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: CO 2 Emissions from Fossil Fuel Burning 35% higher than before industrial revolution Oceans = CO 2 sink Forests = CO 2 sink and source 24 billion metric tons CO 2 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 to ozone 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 change by 2100 is between 1.5 and 4.5 C o

Fourth Assessment CO 2 Concentrations

Sources of CO 2 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 CO 2 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 CO 2 is not a major factor True False True False

Reducing CO 2 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

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 CO 2 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 + O 2 O + O Reaction #2: Free O + O 2 O3O3 Reaction #3: Free O + O 3 O 2 + O 2 Reaction #4: UV light + O 3 O + O 2

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: CFCl 3 + UV Cl + CFCl 2 Reaction #6: Cl + O 3 ClO + O 2 Reaction #7: ClO + ClO 2Cl + O 2 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 bromine in 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”