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 Assymmetric Stretch
Bending motion 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 Tropospheric Abundance (%)
CO2 1 0.0375
CH4 23 0.0018
N2O 296 0.00031
H2O 0.1 variable
O3 2000 0.000004
CCl3F 21000 0.000000028
CCl2F2 25000 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%)
• Component of Natural Gas
• Decayed vegetable matter in wetlands
Man-made Sources
• 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
1996 Conc;
ppb
2000Conc;
ppb
CO2 55 % 290,000 360,000 370,000
CFC’s 25 % 0 3 7
CH4 15 % 900 1700 1800
N2O, O3 5 % 285 310 315
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 Warminghttp://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 ParkAll but 37 of 150 glaciers in the park
have melted since 1850.
Glacier National Park1957 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 WarmingHighly Plausible
•Global Av Surface Warming•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 Uncertain
•Local Details of Climate Change•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 isthat 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 Ozone Depletion
Possible Consequences:
Altered climate and agricultural productivity
Increased sea level
Increased skin cancer, damage to phytoplankton
Possible Responses:
Use less fossil fuel and less deforestation
Eliminate use of CFC’s
Global Warming vs. Ozone Depletion
Global Warming Ozone Depletion
Region of the Atmosphere:
Mostly troposhere Stratosphere
Major Substances Involved:
CO2, CH4, N2O O3, O2, CFC
Radiation Involved:
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 Problem:
More greenhouse gases increase avg global temp
Less ozone conc increases UV exposure
Source of Problem:
CO2 released from burning fossil fuels & 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.