Chapter 20 The Atmosphere: Climate, Climate Change, and Ozone Depletion Copyright © 2008 Pearson Prentice Hall, Inc. Environmental Science Tenth Edition.

Chapter 20The Atmosphere:

Climate, Climate Change,and Ozone Depletion

Copyright © 2008 Pearson Prentice Hall, Inc.

EnvironmentalScienceTenth Edition

Richard T. Wright

Hurricane Katrina in Gulf of Mexico (August 28, 2005)

The Atmosphere: Climate, Climate Change, and Ozone Depletion

• Atmosphere and weather

• Climate

• Global climate change

• Response to climate change

• Depletion of the ozone layer

Atmosphere and Weather

• Atmospheric structure

• Weather

Atmospheric Structure

Some Terms

• Weather: day-to-day variations in temperature, air pressure, wind, humidity, and precipitation – all mediated by the atmosphere

• Climate: result of long-term weather patterns in a region

• Meteorology: scientific study of weather and climate

Weather: Solar Energy Balance

Most solar energy absorbed by atmosphere, oceans, and land

Weather: Convection Cell

Tornadoes

• Cold low pressure air mass collides with a warm high pressure air mass

http://www.photolib.noaa.gov/nssl/nssl0065.htm

Fujita Scale Measures the Intensity of Tornadoes

• F-0: 40-72 mph, chimney damage, tree branches broken

• F-1: 73-112 mph, mobile homes pushed off foundations or overturned

• F-2: 113-157 mph, considerable damage, mobile homes demolished, trees uprooted

Fujita Scale Measures the Intensity of Tornadoes

• F-3: 158-205 mph, roofs and walls torn down, trains overturned, cars thrown

• F-4: 207-260 mph, well-constructed walls leveled

• F-5: 261-318 mph, homes lifted off foundation and carried considerable distances, autos thrown as far as 100 meters

Climate

• Climates in the past

• Ocean and atmosphere

Climate

• Also defined as the average trend in temperature and rainfall that produces a unique assemblage of plants and animals

• On the next slide identify climates A to E, e.g., low average rainfall and high average temperature = hot desert

Identify Climates A to E

Precipitation

Tem

per

atu

re

Low High

High

A

B

C

D

E

Climates in the Past

Past Climates

El Niño: What Happened?

• Jet streams shifted from normal course.

• Cause unknown.

April May

June

El Niño: What Happened?

• Development of warm water in the eastern Pacific over time.

• Reversal in trade winds that normally blow from an easterly direction.

El Niño: What Happened?

• Warm water spread to the east.

• Global patterns in moisture and evaporation changed = climate shifts.

The El Niño Effects

• Landslides on the California coast• Mildest hurricane season in many years• Rain five times normal in an East Africa

drought region• Record crop harvests in India, Australia

and Argentina

La Niña: What Happened?

• Easterly trade winds re-established with greater intensity

• Upwelling of colder water from ocean depths.

• Jet streams are weakened• Global patterns in moisture and

evaporation return to “normal”

Ocean and Atmosphere

• Covers 75% of the Earth’s surface

• Major source of water to hydrological cycle

• Major source of heat to atmosphere

• Stores and conveys heat

The Oceanic Conveyor System

The Ocean Conveyor System

• Thermohaline circulation: effects that temperature and salinity have on density of water– Conveyor system moves water masses from

the surface to deep oceans and back again– Cool northern waters more dense and sink to

depths of 4,000 m = North Atlantic Deep Water (NADW)

The Ocean Conveyor System

– Deep water spreads southward to south Africa and joined by cold Antarctic waters

– Spread northward into Indian and Pacific oceans as deep currents

– Current slows down, warms up, becomes less dense, rises to the surface and moves back to North Atlantic

– Produces a warm climate in Europe

The Ocean Conveyor System

• Factors that could alter the conveyor system.– Appearance of unusually large quantities of

fresh water – melting icebergs– Global warming

Global Climate Change

• The Earth as a greenhouse

• The greenhouse gases

• Evidence of climate change

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

Greenhouse Gases: CO2 Emissions from Fossil Fuel Burning

• 35% higher than before industrial revolution

• Oceans = CO2 sink

• Forests = CO2 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

Intergovernmental Panel of Climate Change (IPCC): Fourth Assessment

• 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

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

Reducing CO2 Emissions (True or False)

• Make and enforce energy conservation rules

• Rely on the government

• Adopt the precautionary principle

• Raise the minimum driving age to 18 years

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

Depletion of Ozone Layer

• Radiation and importance of the shield

• Formation and breakdown of the shield

• Coming to grips with ozone depletion

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 Shield

Reaction #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 ________?

Coming to Grips with Ozone Depletion

• Montreal Protocol: scale CFC production back 50% by 2000

• Most industrialized countries no long 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”

End of Chapter 20

PPT by Clark E. Adams