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Chapter 9LectureOutline

Learning OutcomesAfter studying this chapter, you should be able to answer the following questions:

• What or where is the stratosphere, and why do we care?• Explain the greenhouse effect and how it is changing our

climate.• What is the ENSO cycle, and how does it affect weather

patterns?• Is it too late to do anything about global climate change?• Why has the United States refused to ratify the Kyoto Protocol?• Why has stratospheric ozone been disappearing? Should we

worry about it?• What are the main sources and effects of air pollution?• Has world air quality been getting better or worse?• What is the “new source review”? 9-2

Climate is an angry beast, and we are poking it with sticks.

–Wallace Broecker

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9.1 The Atmosphere Is a Complex System• Clean, dry air is

– 78 percent nitrogen – Almost 21 percent oxygen,– The remaining 1 percent composed of argon, carbon

dioxide (CO2), and a variety of trace gases. – Water vapor concentrations vary from near 0 to 4

percent, depending on air temperature and available moisture.

• Minute particles and liquid droplets—collectively called aerosols —also are suspended in the air.

• Atmospheric aerosols play important roles in the earth’s energy budget and in rain production.

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The Atmosphere

• Within the troposphere, air circulates in great vertical and horizontal convection currents.

• The stratosphere has almost no water vapor and nearly 1,000 times more ozone (O3).

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The sun warms our world

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The greenhouse effect

• Following the second law of thermodynamics, absorbed energy is gradually reemitted as lower-quality heat energy.

• A brick building, for example, absorbs energy in the form of light and reemits that energy in the form of heat.

• This phenomenon is called the greenhouse effect because the atmosphere, loosely comparable to the glass of a greenhouse, transmits sunlight while trapping heat inside.

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Water stores heat, and winds redistribute it

• Much of the incoming solar energy is used to evaporate water.

• Every gram of evaporating water absorbs 580 calories of energy as it transforms from liquid to gas.

• Globally, water vapor contains a huge amount of stored energy, known as latent heat.

• When water vapor condenses, returning from a gas to a liquid form, the 580 calories of heat energy are released.

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Ocean currents also modify our climate

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9.2 Climate Can Be an Angry Beast

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What causes catastrophic climatic swings?• Milankovitch cycles

– Named after Serbian scientist Milutin Milankovitch, who first described them in the 1920s.

– are periodic shifts in the earth’s orbit and tilt

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The El Niño/Southern Oscillationcan have far-reaching effects

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9.3 Global Warming Is Happening

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Greenhouse gases have many sources

• The lowest emissions in the world are in Chad, where per capita production is only one-thousandth that of the United States.

• Some countries with high standards of living release relatively little CO2. Sweden, for example, produces only 6.5 tons per person per year.

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Evidence of climate change is overwhelming

• Over the last century the average global temperature has climbed about 0.6°C (1°F).

• Permafrost is melting; houses, roads, pipelines, sewage systems, and transmission lines are being damaged as the ground sinks beneath them.

• Arctic sea ice is only half as thick now as it was 30 years ago.• Alpine glaciers everywhere are retreating rapidly .

– Mount Kilimanjaro has lost 85 percent of its famous ice cap since 1915.

• The higher levels of CO 2 being absorbed are acidifying the oceans, and could have adverse effects on sea life.

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Evidence continued…

• Sea level has risen worldwide approximately 15–20 cm (6–8 in.) in the past century.

• Satellite images and surface measurements show that growing seasons are now as much as three weeks longer in a band across northern Eurasia and North America than they were 30 years ago.

• Droughts are becoming more frequent and widespread.• Biologists report that many animals are breeding earlier or

extending their range into new territory as the climate changes.• Coral reefs worldwide are “bleaching,” losing key algae and

resident organisms,

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The Stern review recommends four key elements for combating climate change.

• Emissions trading to promote• cost-effective emissions reductions.• Technology sharing that would double research

investment in clean energy technology and accelerate spread of that technology to developing countries.

• Reduce deforestation, which is a quick and highly cost-effective way to reduce emissions.

• Help poorer countries by honoring pledges for development assistance to adapt to climate change.

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9.4 The Kyoto Protocol Attempts toSlow Climate Change

• the Kyoto Protocol , this treaty sets different limits for individual nations, depending on their output before 1990.

• At a Kyoto follow-up meeting held in Bali in 2007, the United States finally acquiesced to global pressure and signed an action plan that commits all developed countries to adopt mitigation plans.

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There are many ways we cancontrol greenhouse emissions

• Double the fuel economy for 2 billion cars from 30 to 60 mpg.• Cut average annual travel per car from 10,000 to 5,000 miles.• Improve efficiency in heating, cooling, lighting, and appliances

by 25 percent.• Update all building insulation, windows, and weather

stripping to modern standards.• Boost efficiency of all coal-fired power plants from 32 percent

today to 60 percent (through co-generation of steam and electricity).

• Replace 800 large coal-fired power plants with an equal amount of gas-fired power (four times current capacity).

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9.5 Air Pollution

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Indoor air can be more dangerousthan outdoor air

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9.6 Interactions Between ClimateProcesses and Air Pollution

• Air pollutants can travel far• Dust and fine aerosols can be carried great

distances by the wind.• Pollution from the industrial belt between the

Great Lakes and the Ohio River Valley regularly contaminates the Canadian Maritime Provinces and sometimes can be traced as far as Ireland.

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Stratospheric ozone is declining

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9.7 Effects of Air Pollution

• Polluted air is unhealthy– Consequences of breathing dirty air include increased

probability of heart attacks, respiratory diseases, and lung cancer.

• Plants are sensitive to pollutants– In the early days of industrialization, fumes from furnaces,

smelters, refineries, and chemical plants often destroyed vegetation and created desolate, barren landscapes around mining and manufacturing centers.

• Synergistic effects in which the injury caused by exposure to two factors together is more than the sum of exposure to each factor individually.

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Effects continued…• Smog and haze reduce visibility

– Grand Canyon National Park, where maximum visibility used to be 300 km (185 mi), is now so smoggy on some days visibility is only 20 km (12.5 mi) across the canyon.

• Acid deposition has many effects– Acid precipitation, the deposition of wet, acidic solutions or

dry, acidic particles from the air, became widely recognized as a pollution problem only in the last 20 years.

– The most notable aquatic effects of acid deposition are the reduction of trout, salmon, and other game fish, whose eggs and fry die below pH 5.

– Forest damage: On Mount Mitchell in North Carolina, nearly all the trees above 2,000 m (6,000 ft) are losing needles, and about half are dead.

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Forest damage by acid rain

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9.8 Air Pollution Control

• Particulate removal involves filtering air emissions. Filters trap particulates in a mesh or electrostatic precipitators are used.

• Sulfur removal is important because sulfur oxides are among the most damaging of all air pollutants in terms of human health.

• Nitrogen oxides (NOx) can be reduced in both internal combustion engines and industrial boilers.

• Hydrocarbon controls mainly involve complete combustion or the control of evaporation.

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Types of Air Pollution Control

• Electrostatic precipitators are the most common particulate controls in power plants.

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Clean air legislation is controversial

• The Clean Air Act of 1963 was the first national legislation in the United States aimed at air pollution control.

• In 1970, an extensive set of amendments essentially rewrote the Clean Air Act.

• A 2002 report concluded that simply by enforcing existing clean air legislation, the United States could save at least another 6,000 lives per year and prevent 140,000 asthma attacks.

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9.9 Current Conditions and FutureProspects

• Although the United States has not yet achieved the Clean Air Act goals in many parts of the country, air quality has improved dramatically.

• The outlook is not so encouraging in other parts of the world.

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There are signs of hope

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Practice Quiz

1. What are the “stabilization wedges” suggested by Pacala andSocolow at Princeton University (see table 9.2)? How manywedges do we need to accomplish to flatten our CO2 emissions?2. What is the greenhouse effect, and how does it work?3. Why are we worried about greenhouse gases?4. What is the thermohaline ocean conveyor and what is

happening to it?5. Describe the El Niño/Southern Oscillation.

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Practice Quiz continued…

6. What gas, action, and country make the largest contribution to

global warming?7. What has been the greatest air pollution control success in theUnited States since 1970?8. Define primary air pollutant, secondary air pollutant,

photochemical oxidant, point source, and fugitive emissions.9. What is destroying stratospheric ozone, and where does thishappen?10. What is the “new source review”?

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