Download Global Atmospheric Changes

Chapter 3
The Chemistry of Global Warming
Sections 3.4 & 3.8-end
Chapter 3; The Chemistry of
Global Warming
1. Global Warming and the Enhanced
Greenhouse Effect
2. Carbon Dioxide Concentrations &
Average Global Temperature
3. Carbon Dioxide Cycle
4. Molecular Structure (3-D) Shape
5. Why Some Gases are Greenhouse
Gases; while other are not
Chapter 3; The Chemistry of
Global Warming
6. Other Greenhouse Gases and Global
Warming Potential (GWP)
7. Molar Mass and Mass Percent
8. Possible Effects of Global Warming
9. Global Warming vs. Ozone Hole
10. Quantitative Aspects
Gases
Greenhouse Gases
•
•
•
•
•
Carbon dioxide; CO2
Water; H2O
CFC’s
Nitrous Oxide; N2O
Methane; CH4
NOT Greenhouse
Gases
• Nitrogen; N2
• Oxygen; O2
• Argon; Ar
Different Types of Electromagnetic Radiation
Do Different “Things” to Molecule
Vibrations of Molecules
• Bond Stretching
• Molecule Bending
It takes less energy to bend a molecule than stretch a bond.
Vibrations of CO2 Molecule
Symmetric Stretch
Bending motion
Assymmetric Stretch
Bending motion
For a bending or stretching motion to
absorb IR radiation; it must change
the dipole moment of the molecule
-
Symmetric Stretch;
IR Inactive
-
+
-
+
-
Antisymmetric Stretch;
IR Active
- +
-
Electronegativity- Measure of an
atom’s attraction for the electrons it
shares in a covalent bond.
Infrared Spectrum of CO2
Infrared Spectrum of Water (H2O) Vapor
Greenhouse Gas Requirements
• Minimum of 2 atoms needed for stretching
bonds
– Two atoms must be different in order for
vibration to change the dipole moment of
molecule
• Minimum of 3 atoms needed to bend a
molecule
Why Argon, Ar, Can Not Be a
Greenhouse Gas
1. Argon is in atomic form. Thus, there is
no bond to another atom. So it can’t
absorb IR to stretch a bond it doesn’t
have.
2. Argon can’t absorb IR to bend a
molecule since a minimum of 3 atoms is
needed and it has only 1 atom.
Global Warming Potential –
Represents the Relative Contribution a
Molecule Has in Global Warming
1. How Long a Molecule in the
Troposphere/ Is There a Way to Remove
Molecule From Troposphere?
2. Does the Molecule Absorb in the Window
Region?
3. Amount of Molecule in the Troposphere
Global Warming Potential (GWP)
Substance
GWP
CO2
CH4
N2O
H2O
O3
CCl3F
CCl2F2
1
23
296
0.1
2000
21000
25000
Tropospheric
Abundance (%)
0.0375
0.0018
0.00031
variable
0.000004
0.000000028
0.000000026
IR Spectrum of CO2 and H2O Overlapped Leaves
“Window” Region when Neither Absorbs IR Energy
Window
Increasing the GWP of a
Greenhouse Gas
•
When a different greenhouse gas
absorbs in the window region of the IR
spectrum; it will have a higher GWP
•
•
•
*Biggest Effect
The higher the tropospheric abundance;
higher GWP
The higher the lifetime of the molecule;
higher GWP
Methane; CH4
Natural Sources (~40%)
Man-made Sources
• Component of Natural
Gas
• Decayed vegetable
matter in wetlands
•
•
•
•
•
Oil wells
Landfills
Rice paddies
Cattle and sheep
Frozen methane
hydrate cages
Frozen Methane Hydrate Cages
Methane Absorbs at the Edge of
Window Region of IR Spectrum
Methane Absorbs at the Edge of
Window Region of IR Spectrum
Nitrous Oxide, N2O; “Laughing Gas”
Manmade Sources
• Dental/medical Use
• Fertilizers
• Burning
Biomass/catalytic
converters
• Production of nylon
and nitric acid
• Absorbs in the
Window Region of IR
Spectrum
Nitrous Oxide, N2O, Absorbs in the
Window Region of the IR Spectrum
Nitrous Oxide Absorbs in the
Window Region of IR Spectrum
Gas
Human
Cont. to
Global
Warming
1896
Conc;
ppb
CO2
55 %
290,000 360,000 370,000
CFC’s
25 %
0
3
7
CH4
15 %
900
1700
1800
285
310
315
N2O, O3 5 %
1996
Conc;
ppb
2000Con
c;
ppb
Human Contribution of Different
Greenhouse Gases to Global Warming
Feedback
• Positive; Amplifies/reinforces ongoing
trend
• Negative; Diminish/reverse trend to
maintain status quo
Possible Impacts of Global
Warming
•
•
•
•
•
•
•
Sea Levels
Forests
Biodiversity
Food Production
Water
Weather
Health
Climate Change and Sea Level
Early Warning Signs of Global Warming
http://www.climatehotmap.org/
FINGERPRINTS: Direct manifestations of a widespread
and long-term trend toward warmer global temperatures
http://www.climatehotmap.org/
• Heat waves and periods of unusually
warm weather
• Ocean warming, sea-level rise and
coastal flooding
• Glaciers melting
• Arctic and Antarctic warming
Glacier National Park
All but 37 of 150 glaciers in the park
have melted since 1850.
Glacier National Park
1957
1998
Global Climate Change
Melting
permafrost
HARBINGERS: Events that foreshadow the types
of impacts likely to become more frequent and
widespread with continued warming.
• Spreading disease
• Earlier spring arrival
• Plant and animal range shifts and
population changes
• Coral reef bleaching
• Downpours, heavy snowfalls, and
flooding
• Droughts and fires
Coral Bleaching
Possible Consequences of Global Warming
Highly
•Global Av Surface Warming
Plausible •Global Avg. Precipitation Increase
•Reduction in Sea Ice
•Surface Winter Warming at High Altitudes
Plausible •Global Sea Level Rise
•More Summer Mid-altitude Drying
•High Latitude Precipitation Increase
Highly
•Local Details of Climate Change
Uncertain •Regional Distribution of Precipitation
•Regional Vegetation Changes
•Increase in Tropical Storm
Intensity/Frequency
Ways an Individual Can Help
Reduce Global Warming
• Reduce use of fossil fuels; car pool, use
mass transit, walk, bike
• Use energy efficient appliances and light
bulbs
• Plant trees (Cool house with shade trees)
• Use solar energy to heat household as
much as possible
Fig.03.p158
A major point of
disagreement of the
Kyoto Protocol is
that developing
countries do not have
to cut emissions as
much as developed
countries.
Greenhouse gas
emissions are
expected to increase
faster in developing
rather than
developed countries
Global Warming vs. Ozone Depletion
Global Warming
Possible
Altered climate and
Consequences: agricultural
productivity
Increased sea level
Possible
Use less fossil fuel
Responses:
and less
deforestation
Ozone
Depletion
Increased skin
cancer, damage
to
phytoplankton
Eliminate use of
CFC’s
Global Warming vs. Ozone Depletion
Region of
the
Atmosphere:
Major
Substances
Involved:
Radiation
Involved:
Global Warming
Ozone Depletion
Mostly troposhere
Stratosphere
CO2, CH4, N2O
O3, O2, CFC
Infrared radiation
vibrates molecule &
remit energy to
Earth
UV Radiation
breaks apart O2 and
O3 & is filtered in
process
Global Warming vs. Ozone Depletion
Global Warming
Ozone Depletion
Nature of More greenhouse
Problem: gases increase avg
global temp
Less ozone conc
increases UV
exposure
Source
CO2 released from
of
burning fossil fuels &
Problem: deforestation
CH4 from agriculture
CFC’s (from
refrigerants, solvents,
foaming agents)form
Cl free radical that
destroys ozone
Determining the Amount of CO2 Produced
by Burning Gasoline or Coal
1. Look at balanced chemical equation to
determine the ratio of CO2 produced for
burning each fuel.
Determining the Amount of CO2
Produced by Burning Gasoline or Coal
2. Determine the molar mass of fuel and
CO2 to set up appropriate ratio.
Molar Mass (Carbon dioxide, CO2) = molar mass C + 2 (molar mass O)
Molar Mass coal 2 = molar mass C
Ratio = (molar mass CO2/ molar mass C)
Determining the Amount of CO2
Produced by Burning Gasoline or Coal
3. Convert amount of fuel to grams and use
ratio to calculate mass of CO2 produced.