Chapter 3: Global Warming

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Chapter 3 Global Warming
Chem 100 Lecture 6 February
3, 2005
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Concentration trend of Greenhouse gases
http//earthobservatory.nasa.gov/Library/GlobalWar
ming/warming4.html
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Greenhouse factor

• Greenhouse gases do not have the same ability to
  absorb IR light
• The greenhouse factor gives the relative
  contribution of each substance to global warming.
• Depends on
• The of active vibrations
• The number of active vibrations depend on
  molecular shapedo IR tutor if you havent
  already!!!
• The change in electric field distribution

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CO2

• Most important greenhouse gas b/c of its large
  concentration in the atmosphere because it is a
  byproduct of fuel combustion (so it will keep
  rising)
• Just how much CO2 (in terms of mass) is released
  when a gallon of gasoline is burned?
• C8H18 O2 ? 8CO2 9H2O
• So 1 molecule of C8H18 ? 8 molecules of CO2
• Does NOT say 1 gallon of C8H18 ? 8 gallons of CO2
• How to get from mass to gallons?
• How many C8H18 molecules are in 1 gallon?
• Firsthow much to molecules weigh???

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• Intro to atomic mass units
• Remember, the mass of an atom is mainly due to
  protons and neutrons.
• Atoms are measured in atomic mass units
• An atomic mass unit is a unit used to express the
  relative masses of atoms. One atomic mass unit
  is equal to 1/12 the mass of a carbon-12 atom
  (the standard).
• A carbon-12 atom has a relative mass of 12 u
• An atom with a mass equal to 1/12 the mass of a
  carbon-12 atom would have a relative mass of 1u.
• An atom with a mass equal to twice the mass of a
  carbon-12 atom would have a relative mass of 24
  u.
• Note A single proton has a mass of 1u. A
  single neutron has a mass of 1u.

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Atomic weight

• The masses of each atom (in amu) are given in the
  periodic tableremember that the mass represents
  all isotopes their natural abundance, so the
  mass shown is the mass of the average atom.

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Example Boron

• A specific example of the use of the equation is
  shown below for the element boron that consists
  of 19.78 boron-10 with a mass of 10.01 u, and
  80.22 boron-11 with a mass of 11.01u.
• This calculated value is seen to agree with the
  value given in the periodic table.

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Mass of a single atom?

• 1 amu 1.66 x 10-24 g
• So for C-12 ( C)
• 12 amu x 1.66x10-24 g 1.99 x 10-23 g
• It is inconvenient to work with such small
  unitsinstead chemists work with a mole
  (Avogadros number) of atoms

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1amu
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Moles many are scared of this!

• The term Mole (mol) is just a number equal to
  6.02 x 1023, just as a dozen is a number equal to
  12.
• 1 C atom has mass of 12.01u
• 1 mol of C atoms has mass of 12.01g
• 1 P atom has mass of 30.97u
• 1 mol of P atoms has mass of 30.97g

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1 Mole 6.02x1023!!!!

• A one-mole sample of any element will contain the
  same number of atoms as a one-mole sample of any
  other element (6.02x1023).
• One mole of molecules 6.02x1023 molecules
• One mole of ANYTHING 6.02x1023 things
• One mole of pennies 6.02x1023 pennies
• If distributed evenly among the 5.5 billion
  people on earth, everyone gets
• 6.02 x 1023 pennies 1.1 x 1014 pennies
• 5.5 x 109 people or 1.1 x1012 dollars!

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More examples of the mole concept

• 1 mole Na 22.99 g Na 6.02 x 1023 Na atoms
• 1 mole Ca 40.08 g Ca 6.02 x 1023 Ca atoms
• 1 mole S 32.06 g S 6.02 x1023S atoms

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What about the mass of molecules?

• Because molecules are made up of atoms, the
  molecular weight of a molecule is obtained by
  adding together the atomic weights of all the
  atoms in the molecule.
• The formula for a molecule of carbon dioxide is
  CO2. This means one molecule of CO2 contains 1
  atoms of carbon, C, and two atoms of oxygen, O.
  The molecular weight of CO2 is then the sum of
  one atomic weight of C and two atomic weights of
  O.

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Molecular mass

• Again, we are chemists (at least for this
  class!), so we work on the mole scale
• 1 mole of C 12 g
• 1 mole of O 16 g
• 1 mole of CO2 12 2(16) 44 g
• We say the molecular mass or molecular weight of
  CO2 is 44 g/mol

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Back to our problem
What mass of CO2 is released when a gallon of
gasoline is burned?
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• C8H18 O2 ? 8CO2 9H2O
• 1 molecule of C8H18 ? 8 molecules of CO2
• 1 mole of C8H18 ? 8 moles of CO2
• If we know how many moles of C8H18 are in 1
  gallon of gas, we can find out how many moles of
  CO2 are produced (8 x the amount).
• Then, using the molecular mass of CO2 (44 g/mol)
  we can convert moles of CO2 to g of CO2

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Moles of C8H18 in 1 gallon of gas

• In order to find the number of moles of C8H18 in
  1 gallon of gasoline, need to know
• Molecular weight of C8H18
• 8 x (12.01 g/mol) (18 x 1.01 g/mol) 114.3
  g/mol
• Mass of 1 gallon of C8H18

Density of C8H18

• Moles of C8H18 in one gallon of gas

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Mass of CO2 produced?

• First how many moles of CO2 produced?
• What is the mass of 186 moles of CO2?
• In lbs? (Easier for us to conceptualize)

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The Carbon cycle

• We are interested in the carbon cycle, we want
  to know how much of the 18 lbs of CO2 is C.

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Human activity

• Human activity is increasing atmospheric carbon
  by 3 billion metric tons (3 bmt). How much CO2
  are we putting in the atmosphere?

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Effect of Global Warming

• Its difficult to determine exactly what will
  happenthere are many feedback mechanisms (some
  were probably not even aware of).
• For example, an increase in temperature will mean
  that the oceans cant hold as much CO2, so CO2
  will be released into the atmosphere, making the
  problems worse.

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But

• With higher ocean temps, more phytoplankton may
  growthe phytoplankton use CO2 in photosynthesis,
  so atmospheric CO2 levels may decrease again.
• But warming oceans may cause different
  circulation patterns which may inhibit
  phytoplankton growth
• Take home point there are a lot of variables
  and no one really knows.

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NASAs worst case scenario
Global temp increases by 2oC by 2030 if our
current rate of CO2 emission continues

• Small changes in global temp have a large impact
  on climate
• During the last Little Ice Age the global temp
  only dropped by 1oC
• Ocean levels likely will rise somewhat from
  glacier melting
• (one estimate is b/w 9 and 88 cmstill bad
  news for coastal cities)
• Expect many extinctionschanges in climate will
  be fast, so species that reproduce slowly (such
  as trees) will not be able to adapt.
• Increase in vector-borne diseases like malaria
• Mosquitoes love warmer, wetter weather.
• Countries closer to the poles might have a longer
  growing season, but most other countries will
  suffer
• Droughts, high temp

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Has global warming started?

• Difficult to tellweve had lots of volcanic
  eruptions recently
• increases the number of particles in the
  atmosphere
• Particles reflect sunlight
• Particles encourage cloud formation
• Clouds reflect sunlight
• Concentration of CO2 has definitely increased in
  the past 100 years, and the increase is likely
  due to human activities
• Seems to be an increase in average global temp
  over the past 100 years, but this may be too
  short a time to really tell

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NASA Satellitesanother tool

• The EOS Terra satellite, launched in December
  1999, retrieves global readings of land surface
  temperatures, snow cover, atmospheric aerosol
  levels, cloud properties, methane, vegetation
  density, and a host of other variables that
  influence climate on a global scale. The
  measurements are taken over the entire globe once
  a day at high resolution. Taking measurements by
  satellite is much more efficient, consistent, and
  timely than taking measurements on the planets
  surface.
• Better data may help us come up with better
  models!!!

http//earthobservatory.nasa.gov/Library/GlobalWar
ming/warming6.html
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Computer modelsa major tool in global warming
research

• Climatic computer models help simulate whether
  temperatures will increase and what effects this
  might have on climate.
• Input estimates of future greenhouse gas
  production and run the model
• Climate modelers must consider a myriad of
  factors, boil them down into an equation, and
  link the equations together to form a model
• Climatologists cant always agree on how big a
  role certain factors will play
• Leads to different model results

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What to do to prevent/stop global warming?
3 approaches

• Wait and See/Study Further
• The situation is too uncertain right now to
  best use available funds.
• The questions remain
• Is it occurring?
• How will the earth respond?
• The problem
• Once action is taken, it may take awhile to see
  results

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2. Respond immediately

• Start cooling off the earth
• Can release volcanic-like particles into the
  atmosphere to reflect sunlight
• Problem Sulfuric particles will likely
  contribute to acid rain
• Problem How to avoid cooling off the planet too
  much?

• Increase phytoplankton growth by seeding the
  oceans with iron (a limiting nutrient)
• Problem Preliminary research showed that
  phytoplankton grew with increased iron, but so
  did the zooplankton that feed on the
  phytoplankton. Net effect zero.

http//earthobservatory.nasa.gov/Library/CarbonCyc
le/carbon_cycle5.html
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3. Do Nothing/Business as Usual

• Some people believe that climate change is
  inevitable and that well just have to learn to
  live with the consequences.

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We can slow global warming down

• Start limiting our CO2 emissions
• Reduce fossil fuel use
• Encourage other sources of power (wind, fuel
  cells)
• Currently, much of the alternative energy options
  are more expensive and less practical
• As incentive for change may need to tax fuels,
  heavy CO2 producing industries, etc
• Effect on economy?
• Give tax incentives to buyers of fuel efficient
  cars, energy efficient appliances, solar power,
  etc.
• Limit global emissions
• Start buying and selling pollution rights

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Carbon Sequestration

• Can refer to planting trees as environmental
  sinks that absorb CO2
• Also refers to chemically removing CO2 from
  exhaust.
• The recovered gas could be
• dissolved deep in the ocean
• Pumped into empty oil and/or natural gas wells

• Trapped in a mineral form such as calcium
  bicarbonate Ca(HCO3)2 which could then be buried

http//www.netl.doe.gov/coal/Carbon20Sequestratio
n/Core20RD/sequestration.html
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• CO2 is currently recovered from combustion
  exhaust by using amine absorbers and cryogenic
  coolers.
• Using present technology, estimates of
  sequestration costs are in the range of 100 to
  300/ton of carbon emissions avoided. The goal is
  to reduce the cost of carbon sequestration to 10
  or less per net ton of carbon emissions avoided
  by 2015.

Info from http//www.fe.doe.gov/programs/sequest
ration/overview.html
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Interactive Carbon Sequestration Model

• http//www.netl.doe.gov/coal/Carbon20Sequestratio
  n/Core20RD/sequestration.html

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Kyoto Protocol
http//vitalgraphics.grida.no/kyoto/
US expected to reduce emissions 7 below 1990
levels EU
8 Canada Japan
6 The agreement does not take into effect
until 90 days after 55 countries accounting for
55 of total 1990 CO2 emissions have ratified it.
Hasnt happened yet.
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Some Issues with Kyoto Protocol

• Developing countries do not have to meet the same
  CO2 emissions
• Their production of CO2 is on the rise.
• Proper carbon credit for sequestration of
  carbon in forests

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