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Lesson 11 Air Pollution – Past and Future Trouble -- Part 1
© Penn State Biology – BISC 003: Environmental Science
1 In lesson 11 you will…
• Consider the components of the atmosphere and how the world's climatic patterns are established.
• Understand the greenhouse effect and how it is connected to, but not identical with, global climate change.
• Investigate causes and effects of global climate change, and discuss what we can/should do about it.
• Understand how CFCs, or chlorofluorocarbon, affect the ozone layer.
• Examine the major types of air pollution and how they impact both human and ecosystem health.
• Understand the types of smog and how they are formed.
• Understand the significance of acid deposition, or acid rain.
© Penn State Biology – BISC 003: Environmental Science
2 Until recently, global climate change was an issue that few politicians wanted to discuss or address. It is scientifically
challenging to predict and explain climate change, and socially it seems to be an issue that people are somewhat content
to ignore. We are conducting a giant climatic experiment on earth and the results will only be fully manifested after the
fact. By the time some skeptics are satisfied as to the reality of the problem, it is likely too late.
Pascal was a mathematician and physicist who experienced a religious conversion late in life. Always the scientist, he
proposed a logical argument for believing in a higher power. Paraphrased, Pascal's argument goes like this:
If you believe in God and there is a God, you are safe. If you believe in God and there is no God, you have lost nothing.
But if you do not believe and there is a God, you are damned.
This argument can also be applied to human-caused climate change: If we address greenhouse gas emissions and global
climate change manifests, we can lessen the impact. If we address greenhouse gas emissions and global climate change
does not manifest, we have lost nothing. But if we do nothing to reduce greenhouse gas emissions and global climate
change manifests in the worst case predictions, we are dammed as surely as Pascal's atheist. Do you agree with this
argument?
© Penn State Biology – BISC 003: Environmental Science
3 This cartoon makes the same point, someone in the audience asks a presenter at a climate summit meeting “what if it’s a
hoax and we create a better world for nothing?” More energy efficiency and a switch from fossil fuels to renewable energy
sources have many benefits besides reducing CO2 emissions. It does seem likes like a win -win situation.
© Penn State Biology – BISC 003: Environmental Science
4 Weather and Climate
One area of confusion about climate change comes from the popular press. We read headlines like "Temperatures soar to
record highs- global warming has arrived“and "The flood waters are rising-is this climate change?" Unfortunately, climate
change will only be confirmed after it has fully manifested. Often, weather, which is day to day changes in temperature
and rainfall is confused with climate, which is long term temperature and rainfall trends, or long-term weather trends.
It is impossible to tell if one heat wave or one extreme weather event like a hurricane, drought or flood is a result of
human-caused climate change, but warmer temperatures and more frequent extreme weather events are among the
predicted effects.
Check out the short “Trends and Variation” video in the lesson 11 course content the video library for a nice illustration of
the difference between weather and climate.
http://www.joabbess.com/tag/global-warming-science/
http://mediamatters.org/research/200812190013
© Penn State Biology – BISC 003: Environmental Science
5 What sets the globe's climate trends is a combination of factors including, but not limited to, ocean currents, prevailing
winds, and solar energy. Your text does a good job of outlining factors that set the globe's climatic trends, read through
this section, but you do not have to memorize all the details.
Another important factor determining earth’s climate is the greenhouse effect, which is essential for life on earth as we
know it. When solar energy reaches the earth, some hits Earth's surface and warms it. Some of this heat is reradiated
from the surface back to the atmosphere. In a planet like Mars that lacks greenhouse gasses, the infrared heat energy is
lost to the cosmos. Earth’s atmosphere on the other hand have greenhouse gasses such as carbon dioxide, water vapor,
methane and others that absorb this energy and reradiate it back to the earth's surface. This effect, known as the
greenhouse effect, keeps the earth habitable. Without greenhouse gasses, the earth's mean temperature would hover
around 0 degrees F instead of the current 59 degrees.
So the greenhouse effect is a good thing. However, the majority of climate scientists now believe that we are seeing a
magnification of the greenhouse effect that is caused by increasing concentrations of greenhouse gasses in the
atmosphere as a result of human activities. Or in other words, this enhancement of the greenhouse effect is causing a
change in the global climate. At the core of the scientific climate change debate is NOT a question of "if" but of "when and
how much?" Future climate predictions based on computer models include an increase in the average global temperature,
or global warming, but also changes in precipitation, shifts in ocean currents, and potentially even colder temperatures in
some areas, like Europe. But before we talk more about the effects of global climate change, let's take a look at the
evidence.
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6 To measure and estimate past global temperatures and CO2 concentrations scientists have used routine measurements,
written records and maybe most importantly various natural archives.
Charles Keeling started measuring CO2 concentrations in Hawaii in 1957. It was then approximately 280 ppm CO2 in
earth’s atmosphere. PPM stands for parts per million, there are 280 carbon dioxide molecules for every molecule of air,
and of those molecules 79% are nitrogen. His data show that carbon dioxide levels in the atmosphere are steadily
increasing in a cyclic manner. The wiggly line illustrating that CO2 concentrations change with the seasons and this can
be explained by higher rates of photosynthesis in the summer in the Northern hemisphere. In 2013 we past 400 ppm!
That is an increase of 43% in half a century.
We do have some written records of historic climate measurements, but natural archives such as sediments, tree rings,
pollen, sea shells, coral reefs and ice cores have proven to be very useful tools in estimating historic temperature and
CO2 concentrations. The most compelling evidence comes from air bubbles in ice cores drilled in Antarctica and
Greenland. These data suggest that carbon dioxide levels in the atmosphere are higher today than they have ever been
before, as can be seen by the red “Mauna Loa” line in the upper right corner of the bottom graph. There is a positive
correlation between atmospheric CO2 concentrations, the red line in the bottom graph, and the average temperatures, the
blue line, throughout the past 400,000 years. The atmospheric CO2 concentration has a significant effect on earth’s
climate.
Additionally, the text book includes a long list of signs that indicate that we are already experiencing global climate
change. We will get back to these measured effects shortly.
© Penn State Biology – BISC 003: Environmental Science
7 So that seems relatively straight forward, but why is global climate change such a complicated problem?
There are other factors in addition to the increase in greenhouse gasses that impact global climate trends.
Sulfate aerosols, either from air pollution or from volcanic eruptions, can have a cooling effect. The oceans are the great
unknown in the climate equation. First they are able to absorb a large amount of CO2, thereby slowing the buildup of CO2
in the atmosphere. As the oceans are getting warmer, water vapor in the atmosphere increases. If the resulting clouds are
low, they may have a cooling effect as heat is reflected, whereas if clouds are high, they will amplify the effect by keeping
heat in.
Ocean currents complicate things further. Increasing ice melts on Greenland and in the Arctic may result in a slowdown of
the Atlantic Ocean currents that carry warm water from the Gulf of Mexico to Europe. This change in ocean current may
actually result in a colder climate in Europe.
Snow and ice melt may magnify the warming effect because of decreased reflection of sunlight. Think of a blacktop in the
spring: as ice and snow melt, a darker surface is exposed and this has a warming effect.
Cosmic factors such as sunspots and Milankovitch cycles may mask, amplify, or depress climate change.
Plants play a role too. Some global climate change skeptics say that the extra CO2 will just act as a plant fertilizer and be
a good thing. And yes, CO2 is a substrate in the photosynthetic reaction and CO2 is occasionally pumped into
greenhouses to increase plant growth. However, the effect in an open, natural setting is not as straight forward. Extra
CO2 may lead to increased growth of some plant species, but the bottom line is that increased growth ultimately will lead
to increased decay and the CO2 will eventually go back into the atmosphere. Especially with deforestation and habitat
destruction we are not likely to have enough biomass to "reabsorb" all the carbon dioxide tied up in coal, oil and gas.
Climate scientists incorporate all these factors, both natural and anthropogenic, into computer models to make predictions
for future climate trends. This is explained well by the "Exploring Science. How do we know that climate change is humancaused?" in the text book
© Penn State Biology – BISC 003: Environmental Science
8 When scientists incorporate all these factors into climate models the predicted temperature for the past century matches
well with what is actually observed. The black line is measured temperature. The grey line represents all factors included
in climate models. The light blue line is anthropogenic or human-caused factors, mostly an increase in atmospheric
greenhouse gasses. When the increase in greenhouse gasses caused by human activities is omitted from climate
models, as seen here with the darker blue line, there is no longer a match between the climate models and the measured
or observed temperature. This is why the large majority of climate scientists now are convinced that humans are
responsible for the overall warming of earth’s climate.
© Penn State Biology – BISC 003: Environmental Science
9 The Effects of Global Climate Change
The possible effects of climate change read like a disaster movie synopsis. The sea level will certainly rise. Think about
where people live; along the coasts in urban areas, and who will suffer the most; the developing nations who are also the
least able to afford to protect themselves against rising sea levels. The CO2 absorbed by the world’s oceans is making
the water more acidic, which poses a challenge for many aquatic organisms. Increasing water temperatures are also
creating problems, especially for coral reefs. On land there is likely to be a change in crop production; models suggest
that the most productive lands will move north. There will also be changes in precipitation. Many climate models forecast
drought over land masses where there is not much fresh water to begin with, including the U.S. Midwest. Other areas,
including Pennsylvania in the winter, will most likely see an increase in precipitation. Another predicted effect is a change
in forest composition. The question is whether trees will be able to move north, through seed dispersal, fast enough to
keep up with the warming. Climate change will put more pressure on biodiversity, resulting in an even greater acceleration
of species extinction. Finally, increases in weather extremes such as tornados, hurricanes, and heat waves are part of
most climate models.
© Penn State Biology – BISC 003: Environmental Science
10 So what is the world doing about the global climate change problem?
Since this is a global problem, international collaboration is essential. The Kyoto protocol is an international treaty signed
by 160 countries, where 37 developed nations committed to cut greenhouse gas emissions by 5% below 1990 levels by
2012. The Kyoto protocol went into effect in 2005. Despite the United States’ leading role in the development of this
treaty, the U.S. senate voted 95 - 0 not to ratify the treaty in a show of unity rarely seen in these days of partisan politics.
One of the arguments against signing the treaty was that the larger developing countries, like China and India, did not
have to commit to reducing their greenhouse gas emissions Add to this that a large portion of the general public does not
want to deal with climate change as it is so hard to comprehend, and many taxpayers do not want to pay for it.
For recent news about international collaboration and agreements in regard to greenhouse gas reductions, do a search
for news from the annual United Nations Climate Change conference.
A cap -and- trade system gives companies permission to release a set amount of CO2. Companies that are able to
reduce their emissions, either through energy conservation or a switch to renewable energy sources, can sell their permits
to companies that emit more than their permit allows. Some countries have carbon taxes added to oil and other fossil
fuels to encourage less use. What do you think of these methods? Are you willing to pay more for your personal CO2
emissions?
In addition to penalizing the use of fossil fuels, incentives, such as tax breaks and governmental subsidies can be used to
encourage renewable energy.
© Penn State Biology – BISC 003: Environmental Science
11 As individuals can contribute by reducing our carbon footprint, you get to calculate your personal carbon footprint in
lesson 12. In the meantime, check out the "What can you do?" section in the text book that outlines how various changes
you can make in your daily life results in reduced CO2 emissions, measured as lbs of CO2 per year.
To reduce the amount of CO2 released from your traveling you can carpool, use public transportation, walk and bike more
and use a fuel efficient vehicle. By eating less meat and more locally produced food you will limit your emissions. And as
previously discussed, at home there are many ways you can conserve energy. Remember that a large percentage of our
electricity is produced by burning coal. We can also consider using more renewable energy sources at home, either
through a green electricity provider or by installing small renewable energy systems.
Around the world there are an increasing number of countries, individual states, cities, businesses, non-profit
organizations, and individuals that are taking action to reduce CO2 emissions. As Mahatma Gandhi said, "You must be
the change you wish to see in the world."
© Penn State Biology – BISC 003: Environmental Science
12 This is part 2 of lesson 11, Air Pollution – Past and Future Trouble. We started with future troubles, global climate change
and will now continue with other air pollution problems, many of whom improvements have been made and the current
situation is better than the past.
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Let us compare the carbon dioxide/climate change story with the chlorofluorocarbons/ozone story. What is ozone
anyway? Ozone is triplet oxygen with chemical formula O3 . Most atmospheric oxygen is in the form of O2, two oxygen
atoms forming one molecule. Ozone is a highly reactive, "unhappy" molecule that oxidizes other compounds. At ground
level, ozone is a bad thing. In the lower atmosphere, it is out of place and causes trouble for people, plants, and materials.
In the upper atmosphere (above troposphere ~15 miles up) there is a "layer" of ozone, or maybe more accurately a zone
of ozone. In this area, ozone is a very good thing, as it acts as a protective agent and screens out ultra violet radiation. UV
radiation is higher energy radiation that can damage cells.
Ozone is essentially self-sustaining-it absorbs UV radiation while regenerating itself. 99% of the UV radiation from the sun
never reaches the surface of the earth because of the ozone layer.
What is the problem with CFCs? CFCs are chlorofluorocarbons, essentially a solution to a problem that became a
problem. These compounds were and are extraordinarily useful and stable molecules that were used as a coolant, a
solvent, a cleaner, in the production of styrofoam and as an aerosol propellant. They were heralded as a godsend. They
replaced ammonia and other toxic coolants in refrigerators and cooling systems. At ground level, CFCs do not break
down; they do not react with other compounds, do not dissolve in water, and are in the form of gas at room temperature-so there is no trouble with bioaccumulation. Unfortunately, the stability of these molecules was the downfall. What is the
fate of CFCs under extreme conditions?
Two California chemists, Sherwood Rowland and Mario Molina, speculated on the fate of CFCs in the upper atmosphere.
Even though at ground level no problems with CFCs were expected, they wanted to know what would happen when these
compounds were exposed to UV radiation. Herein lay the problem: UV radiation is capable of breaking down CFCs. When
exposed to ultraviolet radiation, CFCs break down and liberate a "naked" chlorine atom that is highly reactive. These
reactive chlorine atoms react with ozone, disrupting the cycle by bleeding off O3 such that ultimately, O3 is lost and the
layer thins. In 1974, as a result of the work of Rowland and Molina, the suggestion was raised that CFCs be banned.
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The loss of ozone ultimately means that more UV radiation will hit the earth's surface. For humans, this means increasing
rates of skin cancer and cataracts. Though there is a long time lag between exposure and manifestation, high exposure to
UV can lead to the most common types of skin cancer. We can protect ourselves to a certain extent (clothes, sunscreen,
sunglasses), but other organisms cannot. Any organism's tissue can be damaged because UV radiation does cause
mutations. Plants may be more sensitive than animals. From the direct destruction of phytoplankton to the stunted growth
of angiosperms, photosynthetic organisms will not know what hit them. Plants could be exposed to UV levels unseen in
evolutionary history, and though plants are amazing as you well know, they have only limited defenses for increased UV.
What happened with the rest of the story? By 1979, CFCs were banned as aerosol propellants primarily due to consumer
pressure. By 1984, analysis of satellite data detected thinning of the ozone layer over Antarctica with a 40-50% loss of
ozone on a seasonal basis. The poles are particularly sensitive to depletion of ozone due to long, dark winters. By 1987,
the Montreal Protocol was signed by 36 nations, who agreed to cut CFC emissions. The treaty was further expanded in
1990 and 1992 to phase out production of CFCs. Though there are some problems with cheating and black market
trading of CFCs, global production has dropped dramatically. Scientists are predicting that the ozone layer will be restored
in about 50 years, a great success story.
Why was world cooperation possible in this case, whereas carbon dioxide and climate change is such a battle?
Data is much easier to interpret: the CFC/ozone chemistry is much easier to comprehend than climate trends.
Less economic impact: though the chemical companies kicked and screamed, so to speak, CFCs are not as pervasive in
day to day life as carbon dioxide from fossil fuels is.
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Smogs and What They Are Made Of
Smog, another air pollution problem, has been around since humans starting burning things, but it was not until the
Industrial Revolution that we gave it a name. "Smog" is a fusion of smoke and fog, a term first used to describe the
industrial smoke of cold industrial cities. Industrial smog originates primarily from stationary sources, such as coal fueled
power plants and heavy industry, and is made of sulfur dioxide and suspended particles. Industrial smog is the first
historical smog, and the one that has directly killed the most people.
The problem with smog is that it is magnified by thermal inversions. Under normal conditions, there is an atmospheric
temperature gradient. Warm air at ground level and cooler air above sets up convection currents that dilute air pollutants.
During a thermal inversion, this is turned on its head. During such an event, a high pressure system or a cool ocean
breeze sends in a layer of cool air that displaces the normally warm ground level air. The cool air is trapped under a warm
air lid, which leads to decreased convection currents--and most pollutants are then trapped at ground level. It was such an
event that led to the death of 20 people in Donora, Pennsylvania in 1948. This event was caused by industrial smog from
a smelter and home heating with coal, combined with a thermal inversion. Similar inversions can occur on a daily basis in
the hot summer months in basin cities like Los Angeles and Mexico City.
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The more prevalent type of smog in the United States today is photochemical smog. Unlike industrial smog,
photochemical smog is mostly from mobile sources; cars and planes. It is a mixture of secondary air pollutants. The
process starts with nitrogen dioxide (a result of nitrogen compounds in oil burned at high temperature). This compound is
a yellow to brown gas that irritates eyes. This gas can react with UV light from the sun to make nitrogen oxide (NO) and
singlet oxygen (O). Singlet oxygen can go on to produce ozone when it reacts with atmospheric O2 and PAN (peroxyacyl
nitrates) and aldehydes when it reacts with volatile organic compounds (VOCs).
Ozone, a major component in photochemical smog, is a health concern, especially for those with respiratory problems.
Although some areas in the US have seen a decrease in tropospheric ozone concentrations over the last couple decades,
it is still very much a concern. It is not uncommon to have ozone or air quality alert days in the major cities in the United
States during the summer. Tropospheric ozone also affects plants. The loss in soybean yield due to ozone damage was
estimated to 2 billion dollars in 2009 in a study done by the USDA. When it comes to ozone remember: "Good up there;
bad down here."
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Cleaning Up Our Act
The atmosphere you breathe today in the United States is better because of the Clean Air Act of 1970. Initially, standards
were set to address industrial smog, but these have been expanded and modified to try to address photochemical smog
as well. The Act established criteria pollutants: sulfur dioxide, carbon monoxide, particulates, hydrocarbons, nitrogen
oxides, photochemical oxidants and lead-here is where you see that carbon dioxide is not classified as a pollutant. The
Clean Air Act also set new source performance standards for power plants that led to taller smoke stacks (to dilute the
emissions), a reduction in the use of high sulfur coal, and a dramatic reduction in particulate emissions (scrubbers and
filters: removal prior to release).
As a result of the Clean Air Act, the air quality in the U.S. has improved, but there is still room for improvement.
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Acid deposition or acid rain is the last air pollution problem we will discuss. As you know by now, most electricity in the
United States is generated in coal burning plants. Though the particulates are substantially lower as a result of the Clean
Air Act, power plants still release large quantities of sulfur dioxide and nitrogen oxides. When sulfur dioxide or nitrogen
dioxide dissolves in atmospheric water, it acidifies this water through the production of sulfuric acid and nitric acid
respectively. This then leads to acid deposition or acid rain, often far away from the original pollution source. An acid is a
compound that, when dissolved in water, releases hydrogen ions and lowers the pH of the solution. Acids are corrosive,
and they react with various materials and damage them. Most organisms prefer a pH of about 6 to 8, basically hovering
around neutral pH. Any deviation from this can be problematic.
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Aquatic ecosystems are particularly sensitive to pH changes. This makes sense, as aquatic organisms would be
continuously bathed in an acid solution. Beyond aquatic systems, acid deposition impacts trees and plant life, particularly
confers or needle trees. The most damage is in areas with thin, already acidic soils in that such soils are unable to buffer
pH changes. Beyond the pH effect, acids alter nutrient and toxic salt mobility, resulting in damage to sensitive plants. The
effects include a decrease in root growth (often, roots see the first effects), defoliation (loss of leaves), and a generalized
reduced growth and vigor. Acid deposition can also damage human structures, particularly stone structures like limestone
and marble. In an acid solution, such minerals become soluble and wash away.
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To summarize, an increase in greenhouse gas emissions and the resulting change in global climate is the biggest air
pollution problem we are faced with today. Although the climate change problem may seem overwhelming and daunting,
we have solved many air pollution problems in the past. With continued scientific research, economic incentives for
change, a society and government that are willing to take action and international collaboration I believe it is still possible
to slow down our greenhouse emissions and avoid the most drastic changes in earth’s climate.
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