Environmental Science: Toward a Sustainable Future Richard T. Wright Chapter 20 The Atmosphere: Climate, Climate Change, and Ozone Depletion PPT by Clark E. Adams

El Niño: What Happened? Jet streams shifted from normal course April May Jet streams shifted from normal course Cause unknown 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: Fig. 20-1 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 reestablished with greater intensity Upwelling of colder water from ocean depths Jet streams are weakened Global patterns in moisture and evaporation return to “normal”

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

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 Ocean and atmosphere Climates in the past

Climate 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 Temperature Low High A B C D E Precipitation

Climates in the Past

Past Climates

Ocean and Atmosphere Covers 75% of the Earth’s surface Major source of water to hydrologic cycle Major source of heat to atmosphere Stores and conveys heat

The Ocean 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 freshwater – 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 Hydrologic cycle Animal husbandry Chemical fertilizers* Refrigerants* * = Long residence times and contribute to ozone depletion

Atmospheric CO2 Concentrations

Global Surface Temperatures

Global Carbon Cycle

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

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 change by 2100 is between 1.5 and 4.5oC

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 2000 U.S. Climate Change Assessment (Table 20-3) Increased warming Differing regional impacts Vulnerable ecosystems Widespread water concerns Agriculture largely unaffected Forest growth to increase Coastlines – rising sea levels

Responses to Climate Change Response 1: mitigation = reduce CO2 emissions Response 2: adaptation = accepting and learning to live with the consequences of climate change

Framework Convention on Climate Change (FCC) Relied on voluntary approach to reduce CO2 emissions Developing countries continue toward developed nation status using fossil fuels

Framework Convention on Climate Change (FCC) To achieve a 7% reduction by 2010 requires a 25% reduction of present use By 2010 CO2 emissions will have increased by 30%

Framework Convention on Climate Change (FCC) Bottom line: need 60% reduction (144 ppm) in CO2 emission worldwide NOW to stabilize greenhouse gas concentrations at today’s levels

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 + O3 O + 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 2 Cl + O2 Which reaction releases Cl from CFCs? Which reaction generates more Cl? Chlorine is a catalyst that destroys the production of ________?

Montreal Protocol 1987 – scale back CFC production by 50% by 2000

Coming to Grips with Ozone Depletion: Montreal Protocol 1990 – amendment to completely phase out ozone-destroying chemicals by 2000 1992 – amendment to completely phase out ozone-destroying chemicals by 1996 Why the rush?

Ozone Hole: 11 million sq.mi.

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