Climate Change, Ozone Loss and Air Pollution

Chapter 12

Key Concepts

• 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 10-50 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

• 20th C was hottest in the past 1000 years

• Global temp has risen 0.6°C (1.1°F) since 1861

• 16 warmest years on record since 1980, 10 warmest since 1990

• Glaciers and sea ice are melting

• 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)

• Air Conditioners

• Refrigerators

• Spray cans

• Cleaners for electronic parts

• Sterilizing medical instruments

• Fumigants for granaries and cargo ships

Ozone Depletion in the Stratosphere

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 pollutant)

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

• 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.

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

Solutions to Acid Deposition

Indoor Air Pollution

Radon

• Radioactive radon-222

• Lung cancer threat

• Occurs in certain areas based on geology

• Associated with uranium and organic material in rock

Effects of Air Pollution on People

• 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:

– 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?

• CO

• CO2

• NOx

• VOCs

• PM

• And can lead to formation of secondary pollutants

Emission Reduction

Reducing Motor Vehicle Air Pollution

Reducing Indoor