Download Chapter 9 Air: Climate and Pollution

Chapter 9
Air: Climate
and Pollution
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
“Troposphere, whatever, I told you
before I’m not a scientist. That’s why
I don’t want to have to deal with global
warming, to tell you the truth.”
--Supreme Court Justice Antonin Scalia,
(while deciding EPA's responsibility to regulate CO2)
9-2
CASE STUDY: When Wedges do
More than Silver Bullets
9-3
9.1 What is the Atmosphere?
• Earth’s atmosphere consists of gas molecules, mostly
nitrogen and oxygen and a variety of other trace gases,
about 300 mi above the earth's surface.
• Minute particles and liquid droplets—collectively called
aerosols—also are suspended in the air.
• The atmosphere has four distinct zones of contrasting
temperature, due to differences in absorption of solar
energy.
• The layer closest to the earth’s surface, the troposphere,
experiences daily temperatures changes, wind, and
precipitation that we collectively call weather.
9-4
4 Distinct Zones of the Atmosphere
• Within the troposphere,
air circulates in great
vertical and horizontal
convection currents.
• The stratosphere has
almost no water vapor
and nearly 1,000 times
more ozone (O3).
9-5
Convection Cells Circulate
Air, Water Vapor and Heat
9-6
The Atmosphere Captures
Energy–Selectively
• The sun supplies the Earth with abundant energy,
especially near the equator.
• Of the solar energy that reaches the outer
atmosphere:
• ¼ is reflected by clouds and atmospheric gases
• ¼ is absorbed by carbon dioxide, water vapor, ozone,
methane, and a few other gases.
• ½ of incoming solar radiation (insolation) reaches the
Earth’s surface.
9-7
The Sun Warms Our World
9-8
The Greenhouse Effect
• Following the second law of thermodynamics,
absorbed energy is gradually reemitted as lowerquality heat energy.
• A brick building, for example, absorbs energy in
the form of light and reemits that energy in the
form of heat.
• This phenomenon is called the greenhouse effect
because the atmosphere, loosely comparable to
the glass of a greenhouse, transmits sunlight
while trapping heat inside.
9-9
Ocean Currents Also Modify
Our Climate
9-10
9.2 Climate Changes Over Time
• How stable is climate? That depends upon the time
frame you consider. Over centuries and millennia, we
know that climate shifts somewhat, but usually we
expect little change on the scale of a human lifetime.
• The question now is whether that is a reasonable
expectation.
• If climate does shift, how fast might it change, and
what will those changes mean for the environmental
systems we depend on?
9-11
Correlation Between Historic CO2
Levels and Historic Temperatures
12
What Causes Natural Climatic Swings?
• Modest climate
changes correspond
to an 11-year cycle
in the Sun’s intensity
called Milankovitch
Cycles.
• These cycles are
caused by changes in
the Earth’s orbit,
rotation and the
wobble of its axis.
9-13
The El Niño/Southern Oscillation
Can Have Far-reaching Effects
• The climate also changes
according to oscillations in
the ocean and atmosphere.
• El Niño/ Southern
Oscillation (ENSO) is the
most famous.
• ENSO affects weather
throughout the Pacific,
causing heavy monsoons or
serious droughts.
9-14
How Do We Know the Climate is
Changing Faster than Usual?
• Many scientists consider anthropogenic (humancaused) global climate change to be the most
important environmental issue of our times.
• The first evidence that human activities are
increasing atmospheric CO2 came from an
observatory on Mauna Loa volcano in Hawaii.
• Measurements show CO2 levels increasing about
0.5% per year since 1958.
15
CO2 and Temperature Readings From
Mauna Loa Volcano in Hawaii
9-16
Scientific Consensus is Clear
• Because the climate is so complex, climate scientists
worldwide collaborated in collecting and sharing
data, and in programming models to describe how
the climate system works.
• Evidence shows minor differences among models,
but no disagreement about the direction of change.
• The evidence shows unequivocally, that climate is
changing, and the global average temperature is a
warming.
9-17
What is the IPCC?
• The most comprehensive effort to describe the state
of climate knowledge is that of the
Intergovernmental Panel on Climate Change (IPCC).
• The IPCC brings together scientists and government
representatives from 130 countries with the aim to
review scientific evidence on the causes and likely
effects of climate change.
• In 2007, the IPCC issued its 4th Assessment Report.
The conclusion is a 90% certainty that observed
climate change is caused by human activity.
• Subsequent reports raised that to a 99% certainty.
9-18
Changes in Heat Waves, Sea Level,
and Storms are Expected
• Observations since 2007 show that all the IPCC scenarios were too
conservative – Greenhouse gas emissions, temperature rises, sea level, and
energy use have accelerated faster than IPCC projections.
• Droughts, floods, crop failure, and waves of refugees may result.
9-19
Evidence of Climate Change is
Overwhelming
• Over the last century, the average global temperature has
climbed about 0.6 degree C (1 degree F).
• Permafrost is melting; houses, roads, pipelines, sewage
systems, and transmission lines are being damaged as the
ground sinks beneath them.
• Arctic sea ice is only half as thick now as it was 30 years ago.
• Alpine glaciers everywhere are retreating rapidly.
– Mount Kilimanjaro has lost 85 percent of its famous ice cap since
1915.
• The higher levels of CO2 being absorbed are acidifying the
oceans, and could have adverse effects on sea life.
9-20
Evidence continued…
• Sea level has risen worldwide approximately 15–20 cm
(6–8 in.) in the past century.
• Satellite images and surface measurements show that growing
seasons are now as much as three weeks longer in a band
across northern Eurasia and North America than they were 30
years ago.
• Droughts are becoming more frequent and widespread.
• Biologists report that many animals are breeding earlier or
extending their range into new territory as the climate
changes. Others are dying out because their environment is
changing.
• Coral reefs worldwide are “bleaching,” losing key algae and
resident organisms.
9-21
Policy Makers Have Made Little
Progress in Finding Solutions
• Climate control is a classic free-rider problem, in
which nobody wants to take action for fear that
someone else might benefit from their sacrifices.
• Climate scientists point out that shifting our energy
strategy from coal to wind, solar, and greater
efficiency, could produce millions of new jobs and
save billions in health care costs associated with coal
burning.
9-22
The Main Greenhouse Gases are
CO2, CH4, and N2O
• Carbon dioxide is by far the most important of these
because of its abundance, and because it lasts for
decades or centuries in the atmosphere.
• If current trends continue, CO2 concentrations could
reach about 500 ppm (approaching 2X the preindustrial level of 280 ppm) by the end of the 21st
century.
9-23
Contributions to Global Warming
From Different Gases
9-24
Controlling Emissions is Cheap
Compared to Climate Change
• A 2010 study by the Pew Trust estimates the cost of lost
ecological services by 2100. Costs included factors such as
lost agricultural productivity from drought, damage to
infrastructure from flooding and storms, lost biological
productivity, health costs from heat stress, and lost water
supplies.
• The Pew report found that climate change is likely to cost
between $5 trillion and $90 trillion by 2100.
• The Stern report estimates a cost of only about 1% of
global GDP to avoid the worst impacts of climate change.
9-25
Responses to Disputes
Over Climate Change
• Climate scientists offer the following responses to
some of the claims in the popular media:
– Reducing climate change requires abandoning our current
way of life (no, but it does require that we use different
energy sources).
– There is no alternative to current energy systems (Europe
and China are showing this to be false).
– A comfortable lifestyle requires high CO2 output (data show
this is false).
– Natural changes such as solar variation can explain
observed warming (changes are slight and do not coincide
with the climate changes observed).
9-26
Responses to Disputes
Over Climate Change
– The climate has changed before, so this is nothing new
(Today’s CO2 level exceeds anything the Earth has seen).
– Temperature changes are leveling off (True on short time
frames sometimes, but over decades the trends in surface
air temperatures and in sea level continue to rise).
– We had cool temperatures and snowstorms last year, not
heat and drought (Regional differences in temperature and
precipitation trends are predicted by climate models).
– Climate scientists don’t know everything, and they have
made errors and misstatements (fraud in data collection is
almost unheard of in science).
9-27
9.4 Envisioning Solutions
• Former president Bill Clinton has argued that
combating climate change doesn’t have to mean
economic hardship.
• It could be the biggest development stimulus since
World War II, creating millions of jobs and saving
trillions of dollars in foreign fuel imports.
• What are some of the strategies we have available?
9-28
There Are Many Ways We Can
Control Greenhouse Emissions
• We can reduce dependence on coal, which produces
more CO2 per energy unit than any other fuel.
• We could institute fees for selling fossil fuels–these
would help fossil fuel prices represent their many
hidden costs.
• We can invest in new technologies and energy
efficiency.
• We can institute emissions trading, by instituting a
legal cap on emissions, then allowing companies to
buy and sell shares of that total cap.
9-29
International Protocols Have Tried
to Establish Common Rules
• In 1992 The United Nations Earth Summit meeting in
Rio de Janeiro set an objective of stabilizing
greenhouse gas emissions.
• In Kyoto, Japan, in 1997, 160 nations agreed to roll
back CO2, methane, and nitrous oxide emissions
about 5 percent below 1990 levels by 2012, but
China and India were exempted from the agreement
and the U.S. never ratified this agreement.
• The 2009 Copenhagen climate conference had little
more immediate success than did Kyoto.
9-30
A Wedge Approach Could Fix the
Problem
• Accomplishing just half
of these wedges could
level off our emissions.
• Accomplishing all of
them could return to
levels well below those
envisioned in the Kyoto
protocol.
31
Local Initiatives Are Everywhere
• Britain has already started to substitute natural gas
for coal, promote energy efficiency in homes and
industry, and raise its already high gasoline tax.
• New Zealand Prime Minister Helen Clark pledged
that her country will be the first to be “carbon
neutral”.
• Germany has reduced its CO2 emissions at least 10
percent by switching from coal to gas and by
encouraging energy efficiency throughout society.
• Denmark now gets 20% of its electricity from
windmills.
32
Can We Control Carbon Better?
• It is possible, though expensive, to store CO2 by
injecting it deep into geologic formations.
• Around the world, deep, briny aquifers could store a
century’s worth of CO2 output at current fossil fuel
consumption rates.
9-33
9.5 Air Pollution
9-34
We Describe Pollutants
According to Sources
• In the U.S., principal pollutants are identified and
regulated by the Clean Air Act of 1970.
• A point source is a smokestack or some other
concentrated pollution origin.
• Primary pollutants are released in a harmful form.
• Secondary pollutants become hazardous after
reactions in the air.
• Fugitive or nonpoint-source emissions are those
that do not go through a smokestack.
9-35
What are Criteria Air Pollutants?
• Conventional or criteria pollutants are a group of
seven major pollutants (sulfur dioxide, carbon
monoxide, particulates, volatile organic compounds,
nitrogen oxides, ozone, and lead) that contribute the
largest volume of air-quality degradation and are
considered the most serious threat of all air
pollutants to human health and welfare.
• Transportation and power plants are the dominant
sources of most criteria pollutants.
9-36
Anthropogenic Sources of
Criteria Air Pollutants
9-37
Unconventional Pollutants
• The EPA also monitors unconventional pollutants,
compounds that are produced in less volume than
conventional pollutants, but that are especially toxic
or hazardous.
• Among these are asbestos, benzene, beryllium,
mercury, polychlorinated biphenyls (PCBs), and vinyl
chloride.
• In 2009, the EPA announced that it would add CO2
and other greenhouse gases to its list of regulated
pollutants. This decision remains controversial.
9-38
Indoor Air Can Be More Dangerous
Than Outdoor Air
9-39
Dust Blowing From the Sahara
• Dust from North Africa
regularly crosses the
Atlantic and
contaminates the air in
Florida and the
Caribbean Islands.
• This dust can carry
pathogens and is
thought to be the source
of diseases attacking
Caribbean corals.
9-40
Ozone in the Stratosphere is
Harmed by CFCs
• Antarctica’s
exceptionally cold
winter temperatures
help break down
ozone.
• During the Antarctic
spring, conditions are
ideal for rapid ozone
destruction.
9-41
CFC Control has Shown
Remarkable Success
• In 1987 an international meeting in Montreal,
Canada, produced the Montreal Protocol, the first of
several major international agreements on phasing
out most uses of CFCs by 2000.
• As evidence accumulated, showing that losses were
larger and more widespread than previously thought,
the deadline for the elimination of all CFCs was
moved up to 1996.
• CFCs are now being removed from the atmosphere
more rapidly than they are being added.
9-42
Success of the Montreal Protocol
9-43
Urban Cities Create
Heat Islands
• Heat islands occur in cities.
• Concrete and brick surfaces in cities absorb large
amounts of solar energy. A lack of vegetation or water
results in very slight evaporation; instead, available
solar energy is turned into heat.
• As a result, temperatures in cities are frequently 3–5
degrees Celsius warmer than in the surrounding
countryside, a condition known as an urban heat island.
9-44
9.7 Effects of Air Pollution
• Polluted air is unhealthy
– Consequences of breathing dirty air include increased
probability of heart attacks, respiratory diseases, and lung
cancer.
• Plants are sensitive to pollutants
– In the early days of industrialization, fumes from furnaces,
smelters, refineries, and chemical plants often destroyed
vegetation and created desolate, barren landscapes
around mining and manufacturing centers.
9-45
Acid Precipitation Kills Vegetation
9-46
Acid Precipitation Over the
United States
9-47
Effects continued…
• Smog and haze reduce visibility
– Grand Canyon National Park, where maximum visibility used
to be 300 km (185 mi), is now so smoggy on some days that
visibility is only 20 km (12.5 mi) across the canyon.
9-48
Buildings and Monuments
Show Clear Damage
• Air pollution is destroying
some of the oldest and
most glorious buildings
and works of art.
• Smoke and soot coat
buildings, paintings, and
textiles.
• Acids dissolve limestone
and marble, destroying
features and structures of
historic buildings.
9-49
9.8 Air Pollution Control
• Particulate removal involves filtering air emissions.
Filters trap particulates in a mesh, or electrostatic
precipitators are used.
• Sulfur removal is important because sulfur oxides are
among the most damaging of all air pollutants in
terms of human health.
• Nitrogen oxides (NOx) can be reduced in both
internal combustion engines and industrial boilers.
• Hydrocarbon controls mainly involve complete
combustion or the control of evaporation.
9-50
Clean Air Legislation is Controversial
• The Clean Air Act of 1963 was the first national
legislation in the United States aimed at air pollution
control.
• In 1970, an extensive set of amendments essentially
rewrote the Clean Air Act.
• A 2002 report concluded that simply by enforcing
existing clean air legislation, the United States could
save at least another 6,000 lives per year and prevent
140,000 asthma attacks.
9-51
Cap and Trade Agreements are
One Way to Control Air Pollution
• A cap-and-trade approach sets maximum emission
levels for pollutants.
• Facilities can then buy and sell emission “credits,” or
permitted allotments of pollutants.
• Companies can decide if it’s cheaper to install
pollution control equipment or to simply buy
someone else’s credits.
• Cap-and-trade has worked well for sulfur dioxide.
9-52
9.9 Current Conditions and
Future Prospects
• Although the United States has not yet
achieved the Clean Air Act goals in many parts
of the country, air quality has improved
dramatically.
• The outlook is not so encouraging in other
parts of the world.
9-53