ENVIRONMENT GLOBAL WARMING

Ozone Depletion

NATIONAL GEOGRAPHIC - 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.”

NATURAL CAPITAL DEGRADATION

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

Wildlife

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

WHAT CAN YOU DO?

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.

 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.

SOLUTIONS

Global Warming

Prevention – Cleanup

Prevention

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

Cleanup

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.

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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.

WHAT CAN YOU DO?

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

The structure of our atmosphere

THE STRUCTURE OF THE 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.

Bibliography:

Books:

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.

 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.

RESEARCH FRONTIER

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.