Chapter 21

Global Warming and Ozone Loss

An Enormous Cloud of Air Pollutants and Ash from Mt. Pinatubo on June 12, 1991

Global Warming and Global Cooling

Are Not New (1)• Over the past 4.7 billion years the climate has been

altered by– Volcanic emissions– Changes in solar input– Movement of the continents– Impacts by meteors

• Over the past 900,000 years– Glacial and interglacial periods

Global Warming and Global Cooling

Are Not New (2)• Over the past 10,000 years

– Interglacial period

• Over the past 1,000 years– Temperature stable

• Over the past 100 years– Temperature changes; methods of determination

Fig. 19-2, p. 498

Stepped Art

Our Climate, Lives, and Economies Depend on the Natural Greenhouse

Effect• Without the natural greenhouse effect

– Cold, uninhabitable earth

Science: Ice Cores Are Extracted by Drilling Deep Holes in

Ancient Glaciers

Human Activities Emit Large Quantities of Greenhouses Gases

(1)• Since the Industrial Revolution

– CO2, CH4, and N2O emissions higher

– Main sources: agriculture, deforestation, and burning of fossil fuels

• Correlation of rising CO2 and CH4 with rising global temperatures

• Countries with the largest CO2 emissions

Fig. 19-4, p. 500

Stepped Art

A. Major Greenhouse Gases: H2O, CO2, CH4, N2O, CFC’s

1. p465, graphs (y-axis: ppm)

a) CO2 and temperature change

1) fluctuation due to more photosynthesis in

summer

b) methane and nitrous oxide concentrations

have dramatically increased also

c) Methane

1) from landfills, anaerobic decompositiion (swamps, rice paddies, termites, cows), leaks in pipeline

2) 25X more effective than CO2 per molecule (why is CO2 most important greenhouse gas?) 3) last 9-15 years in troposphere 4) methane hydrate (stable complex below tundra)

d) nitrous oxide (NO2) 1) traps heat in troposphere and depletes ozone in stratosphere 2) released from nylon production, burning biomass and coal, breakdown of nitrates (fertilizer, waste)

3) 230 X more effective than CO2 per molecule 4) lasts 120 years

perfluorcarbons (CF4) are also greenhouse gases (from Al production)

CO2 Emissions

B. Developed countries produce 60% of CO2 emissions from human activities

(mostly from fossil fuels)

1. U.S. = 25%, China, EU ,

Indonesia, Russia ,

Japan , India

The Atmosphere Is Warming Mostly Because of Human

Activities (1)• Intergovernmental Panel on Climate Change

(IPCC)– 90–99% likely that lower atmosphere is warming– 1906–2005: Ave. temp increased about 0.74˚C– 1970–2005: Annual greenhouse emissions up 70%– Past 50 years: Arctic temp rising almost twice as fast

as the rest of the earth– Melting of glaciers and floating sea ice– Prolonged droughts: increasing– Last 100 years: sea levels rose 10–20 cm

Computer models predict greenhouse warming

1. most sophisticated climate models are general circulation models (GCM)

a) take greenhouse gases, ocean circulation, aerosols from volcanoes and from pollutants

b) one idea shows a series of models in sequence, starting with greenhouse effect

Fig. 19-A, p. 502

Sun

Troposphere

Cooling from increase

Aerosols Greenhouse gases Warming

from decrease

CO2 removal by plants and soil organisms

CO2 emissions from land clearing, fires, and decay

Heat and CO2 removal

Heat and CO2 emissions

Ice and snow cover

Shallow ocean

Land and soil biotaLong-term storageNatural and human emissions

Deep ocean

Antarctica

GreenlandGreenland

Figure 18-14Page 458

Ocean currents transport heatGulf Stream blocked by cold, fresh water (less dense)“Day after Tomorrow”

Is a Hotter Sun the Culprit?

• Since 1975– Troposphere has warmed– Stratosphere has cooled

• This is not what a hotter sun would do

Can the Oceans Save Us?• Solubility of CO2 in ocean water

• Warmer oceans– CO2 levels increasing acidity

– Effect on atmospheric levels of CO2

– Effect on coral reefs

• Antarctica’s Southern Ocean and the North Atlantic Ocean– Decrease in CO2 uptake

– Significance on global CO2 levels

There Is Uncertainty about the Effects of Cloud Cover on Global

Warming• Warmer temperatures create more clouds

– Thick, light-colored low altitude clouds: decrease surface temperature

– Thin, cirrus clouds at high altitudes: increase surface temperature

• Effect of jet entrails on climate temperature

Ice core analysis

(air trapped in bubbles in glaciers) shows: a) water vapor concentration has stayed

constant b) 1860 1995

[CO2] 280 ppm 364 ppmsee graph p 465

1) CO2 level corresponds to temperature levels during past 160,000 yrs

-humans appeared 60,000 years ago

7. Average Temperature

average temperature rose 0.3% (1946 - 1995)

8. 1991-1995 was hottest half decade (1995 was hottest year)

a) despite Mt Pinatubo’s ash and aerosols (1991)

9. 1900 - 1990, ocean level rose 3.5 - 7 inches

E. Future

1. Intergovernmental panel on climate change (IPCC) states mean temperature will rise 1.0-3.5oC between 1990 to 2100 2. northern hemisphere warms faster (more land) 3. as temperature rises, evaporation rises,

precipitation increases, more heavy rains and snows

4. due to expansion mostly, ocean level will rise 19 inches (1900 - 2100)

4. Clouds and Albedo

a) warming (absorb and reflect heat: high cirrus clouds) or cooling (shade: low cumulus

clouds) effect b) albedo: ability to reflect light off earth’s

surface 1) melting ice cap reduces albedo ---> temp

up (pos fbk loop)

7. human response

• a) temp up ---> air cond up --->

fossil fuel consump up ---> CO2 up

G. Effects of a Warmer World

1. if slow ---> relocate, if too fast ---> no time to relocate

2. climate bands move northa) ok if ...

1) soil is good 2) money is avail for infrastructure

(storage, irrigation)b) N.A. ---> Canada ... no China ---> north ... yes Ukraine ---> Siberia ... no

Melting of Alaska’s Muir Glacier

between 1948 and 2004

Sea Levels Are Rising (1)

• Expansion of warm water

• Melting of land-based ice

• What about Greenland?

Science Focus: Melting Ice in Greenland

• Largest island: 80% composed of glaciers

• 10% of the world’s fresh water

• 1996–2007: net loss of ice doubled

• Effect on sea level if melting continues

More Effects

3. rising sea level ---> flood productive productive wetlands 4. increasing ocean temp ---> destroy coral reefs 5. lakes, streams dry up ---> pop moves 6. trees may not be able to move north fast enough 7. drying ---> wildfires 8. biodiversity down b/c no time for migration 9. rising sea level ---> lowlands and deltas in

China. India and Bangladesh floodeda) Netherlands needs $ 3-5 trillion to raise

dikes

Sea Levels Are Rising (2)

• Projected irreversible effect– Degradation and loss of 1/3 of coastal estuaries,

wetlands, and coral reefs– Disruption of coastal fisheries– Flooding of

• Low-lying barrier islands and coastal areas• Agricultural lowlands and deltas

– Contamination of freshwater aquifers– Submergence of low-lying islands in the Pacific and

Indian Oceans and the Caribbean

Low-Lying Island Nation: Maldives in

the Indian Ocean

Permafrost Is Likely to Melt: Another Dangerous Scenario

• Carbon present as CH4 in permafrost soils and lake bottoms

• 2004: Arctic Climate Impact Assessment– 10–20% of the permafrost might melt this century

• Effect on global warming

Extreme Weather Will Increase in Some Areas

• Heat waves and droughts in some areas

• Prolonged rains and flooding in other areas

• Will storms get worse? – More studies needed

• Hurricanes Katrina and Rita

Climate Change Will Shift Areas Where Crops Can Be Grown

• Regions of farming may shift– Decrease in tropical and subtropical areas– Increase in northern latitudes

• Less productivity; soil not as fertile

• Genetically engineered crops more tolerant to drought

H. Solutions 1. expensive to deal with

a) boiled frog syndrome: frog won’t complain until it was too late

2. CO2 from natural gas per joule = 1/2 CO2 from coal per joule a) watch pipeline leaks

3. phase out gov subsidies, phase in carbon tax on coal and oil

a) based on CO2 emissions b) reduce other taxes to compensate c) sell greenhouse gas emission credits (Chicago stock exchange)

Solutions cont.4. provide energy conserv tech to dev countries

a) solar cookers5. technofixes

a) add iron to oceans ---> algae pop up ---> photosyn up ---> $ billions/yrb) inject sulfate particulates (like volcanic erupt) ---> pollution, O3 destruction

Avoiding Catastrophe: We Can Reduce the Threat of Climate

Change (3)• Output solutions

– Massive global tree planting; how many?• Wangari Maathai

• Great Wall of Trees: China and Africa

– Plant fast-growing perennials on degraded land

– Capturing and storing CO2

Some Output Methods for Removing CO2 from the

Atmosphere and Storing It

Case Study: Is Capturing and Storing CO2 the Answer? (1)

• Carbon capture and storage (CCS)

• Several problems with this approach– Power plants using CCS

• More expensive to build• None exist

– Unproven technology– Large inputs of energy to work

• Increasing CO2 emissions

Case Study: Is Capturing and Storing CO2 the Answer? (2)

• Problems with carbon capture and storage cont…– Promotes the continued use of coal (world’s

dirtiest fuel)– Effect of government subsidies and tax breaks

– Stored CO2 would have to remain sealed forever: no leaking

Governments Can Help Reduce the Threat of Climate Change

• Strictly regulate CO2 and CH4 as pollutants

• Cap-and-trade approach

• Increase subsidies to encourage use of energy-efficient technology

• Technology transfer

Some Companies and Schools Are Reducing Their Carbon

Footprints (1)• Major global companies reducing greenhouse gas

emissions– Alcoa– DuPont– IBM– Toyota– GE– Wal-Mart

• Fluorescent light bulbs

• Auxiliary power units on truck fleets

Some Companies and Schools Are Reducing Their Carbon

Footprints (2)• Colleges and universities reducing greenhouse gas

emissions– Oberlin College, Ohio, U.S.– 25 Colleges in Pennsylvania, U.S.– Yale University, CT, U.S.

• What is your carbon footprint?

• What can you do?

Kyoto Protocol

• 161 nations met in 1997

• Requires cutting of emissions of CO2, CH4, and N2O to %5.2 below 1990 levels by 2012

• Ratified by120 countries by 2004

• In 2001, Bush withdraws US from treaty b/c too expensive, China, etc are exempt

What is being done

• Great Britain has reached Kyoto goal

• China has reduced CO2 emissions

• BP, DuPont, Toyoto, IBM have established CO2 emission targets

• 500 cities (110 in US) have established programs to reduce greenhouse gas emissions

Ozone Depletion in the Stratosphere

• Less ozone in the stratosphere allows more UV radiation to reach the earth’s surface

• CFCs are inert, long-lived, and inexpensive• In 1974 Rowland and Molina (1995 Nobel

Prize in chemistry) found that CFCs were lowering ozone concentrations

• Ozone Hole (thinning) occurs during 4 month period over Antartica

b) CFC’s

1) deplete ozone in stratosphere

2) global warming in the troposphere (900-8300 times more effective than CO2 per molecule

3) main sources: from leaking air conditioners, refrigerators, styrofoam, propellants in developing countries

4) lasts in stratosphere 65-135 yrs

5) Montreal Protocol 36 nations in 1987 agree to phase out CFC’s, deadlines moved up at subsequent meetings (Copenhagen Protocol)

Polar Vortex

• Swirling mass of air, isolated from rest of atmosphere, collects CFCs

• In Antarctic spring, CFCs and sunlight produce ClO leading to rapid destruction of ozone, O3. Affects Australia.

UV Radiation

• Causes skin cancer: squamous cell, basal cell, and melanoma (highest fatality)

• Tanning parlors increase incidence of melanoma

Montreal Protocol

• 1987, 36 countries met• Cut CFC emissions by 35% between 1989

and 2000.• Copenhagen Protocol, 1992, accelerated

phasing out (signed by 177 countries)• Example of global cooperation• CFCs have been cooling troposphere, so

reduction may increase global warming

Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl3, breakingoff a chlorine atom and leaving CFCl2.

UV radiation

Sun

Once free, the chlorine atom is off to attack another ozone moleculeand begin the cycle again.

A free oxygen atom pulls the oxygen atom off the chlorine monoxide molecule to form O2.

The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO).

The chlorine atom attacksan ozone (O3) molecule, pulling an oxygen atom off it and leaving an oxygen molecule (O2).

Cl

Cl

ClC

F

Cl

Cl

OO

Cl

OO

O

Cl

O

OO

ClO

O

Summary of ReactionsCCl3F + UV Cl + CCl2FCl + O3 ClO + O2

Cl + O Cl + O2

Repeated many times

Figure 18-26Page 473

Antarctic

Figure 18-30 (1)Page 475

Arctic

Figure 18-30 (2)Page 475