(11) Air

Ozone Depletion



How Have We Depleted Ozone in the Stratosphere and What Can We Do about It?

Concept 15-6A Widespread use of certain chemicals has reduced ozone levels in the stratosphere, which allows more harmful ultraviolet radiation to reach the earth’s surface.

Concept 15-6B To reverse ozone depletion, we must stop producing ozone-depleting chemicals, and adhere to the international treaties that ban such chemicals

Human Activities Threaten the Ozone Layer

A layer of ozone in the lower stratosphere keeps about 95% of the sun’s harmful UV radiation from reaching the earth’s surface. Measurements made using balloons, aircraft, and satellites show considerable seasonal depletion (thinning) of ozone concentrations in the stratosphere above Antarctica and the Arctic. Similar measurements reveal a lower overall thinning everywhere except over the tropics.

Based on these measurements and mathematical and chemical models, the overwhelming consensus of researchers in this field is that ozone depletion in the stratosphere poses a serious threat to humans, other animals, and some primary producers (mostly plants) that use sunlight to support the earth’s food webs (Concept 15-6A).

This situation began when Thomas Midgley, Jr., a General Motors chemist, discovered the first chlorofluorocarbon (CFC) in 1930. Chemists soon developed similar compounds to create a family of highly useful CFCs, known by their trade name as Freons.

These chemically unreactive, odorless, nonflammable, nontoxic, and noncorrosive compounds seemed to be dream chemicals. Inexpensive to manufacture, they became popular as coolants in air conditioners and refrigerators, propellants in aerosol spray cans, cleaners for electronic parts such as computer chips, fumigants for granaries and ship cargo holds, and bubbles in plastic foam used for insulation and packaging.

It turned out that CFCs were too good to be true. Starting in 1974 with the work of chemists Sherwood Rowland and Mario Molina (Individuals Matter, below), scientists demonstrated that CFCs are persistent chemicals that destroy protective ozone in the stratosphere. Measurements and models indicate that 75–85% of the observed ozone losses in the stratosphere since 1976 were caused by CFCs and other ozone-depleting chemicals (ODCs) released into the atmosphere by human activities beginning in the 1950s.

Ozone Levels over the Earth’s Poles Drop for a Few Months Each Year

In 1984, researchers analyzing satellite data discovered that 40–50% of the ozone in the upper stratosphere over Antarctica disappeared each year during October and November. This observed loss of ozone has been called an ozone hole. A more accurate term is ozone thinning because the ozone depletion varies with altitude and location.

When the southern hemisphere’s winter ends and partial sunlight returns to Antarctica in October, huge masses of ozone-depleted air above Antarctica flow northward and linger for a few weeks over parts of Australia, New Zealand, South America, and South Africa. This raises biologically damaging UV-B levels in these areas by 3–10% and in some years by as much as 20%. In 2006, there was a record seasonal loss of ozone over an area of Antarctica about the size of North America.

In 1988, scientists discovered that similar but usually less severe ozone thinning occurs over the Arctic from February to June, resulting in a typical ozone loss of 11–38% (compared to a typical 40–50% loss above Antarctica). When the mass of air above the Arctic breaks up each spring, large masses of ozone-depleted air flow south to linger over parts of Europe, North America, and Asia.

Models indicated that the Arctic is unlikely to develop the large-scale ozone thinning found over the Antarctic. They also project that ozone depletion over the Antarctic and Arctic will be at its worst between 2010 and 2019.

Why Should We Worry about Ozone Depletion?

Why should we care about ozone loss? One effect is that more biologically damaging UV-A and UV-B radiation will reach the earth’s surface (Concept 15-6A). This will give people worse sunburns, more eye cataracts, and more skin cancers.

The most dangerous type of skin cancer is malignant melanoma. It kills about one-fourth of its victims (younger than age 40) within 5 years, despite surgery, chemotherapy, and radiation treatments. Each year it kills at least 48,000 people (including 7,700 Americans), mostly Caucasians, and the number of cases and deaths is rising in many countries. People who experience three or more blistering sunburns before age 20 are five times more likely to develop malignant melanoma than are those who have never had severe sunburns.

The most serious threat from ozone depletion is that the resulting increase in UV radiation can impair or destroy phytoplankton, especially in Antarctic waters. These tiny marine plants play a key role in removing CO2 from the atmosphere and when they die and sink to the ocean floor, they take their carbon out of circulation for millions of years as a part of the carbon cycle.

Furthermore, ozone depletion and global warming can interact to further decrease the vital populations of phytoplankton in Antarctic waters. Scientists project that global warming can slow down the upwelling of nutrients that support these populations of phytoplankton. In other words, populations of Antarctic phytoplankton could decrease sharply because of a combination of fewer nutrients and increased UV radiation.

We Can Reverse Stratospheric Ozone Depletion

According to researchers in this field, we should immediately stop producing all ODCs (Concept 15-6B). However, even with immediate and sustained action, models indicate it will take about 60 years for the ozone layer to return to 1980 levels and about 100 years for recovery to pre-1950 levels. Good news. Substitutes are available for most uses of CFCs, and others are being developed. In 1987, representatives of 36 nations met in Montreal, Canada, and developed the Montreal Protocol. This treaty’s goal was to cut emissions of CFCs (but not other ODCs) by about 35% between 1989 and 2000. After hearing more bad news about seasonal ozone thinning above Antarctica in 1989, representatives of 93 countries met in London in 1990 and then in Copenhagen, Denmark, in 1992. They adopted the Copenhagen Protocol, an amendment that accelerated phasing out key ODCs. These landmark international agreements, now signed by 189 countries, are important examples of global cooperation in response to a serious global environmental problem. If nations continue to follow these agreements, ozone levels should return to 1980 levels by 2068 (18 years longer than originally projected) and to 1950 levels by 2100 (Concept 15-6B). The longer healing time results from a connection between global warming of the troposphere and repair of the ozone layer.Warming of the troposphere makes the stratosphere cooler, which slows down the rate of its ozone repair.

The ozone protocols set an important precedent by using prevention to solve a serious environmental problem. Nations and companies agreed to work together to solve this global problem for three reasons. First, there was convincing and dramatic scientific evidence of a serious problem. Second, CFCs were produced by a small number of international companies. Third, the certainty that CFC sales would decline over a period of years unleashed the economic and creative resources of the private sector to find even more profitable substitute chemicals. However, the most widely used substitutes cause some ozone depletion and must also be phased out.

Sherwood Rowland and Mario Molina-A Scientific Story of Courage and Persistence

In 1974, calculations by chemists Sherwood Rowland and Mario Molina at the University of California–Irvine indicated that CFCs were lowering the average concentration of ozone in the stratosphere. They shocked both the scientific community and the $28-billion-per-year CFC industry by calling for an immediate ban of CFCs in spray cans, for which substitutes were available.

The research of these two scientists led them to four major conclusions. First, these persistent CFCs remain in the atmosphere. Second, over 11–20 years these compounds rise into the stratosphere through convection, random drift, and the turbulent mixing of air in the lower atmosphere.

Third, once they reach the stratosphere, the CFC molecules break down under the influence of high-energy UV radiation. This releases highly reactive chlorine atoms (Cl), as well as atoms of fluorine (F) and bromine (Br), all of which accelerate the breakdown of ozone (O3) into O2 and O in a cyclic chain of chemical reactions. As a consequence, ozone is destroyed faster than it forms in some parts of the stratosphere.

Fourth, each CFC molecule can last in the stratosphere for 65–385 years, depending on

its type. During that time, each chlorine atom released during the breakdown of CFC can

convert hundreds of O3 molecules to O2. The CFC industry, a powerful, well-funded adversary with a lot of profits and jobs at stake (led by DuPont), attacked Rowland’s and Molina’s calculations and conclusions. The two researchers held their ground, expanded their research, and explained their results to other scientists, elected officials, and the media. After 14 years of delaying tactics, DuPont officials acknowledged in 1988 that CFCs were depleting the ozone layer and they agreed to stop producing them.

In 1995, Rowland and Molina received the Nobel Prize in chemistry for their work. In awarding the prize, the Royal Swedish Academy of Sciences said that they contributed to “our salvation from a global environmental problem that could have catastrophic consequences.”


Effects of Ozone Depletion Human Health

Worse sunburns

More eye cataracts

More skin cancers

Immune system suppression

Food and Forests

Reduced yields for some crops

Reduced seafood supplies from reduced phytoplankton

Decreased forest productivity for UV-sensitive tree species


Increased eye cataracts in some species

Decreased populations of aquatic species sensitive to

UV radiation

Reduced populations of surface phytoplankton

Disrupted aquatic food webs from reduced phytoplankton

Air Pollution and Materials

Increased acid deposition

Increased photochemical smog

Degradation of outdoor paints and plastics

Global Warming

While in troposphere, CFCs act as greenhouse gases


Reducing Exposure to UV Radiation

Stay out of the sun, especially between 10 A.M. and 3 P.M.

Do not use tanning parlors or sunlamps.

When in the sun, wear protective clothing and sunglasses that protect against UV-A and UV-B radiation.

Be aware that overcast skies do not protect you.

Do not expose yourself to the sun if you are taking antibiotics or birth control pills.

When in the sun, use a sunscreen with a protection factor of at least 15.

Examine your skin and scalp at least once a month for moles or warts that change in size, shape, or color and sores that keep oozing, bleeding, and crusting over. If you observe any of these signs, consult a doctor immediately.

Volcanic Eruptions, Climate Change, and Sustainability

We have seen that human activities play a major role in warming the troposphere and depleting ozone in the stratosphere. Occasional large volcanic eruptions also emit CO2 and other pollutants into the lower atmosphere. But about three-fourths of current emissions of CO2 come from human activities, especially the burning of fossil fuels. Thus, energy policy and climate policy are closely connected. The four scientific principles of sustainability can be used to help reduce the problems of air pollution, global warming, and stratospheric ozone depletion. We can reduce reduce inputs of air pollutants, greenhouse gases, and ODCs into the atmosphere by relying more on direct and indirect forms of solar energy than on fossils fuels; reducing the waste of matter and energy resources and recycling and reusing matter resources; mimicking biodiversity by using a diversity of carbon-free renewable energy resources based on local or regional availability; and reducing human population growth and wasteful resource consumption.

We can also find substitutes for ODCs and emphasize pollution prevention. Each of us has an important role to play in protecting the atmosphere that sustains life and supports our economies.

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(9) Air Pollution

 Air Pollution Causes, Effects And Solutions!

Air Pollution


What Can We Do about Global Warming?

CONCEPT 15-5A We can slow the rate of warming and climate change by increasing energy efficiency, relying more on renewable energy resources, greatly reducing greenhouse gas emissions, and slowing population growth.

CONCEPT 15-5B Governments can subsidize energy efficiency and renewable energy use, tax greenhouse gas emissions, and cooperate internationally, and individuals and institutions can sharply reduce their greenhouse gas emissions.

Dealing with Climate Change Is Difficult

What to do about climate change on the only planet we have should be one of the most urgent scientific, political, and ethical issues of this century. But the following characteristics of the problem make it difficult to deal with:

• The problem is global. Dealing with this threat will require unprecedented international cooperation.

• The effects will last a long time. Once climate change is set into motion, its effects will last hundreds to thousands of years.

• The problem is a long-term political issue. Voters and elected officials generally respond well to short-term problems, but have difficulty acknowledging and coping with long-term threats.

• The harmful and beneficial impacts of climate change are not spread evenly. There will be winners and losers from moderate climate change. Winning nations are less likely to bring about controversial changes or spend large sums of money to slow down something that will benefit them.

The catch:

We will not know who will benefit and who will suffer until it is too late to avoid harmful effects, and at some temperature threshhold, essentially everyone will be harmed.

• Many actions that might reduce the threat of climate change, such as phasing out fossil fuels, are controversial because they can disrupt economies and lifestyles.

Despite these problems, most climate experts argue that the world must face up to the urgent problem of global climate change. This will require reaching a political tipping point in which individuals and elected officials shift from ignorance and denial to awareness and urgent action to deal with this serious threat.

What Are Our Options?

There are two basic approaches to global warming. One is to drastically reduce greenhouse gas emissions to slow down the rate of temperature increase and to shift to noncarbon-based energy options in time to prevent runaway positive feedback processes that set into motion major climate changes. The other is to recognize that some warming is unavoidable and to devise strategies to reduce its harmful effects. Most analysts believe

we need a mix of both approaches. In 2005, national academies of sciences from the United States, the United Kingdom, Germany, Italy, France, Russia, Japan, Canada, Brazil, China, and India joined together in an unprecedented statement saying that the scientific evidence on global climate change is clear enough for government leaders to commit to prompt action now. Any delay, they said, “will increase environmental damage and likely incur a greater cost.”

In 2006, then U.N. Secretary General Kofi Annan said: “Let there be no more denial. Let no one say we cannot afford to act. It is increasingly clear that it will cost far less to cut greenhouse gas emissions now than to deal with the consequences later. And let there be no more talk of waiting until we know more. . . . The question is not whether climate change is happening or not, but whether, in the face of this emergency, we ourselves can change fast enough.”

We Can Reduce the Threat of Global Warming

The good news is that we know what to do to slow the rate and degree of global warming caused by our activities. These solutions come down to four major strategies: improve energy efficiency to reduce fossil fuel use; shift from nonrenewable carbon-based fossil fuels to carbon-free renewable energy resources; stop cutting down tropical forests; and capture and store as much CO2 as possible in soil, vegetation, underground, and in the deep ocean (Concept 15-5A). The effectiveness of these strategies would be enhanced by reducing population, which would decrease the number of fossil fuel consumers and CO2 emitters, and by reducing poverty, which would decrease the need of the poor to clear more land for crops and fuelwood. These strategies follow the four scientific principles of sustainability.


Global Warming

Prevention – Cleanup


Cut fossil fuel use (especially coal)

Shift from coal to natural gas

Improve energy efficiency

Shift to renewable energy resources

Transfer energy efficiency and renewable energy technologies to developing countries

Reduce deforestation

Use more sustainable agriculture and forestry

Limit urban sprawl

Reduce poverty

Slow population growth


Remove CO2 from smokestack and vehicle emissions

Store (sequester) CO2 by planting trees

Sequester CO2 deep underground

Sequester CO2 in soil by using no-till cultivation andtaking cropland out of production

Sequester CO2 in the deep ocean

Repair leaky natural gas pipelines and facilities

Use animal feeds that reduce CH4 emissions from cows (belching and flatulence)

Methods for slowing atmospheric warming during this century (Concept 15-5A). Question: Which five of these solutions do you think are the most important? Why

Let us look more closely at some of these possible solutions.

Solutions: methods for removing some of the carbon dioxide from the atmosphere or from smokestacks and storing it in plants, soil, deep underground reservoirs, and the deep ocean. Question: Which two of these solutions do you think are the most important? Why?

Is Capturing and Storing CO2 the Answer?

Have several techniques for removing some of the CO2 from the atmosphere and from smokestacks and storing (sequestering) it in other parts of the environment. One way is to plant trees to store it in biomass while controlling insects and diseases that kill trees. But this is a temporary approach, because trees release their stored CO2 back into the atmosphere when they die and decompose or if they burn.

Planting large numbers of carbon-storing trees in tropical areas and slowing tropical deforestation can help slow global warming by absorbing carbon dioxide and evaporating water into the atmosphere, which increases cloudiness and helps cool the atmosphere above them. But a 2006 study by a team of scientists from Lawrence Livermore Laboratory, Université Montpeller II, and the Carnegie Institution found that planting more trees in temperate regions such as the United States and Europe may enhance global warming.

Their models showed that the less dense canopies of these temperate forests reflect less sun light, absorb more heat, and evaporate much less cloudforming water vapor than tropical forests. Thus, they can warm the ground below and contribute to global warming.

A second approach is to plant large areas with fastgrowing plants such as switchgrass that can remove CO2 from the air and store it in the soil. But warmer temperatures can increase decomposition in soils and return some of this CO2 to the atmosphere.

A third strategy is to reduce the release of carbon dioxide and nitrous oxide from soil. This can be done through no-till cultivation and by setting aside degraded crop fields as conservation reserves.

A fourth approach is to remove some of the CO2 from smokestacks and pump it deep underground into unmineable coal seams and abandoned oil fields or to liquefy it and inject it into thick sediments under the sea floor. Cleaner coal-fired power plants that could remove some of the CO2 from smokestack emissions could be built within 5–10 years. But they are much more expensive to build and operate than conventional coal-burning plants are and thus would raise the price of electricity for consumers.

Without strict government regulation of CO2 emissions and carbon taxes or carbon-trading schemes, utilities and industries have no incentive to build such plants. According to the U.S. Department of Energy, the cur rent costs of carbon capture and storage systems have to be reduced by a factor of ten for these systems to be available and widely used.

Scientists say that no country should build any more traditional coal-burning power plants unless they are designed to be able to capture and store most of the CO2 they emit. China and India worry that making a shift to cleaner technologies will slow their economic growth by raising costs. But Rob Watson, an expert on China’s environmental problems, points out that leaders of China and India need to recognize that going green is an opportunity to save money by reducing pollution and resource waste and to make money by developing low-cost innovative solutions to environmental problems that can be sold in the global marketplace.

Governments Can Help Reduce the Threat of Climate Change

Governments can use four major methods to promote the solutions (Concept 15-5B). One is to regulate carbon dioxide as a pollutant. Second, governments could phase in carbon taxes on each unit of CO2 emitted by fossil fuel use or energy taxes on each unit of fossil fuel that is burned. Decreasing taxes on income, labor, and profits to offset such taxes could help make such a strategy more politically acceptable. In other words, tax pollution, not payrolls. In 2006, voters in the U.S. city of Boulder, Colorado, approved a plan to charge residences and businesses a carbon tax based on how much electricity they use.

The tax revenues will fund energy audits for homes and businesses and visits by energy experts to provide information on ways to save energy. Residents choosing to use electricity produced by wind power will not have to pay the tax.

A related approach is to place a cap on total CO2 emissions in a country or region, to issue permits to release CO2, and then to let polluters trade their permits in the marketplace. This cap-and-trade strategy has a political advantage, but it would be difficult to manage because there are so many CO2 emitters including industries, power plants, motor vehicles, buildings, and homes. A third strategy is to level the economic playing field by greatly increasing government subsidies to businesses and individuals for using energy-efficiency technologies, carbon-free renewable-energy technologies, carbon capture and storage, and more sustainable agriculture.

This would also include phasing out or sharply reducing subsidies and tax breaks for using fossil fuels, nuclear power, and unsustainable agriculture. A fourth strategy would focus on technology transfer. Governments of developed countries could help fund the transfer of the latest green technologies to develop developing countries, which can then bypass older energywasting and polluting technologies. Increasing the current tax on each international currency transaction by a quarter of a penny could finance this technology transfer, which would then generate wealth for developing countries and help stimulate a more environmentally sustainable global economy.

Governments Can Enter into International Climate Negotiations: The Kyoto Protocol

In December 1997, more than 2,200 delegates from 161 nations met in Kyoto, Japan, to negotiate a treaty to help slow global warming. The first phase of the resulting Kyoto Protocol went into effect in January 2005 with 189 countries (not including the United States and Australia) and the U.S states of California and Maine participating in the agreement. It requires 38 participating developed countries to cut their emissions of CO2, CH4, and N2O to an average of at least 5.2% below their 1990 levels by 2012. Developing countries were excluded from having to reduce greenhouse gas emissions in this first phase because such reductions would curb their economic growth. In 2005, countries began negotiating a second phase that is supposed to go into effect after 2012.

The protocol also allows trading of greenhouse gas emissions among participating countries. For example, a country or business that reduces its CO2 emissions or plants trees receives a certain number of credits. It can use these credits to avoid having to reduce its emissions in other areas, or it can bank them for future use or sell them to other countries or businesses.

Some analysts praise the Kyoto agreement as a small but important step in attempting to slow projected global warming. They hope that rapidly developing nations such as China, Brazil, and India will agree to reduce their greenhouse gases in the second phase of the protocol. Others see the agreement as a weak and slow response to an urgent global problem.

In 2001, President George W. Bush withdrew U.S. participation from the Kyoto Protocol, arguing that participation would harm the U.S. economy. He also objected to the agreement because it does not require emissions reductions by developing countries such as China and India, which produce large and increasing emissions of greenhouse gases.

Most analysts believe that the United States, which has the second highest CO2 emissions and highest per capita emissions of any country, should use its influence to improve the treaty rather than to weaken and abandon it. A 2006 poll by the nonprofit, nonpartisan Civil Society Institute found that 83% of Americans want more leadership from the federal government in dealing with the threat of global warming.

In 2007, the European Union put climate change at the center of its foreign policy and began focusing on developing a new treaty with China that emphasizes sharp reductions in greenhouse gas emissions.

We Can Move beyond the Kyoto Protocol

In 2004, environmental law experts Richard B. Stewart and Jonathan B. Wiener proposed that countries work together to develop a new strategy for slowing global warming. They concluded that the Kyoto Protocol will have little effect on future global warming without support and action by the United States, China, and India.

In 2005, China, India, and other developing countries accounted for 37% of the world’s greenhouse gas emissions. By 2050, the International Energy Agency projects that their share could be 55%. Stewart and Wiener urge the development of a new climate treaty among the United States, China, India, Russia, Australia, Japan, South Korea, the European Union, and other major greenhouse gas emitters. The treaty would also create an emissions trading program that includes developing countries omitted from the trading plan under the first phase of the Kyoto Protocol. In addition, it would set achievable 10-year goals for reducing emissions over the next 40 years and evaluate global and national strategies for adapting to the harmful ecological and economic effects of global warming.

Some Governments, Businesses, and Schools Are Leading the Way

Some governments, businesses, and schools are tackling climate change problems on their own (Concept 15-5B). In 2005, the European Commission proposed a plan to increase the European Union’s use of renewable energy to 12% by 2010 and cut energy use by 20% by 2020. Together these two achievements would cut EU carbon dioxide emissions by nearly one-third. Since 1990, local governments in more than 600 cities around the world (including 330 U.S. cities) have established programs to reduce their greenhouse gas emissions. The first major U.S. city to tackle global warming was Portland, Oregon. Between 1993 and 2005, the city cut its greenhouse gas emissions back to 1990 levels, while national levels rose by 16%. The city promotes energy-efficient buildings and the use of electricity from wind and solar sources. It has also built bicycle trails and greatly expanded mass transit. Far from hurting its economy, Portland has experienced an economic boom, saving $2 million a year on city energy bills.

In 2006, California, with the world’s sixth largest economy, passed a law to cut its greenhouse gas emissions to 1990 levels (a 25% reduction) by 2020 and to 80% below 1990 levels by 2050. The EPA sued California, arguing that EPA and thus the state had no legal right to regulate CO2 emissions. But California won this Supreme Court case, and at least ten other states plan to adopt its standards.

In 2007, the premier of British Columbia, Canada, stated that he would cut CO2 emissions by a third by building no more coal plants, embracing wind power, toughening car emission standards, reducing pollution by the powerful oil and gas industry, and leasing hybrid cars for government use. He proposed making British Columbia the continent’s greenest spot. He also proposed forming an alliance with California to create a Pacific Coast bloc of provinces and states to deal with climate change without waiting for their federal governments to act.

A growing number of major global companies, such as Alcoa, DuPont, IBM, Toyota, General Electric, and British Petroleum (BP), have established targets to reduce their greenhouse gas emissions by 10–65% from 1990 levels by 2010. Since 1990, the chemical company DuPont has slashed its energy usage and cut its greenhouse emissions by 72%. In the process, it has saved $3 billion while increasing its business by 30%.

General Electric, BP America, Duke Energy, Caterpillar, Pacific Gas and Electric, Wal-Mart, and some firms managing large pension funds are among several major companies that in 2007 urged the U.S. Congress to regulate CO2 as a pollutant and impose mandatory carbon-emission caps on all U.S. businesses.

The goal would be to reduce U.S. greenhouse gas emissions by 60–90% from 1990 levels, mostly by using a cap-and-trade system. Such companies have established the Global Roundtable on Climate Change. Individuals can send a message to politicians and business leaders around the world by visiting the roundtable’s website at www.nextgenerationearth.org . These and many other major companies see an enormous profit opportunity by going green and developing energy-efficient and clean-energy technologies such as fuel-efficient cars, wind turbines, solar-cell panels, biofuels, and coal gasification and carbon removal and storage technologies. A 2006 study found that companies lagging behind in these efforts are putting their stockholders at risk of losses and lawsuits for failure to take advantage of the rapidly growing international marketplace for green technologies.

Some colleges and universities are also taking action. Students and faculty at Oberlin College in Ohio (USA) have asked their board of trustees to reduce the college’s CO2 emissions to zero by 2020 by buying or producing renewable energy. In the U.S. state of Pennsylvania, 25 colleges have joined to purchase wind power and other forms of carbon-free renewable energy. In 2005, the president of Yale University committed the school to cutting its considerable greenhouse gas emissions 44% by 2020. The student Task Force for Environmental Partnership handed out 2,000 compact fluorescent light bulbs in exchange for incandescent light bulbs. The program paid for itself in four months through the savings on electric bills.

You can go to sites like www.gocarbonzero.org  nature www.org/climatecalculator , www.carbonfootprint.com, and www.climatecrisis.net/takeaction/carboncalculator  to calculate your carbon footprint: the amount of carbon dioxide you generate. Most of these websites and others such as www.climatecare.org www.nativeenergy.com , www.myclimate.com , www.carbon-clear.com  and www.clean-air-coolplanet.org  suggest ways for you to offset some of your carbon dioxide emissions.

However, critics of such carbon-offset schemes say that most of them are primarily ways to ease consumer guilt while encouraging individuals to continue producing greenhouse gases instead of making carboncutting lifestyle changes.


We Can Prepare for Global Warming

According to the latest global climate models, the world needs to make a 60–80% cut in emissions of greenhouse gases by 2050 (some say by 2020) to stabilize their concentrations in the atmosphere. However, because of the difficulty of making such large reductions, many analysts believe that, at the same time, we should begin to prepare for the possible harmful effects of long-term atmospheric warming and climate change. However, critics fear that emphasizing this approach will decrease the more urgent need to reduce greenhouse gas emissions.


Reducing CO2 Emissions

Drive a fuel-efficient car, walk, bike, carpool, and use mass transit

Use energy-efficient windows

Use energy-efficient appliances and lights

Heavily insulate your house and seal all air leaks

Reduce garbage by recycling and reusing more items

Insulate your hot water heater

Use compact fluorescent light bulbs

Plant trees to shade your house during summer

Set your water heater no higher than 49°C (120°F)

Wash laundry in warm or cold water

Use a low-flow shower head

Buy products from, or invest in, companies that are trying to reduce their impact on climate

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(9) Air

The structure of our atmosphere



Atmospheric Structure

The late astronomer and author Carl Sagan (1934-1996) famously described Earth when viewed from deep space as ‘‘a pale blue dot.’’ His description, which was intended to highlight the fragility of the planet, points out the visual effect of Earth’s atmosphere. Viewed from space, the optical properties of the atmosphere surrounding Earth haloes the planet in a thin film of blue.

Compared to Earth’s diameter, which averages about 7,800 mi (12,550 km), the atmosphere, which peters out to the near-vacuum of space at an altitude of approximately 620 mi (1,000 km), is paper-thin. Furthermore, most of the planet’s weather is accounted for by the regions of the atmosphere within 35 mi (56 km) of the surface.

The atmosphere of the primordial Earth was different in composition from the atmosphere that cocoons the planet now. The appearance and evolution of life on Earth influenced atmospheric structure. The susceptibility of the atmosphere to change is the root of global warming, which all but a small minority of climate researchers now concede is a consequence of human activities.

Historical Background and Scientific Foundations

Earth is about 4.5 billion years old. The newly formed planet had no atmosphere, but as the planet cooled, the release of various gases created an atmosphere that was likely very different from that of the present day.

Although the composition of this primordial atmosphere is still debatable, the majority of scientists who study the early climate agree that the atmosphere was probably rich in carbon (C) and nitrogen (N), and lacked oxygen (O). As life began, the atmosphere changed, with carbon dioxide (CO2) decreasing and oxygen appearing and accumulating.

The present-day atmosphere consists predominantly of nitrogen (an average of 78% of the total material) andoxygen (average of 21%). The remaining 1% of the atmosphere consists of the so-called trace gases-argon (Ar), helium (He), hydrogen (H), krypton (Kr), neon (Ne), methane (CH4), ozone (O3), and xenon (Xe)-as well as carbon dioxide and water vapor.

The atmosphere is not a single layer. Rather, it consists of regions that are separated from one another by narrow zones of transition. The atmosphere gives way to space at an altitude of approximately 620 mi (1,000 km).

The atmosphere is also not uniform in the density of the constituent gases. Instead, over 99% of the mass of the atmosphere is concentrated within 25 mi (40 km) of Earth’s surface. Finally, the atmosphere is not uniform in temperature. As anyone who has climbed a mountain can attest, air temperature decreases with altitude, as the heat-absorbing gases become more dilute. Atmospheric temperature drops by about 11ºF (6ºC) for every 0.6 mi (1 km) of altitude in the atmospheric layer immediately above Earth’s surface.

This layer is called the troposphere. The upper range of the troposphere varies depending on latitude. At higher latitudes, it is about 5 mi (8 km) high, while at the equator it is upwards of 11 mi (18 km) high. The troposphere contains almost all (99%) of the atmospheric water vapor. Again, there is geographic variation, with water vapor concentration being up to 3% of total atmospheric content above the equator, but less toward the poles.

Weather occurs exclusively in the troposphere. Indeed, the meaning of the word troposphere (‘‘region of mixing’’) reflects the importance of air currents in this layer. Pollutants that enter the troposphere will be evenly dispersed within days; some of the chemicals will return to the surface in precipitation, as occurs in acid rain.

The troposphere is separated from the next layer of the atmosphere, the stratosphere, by a thin transition region called the tropopause. The stratosphere is approximately 25 mi (40 km) thick. It begins about 6.3 mi (10 km) above Earth’s surface, 1.5 mi (2.4 km) above the peak of Mt. Everest. Commercial aircraft cruise at altitudes that are in the lower to middle portions of the stratosphere.

The temperature within the stratosphere also varies with height, but in a different pattern to that of the troposphere. The temperature does not vary up to an altitude of about 15 mi (24 km), after which it gradually increases until reaching the next atmospheric transition zone, which is called the stratopause. This temperature pattern, with warmer air overlying colder air, is known as an inversion. Glimpsing a towering thunderhead on a summer’s day provides a visual example of the influence of the inversion; the thunderhead flattens off when the warm rising air in the cumulus cloud contacts the cooler air in the lower stratosphere, which halts the rising of the air.

The increasing temperature with altitude in the stratosphere acts to make this layer more stable than the underlying troposphere. Another contributor to this stability, and the reason for the stratospheric temperature inversion, is ozone. Ozone is a three-oxygen compound that absorbs incoming ultraviolet radiation from sunlight. This retention of heat is what maintains temperature with increasing altitude.

Beyond the stratopause lies the mesosphere. This atmospheric layer extends to approximately 50 mi (80 km) above the surface. There is little water vapor or ozone in this layer, hence, temperatures are low and keep decreasing with altitude. As well, the levels of oxycruise at altitudes that are in the lower to middle portions of the stratosphere.

The temperature within the stratosphere also varies with height, but in a different pattern to that of the troposphere. The temperature does not vary up to an altitude of about 15 mi (24 km), after which it gradually increases until reaching the next atmospheric transition zone, which is called the stratopause. This temperature pattern, with warmer air overlying colder air, is known as an inversion. Glimpsing a towering thunderhead on a summer’s day provides a visual example of the influence of the inversion; the thunderhead flattens off when the warm rising air in the cumulus cloud contacts the cooler air in the lower stratosphere, which halts the rising of the air.

The increasing temperature with altitude in the stratosphere acts to make this layer more stable than the underlying troposphere. Another contributor to this stability, and the reason for the stratospheric temperature inversion, is ozone. Ozone is a three-oxygen compound that absorbs incoming ultraviolet radiation from sunlight. This retention of heat is what maintains temperature with increasing altitude.

Beyond the stratopause lies the mesosphere. This atmospheric layer extends to approximately 50 mi (80 km) above the surface. There is little water vapor or ozone in this layer, hence, temperatures are low and keep decreasing with altitude. As well, the levels of oxygen and nitrogen are far less than in the troposphere and stratosphere; mesospheric air pressure (the number of atoms per given area) is 1,000 times less than air pressure at sea level.

A transition layer called the mesopause separates the mesosphere from the thermosphere. The thermosphere extends to about 75 mi (121 km) above Earth’s surface. The thermosphere is home to the International Space Station and orbits of the space shuttle.

The final layer of the atmosphere is the exosphere. Beyond lies the near-vacuum of space.

Impacts and Issues

Because regions of the atmosphere determine weather patterns and the global climate, atmospheric changes can be profound. The documented increase in the atmospheric levels of carbon dioxide, chlorofluorocarbons (CFCs), methane, and nitrous oxide (N2O), which are collectively known as greenhouse gases, is driving an increase in the temperature of the troposphere that has been termed global warming.

The final greenhouse compound is ozone. Degradation of ozone in the stratosphere has been accelerated from the naturally occurring rate due to the presence of human-made compounds including CFCs and hydro chlorofluorocarbons (which are used in air conditioners, refrigerators, and aerosol cans), halons (an ingredient of fire extinguishers), methyl chloroform (C2H3Cl3), and methyl bromide (CH3Br) is allowing more ultraviolet light to reach Earth’s surface.

The energy of ultraviolet light is sufficient to permit the light to penetrate into the upper layers of the skin and even to slice apart the genetic material inside cells. Consequences include skin damage such as sunburn and, more ominously, the increased tendency of the genetically damaged cells to become cancerous.

Although in the past it was argued that global warming was a natural phenomenon, only a tiny minority of scientists continue to hold this view. The vast majority of scientists now accept that human activities are at the heart of global warming today.

For example, carbon dioxide released into the atmosphere by the burning of fossil fuels and the burning of felled lumber from deforested regions, as two examples, account for almost half of the atmospheric warming caused by human activity. In another example, the build-up of CFCs not only stimulates ozone breakdown, but increases the retention of heat, since CFCs are a powerful greenhouse gas. Indeed, one molecule of CFC has about 20,000 times the heat-trapping power as a molecule of carbon dioxide.

The pollution of the atmosphere near Earth’s surface with noxious compounds can be unhealthy. An example from 2007 is Beijing, China. Air pollution in Beijing, which is mainly caused by the millions of vehicles operating daily in the mega-city, has become a great concern to officials of the International Olympic Committee responsible for ensuring that Beijing is ready to host the Summer Olympics in 2008. Events such as the marathon may need to be shifted to early morning, when air pollution is less. Alternatively, the government has proposed a ban on all vehicles in Beijing during the games.

Words To Know

Acid Rain: A form of precipitation that is significantly more acidic than neutral water, often produced as the result of industrial processes.

Chlorofluorocarbons: Members of the larger group of compounds termed halocarbons. All halocarbons contain carbon and halons (chlorine, fluorine, or bromine). When released into the atmosphere, CFCs and other halocarbons deplete the ozone layer and have high global warming potential.

Fossil Fuels: Fuels formed by biological processes and transformed into solid or fluid minerals over geological time. Fossil fuels include coal, petroleum, and natural gas. Fossil fuels are nonrenewable on the timescale of human civilization, because their natural replenishment would take many millions of years.

Inversion: A type of chromosomal defect in which a broken segment of a chromosome attaches to the same chromosome, but in reverse position.

Ozone: An almost colorless, gaseous form of oxygen with an odor similar to weak chlorine. A relatively unstable compound of three atoms of oxygen, ozone constitutes, on average, less than one part per million (ppm) of the gases in the atmosphere. (Peak ozone concentration in the stratosphere can get as high as 10 ppm.) Yet ozone in the stratosphere absorbs nearly all of the biologically damaging solar ultraviolet radiation before it reaches Earth’s surface, where it can cause skin cancer, cataracts, and immune deficiencies, and can harm crops and aquatic ecosystems.

Trace Gases: Gases present in Earth’s atmosphere in trace (relatively very small) amounts. All greenhouse gases happen to be trace gases, though some are more abundant than others; the most abundant greenhouse gases are CO2 (0.037% of the atmosphere) and water vapor (0.25% of the atmosphere, on average).

Water Vapor: The most abundant greenhouse gas, it is the water present in the atmosphere in gaseous form. Water vapor is an important part of the natural greenhouse effect. Although humans are not significantly increasing its concentration, it contributes to the enhanced greenhouse effect because the warming influence of greenhouse gases leads to a positive water vapor feedback. In addition to its role as a natural greenhouse gas, water vapor plays an important role in regulating the temperature of the planet because clouds form when excess water vapor in the atmosphere condenses to form ice and water droplets and precipitation.



Barry, Roger G. Atmosphere, Weather and Climate. Oxford, U.K.: Routledge, 2003.

Lutgens, Frederick K., Edward J. Tarbuck, and Dennis Tasa. The Atmosphere: An Introduction to Meteorology. New York: Prentice Hall, 2006.

Trefil, Calvo. Earth’s Atmosphere. Geneva, IL: McDougal Littell, 2005.

Ward, Peter. Out of Thin Air: Dinosaurs, Birds, and Earth’s Ancient Atmosphere. Washington, DC: Joseph Henry Press, 2006.

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(8) Air Pollution

 Air Pollution Causes More than 6 Million Deaths Worldwide

Air quality to suffer with global warming

Air Quality and Climate Change

Air Pollution - Comes From Many Sources


What Are Some Possible Effects of a Warmer Atmosphere?

CONCEPT 15-4 Some areas will benefit from a warmer climate and others will suffer from melting ice, rising sea levels, more extreme weather events, increased drought and floods, and shifts in locations of wildlife habitats and agricultural areas.

 Global Warming Can Have Harmful and Beneficial Effects

A warmer global climate could have a number of harmful and beneficial effects for humans, other species, and ecosystems, depending mostly on where they are located and on how rapidly the temperature changes. Some areas will benefit because of less severe winters, more precipitation in some dry areas, less precipitation in wet areas, and increased food production.

Other areas will suffer harm from excessive heat, drought, and decreased food production (Concept 15-4).

According to the IPCC, the world’s poor, who are least responsible for global warming, and wild species in the tropics (especially Africa and parts of Asia) will suffer the most harm.

According to a study by Agiuo Dai and his colleagues, between 1979 and 2002, the area of the earth’s land (excluding Antarctica) experiencing severe drought tripled and affected an area the size of Asia, mostly because of global warming. This browning of the land is expected to increase sharply and decrease water supplies and biodiversity in many areas. According to the 2007 IPCC report, hundreds of millions of people would suffer from water scarcity, with just a small rise in temperatures. However, if the average temperature rose by more that 4 C°(7 F°), 1.1 to 3.2 billion people might suffer from water shortages. According to the IPCC, areas projected to have increased drought by 2080–2099 include the western United States, the Mediterranean basin, southern Africa, southern and eastern Australia, and northeastern Brazil. The same report projected more days of heavy rain with increased flooding in areas of Canada, most of Europe, and the northern parts of the United States.


Predicting the effects of global warming in different parts of the world

Ice and Snow Are Melting in the Arctic

Environmental scientists are alarmed by recent news that parts of the Arctic are warming two to three times faster than the rest of the earth. Over the past 30 years, snow cover in the Arctic has declined by about 10%, mountain glaciers are melting and retreating, and permafrost is beginning to thaw in some areas. The melting of such reflective ice and snow exposes much darker land and water, which absorb more solar energy, and accelerates global warming.

In 2006, the U.S. National Oceanic and Atmospheric Administration issued a State of the Arctic report in which researchers predicted Arctic summers without floating sea ice by 2040 and perhaps much earlier. Because sea ice floats, it does not contribute to a rising sea level when it melts. However, open water reflects much less sunlight and absorbs more heat than do reflective ice or snow. Hence, floating ice turning to water during the Arctic summer will accelerate the warming of the lower atmosphere. The Arctic’s contribution to a rising sea level will come from land-based ice and snow that melts and runs into the sea. This is especially true in Greenland, a large mountainous island, which is covered almost completely by glaciers that are up to 3.2 kilometers (2 miles) deep. These glaciers contain about 10% of the world’s freshwater-enough water to raise the global sea level by as much as 7 meters (23 feet) if the glaciers all melt. This would flood many coastal cities and large areas of farmland.

Until recently scientific models of Greenland assumed that this huge solid block of ice would take thousands of years to melt. But recent satellite measurements made by scientists at the University of Kansas Jet Propulsion Laboratory show that Greenland’s net loss of ice more than doubled between 1996 and 2006 and is not being replaced by increased snowfall. Even partial melting will accelerate the projected average sea level rise during this century. Some climate scientists, such as James Hansen (Core Case Study), warn that once Greenland’s glacier starts to disintegrate they could reach a tipping point beyond which the breakup would occur very rapidly.

Mountaintop glaciers are affected by two climatic factors: snowfall that adds to their mass during the winter and warm temperatures that spur melting during the summer. As temperatures go up, melting exceeds snowfall and the glaciers begin receding. During the last 25 years, many of the world’s mountaintop glaciers have been melting and shrinking at accelerating rates. For example, climate models predict that by 2070, Glacier National Park in the United States will have no glaciers. In 2007, scientists projected that at their current rate of melting most glaciers will disappear from Europe’s Alps somewhere between 2037 and 2059. As mountain glaciers disappear, at least 300 million people in countries such as Bolivia, Peru, Ecuador, and India, who rely on meltwater from such glaciers could face severe water shortages.

Sea Levels Are Rising

According to the 2007 IPCC report, the world’s average sea level is very likely (90-99% certainty) to rise 8–59 centimeters (0.6–1.9 feet) during this century-about two-thirds of it from the expansion of water as it warms, and the other third from the melting of land-based ice.

However, larger rises in sea levels of up to 1 meter (39 inches) by 2100 cannot be ruled out if glaciers in Greenland reach a tipping point and continue melting at their current or higher rates as the atmosphere warms.

According to the IPCC, the projected increases in sea levels during this century could:

  •          Threaten at least one third of the world’s coastal estuaries, wetlands, and coral reefs,
  •          Disrupt many of the world’s coastal fisheries,
  •        Flood low-lying barrier islands and cause gently sloping coastlines (especially on the U.S. East Coast) to erode and retreat inland,
  •          Flood agricultural lowlands and deltas in coastal areas where much of the world’s rice is grown,
  •         Contaminate freshwater coastal aquifers with saltwater,
  •         Submerge some low-lying islands in the Pacific Ocean, the Caribbean Sea, and the Indian Ocean, and
  •      Flood coastal areas, including some of the world’s largest cities, and displace at least 100 million people, especially in China, India, Bangladesh, Vietnam, Indonesia, and Japan.

Permafrost Is Melting: Another Dangerous Scenario

Global warming could be accelerated by an increased release of methane (a greenhouse gas 23 times more potent, per volume, than carbon dioxide) from four major sources: natural decay in swamps and other freshwater wetlands, decay from garbage in landfills, melting permafrost in soils and lake beds, and ice-like compounds called methane hydrates trapped beneath arctic permafrost and on the deep ocean floor.

The amount of carbon locked up as methane in permafrost soils is 50–60 times the amount emitted as car bon dioxide from burning fossil fuels each year. Significant amounts of methane and carbon dioxide would be released into the atmosphere if the permafrost in arctic areas melts. This is already happening on a small scale in parts of North America and Asia, and as the earth gets warmer, it could accelerate. According to the 2004 Arctic Climate Impact Assessment, 10–20% of the Arctic’s current permafrost might thaw during this century and decrease the area of Arctic tundra.

A warmer atmosphere could melt more permafrost and increase emissions of CH4 and CO2. This would cause more warming and more permafrost melting, which would cause still more warming.

Ocean Currents Are Changing but the Threat Is Unknown

Ocean currents, which on the surface and deep down are connected, act like a gigantic conveyor belt, moving CO2 and heat to and from the deep sea, and transferring hot and cold water between the tropics and the poles.

Scientists are concerned that melting of land-based glaciers from global warming (especially in Greenland) and increased rain in the North Atlantic could add enough freshwater to the ocean in the arctic area to slow or disrupt this conveyor belt. Reaching this tipping point would drastically alter the climates of northern Europe, northeastern North America, and probably Japan. The exact nature and likelihood of this possible threat is still unknown, but most climate scientists do not see it as a major threat in the near future.

Extreme Weather Will Increase in Some Areas

Global warming is projected to alter the hydrologic cycle and shift patterns of precipitation, causing some areas to get more water and other areas to get less. This could shift the locations of areas where crops could be grown and where people could live (Concept 15-4).

According to the IPCC, global warming will increase the incidence of extreme weather such as prolonged, intense heat waves and droughts, which can kill large numbers of people and expand deserts. At the same time, other areas will experience increased flooding from heavy and prolonged precipitation.

Researchers have not been able to establish that global warming will increase the frequency of tropical hurricanes and typhoons. But a 2005 statistical analysis by MIT climatologist Kerry Emmanuel and six other peer-reviewed studies published in 2006 indicated that global warming, on average, could increase the size and strength of such storms in the Atlantic by warming the ocean’s surface water.

On the other hand, some researchers blame the recently increased ferocity of tropical Atlantic hurricanes on natural climate cycles. More research is needed to evaluate these opposing hypotheses. More research is needed to evaluate the scientific controversy over the effects of global warming on hurricane frequency and intensity.

Maldives in the Indian Ocean, even a small rise in sea level could spell disaster for most of its 295,000 people. About 80% of the 1,192 small islands making up this country lie less than 1 meter (39 inches) above sea level. Rising sea levels and higher storm surges during this century could flood most of these islands and their coral reefs.


Global Warming Is a Major Threat to Biodiversity

According to the 2007 IPCC report, changes in climate are now affecting physical and biological systems on every continent. A warmer climate could expand ranges and populations of some plant and animal species that can adapt to warmer climates, including certain weeds, insect pests such as fire ants and ticks, and disease-carrying organisms.

Changes in the structure and location of wildlife habitats could cause the premature extinction of as many as 1 million species during this century (Concept 15-4). One of the first mammal species to go may be the polar bear (see front cover), as arctic sea ice, on which the bears hunt seals and other marine mammals, diminishes. By 2050, polar bears may be found mostly in zoos.

The ecosystems most likely to suffer disruption and species loss are coral reefs, polar seas, coastal wetlands, arctic and alpine tundra, and high-elevation mountaintops.

Forest fires may increase in some areas. Shifts in regional climate would also threaten many parks, wildlife reserves, wilderness areas, and wetlands-wiping out more biodiversity. In other words, slowing global warming would help sustain the earth’s biodiversity.

Global Warming Will Change Locations of Areas Where Crops Can Be Grown

Farming depends on a stable climate, probably more than any other human endeavor. Global warming will upset this stability by shifting climates and speeding up the hydrologic cycle (Concept 15-4).

Agricultural productivity may increase in some areas and decrease in others. For example, models project that warmer temperatures and increased precipitation at northern latitudes may lead to a northward shift of some agricultural production from the breadbasket of the midwestern United States to midwestern Canada.

But overall food production could decrease because soils in midwestern Canada are generally less fertile than those to the south. Crop production could also increase in Russia and Ukraine. In 2007, a panel of scientists from six Chinese government agencies warned that rising temperatures during the second half of this century could slash the country’s grain production by over a third, melt glaciers, increase pressure on its already scarce water resources in many areas, change its forest industry, and cause flooding in coastal areas that include 21 of its 33 largest cities.

Models predict a decline in agricultural productivity in tropical and subtropical regions, especially in Southeast Asia and Central America, where many of the world’s poorest people live. In addition, flooding of river deltas due to rising sea levels could reduce crop and fish production in these productive agricultural lands and coastal aquaculture ponds. According to the IPCC, for a time, food will be plentiful because of the longer growing season in northern regions. But by 2050, 200–600 million people could face starvation from decreased food production.

Global Warming Could Threaten the Health of Many People

According to the IPCC and a 2006 study by U.S National Center for Atmospheric Research, heat waves in some areas will be more frequent and prolonged, increasing death and illness, especially among older people, those with poor health, and the urban poor who cannot afford air conditioning. During the summer of 2003 (based on a detailed analysis in 2006 by Earth Policy Institute), such a heat wave killed about 52,000 people in Europe-almost two-thirds of them in Italy and France.

On the other hand, in a warmer world fewer people will die from cold weather. But a 2007 study by Mercedes Medin-Ramon and his colleagues suggested that increased heat-related deaths would be greater than the drop in cold-related deaths.

Incidences of tropical infectious diseases such as dengue fever and malaria are likely to increase if mosquitoes that carry them spread to temperate and higher elevation areas that are getting warmer. A 2006 study by Nils Stenseth at the University of Oslo found that the bacterium that causes bubonic plague, which killed more than 20 million people in the Middle Ages, could spread if the flea populations increase as temperatures rise. In addition, hunger and malnutrition will increase in areas where agricultural production drops.

A 2005 WHO study estimated that each year, climate change already prematurely kills more than 160,000 people-an average of 438 people a day-and that this number could double by 2030. In addition, the WHO estimates that climate change causes 5 million sicknesses each year. By the end of this century, the annual death toll from global warming could be in the millions.

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(1) Air

Air Quality 101: The Basics


Without the layer of air that surrounds our planet, neither we nor any of the other forms of life that have evolved on Earth could exist. The general term for this layer of air is ‘atmosphere’, a word derived from the Greek atmos (vapour) and sphaira (ball or sphere). Of all the subsystems within the environmental system, the atmosphere has a number of unique characteristics. It is continuous around the Earth, but compared with the size of the Earth, the atmosphere is a thin shell. The part of the atmosphere we know best and live in – the troposphere – is an even thinner shell, only around 12 kilometres (7.5 miles) thick. If the Earth were the size of an apple, the atmosphere would have the thickness of the apple peel, yet this thin film of gases fulfils many essential functions. It is in the troposphere that all weather occurs; it is only here that life exists. Wind systems and rainfall patterns result from the differential heating by solar energy of the Earth’s surface and, subsequently, the atmosphere. Such weather manifestations are visible from space.

Have you ever thought about how much air you need to breathe each day? We take the air for granted, but think how long you can go without food or water compared to how long you can hold your breath. The basic biological air requirements for a person weighing around 68 kg.

Air requirements for human activity at typical ground-level pressure (100 kPa)

Activity l min−1 l hour−1

Resting 7.4 444

Doing light work 28 1680

Doing heavy work 43 2580

Based on this information, if we take a working day to comprise 7 hours of heavy work, 7 hours of light work and 10 hours of rest, we need 34 260 litres or 34.26 m3 of air per day. Taking the density of air as 1.29 kg m−3, the mass of air required comes to 44.20 kg. In comparison, we eat no more than about 1.5 kg of food each day, so our air requirement is nearly 30 times our food requirement. Similarly, we probably drink no more than about 2.5 kg of water each day. This indicates why air quality is so important; any contamination needs to be much lower in air than in food and water if we are to ensure that our total intake of potentially harmful substances does not put our health at risk. We cannot choose the air we breathe.

In our modern, technological society, we also need air to burn fuels for heating and for transport.

What is air pollution?

The United Kingdom is where the industrial revolution began, bringing with it a legacy of damage to the natural environment and public health. Resources such as water, coal and minerals were exploited, and by the middle of the nineteenth century the air and water were choked with industrial emissions. Indeed, the image of a prospering industry was of smoking chimneys. The first measures to protect the environment can also be traced back to this period. The air is obviously an important part of the environment to protect – it is essential for the survival of all higher forms of life on the planet. While seemingly vast, the atmosphere accounts for only about 1% of the diameter of the Earth. It is also continuous and so may be contaminated by activities perhaps hundreds or even thousands of miles away. We usually refer to this contamination as air pollution. The World Health Organization (WHO, 2013) has defined air pollution as: chemical, physical or biological agent that modifies the natural characteristics of the atmosphere.

There are two aspects of air pollution that are of major importance to life on Earth. Some constituents of the atmosphere may have a directly harmful effect on life forms, and other constituents may cause significant damage through changing the Earth’s radioactive balance. The spatial continuity of the atmosphere makes it nearly impossible to contemplate remediation, so pollutant releases to atmosphere must be considered with caution. Pollutants can be transported great distances, having an impact far from the emission source. A well-known example of this is the catastrophic fire and subsequent explosion at the Chernobyl Nuclear Power Plant in April 1986, in what was then the Soviet Union. This had a widespread effect across much of Europe, with pastures as far away as Wales and the Lake District – around 2300 km from the source – being contaminated due to airborne pollution.

* Published in Linkedin

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(6) Air Pollution

Air Pollution


Concept 15-3 Evidence indicates that the earth’s atmosphere is warming rapidly, mostly because of human activities, and that this will lead to significant climate change during this century with severe and long-lasting consequences for humans and many other forms of life.

Global Warming and Global Cooling Are Not New

Changes in the earth’s climate are neither new nor unusual. Over the past 4.7 billion years, the planet’s climate has been altered by volcanic emissions (Core Case Study), changes in solar input, continents moving slowly as a result of shifting tectonic plates, impacts by large meteors, and other factors.

Over the past 900,000 years, the atmosphere has experienced prolonged periods of global cooling and global warming. These alternat ing cycles of freezing and thawing are known as glacial and interglacial (between ice ages) periods.

Some analysts hypothesize that climate change after the last ice age ended about 13,000 years ago was an important factor leading nomadic hunter–gatherers to settle down and invent agriculture. For roughly 10,000 years, we have had the good fortune to live in an interglacial period characterized by a fairly stable climate and a steady average global surface temperature, bottom left). These conditions allowed agriculture, and then cities, to flourish. For the past 1,000 years, the average temperature of the atmosphere has remained fairly stable but began rising during the last century when people began clearing more forests and burning fossil fuels. Past temperature changes such as those are estimated by analysis of: radioisotopes in rocks and fossils; plankton and radioisotopes in ocean sediments; tiny bubbles of ancient air found in ice cores from glaciers; temperature measurements taken at different depths from boreholes drilled deep into the earth’s surface; pollen from the bottoms of lakes and bogs; tree rings; historical records; insects, pollen, and minerals in different layers of bat dung deposited in caves over thousands of years; and temperature measurements taken regularly since 1861.

We Are Making the Earth’s Natural Low-Grade Fever Worse

Along with solar energy, a natural process called the greenhouse effect warms the earth’s lower atmosphere and surface. Life on the earth and the world’s economies are totally dependent on the natural greenhouse effect-one of the planet’s most important forms of natural capital. The oceans are another factor shaping the earth’s climate because they remove carbon dioxide and heat from the atmosphere and move stored heat from one place to another in water currents. Swedish chemist Svante Arrhenius first recognized the natural greenhouse effect in 1896. Since then, numerous laboratory experiments and measurements of temperatures at different altitudes have confirmed this effect-now one of the most widely accepted theories in the atmospheric sciences. It occurs primarily because of the presence of four natural greenhouse gases-water vapor (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Since the beginning of the Industrial Revolution about 275 years ago, human actions have led to significant increases in the concentration of earth-warming CO2, CH4, and N2O in the lower atmosphere-mainly from agriculture, deforestation, and burning fossil fuels.

There is considerable and growing evidence that these inputs of greenhouse gases from human activities are causing an enhanced greenhouse effect, popularly known as global warming. In 2006, researchers at the British Antarctic Survey analyzed air bubbles in ice cores from Antarctica going back 800,000 years. Their data indicated that current levels of CO2 are higher than at any other time during that period and are now increasing at an unprecedented rate.

In 2007, the largest CO2 emitting countries in order were China, the United States, the European Union, Indonesia, Russia, Japan, and India. Global CO2 emissions are growing exponentially at an increasing rate.

  1. United States has been responsible for 25% of the world’s cumulative CO2 emissions, compared to China’s 5% contribution. But coal-fired power plants provide over 70% of China’s electricity compared to 50% in the United States. And China’s oil consumption and use of coal to produce electricity are soaring.
  2. China’s total CO2 emissions are high and growing rapidly, its per capita emissions are low. For example, the United States emits about seven times more CO2 per person than China does. China points out that current global warming has been caused mostly by the long-term historic emissions by developed countries and their high per capita emissions.

Critics respond that if China does not radically change to more sustainable forms of production, power generation, transport, and building design, its projected economic miracle will turn into an unsustainable econightmare. Because CO2 mixes freely in the atmosphere, every country’s climate is affected by any one country’s actions.

In 1988, the United Nations and the World Meteorological Organization established the Intergovernmental Panel on Climate Change (IPCC) to document past climate changes and project future changes. The IPCC network includes more than 2,500 climate experts from 130 nations. In its 2007 report, based on more than 29,000 sets of data, the IPCC listed a number of findings indicating that it is very likely (a 90-99% probability) that the lower atmosphere is getting warmer (Concept 15-3) and that human activities are the primary cause of the recent warming.

According to the 2007 IPCC report, here is some of the evidence that supports its conclusions.

• Between 1906 and 2005, the average global surface temperature has risen by about 0.74 C° (1.3 F°). Most of this increase has taken place since 1980.

• Actual temperature measurements indicate that the 13 warmest years since 1861 (when temperature measurements began) have occurred since 1990. In order, the five hottest years since 1861 have been 2005, 1998, 2002, 2003, and 2006.

• Over the past 50 years, Arctic temperatures have risen almost twice as fast as temperatures in the rest of the world.

• In some parts of the world, glaciers and floating sea ice are melting and shrinking at increasing rates, rainfall patterns are changing, and extreme drought is increasing.

• During the last century, the world’s average sea level rose by 10-20 centimeters (4-8 inches), mostly because of runoff from melting land-based ice and the expansion of ocean water as its temperature increases.

  Enhanced Global Warming

May Have Severe Consequences:

Some Scary Scenarios

So what is the big deal? Why should we worry about a possible rise of only a few degrees in the earth’s average surface temperature? We often have that much change between May and July, or even between yesterday and today. The key point is that we are talking not about normal swings in local weather, but about a projected global change in climate-weather measurements averaged over decades, centuries, and millennia.

Climate scientists warn that the concern is not just about how much the temperature changes but also about how rapidly it occurs. Most past changes in the temperature of the lower atmosphere took place over thousands to a hundred thousand years, top and bottom left). The next problem we face is a rapid increase in the average temperature of the lower atmosphere during this century.

In other words, according to the IPCC and other climate scientists, the earth’s atmosphere is running a fever that is rising fast, mostly because of human activities. Such rapid change could drastically affect life on earth. Humans have built a civilization adapted to the generally favorable climate we have had for the past 10,000 years. Climate models indicate that within only a few decades, we will have to deal with a rapidly changing climate.

A 2003 U.S. National Academy of Sciences report laid out a nightmarish worst-case scenario in which human activities, alone or in combination with natural factors, trigger new and abrupt changes. At that point, the global climate system would reach a tipping point after which it would be too late to reverse catastrophic change for tens of thousands of years. The report describes ecosystems suddenly collapsing, low-lying cities being flooded, forests being consumed in vast fires, grasslands drying out and turning into dust bowls, premature extinction of up to half of the world’s species, prolonged heat waves and droughts more intense coastal storms and hurricanes, and tropical infectious diseases spreading rapidly beyond their current ranges. Climate change can also threaten peace and security as changing patterns of rainfall increase competition for water and food resources, cause destabilizing migrations of tens of millions of people, and lead to economic and social disruption.

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(5) Air Pollution

  Air Pollution


How Should We Deal with Air Pollution?

 CONCEPT 15-2 Legal, economic, and technological tools can help clean up air pollution, but scientists call for much greater emphasis on preventing air pollution.



 Laws Have Reduced Outdoor Air Pollution in the United States

The U.S. Congress passed the Clean Air Acts in 1970, 1977, and 1990. With these laws, the federal government established air pollution regulations for key pollutants that are enforced by states and major cities.

Congress directed the EPA to establish national ambient air quality standards (NAAQS) for six outdoor crite Laws Have Reduced Outdoor Air Pollution in the United States The U.S. Congress passed the Clean Air Acts in 1970, 1977, and 1990. With these laws, the federal government established air pollution regulations for key pollutants that are enforced by states and major cities.

Congress directed the EPA to establish national ambient air quality standards (NAAQS) for six outdoor criteria pollutants-carbon monoxide, nitrogen oxides, sulfur dioxide, suspended particulate matter, ozone, and lead. One limit, called a primary standard, is set to protect human health. Each standard specifies the maximum allowable level, averaged over a specific period, for a certain pollutant in outdoor (ambient) air.

The EPA has also established national emission standards for more than 188 hazardous air pollutants (HAPs) that can cause serious health and ecological effects.

Most of these chemicals are chlorinated hydro- carbons, volatile organic compounds, or compounds of toxic metals.

Great news. According to a 2005 EPA report, combined emissions of the six principal outdoor air pollutants decreased by 53% between 1970 and 2005, even with significant increases in gross domestic product, vehicle miles traveled, energy consumption, and population (Concept 15-2). The decreases for the six pollutants during this period were 99% for lead, 84% for suspended particulate matter, 55% for carbon monoxide, 52% for sulfur dioxide, 29% for nitrogen oxides, and 14% for ground-level ozone. Volatile organic compounds decreased 53% in this period.

The bad news is that although photochemical smog levels dropped in the 1980s, they have fallen very little since 1994. In 2004, the EPA found that 474 of the nation’s 2,700 counties in 31 states had unacceptable levels of ground-level ozone, a major ingredient in unhealthy smog. Reducing smog will require much bigger cuts in emissions of nitrogen oxides from power and industrial plants and motor vehicles. According to the EPA, almost 60% of the U.S. population lives in areas where the air is unhealthy to breathe during part of the year because of high levels of smog pollutants, primarily ozone and very small particles.

 U.S. Air Pollution Laws Can Be Improved

The reduction of outdoor air pollution in the United States since 1970 has been a remarkable success story. It occurred because of two factors. First, U.S. citizens insisted that laws be passed and enforced to improve air quality. Second, the country was affluent enough to afford such controls and improvements. Environmental scientists applaud the success of U.S. air pollution control laws but suggest the following deficiencies.

• The United States continues to rely mostly on pollution cleanup rather than prevention (Concept 15-2). The power of prevention is clear. In the United States, the air pollutant with the largest drop in its atmospheric level was lead (99% between 1970 and 2005), which was largely banned in gasoline. This has prevented a generation of children from suffering lead poisoning.

• The U.S. Congress has failed to increase fuel-efficiency (CAFE) standards for cars, SUVs, and light trucks. CAFÉ standards have been shown to reduce air pollution from motor vehicles more quickly and effectively than any other method. Congress has also failed to enact a feebate program.

• Regulation of emissions from motorcycles and two-cycle gasoline engines remains inadequate. Two-cycle engines used in lawn mowers, leaf blowers, chain saws, jet skis, outboard motors, and snowmobiles emit high levels of pollutants (although less-polluting polluting versions are becoming available). According to the California Air Resources Board, a 1-hour ride on a typical jet ski creates more air pollution than the average U.S. car does in a year, and operating a 100-horsepower boat engine for 7 hours emits more air pollutants than driving a new car 160,000 kilometers (100,000 miles).

• There is little or no regulation of air pollution from oceangoing ships in American ports. According to the Earth Justice Legal Defense Fund, a single cargo ship emits more air pollution than 2,000 diesel trucks or 350,000 cars. Ships burn the dirtiest grades of diesel fuel and threaten the health of millions of dockworkers and other people living in port cities.

• Major airports, which are among the top polluters in urban areas, are exempt from many air pollution regulations.

• As of 2007, the Clean Air Acts did not specifically regulate emissions of the greenhouse gas CO2, which can alter climate and cause numerous harmful ecological, health, and economic effects.

• The acts have failed to deal seriously with indoor air pollution, even though it is by far the most serious air pollution problem in terms of poorer health, premature death, and economic losses from lost work time and increased health costs.

• There is a need for better enforcement of the Clean Air Acts. Under the acts, state and local officials have primary responsibility for implementing federal clean air standards, based on federal funding. However, a 2006 study by the Center for American Progress found that since 1993, enforcement hás become lax because of a sharp drop in federal grants to state and local air quality agencies and relaxed federal inspection standards. According to a 2002 government study, more rigorous enforcement would save about 6,000 lives and prevent 140,000 asthma attacks each year in the United States.

Executives of companies that would be affected by implementing stronger policies claim that correcting deficiencies in the Clean Air Acts would cost too much and harm economic growth. Proponents contend that most industry cost estimates for implementing U.S. air pollution control standards have been many times the actual costs. In addition, implementing such standards hás boosted economic growth and created jobs by stimulating companies to develop new technologies for reducing air pollution emissions-many of which can be sold in the global marketplace. Without intense pressure from citizens, it is unlikely that the U.S. Congress will strengthen the Clean Air Acts. In recent years, in fact, Congress has weakened some air pollution regulations.

 We Can Use the Marketplace to Reduce Outdoor Air Pollution

 Allowing producers of air pollutants to buy and sell government air pollution allotments in the marketplace can help reduce emissions (Concept 15-2). To help reduce SO2 emissions, the Clean Air Act of 1990 authorizes an emissions trading, or cap-and-trade, program, which enables the 110 most polluting power plants in 21 states (primarily in the midwestern and eastern United States) to buy and sell SO2 pollution rights.

Each year, a coal-burning power plant is given a number of pollution credits, which allow it to emit a certain amount of SO2. A utility that emits less SO2 than it is allotted has a surplus of pollution credits. It can use these credits to avoid reductions in SO2 emissions at another of its plants, keep them for future plant expansions, or sell them to other utilities, private citizens, or environmental groups.

Proponents argue that this approach is cheaper and more efficient than having the government dictate how to control air pollution. Critics of this plan contend that it allows utilities with older, dirtier power plants to buy their way out of their environmental responsibilities and continue polluting. This approach also can encourage cheating, because it is based largely on self-reporting of emissions.

Scientists warn that the ultimate success of any emissions trading approach depends on how low the initial cap is set and then on the annual lowering of the cap, which should promote continuing innovation in air pollution prevention and control. Without these elements, emissions trading programs mostly move air pollutants from one area to another without achieving any overall reduction in air quality.

Good news. Between 1990 and 2005, the emissions trading system helped reduce SO2 emissions from electric power plants in the United States by 31% at a cost of less than one-tenth the cost projected by industry.

The EPA estimates that by 2010, this approach will annually generate health and environmental benefits that are 60 times higher than the annual cost of the program.

Emissions trading is also being tried for NOx and perhaps in the future for other air pollutants. However, environmental and health scientists strongly oppose using a cap-and-trade program to control emissions of mercury by coal-burning power plants and industries, because this pollutant is highly toxic and does not break down in the environment. Coal-burning plants choosing to buy permits instead of sharply reducing their mercury emissions would create toxic hot spots with unacceptably high levels of mercury.

In 2002, the EPA reported results from the country’s oldest and largest emissions trading program, in effect since 1993 in southern California. According to the report, this cap-and-trade model fell far short of projected emissions reductions. The same study also found accounting abuses. This highlights the need for more careful government monitoring of all cap-andtrade programs.

 There Are Many Ways to Reduce Outdoor Air Pollution

 Between 1980 and 2002, emissions of SO2 from U.S. electric power plants were decreased by 40%, emissions of NOx by 30%, and soot emissions by 75%.. However, approximately 20,000 older coal-burning plants, industrial plants, and oil refineries in the United States have not been required to meet the air pollution standards required for new facilities under the Clean Air Acts. Officials of states subject to pollution from such plants have been trying to get Congress to correct this shortcoming since 1970. But they have not been successful because of strong lobbying efforts by U.S. coal and electric power industries.

 Reducing Indoor Air Pollution Should Be a Priority

Little effort has been devoted to reducing indoor air pollution even though it poses a much greater threat to human health than does outdoor air pollution. Air pollution experts suggest several ways to prevent or reduce indoor air pollution.


Motor Vehicle Air Pollution


 Use mass transit

Walk or bike

Use less polluting fuels

Improve fuel efficiency

Get older, polluting cars off the road

Give large tax writeoffs or rebates for buying low-polluting, energy efficient vehicles


Indoor Air Pollution


 Cover ceiling tiles and lining of AC ducts to prevent release of mineral fibers

Ban smoking or limit it to wellventilated areas

Set stricter formaldehyde emissions standards for carpet, furniture, and building


Prevent rádon infiltration

Use Office machines in wellventilated areas

Use less polluting substitutes for harmful cleaning agents, paints, and other products

 Cleanup or Dilution

 Use adjustable fresh air vents for work spaces

Increase intake of outside air

Change air more frequently

Circulate a building’s air through rooftop greenhouses

Use efficient venting systems for wood-burning stoves

Use exhaust hoods for stoves and appliances burning natural gas

 In developing countries, indoor air pollution from open fires and leaky and inefficient stoves that burn wood, charcoal, or coal could be reduced. People could use inexpensive clay or metal stoves that burn biofuels more efficiently, while venting their exhaust to the outside, or stoves that use solar energy to cook food. This would also reduce deforestation by cutting demand for fuelwood and charcoal.

 We Need More Emphasis on Pollution Prevention

 Encouraging news. Since 1970, most of the world’s developed countries have enacted laws and regulations that have significantly reduced outdoor air pollution.

Most of these laws emphasize controlling outdoor air pollution by using output approaches. To environmental and health scientists, the next step is to shift to preventing

air pollution. With this approach, the question is not “What can we do about the air pollutants we produce?” but rather “How can we avoid producing these pollutants in the first place?”  Like the shift to controlling outdoor air pollution between 1970 and 2006, this new shift to preventing outdoor and indoor air pollution will not take place unless individual citizens and groups put political pressure on elected officials and economic pressure on companies through their purchasing decisions.


Indoor Air Pollution

 Test for radon and formaldehyde inside your home and take corrective measures as needed.

Do not buy furniture and other products containing formaldehyde.

Remove your shoes before entering your house to reduce inputs of dust, lead, and pesticides.

Test your house or workplace for asbestos fiber levels and check for any crumbling asbestos materials if it was built before 1980.

Do not store gasoline, solvents, or other volatile hazardous chemicals inside a home or attached garage.

If you smoke, do it outside or in a closed room vented to the outside.

Make sure that wood-burning stoves, fireplaces, and keroseneand gas-burning heaters are properly installed, vented, and maintained.

Install carbon monoxide detectors in all sleeping areas.


Air Pollution


 Improve energy efficiency to reduce fossil fuel use

Rely more on lower-polluting natural gas

Rely more on renewable energy (especially solar cells, wind, and solar-produced hydrogen)

Transfer energy efficiency, renewable energy, and pollution prevention technologies to

Developing countries


 Reduce poverty

Distribute cheap and efficient cookstoves or solar cookers to poor families in developing countries

Reduce or Ban indoor smoking

Develop simple and cheap tests for indoor pollutants such as particulates, radon, and formaldehyde


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(4) Air Pollution

Air Pollution: Photochemical Smog


Sunlight Plus Cars Equals Photochemical Smog

Photochemical reaction is any chemical reaction activated by light. Photochemical smog is a mixture of primary and secondary pollutants formed under the influence of UV radiation from the sun.

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