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Chapter 9 Air: Climate and Pollution Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. “Troposphere, whatever, I told you before I’m not a scientist. That’s why I don’t want to have to deal with global warming, to tell you the truth.” --Supreme Court Justice Antonin Scalia, (while deciding EPA's responsibility to regulate CO2) 9-2 CASE STUDY: When Wedges do More than Silver Bullets 9-3 9.1 What is the Atmosphere? • Earth’s atmosphere consists of gas molecules, mostly nitrogen and oxygen and a variety of other trace gases, about 300 mi above the earth's surface. • Minute particles and liquid droplets—collectively called aerosols—also are suspended in the air. • The atmosphere has four distinct zones of contrasting temperature, due to differences in absorption of solar energy. • The layer closest to the earth’s surface, the troposphere, experiences daily temperatures changes, wind, and precipitation that we collectively call weather. 9-4 4 Distinct Zones of 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). 9-5 Convection Cells Circulate Air, Water Vapor and Heat 9-6 The Atmosphere Captures Energy–Selectively • The sun supplies the Earth with abundant energy, especially near the equator. • Of the solar energy that reaches the outer atmosphere: • ¼ is reflected by clouds and atmospheric gases • ¼ is absorbed by carbon dioxide, water vapor, ozone, methane, and a few other gases. • ½ of incoming solar radiation (insolation) reaches the Earth’s surface. 9-7 The Sun Warms Our World 9-8 The Greenhouse Effect • Following the second law of thermodynamics, absorbed energy is gradually reemitted as lowerquality 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. 9-9 Ocean Currents Also Modify Our Climate 9-10 9.2 Climate Changes Over Time • How stable is climate? That depends upon the time frame you consider. Over centuries and millennia, we know that climate shifts somewhat, but usually we expect little change on the scale of a human lifetime. • The question now is whether that is a reasonable expectation. • If climate does shift, how fast might it change, and what will those changes mean for the environmental systems we depend on? 9-11 Correlation Between Historic CO2 Levels and Historic Temperatures 12 What Causes Natural Climatic Swings? • Modest climate changes correspond to an 11-year cycle in the Sun’s intensity called Milankovitch Cycles. • These cycles are caused by changes in the Earth’s orbit, rotation and the wobble of its axis. 9-13 The El Niño/Southern Oscillation Can Have Far-reaching Effects • The climate also changes according to oscillations in the ocean and atmosphere. • El Niño/ Southern Oscillation (ENSO) is the most famous. • ENSO affects weather throughout the Pacific, causing heavy monsoons or serious droughts. 9-14 How Do We Know the Climate is Changing Faster than Usual? • Many scientists consider anthropogenic (humancaused) global climate change to be the most important environmental issue of our times. • The first evidence that human activities are increasing atmospheric CO2 came from an observatory on Mauna Loa volcano in Hawaii. • Measurements show CO2 levels increasing about 0.5% per year since 1958. 15 CO2 and Temperature Readings From Mauna Loa Volcano in Hawaii 9-16 Scientific Consensus is Clear • Because the climate is so complex, climate scientists worldwide collaborated in collecting and sharing data, and in programming models to describe how the climate system works. • Evidence shows minor differences among models, but no disagreement about the direction of change. • The evidence shows unequivocally, that climate is changing, and the global average temperature is a warming. 9-17 What is the IPCC? • The most comprehensive effort to describe the state of climate knowledge is that of the Intergovernmental Panel on Climate Change (IPCC). • The IPCC brings together scientists and government representatives from 130 countries with the aim to review scientific evidence on the causes and likely effects of climate change. • In 2007, the IPCC issued its 4th Assessment Report. The conclusion is a 90% certainty that observed climate change is caused by human activity. • Subsequent reports raised that to a 99% certainty. 9-18 Changes in Heat Waves, Sea Level, and Storms are Expected • Observations since 2007 show that all the IPCC scenarios were too conservative – Greenhouse gas emissions, temperature rises, sea level, and energy use have accelerated faster than IPCC projections. • Droughts, floods, crop failure, and waves of refugees may result. 9-19 Evidence of Climate Change is Overwhelming • Over the last century, the average global temperature has climbed about 0.6 degree C (1 degree 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 CO2 being absorbed are acidifying the oceans, and could have adverse effects on sea life. 9-20 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. Others are dying out because their environment is changing. • Coral reefs worldwide are “bleaching,” losing key algae and resident organisms. 9-21 Policy Makers Have Made Little Progress in Finding Solutions • Climate control is a classic free-rider problem, in which nobody wants to take action for fear that someone else might benefit from their sacrifices. • Climate scientists point out that shifting our energy strategy from coal to wind, solar, and greater efficiency, could produce millions of new jobs and save billions in health care costs associated with coal burning. 9-22 The Main Greenhouse Gases are CO2, CH4, and N2O • Carbon dioxide is by far the most important of these because of its abundance, and because it lasts for decades or centuries in the atmosphere. • If current trends continue, CO2 concentrations could reach about 500 ppm (approaching 2X the preindustrial level of 280 ppm) by the end of the 21st century. 9-23 Contributions to Global Warming From Different Gases 9-24 Controlling Emissions is Cheap Compared to Climate Change • A 2010 study by the Pew Trust estimates the cost of lost ecological services by 2100. Costs included factors such as lost agricultural productivity from drought, damage to infrastructure from flooding and storms, lost biological productivity, health costs from heat stress, and lost water supplies. • The Pew report found that climate change is likely to cost between $5 trillion and $90 trillion by 2100. • The Stern report estimates a cost of only about 1% of global GDP to avoid the worst impacts of climate change. 9-25 Responses to Disputes Over Climate Change • Climate scientists offer the following responses to some of the claims in the popular media: – Reducing climate change requires abandoning our current way of life (no, but it does require that we use different energy sources). – There is no alternative to current energy systems (Europe and China are showing this to be false). – A comfortable lifestyle requires high CO2 output (data show this is false). – Natural changes such as solar variation can explain observed warming (changes are slight and do not coincide with the climate changes observed). 9-26 Responses to Disputes Over Climate Change – The climate has changed before, so this is nothing new (Today’s CO2 level exceeds anything the Earth has seen). – Temperature changes are leveling off (True on short time frames sometimes, but over decades the trends in surface air temperatures and in sea level continue to rise). – We had cool temperatures and snowstorms last year, not heat and drought (Regional differences in temperature and precipitation trends are predicted by climate models). – Climate scientists don’t know everything, and they have made errors and misstatements (fraud in data collection is almost unheard of in science). 9-27 9.4 Envisioning Solutions • Former president Bill Clinton has argued that combating climate change doesn’t have to mean economic hardship. • It could be the biggest development stimulus since World War II, creating millions of jobs and saving trillions of dollars in foreign fuel imports. • What are some of the strategies we have available? 9-28 There Are Many Ways We Can Control Greenhouse Emissions • We can reduce dependence on coal, which produces more CO2 per energy unit than any other fuel. • We could institute fees for selling fossil fuels–these would help fossil fuel prices represent their many hidden costs. • We can invest in new technologies and energy efficiency. • We can institute emissions trading, by instituting a legal cap on emissions, then allowing companies to buy and sell shares of that total cap. 9-29 International Protocols Have Tried to Establish Common Rules • In 1992 The United Nations Earth Summit meeting in Rio de Janeiro set an objective of stabilizing greenhouse gas emissions. • In Kyoto, Japan, in 1997, 160 nations agreed to roll back CO2, methane, and nitrous oxide emissions about 5 percent below 1990 levels by 2012, but China and India were exempted from the agreement and the U.S. never ratified this agreement. • The 2009 Copenhagen climate conference had little more immediate success than did Kyoto. 9-30 A Wedge Approach Could Fix the Problem • Accomplishing just half of these wedges could level off our emissions. • Accomplishing all of them could return to levels well below those envisioned in the Kyoto protocol. 31 Local Initiatives Are Everywhere • Britain has already started to substitute natural gas for coal, promote energy efficiency in homes and industry, and raise its already high gasoline tax. • New Zealand Prime Minister Helen Clark pledged that her country will be the first to be “carbon neutral”. • Germany has reduced its CO2 emissions at least 10 percent by switching from coal to gas and by encouraging energy efficiency throughout society. • Denmark now gets 20% of its electricity from windmills. 32 Can We Control Carbon Better? • It is possible, though expensive, to store CO2 by injecting it deep into geologic formations. • Around the world, deep, briny aquifers could store a century’s worth of CO2 output at current fossil fuel consumption rates. 9-33 9.5 Air Pollution 9-34 We Describe Pollutants According to Sources • In the U.S., principal pollutants are identified and regulated by the Clean Air Act of 1970. • A point source is a smokestack or some other concentrated pollution origin. • Primary pollutants are released in a harmful form. • Secondary pollutants become hazardous after reactions in the air. • Fugitive or nonpoint-source emissions are those that do not go through a smokestack. 9-35 What are Criteria Air Pollutants? • Conventional or criteria pollutants are a group of seven major pollutants (sulfur dioxide, carbon monoxide, particulates, volatile organic compounds, nitrogen oxides, ozone, and lead) that contribute the largest volume of air-quality degradation and are considered the most serious threat of all air pollutants to human health and welfare. • Transportation and power plants are the dominant sources of most criteria pollutants. 9-36 Anthropogenic Sources of Criteria Air Pollutants 9-37 Unconventional Pollutants • The EPA also monitors unconventional pollutants, compounds that are produced in less volume than conventional pollutants, but that are especially toxic or hazardous. • Among these are asbestos, benzene, beryllium, mercury, polychlorinated biphenyls (PCBs), and vinyl chloride. • In 2009, the EPA announced that it would add CO2 and other greenhouse gases to its list of regulated pollutants. This decision remains controversial. 9-38 Indoor Air Can Be More Dangerous Than Outdoor Air 9-39 Dust Blowing From the Sahara • Dust from North Africa regularly crosses the Atlantic and contaminates the air in Florida and the Caribbean Islands. • This dust can carry pathogens and is thought to be the source of diseases attacking Caribbean corals. 9-40 Ozone in the Stratosphere is Harmed by CFCs • Antarctica’s exceptionally cold winter temperatures help break down ozone. • During the Antarctic spring, conditions are ideal for rapid ozone destruction. 9-41 CFC Control has Shown Remarkable Success • In 1987 an international meeting in Montreal, Canada, produced the Montreal Protocol, the first of several major international agreements on phasing out most uses of CFCs by 2000. • As evidence accumulated, showing that losses were larger and more widespread than previously thought, the deadline for the elimination of all CFCs was moved up to 1996. • CFCs are now being removed from the atmosphere more rapidly than they are being added. 9-42 Success of the Montreal Protocol 9-43 Urban Cities Create Heat Islands • Heat islands occur in cities. • Concrete and brick surfaces in cities absorb large amounts of solar energy. A lack of vegetation or water results in very slight evaporation; instead, available solar energy is turned into heat. • As a result, temperatures in cities are frequently 3–5 degrees Celsius warmer than in the surrounding countryside, a condition known as an urban heat island. 9-44 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. 9-45 Acid Precipitation Kills Vegetation 9-46 Acid Precipitation Over the United States 9-47 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 that visibility is only 20 km (12.5 mi) across the canyon. 9-48 Buildings and Monuments Show Clear Damage • Air pollution is destroying some of the oldest and most glorious buildings and works of art. • Smoke and soot coat buildings, paintings, and textiles. • Acids dissolve limestone and marble, destroying features and structures of historic buildings. 9-49 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. 9-50 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. 9-51 Cap and Trade Agreements are One Way to Control Air Pollution • A cap-and-trade approach sets maximum emission levels for pollutants. • Facilities can then buy and sell emission “credits,” or permitted allotments of pollutants. • Companies can decide if it’s cheaper to install pollution control equipment or to simply buy someone else’s credits. • Cap-and-trade has worked well for sulfur dioxide. 9-52 9.9 Current Conditions and Future Prospects • 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. 9-53