depression
• Why the increase in 1945-1950?
• End of WW2, baby boomers
• Why the drop around 1972?
• Gas crisis, OPEC
• Active in atmosphere for 500 to 200 years

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More CO2 Data
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Methane data

• Good fit?
• 58 of methane produced by agriculture
• Rice paddies
• Cows (flatulence)
• Deforestation by fire
• Coal mining
• Coal burning
• Landfills
• Active in atmosphere for 10 years

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N2O data

• Good fit?
• Deforestation by fire
• Use of fertilizers
• Steel refining
• Active in atmosphere for 150 yrs

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CFC Data

• Global CFC emissions decreasing due to Intl law
• All CFCs human made
• Used as propellant and refrigerant
• Active in atmosphere for centuries
• Warming and breaking up ozone molecules
• This is why you shouldnt vent your A/C!

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CFC Dataemissions
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CFC Datasales production
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Equivalent CO2

• 295 ppm in 1750
• 425 in 1990
• Expected to be 600
• in 2035

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Summary

• No doubt equivalent CO2 has increased due to
  human activity
• No doubt this will produce global warming
• How much?

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Summary of 22 climate models
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Estimations of contributions to sea level rise
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Predictions for precipitation and temp. increases

• Warmer temps may promote more rain in some places
• Assuming lots of cloud cover
• Some areas will experience droughts

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Observations

• Not computer models but real data

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Temp/precip changes for U.S. from 1901-1987
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Global temps over 99 years

• Zero is an average of all temps.
• Good fit?
• What if you only saw the points at 1912 and 1974?
• You would say temps have decreased!

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Sea Level Rise 1

• Good fit?
• Zero value is average of measured levels from
  1915-1979
• When was level lowest?
• When was it highest?
• What is the biggest net increase?

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Sea Level Rise 2

• Is 13-14 cm a big increase?
• Depends on where you live!

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Desertification-related warming trends
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Global Precipitation Index

• Y-axis values are percentiles
• .50 is average rainfall for an area
• Has global precip increased?
• Look at regression line

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Temperatures in the stratosphere

• Stratosphere is from 12-50 km high
• Above weather zone
• Good fit?
• Trend?
• Decreasing
• WHY? (stay tuned)

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Summary of observed data

• Global temperatures have increased, but not as
  much as predicted
• Rainfall has increased, but far less than
  predicted
• Sea level has increased more than predicted
• The stratosphere is actually cooling

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Why dont models match observations?

• Human error, computers not sophisticated enough,
  etc.
• Big Reason 1 Clouds are not well understood
• Big Reason 2 Sulfate emissions

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Sulfate (SO4) Emissions

• Produced by steel refining and coal mining
• One localization in eastern U.S.
• SO4 promotes formation of clouds
• Leads to local cooling and higher precip
• Leads to reduction in average temps.

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So whos responsible?

• Industrialized countries?
• U.S., Europe?
• Rapidly deforesting regions?
• Central and South America?
• It depends on how you look at it

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Fossil fuel CO2 emissions by country

• U.S. Highest
• USSR next
• Spain lowest
• Levels for Mexico are pre-NAFTA
• 1988

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Fossil fuel emissions per capita by country

• Per capita per person
• 1988 data
• Pre-NAFTA
• Before German reunification
• U.S. second

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Fossil fuel CO2 emissions per 1000 of GNP

• U.S. way below average
• Meaning U.S. emitted less CO2 for every 1000 of
  GNP than Poland, China, Mexico
• U.S. more efficient or cleaner than some,
  less than others

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What about the big picture?

• How does global warming/greenhouse effect compare
  with natural 1st-and 2nd order climate changes?

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Atmospheric CO2 over 150 K.Y.
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Global temps over 850 K.Y.
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Implications for policy 1

• Greenhouse effect small when compared to 2nd
  order changes
• But greenhouse effect takes place on human
  timescales
• Can we survive it? Probably, but does that mean
  we should have to?

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Implications for policy 2

• Sea level change unimportant for inland residents
• Wealthy countries have better infrastructure to
  cope with flooding of coastal cities
• What about poor countries?

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Implications for policy 3

• Many areas flooded by sea or made into desert,
  but many areas will also be opened up
• Example when Canadian tundra melts
• Again, just because things might balance out,
  should warming be allowed to continue?
• Is there an acceptable number of people who are
  displaced/killed by global climate change?
• If so, what is it?
• Who decides?

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Implications for policy 4

• How is the greenhouse effect stopped?
• Reduction in fossil fuel emissions
• How do we reduce fossil fuel dependence?
• Alternative energy
• Conservation
• Reduction in consumerism
• Education
• TAAS/TAKS requirements for stewardship vs.
  consumerism

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Implications for policy 5

• Rethinking individual consumerism?
• Rethinking national energy policy?
• Rethinking unlimited economic growth as a
  cure-all?
• Reconnecting the economy to the environment?

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Greenhouse Effect Exam 3

• On exam day you will bring this handout
• These will be the two basic questions
• 1. Should we be concerned about global warming?
• Why or why not?
• 2. Are you concerned about global warming
• Why or why not?
• You must use five of the figures in the handout
  to back up your opinion.
• You will be graded on the clarity/quality of your
  opinion, not what your opinion is