Download Chapter 12

Climate Change, Ozone
Loss and Air Pollution
Chapter 12
Key Concepts
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Components of Earth’s atmosphere
Changes in Earth’s climate over time
Possible effects of global warming
Adapting to climate change
Human impacts on the ozone layer
Protecting and restoring the ozone layer
Troposphere
• Where weather happens
• Location - surface to about 10 km.
• Composition - unpolluted air: Nitrogen
(78%) Oxygen (21%). Remaining 1% is
CO2 (0.0365%), H, He, Ar.
– Water vapor is an additional variable
amount, .01% to 5%.
Stratosphere
• Where jets fly (at the bottom of it)
• Location - Above troposphere, about 1050 km. Very thin air - virtually no weather,
and no turbulence.
• Composition- Similar to troposphere,
except
– water vapor is 1000 x less
– ozone is 1000 x greater.
Climate and Weather
• Climate = long-term atmospheric
conditions
• Weather = short-term atmospheric
conditions
• Both climate and weather are dynamic –
they change with time
The Greenhouse Effect
Greenhouse gases
• Carbon Dioxide - fossil fuel burning, land
clearing/burning.
• Methane - Breakdown of organic material
by anaerobic bacteria.
• Nitrous Oxide - Biomass burning,
automobile exhaust.
• Ozone – automobile exhaust
• Chlorofluorocarbons - Refrigerants,
cleaning solvents, propellants.
CO2 measurements
Evidence for Climate Change
1. 20th C was hottest in the past 1000 years
2. Global temp has risen 0.6°C (1.1°F) since
1861
3. 16 warmest years on record since 1980, 10
warmest since 1990
4. Glaciers and sea ice are melting
5. Sea level has risen 100-200 cm over 20th C
Projecting Future Changes in Earth’s
Climate
We can’t do real experiments on the whole
earth’s climate, so how do we predict
future climate change?
• Scale up from small experiments
• Computer models (GCMs)
• Learn from the past
– Paleoclimatology and Paleoecology
Past Climate Changes
CO2 and temperature from ice cores
Paleoecology: biological responses
to past climate change
Projected future global warming
Biological responses to potential
future climate change
Ocean currents “conveyor belt”
Some Possible Effects of a
Warmer World
• See figure
12-10
Solutions: Dealing with the Threat
of Climate Change
Options
• Do more research before acting
– “wait and see” (current US
strategy)
• Act now to reduce risks
because global warming would
have severe impacts
• Act now in same way to reduce
risks of global warming
because it has other benefits to
environment and society (even
if warming doesn’t happen)
Removing CO2 from the Atmosphere
Reducing Greenhouse Gas Emissions
• 1988 - Intergovernmental Panel on Climate Change
(IPCC) established, body of scientists advising UN
on climate change
• 1997 - Representatives of 161 nations met in
Kyoto, Japan for a UN meeting on climate change
• Kyoto Protocol - agreement reached during meeting
to reduce CO2 emissions from 39 developed
countries to 5.2% below 1990 levels by 2012.
• 2001 US pulled out of the agreement.
• Russia’s recent ratification was enough for the
Kyoto Protocol to take effect.
• Will there be a new post-Kyoto treaty?
Ozone in the Stratosphere: the “Ozone
hole”
• Ozone (O3) in the
stratosphere
protects life on the
surface of the earth
from harmful UV
solar radiation.
CFCs
• Chlorofluorocarbons (CFCs) and related
chemicals break down ozone in
stratosphere
• Uses (mostly phased out)
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Air Conditioners
Refrigerators
Spray cans
Cleaners for electronic parts
Sterilizing medical instruments
Fumigants for granaries and cargo ships
Ozone Depletion in the Stratosphere
Seasonal Ozone Layer Thinning at the Poles
Credit: © Science VU/NASA/Visuals Unlimited
Large Antarctic Ozone hole three times the size of the United States. September, 2000.
Loss of the Ozone Layer:
Reasons for Concern
• Increased incidence and severity of
sunburn
• Increase in eye cataracts
• Increased incidence of skin cancer
• Immune system suppression
• Increase in acid deposition
• Lower crop yields and decline in
productivity
Skin Cancers
Solutions: Protecting the Ozone Layer
• CFC substitutes
• Montreal Protocol 1987
• Copenhagen Protocol 1992
• both signed by 177 countries
• CFCs take 10-20 years to get to the
stratosphere
• CFCs take 65-385 years to break down
Future CFC concentrations
Air Pollution
Key Concepts
• Structure and composition of the
atmosphere
• Types and sources of outdoor air pollution
• Types, formation, and effects of smog
• Sources and effects of acid deposition
• Effects of air pollution
• Prevention and control of air pollution
Outdoor Air Pollution
• Primary - Released directly from planet’s surface. Dust,
smoke particles, Nitrogen, Carbon etc.
• Secondary - Formed when primary pollutants react or
combine with one another, or basic elements.
Primary Air Pollutants
Carbon Monoxide—Produced when organic
materials are incompletely burned.
• Single largest source is the automobile.
• Not a persistent pollutant.
• Binds to hemoglobin in blood and makes
the hemoglobin less able to carry oxygen.
• Most dangerous in enclosed spaces.
• Cigarette smoking an important source.
Primary Air Pollutants
Volatile Organic Compounds
• Hydrocarbons - Group of organic
compounds consisting of carbon and
hydrogen.
– Evaporated from automobile fuel or remnants
of fuel incompletely burned.
– Catalytic converters used to burn exhaust
gases more completely.
Primary Air Pollutants
Particulates—Minute pieces of solid
materials dispersed into the atmosphere
(<10 microns).
• Smoke, Asbestos, Dust, Ash
• Can accumulate in lungs and interfere with
the ability of lungs to exchange gases.
Primary Air Pollutants
Sulfur Dioxide (SO2)—Sulfur and oxygen compound
produced when sulfur-containing fossil fuels are
burned.
• Burning coal is primary artificial source
• Volcanoes and hot springs are natural sources
• Mt St Helens releases 50 to 250 tons/day when
active
• Steam Plant recently: 200 tons/day
• After scrubbers installed (cost $250 million): 27
tons/day
• SO2 is also a precursor to acid rain (a secondary
Primary Air Pollutants
• Nitrogen Oxides (NO, NO2)—Formed
when combustion takes place in the air.
– Automobile exhaust is primary source.
– NOx is also a precursor to acid rain and
photochemical smog (both secondary
pollutants) and is a greenhouse gas
Secondary Air Pollutants
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Ozone (O3)
PANs (Peroxyacetyl nitrate)
Aldehydes
all three formed by interaction between
NOx and VOCs.
• Note: - Ozone is a pollutant in the
troposphere, but natural and beneficial in
the stratosphere.
Photochemical Smog
• Brown-air smog
• Some primary
pollutants react under
the influence of
sunlight
(photochemical
reaction), including
NOx, O3, PANs.
Corrosive, irritating.
• Common in urban
areas of the west US:
cars + sun +
mountains.
Credit: © John D. Cunningham/Visuals Unlimited
Los Angeles smog.
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Industrial Smog
• Gray-air smog
• From burning coal and oil
(particulates, sulfur
dioxide, sulfuric acid).
• London was the smog
capitol. In 1952, smog
developed for days, no
atmospheric mixing, 4,000
people died.
• Now mainly a problem in
LDCs with developing
industries and no pollution
control laws.
Thermal inversion
• warm air normally near surface, pollutants
disperse as air rises and mixes
• when cool air trapped under warm air, confined
by mountains, pollutants do not disperse,
intensify with time
Regional Outdoor Air Pollution from
Acid Deposition
• Wet deposition
• Dry deposition
Acid Deposition in the US
Acid Deposition and Humans
• Respiratory diseases
• Toxic metal leaching
• Damage to structures, especially
containing calcium carbonate
• Decreased visibility
• Decreased productivity and
profitability of fisheries, forests, and
farms
Acid Deposition and Aquatic Systems
• Fish declines
• Aluminum toxicity
• Acid shock
Acid Deposition, Plants, and Soil
• Nutrient
leaching
• Heavy metal
release
• Weakens trees
Credit: © Rob & Ann Simpson/Visuals Unlimited
Acid rain-damaged Fraser Fir and Red Spruce trees. Mt. Mitchell State Park, North Carolina.
Solutions to Acid Deposition
Indoor Air Pollution
Radon
• Radioactive radon222
• Lung cancer threat
• Occurs in certain
areas based on
geology
• Associated with
uranium and organic
material in rock
Effects of Air Pollution on People
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Respiratory diseases
Asthma
Lung cancer
Chronic bronchitis
Emphysema
Premature death
Clean Air Act
(1967, 1970, 1977, 1990)
• Series of detailed control requirements the
federal government implements and states
administer.
– All sources subject to ambient air quality regulation.
– New sources subject to more stringent controls.
– Visibility reducing emissions regulated.
• Since passage, EPA reports air pollution cut by
1/3 and acid rain cut by 25%.
• EPA estimates benefits to human and
environmental health outweigh costs 40:1.
National Ambient Air Quality Standards
• NAAQS established for six pollutants:
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Sulfur Dioxide
Nitrogen Oxides
Particulate Matter
Carbon Monoxide
Ozone
Lead
• Experts say two other important pollutants
should be listed:
– Volatile Organic Compounds
– Carbon Dioxide
Control of Air Pollution
• Industrial Activities
– Scrubbers
– Precipitators
– Filters
• Sulfur Removal
– Switch to low-sulfur fuel.
– Remove sulfur from fuel before use.
– Scrubbing gases emitted from smokestack.
So what is in your car’s exhaust?
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CO
CO2
NOx
VOCs
PM
And can lead to formation of secondary
pollutants
Emission Reduction
Reducing Motor Vehicle Air
Pollution
Reducing Indoor
Air Pollution