Chapter 20 (20.3, 20.4, and 20.5)The Atmosphere:Climate Change

and Ozone Depletion

Copyright © 2008 Pearson Prentice Hall, Inc.

The Earth as a Greenhouse

Factors Affecting Global Temperatures

• Cloud cover: cooling• Changes in sun’s intensity: cooling or

warming• Volcanic activity: cooling• Sulfate aerosols: cooling

Intergovernmental Panel of Climate Change (IPCC)

• Assess scientific issues• Evaluate the impact of global climate

change and prospects for adapting to it• Investigate ways of mitigating the

effects

IPCC Assessments

• Third Assessment: Human activities are influencing global climate change

• Fourth Assessment: • global climate change is now occurring• caused by rising levels of anthropogenic

greenhouse gases• global impacts will be unprecedented and

severe

Greenhouse Gases: CO2 Emissions from Fossil Fuel

Burning• 35% higher than before industrial

revolution

• Oceans = CO2 sink

• Forests = CO2 sink and source

• 24 billion metric tons CO2 added each year

Other Greenhouse Gases and Sources

• Water vapor• Methane• Nitrous oxide

• CFCs and other halocarbons

• Hydrological cycle• Animal husbandry• Chemical

fertilizers*• Refrigerants*

* = Long residence times contribute toozone depletion

Evidences of Climatic Change

• 17 of the hottest years on record have occurred since 1980 (Fig. 20-5)

• Wide-scale recession of glaciers• Sea level rising

Predicted mean global temperature changeby 2100 is between 1.5 and 4.5 Co

Fourth Assessment CO2 Concentrations

Sources of CO2 Emissions

Global Carbon Cycle

Radiative Forcing

Heat Capture by the Ocean

Global Mean Sea Level

Muir Glacier in the Past

Muir Glacier Today

Impacts of Global Warming

• Melting of polar ice caps• Flooding of coastal areas• Massive migrations of people

inland

Impacts of Global Warming

• Alteration of rainfall patterns• Deserts becoming farmland and

farmland becoming deserts• Significant losses in crop yields

Reducing CO2 Emissions (True or False)

• Reducing use of fossil fuels• Adopt a wait-and-see attitude• Develop alternative energy sources• Plant trees• Examine other possible causes of

global warming since CO2 is not a major factor

True

False

True

True

False

Reducing CO2 Emissions (True or False)

• Make and enforce energy conservation rules

• Rely only on the government• Adopt the precautionary principle• Raise the minimum driving age to 18

years

False

True

True

True

Key Findings of the Fourth Assessment

• Increased warming – climate change• Differing regional impacts• Heat waves more frequent and last

longer• Vulnerable ecosystems - arctic• Widespread water concerns – increase

in extremes (+ and -) of daily precipitation

Key Findings of the Fourth Assessment

• Agriculture largely unaffected• Thermohaline conveyor system

expected to slow down• Rising sea levels• Storm intensities expected to increase

Arctic Climate Impact Assessment

• Arctic climate is now warming rapidly• Arctic warming and its consequences

will have worldwide implications

Arctic Climate Impact Assessment

• Arctic vegetation zones will shift, and animal ranges and distribution will change

• Reduced sea ice likely to increase marine transport and access to resources

• Thawing ice will disrupt transportation, buildings, and other infrastructure

Decline of Arctic Sea Ice

Arctic Albedo Feedback

What About the Antarctic?

• Holds most of the world’s ice• Could be a huge factor in future sea level rise• Greenland and Antarctic ice sheets hold enough

water to raise sea level by 230 feet

• Losing as much as 36 cubic miles of ice/year – enough to raise sea level by 0.4mm/year

Response to Climate Change

• Response 1: mitigation = reduce CO2 emissions

• Response 2: adaptation = accepting and learning to live with the consequences of climate change

Response I: Mitigation

• Framework Convention on Climate Change• Kyoto Protocol• U.N. Climate Control Conference• U.S. Policy• Global Climate Change Initiative• Climate Change Science Program• National Climate Change Technology Initiative

Response 2: Adaptation

• Reduced crop yields• Water scarcity• Increased heat and moisture = > infectious

diseases and lethal heat waves• Increased intensity and severity of storm

events• Impoverished nations will be most affected –

adaptation not an option

Good Ozone!

Bad Ozone!

Electromagnetic Spectrum

Radiation and Importance of the Shield

• Skin cancer (700,000 new cases each year)

• Premature skin aging• Eye damage• Cataracts• Blindness

Formation of the Ozone Shield

Reaction #1: UV light + O2 O + O

Reaction #2: Free O + O2 O3

Reaction #3: Free O + O3 O2 + O2

Reaction #4: UV light + O3O + O2

Chlorofluorocarbons (CFCs)

• Organic molecules in which both chlorine and fluorine atoms replace some of the hydrogen atoms.

• Sources:• refrigerators and air conditioners• production of plastic foam• cleaner for electronic parts• pressurizing agent in aerosol cans

Breakdown of Ozone ShieldReaction #5: CFCl3 + UV Cl + CFCl2

Reaction #6: Cl + O3 ClO + O2

Reaction #7: ClO + ClO 2Cl + O2

Which reaction releases Cl from CFCs?Which reaction generates more Cl?

Chlorine is a catalyst that destroys the production of ________?

5

7

OZONE

Coming to Grips with Ozone Depletion

• Montreal Protocol: scale CFC production back 50% by 2000• Most industrialized countries no

longer produce or use CFCs

Ozone Loss and Extent of Ozone Hole

Ozone Hole: 11 million sq.mi.

Ozone-depleting substances production and presence in the atmosphere: past,

present, and future

CFCs HCFCs

Relative abundances of chlorine and brominein the stratosphere

The Clean Air Act of 1990: Title IV

• Restricts production, use, emissions, and disposal of ozone-depleting chemicals.

• Regulates the servicing of refrigeration and air-conditioning units.

“Protecting Stratospheric Ozone”