Pollution PoliticsPollution Politics

Permit, Prevent, or Prohibit?Permit, Prevent, or Prohibit?

I. Global Warming Theory I. Global Warming Theory (GWT) as a Research Program(GWT) as a Research ProgramA.A. Hypothesized in early 20Hypothesized in early 20thth century: century:

Relationship between CO2 and Relationship between CO2 and temperature understood in 1920stemperature understood in 1920s

B.B. Largely ignored until 1970s. Why?Largely ignored until 1970s. Why?1.1. Research largely retrospective – focused on Research largely retrospective – focused on

climate reconstruction rather than climate reconstruction rather than predictionprediction

2.2. Research emphasized natural rhythms – Research emphasized natural rhythms – changes in earth’s orbit, solar radiation, etc changes in earth’s orbit, solar radiation, etc – and expected cooling– and expected cooling

3.3. Anthropogenic effects assumed to be trivial Anthropogenic effects assumed to be trivial until environmental movement of 1970suntil environmental movement of 1970s

C. Setting Forth the C. Setting Forth the ProblemProblem

1.1. Question: How do anthropogenic Question: How do anthropogenic emissions affect climate?emissions affect climate?

2.2. Competing Hypotheses:Competing Hypotheses:a.a. They don’t (null hypothesis)They don’t (null hypothesis)b.b. Pollution causes cooling: AerosolsPollution causes cooling: Aerosolsc.c. Pollution causes warming: CO2 and Pollution causes warming: CO2 and

other “warming gases”other “warming gases”

3.3. Research Activity: Develop long Research Activity: Develop long time-series of warming gases, time-series of warming gases, aerosol levels, temperatureaerosol levels, temperature

4. Evolution of temperature 4. Evolution of temperature records: Patterns in noisy records: Patterns in noisy

datadata

Cumulative Knowledge?Cumulative Knowledge?

Confidence intervals: Limited Confidence intervals: Limited knowledgeknowledge

5. Measuring Past CO25. Measuring Past CO2

a.a. Recent measurements: Direct atmospheric Recent measurements: Direct atmospheric sampling, esp. from Mauna Loa (high)sampling, esp. from Mauna Loa (high)

b.b. 1919thth century measurements: Selected century measurements: Selected measurements (control for seasonal measurements (control for seasonal “breathing,” urban environments, sea “breathing,” urban environments, sea breezes vs. urban winds, etc) breezes vs. urban winds, etc) since since switched to Law Dome coreswitched to Law Dome core

c.c. Long-term measurements: Ice cores. Note Long-term measurements: Ice cores. Note that bubbles aren’t trapped in deep cores that bubbles aren’t trapped in deep cores until many years pass (4000 to 6000) but until many years pass (4000 to 6000) but new ice (Law Dome site) has gas from as new ice (Law Dome site) has gas from as recent as 1978recent as 1978

D. Early PredictionsD. Early Predictions

1.1. Invention of GCMs (computerized Invention of GCMs (computerized climate models) allows predictions climate models) allows predictions BUT depends on many unknown BUT depends on many unknown parametersparameters

2.2. Early models ignore ocean circulation, Early models ignore ocean circulation, focus entirely on atmosphere (usually focus entirely on atmosphere (usually without clouds) without clouds) usually predict usually predict massive warming, but fail to massive warming, but fail to “postdict” past temperature changes“postdict” past temperature changes

3.3. Problem of Feedback Loops: The Problem of Feedback Loops: The environment is interconnected, not environment is interconnected, not strictly linearstrictly linear

E. Climate FeedbacksE. Climate Feedbacks

Three of the most important direct Three of the most important direct climatic feedbacks to greenhouse climatic feedbacks to greenhouse forcing are:forcing are: water vapor feedback, water vapor feedback, cloud cover feedback and the cloud cover feedback and the ice-albedo feedback. ice-albedo feedback.

1. Water Vapor Feedback1. Water Vapor Feedback

The concentration of water vapor in The concentration of water vapor in the atmosphere increases rapidly with the atmosphere increases rapidly with rising temperature (about 6%/°C).rising temperature (about 6%/°C). This is the basis for the strong positive This is the basis for the strong positive

water vapor feedback in current climate water vapor feedback in current climate modelsmodels

increases in temperature produce increases in increases in temperature produce increases in atmospheric water vapor which in turn atmospheric water vapor which in turn enhance the greenhouse enhance the greenhouse forcing leading to further warming).forcing leading to further warming).

2. Ice-Albedo Feedback2. Ice-Albedo Feedback

A warmer Earth will have less snow and A warmer Earth will have less snow and ice cover, resulting in a lower global ice cover, resulting in a lower global albedo and consequent absorption of albedo and consequent absorption of more solar radiation. This, in turn more solar radiation. This, in turn causes a further warming of the climate. causes a further warming of the climate. Most GCMs have simulated this positive Most GCMs have simulated this positive

surface albedo feedback, but surface albedo feedback, but significant uncertainties exist over the size significant uncertainties exist over the size

of the effect, particularly for sea-ice of the effect, particularly for sea-ice

3. Cloud Feedbacks3. Cloud Feedbacks

The effects of changes in cloud on a change The effects of changes in cloud on a change of climate have been identified as a major of climate have been identified as a major source of uncertainty in climate models source of uncertainty in climate models clouds contribute to the greenhouse warming clouds contribute to the greenhouse warming

of the climate system by absorbing more of the climate system by absorbing more outgoing infrared radiation (positive feedback), outgoing infrared radiation (positive feedback),

they also produce a cooling through the they also produce a cooling through the reflection and reduction in absorption of solar reflection and reduction in absorption of solar radiation (negative feedback) radiation (negative feedback) generally generally thought to be strongerthought to be stronger

4. Why feedbacks matter: 4. Why feedbacks matter: The SO2 SurpriseThe SO2 Surprise

Environmentalism says that belching out Environmentalism says that belching out clouds of black smoke is probably a bad ideaclouds of black smoke is probably a bad idea

One component of “dirty” exhaust (coal, One component of “dirty” exhaust (coal, diesel, etc.) is sulfur dioxide (SO2) – and diesel, etc.) is sulfur dioxide (SO2) – and associates sulfatesassociates sulfates SO2 is a warming gas BUTSO2 is a warming gas BUT Sulfate aerosols cool AND SO2 helps form clouds, Sulfate aerosols cool AND SO2 helps form clouds,

generating a negative feedback loop that reduces generating a negative feedback loop that reduces warmingwarming

Aerosols are removed form the atmosphere much Aerosols are removed form the atmosphere much more quickly than gasesmore quickly than gases

Result: Limiting some types of emissions may Result: Limiting some types of emissions may accelerate warming (by removing a cooling accelerate warming (by removing a cooling loop) rather than slowing itloop) rather than slowing it

F. FindingsF. Findings1.1. Warming Warming

Gases (GHGs)Gases (GHGs)

a.a. Most of Most of Earth’s Earth’s atmosphere is atmosphere is climatically climatically neutral: neutral: GHGs GHGs present in trace present in trace amounts only amounts only

b.b. Implication: Implication: Relatively small Relatively small releases (on a releases (on a global scale) may global scale) may significantly significantly increase increase concentrations concentrations

c. Trends in GHGsc. Trends in GHGs

Since the mid-1800s, Since the mid-1800s, atmospheric levels of carbon dioxide have atmospheric levels of carbon dioxide have

increased 30 percent (from 280 parts per increased 30 percent (from 280 parts per million to 360 parts per million), million to 360 parts per million),

the concentration of methane has more than the concentration of methane has more than doubled (to about 1.72 parts per million), doubled (to about 1.72 parts per million), andand

nitrous oxide levels have increased by a nitrous oxide levels have increased by a more modest 10-15%.more modest 10-15%.

CFCs have appeared in the atmosphereCFCs have appeared in the atmosphere

The historical dataThe historical data

2. The “Carbon Cycle” – 2. The “Carbon Cycle” – Nature vs. Human Nature vs. Human

ContributionsContributionsa. The Cycle: The earth's natural a. The Cycle: The earth's natural

processes continually exchange processes continually exchange massive quantities of carbon.massive quantities of carbon. Oceans release about 90 billion tonnes of Oceans release about 90 billion tonnes of

CO2 into the atmosphere each year. CO2 into the atmosphere each year. Decaying vegetation adds another 30 Decaying vegetation adds another 30

billion tonnes annually, whilebillion tonnes annually, while another 30 billion tonnes each year is another 30 billion tonnes each year is

released from the natural respiration of released from the natural respiration of living creatures and plants. living creatures and plants.

b. Human Sources of b. Human Sources of CO2CO2

Human activities add an extra 3% to this Human activities add an extra 3% to this natural cycle, or about 7 billion tons per natural cycle, or about 7 billion tons per year. Why worry about a 3% increase?year. Why worry about a 3% increase?

The majority of human CO2 comes from the burning of fossil fuels.

The residence time of CO2 in the atmosphere is ~100 to 200 years

Data Source: Marland et al, 1999. Carbon Dioxide Information Analysis Center.

Cumulative carbon Cumulative carbon emissions, 1950-1996emissions, 1950-1996

7,415

8,504

11,651

15,715

4,235

4,054

2,331

1,361

966

50,795

1,557

2,080

2,118

0 10,000 20,000 30,000 40,000 50,000 60,000

United States

Indonesia

Korea, Rep.

Brazil

Australia

Mexico

South Africa

Canada

India

United Kingdom

Japan

Germany

China

Million tons of carbon

c. Carbon Sinksc. Carbon Sinks Absorption by the oceans and plants Absorption by the oceans and plants

removes the natural -- and much of the removes the natural -- and much of the human -- CO2 from the human -- CO2 from the atmosphere. atmosphere. BUT: The net result of this "carbon cycle" is BUT: The net result of this "carbon cycle" is

a net increase of about 3.1 to 3.5 billion a net increase of about 3.1 to 3.5 billion tonnes of CO2 annually to the atmosphere.tonnes of CO2 annually to the atmosphere.

Implication: Natural cycle dwarfs human Implication: Natural cycle dwarfs human contributions in any one year, but many contributions in any one year, but many years of cumulative “extra” emissions that years of cumulative “extra” emissions that just slightly overload the cycle start to add just slightly overload the cycle start to add upup

d. Humans reduce d. Humans reduce carbon sinkscarbon sinks

d. Humans reduce d. Humans reduce carbon sinkscarbon sinks

Data Source: C.D. Keeling and T.P. Whorf, Atmospheric CO2 Concentrations (ppmv) derived from in situ air samples collected at Mauna Loa Observatory, Hawaii, Scripps Institute of Oceanography, August 1998. A. Neftel et al, Historical CO2 Record from the Siple Station Ice Core, Physics Institute, University of Bern, Switzerland, September 1994. See http://cdiac.esd.ornl.gov/trends/co2/contents.htm

Atmospheric carbon Atmospheric carbon dioxide (CO2):1750 to dioxide (CO2):1750 to

presentpresent

270

280

290

300

310

320

330

340

350

360

370

1750 1800 1850 1900 1950 2000

part

s pe

r m

illio

n vo

lum

e

Siple Station (1750-1970)

Mauna Loa (1958-present)

Data Source: C.D. Keeling and T.P. Whorf, Atmospheric CO2 Concentrations (ppmv) derived from in situ air samples collected at Mauna Loa Observatory, Hawaii, Scripps Institute of Oceanography, August 1998. A. Neftel et al, Historical CO2 Record from the Siple Station Ice Core, Physics Institute, University of Bern, Switzerland, September 1994. See http://cdiac.esd.ornl.gov/trends/co2/contents.htm

Alternate view of same Alternate view of same data…data…

0

50

100

150

200

250

300

350

1750 1800 1850 1900 1950 2000

part

s pe

r m

illio

n vo

lum

e

Siple Station (1750-1970)

Mauna Loa (1958-present)

3. Methane3. Methane A. The good A. The good

news: Unlike news: Unlike carbon dioxide, carbon dioxide, methane is methane is destroyed by destroyed by reactions with reactions with other chemicals other chemicals in the in the atmosphere. atmosphere. Its approximate Its approximate

lifetime is about lifetime is about 10 years. 10 years.

b. The bad newsb. The bad news

On the other hand, on a molecule-On the other hand, on a molecule-for-molecule basis, methane is a for-molecule basis, methane is a much greater absorber of energy much greater absorber of energy than carbon dioxide. than carbon dioxide. As a greenhouse gas, a methane As a greenhouse gas, a methane

molecule is more than 20-times more molecule is more than 20-times more potent than than a carbon dioxide potent than than a carbon dioxide molecule.molecule.

4. Nitrous Oxide4. Nitrous Oxide As a greenhouse gas, its major source is As a greenhouse gas, its major source is

the bacterial breakdown of nitrogen the bacterial breakdown of nitrogen compounds in soils. compounds in soils. When land is deforested and then When land is deforested and then

cultivated, nitrous oxide emissions can cultivated, nitrous oxide emissions can increase, particularly if nitrogen-containing increase, particularly if nitrogen-containing fertilizers are used.fertilizers are used.

Nitrous oxide is even more potent than Nitrous oxide is even more potent than methane as a greenhouse gas. methane as a greenhouse gas. A nitrous oxide molecule may be as much as A nitrous oxide molecule may be as much as

300 times more potent than a molecule of 300 times more potent than a molecule of carbon dioxide in absorbing Earth radiation.carbon dioxide in absorbing Earth radiation.

5. Ozone (O3)5. Ozone (O3)

a. Good (stratospheric) a. Good (stratospheric) ozone: protects ozone: protects against UV radiationagainst UV radiation

b. Bad (tropospheric) b. Bad (tropospheric) ozone: causes smog, ozone: causes smog, acts as a warming gas acts as a warming gas (but breaks down very (but breaks down very quickly – so emission quickly – so emission reductions take only reductions take only weeks to work)weeks to work)

6. CFCs6. CFCs Molecule for molecule, Molecule for molecule,

chlorofluorocarbons are the most chlorofluorocarbons are the most potent of greenhouse gases.potent of greenhouse gases. CFC-12 or "Freon-12" as it is known by its CFC-12 or "Freon-12" as it is known by its

trade name, is 17,700 times more potent trade name, is 17,700 times more potent than carbon dioxide. than carbon dioxide.

Although they exist in only minute Although they exist in only minute quantities in the atmosphere, CFCs are quantities in the atmosphere, CFCs are thought to be responsible for about 20% thought to be responsible for about 20% of the enhanced greenhouse effect.of the enhanced greenhouse effect.

CFCs phased out in most countries due to CFCs phased out in most countries due to destruction of stratospheric ozone (not destruction of stratospheric ozone (not concern about warming)concern about warming)

7. The GHG model: 7. The GHG model: Net “Radiative Forcing” =Net “Radiative Forcing” =

CO2 1CH4 21N2O 300CFCs 3500-7500

+

II. Is GWT a Progressive II. Is GWT a Progressive Research Program?Research Program?

Remember: Every theory fails. Key is Remember: Every theory fails. Key is how theory is modified:how theory is modified: Degenerative = explain failure but nothing Degenerative = explain failure but nothing

else (no new knowledge or predictions).else (no new knowledge or predictions). Progressive = explain failure AND makes Progressive = explain failure AND makes

new testable predictionsnew testable predictions

Let’s see how GWT responded to Let’s see how GWT responded to failures….failures….

A. Temperature A. Temperature AnomaliesAnomalies

1.1. Satellite data – Satellite data – a.a. Challenge: Shows cooling in Challenge: Shows cooling in

atmosphere over timeatmosphere over time

b.b. Response: Must correct for decay in Response: Must correct for decay in satellite orbits over timesatellite orbits over time

c.c. New Prediction? “New” satellites New Prediction? “New” satellites ought to show warmer temps than ought to show warmer temps than “old” satellites, since their orbits “old” satellites, since their orbits haven’t decayed as muchhaven’t decayed as much

2. Weather balloons2. Weather balloons

a.a. Challenge: Weather balloons show Challenge: Weather balloons show cooling in upper atmosphere during cooling in upper atmosphere during daytime, but warming at nightdaytime, but warming at night

b.b. Response: Balloon instruments have Response: Balloon instruments have been better shielded against sunlight been better shielded against sunlight over time – explaining apparent decrease over time – explaining apparent decrease in day temps and increase in night tempsin day temps and increase in night temps

c.c. New prediction? Relaunching vintage New prediction? Relaunching vintage instruments during daytime should show instruments during daytime should show warmer temps than modern instrumentswarmer temps than modern instruments

B. CO2-Warming AnomaliesB. CO2-Warming Anomalies

1.1. The 1940-1975 dipThe 1940-1975 dipa.a. Challenge: Records of atmospheric Challenge: Records of atmospheric

carbon dioxide (CO2) levels since 1940 carbon dioxide (CO2) levels since 1940 show a continual increase, but during show a continual increase, but during this period global temperature this period global temperature decreased until 1975 (and has decreased until 1975 (and has increased since then).increased since then).

B. CO2-Warming AnomaliesB. CO2-Warming Anomalies

1.1. The 1940-1975 dipThe 1940-1975 dipa.a. Challenge: Records of atmospheric carbon Challenge: Records of atmospheric carbon

dioxide (CO2) levels since 1940 show a dioxide (CO2) levels since 1940 show a continual increase, but during this period continual increase, but during this period global temperature decreased until 1975 global temperature decreased until 1975 (and has increased since then).(and has increased since then).

b.b. Response: industrialization poured SO2 Response: industrialization poured SO2 and aerosols into the atmosphere, leading and aerosols into the atmosphere, leading to coolingto cooling

c.c. New prediction? Reduction in aerosols New prediction? Reduction in aerosols should lead to increases in temperatureshould lead to increases in temperature

2. Reverse causality2. Reverse causalitya.a. Challenge: Ice cores from Antarctica show Challenge: Ice cores from Antarctica show

that CO2 levels that CO2 levels lagged behindlagged behind temperature temperature increases during glacial terminations. increases during glacial terminations.

b.b. Response: Glacial terminations correspond Response: Glacial terminations correspond to changes in the Earth’s orbit (Milankovitch to changes in the Earth’s orbit (Milankovitch cycles – more on these in a bit), which cycles – more on these in a bit), which triggered warming. As ice sheets retreated, triggered warming. As ice sheets retreated, thawing permafrost and warming oceans thawing permafrost and warming oceans released CO2 and methane, leading to still released CO2 and methane, leading to still further warmingfurther warming

c.c. New prediction? Vague: “permafrost and New prediction? Vague: “permafrost and oceans” isn’t very specific. GWT researcher oceans” isn’t very specific. GWT researcher acknowledge that “exact mechanism is acknowledge that “exact mechanism is unknown” (i.e. anomaly remains)unknown” (i.e. anomaly remains)

3. Medieval Records3. Medieval Records

a.a. Challenge: Temperature reconstructions Challenge: Temperature reconstructions from tree rings fail to show the Little Ice from tree rings fail to show the Little Ice Age or Medieval Warm PeriodAge or Medieval Warm Period

b.b. Response: These were regional rather Response: These were regional rather than global changes, caused by changes in than global changes, caused by changes in the Gulf Stream and other ocean currentsthe Gulf Stream and other ocean currents

c.c. New prediction? Tree rings from Western New prediction? Tree rings from Western US should show no change when US should show no change when compared to tree rings from Northern compared to tree rings from Northern Europe. Also, newly discovered North Europe. Also, newly discovered North Atlantic corals should show increased Atlantic corals should show increased temps vs. Pacific ones (not yet tested)temps vs. Pacific ones (not yet tested)

Regional Differences in Annual Temperature Regional Differences in Annual Temperature Trends: 1901 - 1990Trends: 1901 - 1990

Source: Watson 2000

Red circles = warming; Blue circles = coolingRed circles = warming; Blue circles = coolingAll stations/trends displayed regardless of statistical significance.All stations/trends displayed regardless of statistical significance.

Source: National Climatic Data Center/NESDIS/NOAA

U.S. Temperature Trends: U.S. Temperature Trends: 1901 to 19981901 to 1998

C. Unanswered questionsC. Unanswered questions

1.1. Cloud formation: Existing GCMs fail to Cloud formation: Existing GCMs fail to model changes in water vapor, which is model changes in water vapor, which is tied to both water temperatures and tied to both water temperatures and cloud formationcloud formation

2.2. Ocean currents: While Gore implies Ocean currents: While Gore implies that we know that the “Global that we know that the “Global Conveyor Belt” is driven by Conveyor Belt” is driven by temperature and salinity, we have been temperature and salinity, we have been unable to identify its natural range of unable to identify its natural range of variation absent temperature changes variation absent temperature changes (no long-term records)(no long-term records)

III. Comparing GWT to the III. Comparing GWT to the “Natural Causes” Research “Natural Causes” Research

ProgramProgramA.A. Precedes GWT: Early climate models Precedes GWT: Early climate models

focused on the role of cycles in the focused on the role of cycles in the Earth’s orbit and tectonic changes Earth’s orbit and tectonic changes (movement of land masses)(movement of land masses)

B.B. Evolution of the Research Program: Evolution of the Research Program: While GWT added anthropogenic to While GWT added anthropogenic to natural causes, the “Natural Causes” natural causes, the “Natural Causes” research program remains convinced research program remains convinced that anthropogenic factors are minorthat anthropogenic factors are minor

C. Orbital forcingC. Orbital forcing

The theory that large scale climate The theory that large scale climate changes (glacials/interglacials) are changes (glacials/interglacials) are due to the variations in precession, due to the variations in precession, eccentricity and obliquity of the eccentricity and obliquity of the Earth’s solar orbit that affects the Earth’s solar orbit that affects the amount of solar radiation received at amount of solar radiation received at the surface of the Earth.the surface of the Earth. Attributed to MilankovitchAttributed to Milankovitch

1. Orbital attributes1. Orbital attributes

The Earth has three fundamental The Earth has three fundamental orbital attributes:orbital attributes: Changes in the tilt of the axis of rotation Changes in the tilt of the axis of rotation

(termed the obliquity)(termed the obliquity) Changes in the shape of the elliptical Changes in the shape of the elliptical

orbit around the sun (termed orbit around the sun (termed eccentricity)eccentricity)

Changes in the date of the Earth’s Changes in the date of the Earth’s closest approach to the Sun (termed closest approach to the Sun (termed precession of the equinox)precession of the equinox)

The tilt of the Earth’s axis variesThe tilt of the Earth’s axis varies

2. Periods of variation2. Periods of variation

The tilt of the Earth’s axis varies The tilt of the Earth’s axis varies over a period of about 41,000 yearsover a period of about 41,000 years

The cycle of orbital eccentricity is The cycle of orbital eccentricity is 90,000 to 100,000 years90,000 to 100,000 years

The precession cycle of the equinox The precession cycle of the equinox is about 23,000 yearsis about 23,000 years

3. Milankovitch Cycles3. Milankovitch Cycles

4. Responses to Orbital 4. Responses to Orbital ForcingForcing

a.a. Most scientists in both programs Most scientists in both programs think this happensthink this happens

b.b. However, Milankovitch cycles have However, Milankovitch cycles have serious unexplained anomalies serious unexplained anomalies (changes in which cycles seem most (changes in which cycles seem most important, glaciations that match no important, glaciations that match no known cycle, etc).known cycle, etc).

c.c. Existing models of these cycles Existing models of these cycles predict gradual cooling, not warming. predict gradual cooling, not warming. Hence, other natural causes have Hence, other natural causes have been added to this research programbeen added to this research program

D. Solar forcingD. Solar forcing

1.1. Argument: Changes in solar output Argument: Changes in solar output change temperatures directly and change temperatures directly and indirectly (through cloud formation)indirectly (through cloud formation)

2.2. Problem: Historical records of solar Problem: Historical records of solar activity are scattered, requiring a great activity are scattered, requiring a great deal of splicing together. Different deal of splicing together. Different methods of splicing = different cycles methods of splicing = different cycles detected.detected.

3.3. Result: Studies of solar forcing tend to Result: Studies of solar forcing tend to find a pattern for known data, but fail find a pattern for known data, but fail after a few years (when new data after a few years (when new data emerges)emerges)

Noise in the dataNoise in the data

Post-1980 DataPost-1980 Data

IV. Is the Natural Causes IV. Is the Natural Causes Program Progressive?Program Progressive?

This analysis ignores other arguments This analysis ignores other arguments about GWT: about GWT: Earth is not warming (debated until early Earth is not warming (debated until early

1990s in peer-reviewed journals)1990s in peer-reviewed journals) Warming is a good thing (some papers Warming is a good thing (some papers

published in 1980s, little since then)published in 1980s, little since then) Warming is irreversible (relatively few Warming is irreversible (relatively few

articles published)articles published) Natural Causes receives most Natural Causes receives most

attention, so is the most obvious attention, so is the most obvious comparison programcomparison program

A. Methane FluxA. Methane Flux

1.1. The explanationThe explanationa.a. Methane is stored below the Methane is stored below the

ocean floor in the form of ocean floor in the form of hydrates (ices) – much more hydrates (ices) – much more than humans will ever releasethan humans will ever release

b.b. Landslides periodically release Landslides periodically release hydrates (which float and hydrates (which float and melt)melt)

2.2. Problem: Anthropogenic Problem: Anthropogenic emissions appear to exceed emissions appear to exceed periodic ocean emissions – periodic ocean emissions – and correspond to and correspond to industrializationindustrialization

B. VulcanismB. Vulcanism1.1. Volcanoes emit CO2 and aerosols that Volcanoes emit CO2 and aerosols that

can insulate earth during winter can insulate earth during winter monthsmonths

Shindell, D.T., Schmidt, G.A., Miller, R., Mann, M.E., Volcanic and Solar forcing of Climate Change During the Pre-Industrial era, Journal of Climate, 16, 4094-4107, 2003.

Volcanic Radiative Summer Cooling

Average summer (Jun-Aug) surface temperature response following eruption of Pinatubo.

Volcanic Winter Dynamic Warming

Ensemble average winter (Dec-Feb) surface temperature response following eruption of Pinatubo.

Shindell, D.T., Schmidt, G.A., Miller, R., Mann, M.E., Volcanic and Solar forcing of Climate Change During the Pre-Industrial era, Journal of Climate, 16, 4094-4107, 2003.

B. VolcanismB. Volcanism1.1. Volcanoes emit CO2 and aerosols that can Volcanoes emit CO2 and aerosols that can

insulate earth during winter monthsinsulate earth during winter months2.2. Problems: Problems:

a.a. Annual volcanic emissions of CO2 are modest Annual volcanic emissions of CO2 are modest (1/50 anthropogenic emissions)(1/50 anthropogenic emissions)

b.b. CO2 levels increase smoothly, with minimal CO2 levels increase smoothly, with minimal spikes during eruption yearsspikes during eruption years

c.c. Recent temperature increases don’t correspond Recent temperature increases don’t correspond with increased volcanismwith increased volcanism

Volcanoes and TemperatureVolcanoes and Temperature

Decreased Decreased volcanism volcanism and and increased increased solar outputsolar output

Increased Increased volcanism volcanism and and decreased decreased solar outputsolar output

GreenhouseGreenhouse

C. OscillationsC. Oscillations

Earlier responses used the El Niño Earlier responses used the El Niño Southern Oscillation as an Southern Oscillation as an explanation for increased explanation for increased temperaturestemperatures

Several cycles of ENSO have passed, Several cycles of ENSO have passed, and temperature increase has and temperature increase has continuedcontinued

El NiEl Niño – Southern ño – Southern OscillationOscillation

D. Water VaporD. Water Vapor

1.1. Most of the “greenhouse effect” warming Most of the “greenhouse effect” warming Earth is due to water vaporEarth is due to water vapor

2.2. Problem: Water vapor is the majority of Problem: Water vapor is the majority of current greenhouse effect (total 33 C/ 91 F) current greenhouse effect (total 33 C/ 91 F) but doesn’t appear to cause CHANGES in but doesn’t appear to cause CHANGES in temperature because water vapor is not temperature because water vapor is not persistent – cycles through atmosphere in persistent – cycles through atmosphere in ~10 days, leading to short-term (not long-~10 days, leading to short-term (not long-term fluctuations). term fluctuations).

3.3. Remember the feedback loop: Higher temps Remember the feedback loop: Higher temps DO increase equilibrium level of water in DO increase equilibrium level of water in atmosphereatmosphere

E. Solar FluxE. Solar Flux

1.1. SunspotsSunspots

a.a. Clearly Clearly related to related to temperattemperature:ure:

As noted, a number of cycles have As noted, a number of cycles have been proposed.been proposed.

Historical Evidence for Historical Evidence for SunspotsSunspots

b. Counter-evidenceb. Counter-evidence

Since 1985 or so, sunspots have Since 1985 or so, sunspots have gone back down – but temps have gone back down – but temps have risenrisen

Similar findings for other common Similar findings for other common measures of solar activitymeasures of solar activity

2. Other Solar Cycles2. Other Solar Cycles

As noted, a nearly infinite number of As noted, a nearly infinite number of cycles can be posited from the solar cycles can be posited from the solar data. Some of them will always line data. Some of them will always line up perfectly with warmingup perfectly with warming

Needed: A Needed: A mechanismmechanism by which by which thisthis cycle (and none of the others) drives cycle (and none of the others) drives climate on Earthclimate on Earth

Why insist on a mechanism?Why insist on a mechanism?

More fun with graphs: What’s More fun with graphs: What’s wrong with this “cycle”?wrong with this “cycle”?

No, you don’t need to understand No, you don’t need to understand German…German…

3. Mars as Evidence?3. Mars as Evidence?

a.a. Martian southern icecap has becomes Martian southern icecap has becomes smaller three summers (about six Earth smaller three summers (about six Earth years) in a rowyears) in a row

b.b. Argument: Simultaneous temperature Argument: Simultaneous temperature change on different planets proves change on different planets proves extra-terrestrial (solar) causeextra-terrestrial (solar) cause

c.c. Objections: Doubts about planetary Objections: Doubts about planetary temperature changes on Mars, solar temperature changes on Mars, solar radiation as cause of Martian warming radiation as cause of Martian warming (which appears to be tied to scale of (which appears to be tied to scale of dust storms)dust storms)

F. ConclusionsF. Conclusions

1.1. General pattern of “Natural Causes” General pattern of “Natural Causes” research program:research program:

a.a. Suggest natural causeSuggest natural cause

b.b. When problems arise, abandon natural When problems arise, abandon natural cause for a different one (or a different cause for a different one (or a different solar cycle)solar cycle)

c.c. New explanation doesn’t explain more data New explanation doesn’t explain more data than old one – instead explains already-than old one – instead explains already-known temperature data without known temperature data without generating new hypotheses about other generating new hypotheses about other observable phenomenaobservable phenomena

2.2. Implication: Program is degenerativeImplication: Program is degenerative

3. Which way have scientists 3. Which way have scientists decided? The 928:0 Claimdecided? The 928:0 Claim

Search phrase = “global climate change”Search phrase = “global climate change” 928 papers, divided into six categories928 papers, divided into six categories

Explicit endorsement of the Explicit endorsement of the consensus positionconsensus position

7575%%

Evaluation of impactsEvaluation of impacts

Mitigation proposalsMitigation proposals

MethodsMethods

2525%%

Paleoclimate analysisPaleoclimate analysis

Rejection of the consensus positionRejection of the consensus position 0%0%

Does the counting method Does the counting method matter?matter?

Including non-article search results (reports, Including non-article search results (reports, conference papers, editorials) gives a few conference papers, editorials) gives a few skeptical assessmentsskeptical assessments

What if papers on natural causes are counted as What if papers on natural causes are counted as anti-GWT? Nearly half of the research papers anti-GWT? Nearly half of the research papers on climate change addressed non-on climate change addressed non-anthropogenic causes – but only a few explicitly anthropogenic causes – but only a few explicitly said they were as important as anthropogenic said they were as important as anthropogenic onesones

Questionable to include all papers on warming Questionable to include all papers on warming impacts as pro-GWT – although none explicitly impacts as pro-GWT – although none explicitly doubted GWTdoubted GWT

Relatively few papers explicitly state GWT Relatively few papers explicitly state GWT (perhaps a few dozen) – scientists tackle (perhaps a few dozen) – scientists tackle extremely specialized puzzles, not the whole extremely specialized puzzles, not the whole program in one gulpprogram in one gulp

IV. Global Warming IV. Global Warming ImpactsImpacts

Most basic impacts (i.e. sea-level Most basic impacts (i.e. sea-level rise) were covered in the Gore film. rise) were covered in the Gore film. Let’s focus on the more complex Let’s focus on the more complex ones…ones…

A. StormsA. Storms

1.1. The basic argument: The basic argument: a.a. Warm water strengthens hurricanesWarm water strengthens hurricanes

b.b. Warming means warmer oceansWarming means warmer oceans

c.c. Therefore, warming means bigger Therefore, warming means bigger hurricaneshurricanes

Atlantic Temperature and Atlantic Temperature and Hurricane Power, 1972-Hurricane Power, 1972-

20052005

2. Puzzles2. Puzzles

a.a. Warming should increase “wind shear” Warming should increase “wind shear” – the difference between winds at high – the difference between winds at high and low altitudes. Wind shear weakens and low altitudes. Wind shear weakens storms.storms.

b.b. Storms form near the equator, so Storms form near the equator, so regional temperature change is more regional temperature change is more important than global temperature important than global temperature changechange

c.c. Warming should reduce differences Warming should reduce differences between equatorial and polar regions, between equatorial and polar regions, reducing mid-latitude stormsreducing mid-latitude storms

B. PrecipitationB. Precipitation

1.1. Warming increases evaporation. Warming increases evaporation. This means:This means:

a.a. Areas downwind of water (i.e. the Areas downwind of water (i.e. the wettest areas of the world) will get wettest areas of the world) will get more precipitationmore precipitation

b.b. Areas far from water (i.e. the dryest Areas far from water (i.e. the dryest areas of the world) will get dryer areas of the world) will get dryer through evaporationthrough evaporation

c.c. Is this testable? Wetter AND Drier? Is this testable? Wetter AND Drier? Need regional predictions…Need regional predictions…

2. Puzzles2. Puzzles

a.a. What about What about Antarctica and Antarctica and Greenland? Greenland? Increased Increased precipitation (snow) precipitation (snow) would help balance would help balance melting ice caps…melting ice caps…

b.b. Significant Significant disagreement disagreement between computer between computer models. Example models. Example of USA of USA

C. “Extreme” WeatherC. “Extreme” Weather

1.1. Blizzards – Range should decrease (fewer cold Blizzards – Range should decrease (fewer cold days in some areas) but frequency should days in some areas) but frequency should increase (because of increased precipitation)increase (because of increased precipitation)

2.2. Tornadoes – Some models predict more Tornadoes – Some models predict more severe updrafts in thunderstorms (which severe updrafts in thunderstorms (which should spawn more tornadoes) but no should spawn more tornadoes) but no consensus on this detailconsensus on this detail

3.3. Heat Waves – Every model predicts more Heat Waves – Every model predicts more severe heat waves over larger areassevere heat waves over larger areas

4.4. Drought – Should become worse in already-Drought – Should become worse in already-dry areas but most areas will get more dry areas but most areas will get more precipitation, not lessprecipitation, not less

D. Sea-Level RiseD. Sea-Level Rise

1.1. Thermal Thermal Expansion – Warm Expansion – Warm water usually water usually takes up more takes up more space than cool space than cool water. Accounts water. Accounts for about 50% of for about 50% of recent (post-1993) recent (post-1993) rise in sea levelrise in sea level

2.2. Ice Melt: Three Ice Melt: Three main sourcesmain sources

a. Glaciersa. Glaciers

Changes Changes in 2002 in 2002 and 2003 and 2003

b. Antarctic Ice Capb. Antarctic Ice Cap Most of the continent will Most of the continent will

remain below freezing year-remain below freezing year-round. Increased round. Increased precipitation may make up precipitation may make up for any melting.for any melting.

Complication: “Ozone hole” Complication: “Ozone hole” over Antarctica may over Antarctica may increase warming if it increase warming if it persistspersists

Antarctic Peninsula: Antarctic Peninsula: Warming trend observed; Warming trend observed; real danger of ice melt but real danger of ice melt but no direct effect on sea level.no direct effect on sea level.

October 7, 2007 temps October 7, 2007 temps

c. Greenlandc. Greenland

Evidence indicates regional warmingEvidence indicates regional warming Ice sheet has been retreating AND Ice sheet has been retreating AND

thickening. How?thickening. How? Increased precipitation from slightly Increased precipitation from slightly

warmer air in interiorwarmer air in interior Increased melting from warmer air and Increased melting from warmer air and

water on edgeswater on edges Yearly loss from melting currently Yearly loss from melting currently

outweighs gain from snowfalloutweighs gain from snowfall No consensus on likely speed, extent No consensus on likely speed, extent

of future meltingof future melting

E. CropsE. Crops1. Zones: Some areas become too warm 1. Zones: Some areas become too warm

for most crops, others become warm for most crops, others become warm enough. Speed probably key.enough. Speed probably key.

2. CO2 and Crop Yields2. CO2 and Crop Yields

a.a. Plants need CO2, so more CO2 Plants need CO2, so more CO2 should increase plant growthshould increase plant growth

b.b. Some studies find that weeds Some studies find that weeds overcome crops more easily in high-overcome crops more easily in high-CO2 environmentsCO2 environments

c.c. Herbicides less effective at higher Herbicides less effective at higher levels of CO2levels of CO2

d.d. Net effect of increased CO2 on food Net effect of increased CO2 on food crops still unknowncrops still unknown

F. Warming F. Warming Cooling? Cooling?

1.1. The Scenario: The Scenario: a.a. Melting ice reduces salinity of North Atlantic Melting ice reduces salinity of North Atlantic

surface waterssurface watersb.b. This reduces the rate at which the waters sink, This reduces the rate at which the waters sink,

thus slowing or stopping the Global Conveyor Belt thus slowing or stopping the Global Conveyor Belt of that transports heat from warm areas to cooler of that transports heat from warm areas to cooler ones (notably Europe)ones (notably Europe)

c.c. Result = regional cooling (another “Little Ice Result = regional cooling (another “Little Ice Age”) in EuropeAge”) in Europe

2.2. The EvidenceThe Evidencea.a. Very little evidence on deep ocean currentsVery little evidence on deep ocean currentsb.b. No evidence of slowing Global Conveyor BeltNo evidence of slowing Global Conveyor Beltc.c. Current models predict net warming in Europe, Current models predict net warming in Europe,

even after a limited slowdown of the Global even after a limited slowdown of the Global Conveyor BeltConveyor Belt

V. Nuclear Weapons and V. Nuclear Weapons and PollutionPollution

Interest in the effects of nuclear war Interest in the effects of nuclear war decreased at the end of the cold War decreased at the end of the cold War but has recently been renewed by but has recently been renewed by India-Pakistan tensionsIndia-Pakistan tensions

A. Nuclear FalloutA. Nuclear Fallout

1.1. Definition: Radioactive particles fall Definition: Radioactive particles fall to earth (fission products, to earth (fission products, contaminated soil and debris)contaminated soil and debris)

2. Dangers of Ionizing 2. Dangers of Ionizing RadiationRadiation

a.a. Alpha radiationAlpha radiationi.i. Composed of Helium nuclei (2 protons, 2 Composed of Helium nuclei (2 protons, 2

neutrons)neutrons)ii.ii. Little danger unless inhaled or ingested – Little danger unless inhaled or ingested –

stopped by a piece of paper (or skin)stopped by a piece of paper (or skin)iii.iii. Very destructive if inhaled or ingested (only Very destructive if inhaled or ingested (only

known example = Alexander Litvinenko, known example = Alexander Litvinenko, poisoned with alpha-emitter Po-210)poisoned with alpha-emitter Po-210)

b. Beta radiationb. Beta radiation

i.i. Consists of electrons emitted by Consists of electrons emitted by radioactive atomsradioactive atoms

ii.ii. Can burn exposed skin – stopped Can burn exposed skin – stopped by clothing, skin, and gogglesby clothing, skin, and goggles

iii.iii. Effective range is only a few feet, Effective range is only a few feet, so exposure to radioactive dust is so exposure to radioactive dust is most likely source of damagemost likely source of damage

c. Gamma radiationc. Gamma radiationi.i. Extremely high energy photons Extremely high energy photons

emitted by the detonation and emitted by the detonation and falloutfallout

ii.ii. Penetrating power is high. Penetrating power is high. Needed to reduce exposure by Needed to reduce exposure by half:half:

d. Neutron radiationd. Neutron radiation

i.i. Produced by blast itself, Produced by blast itself, insignificant in falloutinsignificant in fallout

ii.ii. Induces radioactivity (alpha, beta, Induces radioactivity (alpha, beta, gamma) in materials it encountersgamma) in materials it encounters

iii.iii. Shielding requires light elements Shielding requires light elements (hydrogen, lithium)(hydrogen, lithium)

iv.iv. ““Neutron Bombs” -- permit fusion-Neutron Bombs” -- permit fusion-produced neutrons to escape – kills produced neutrons to escape – kills people even in armored vehicles people even in armored vehicles (explosion still levels civilian (explosion still levels civilian structures)structures)

e. Measures of Radiatione. Measures of Radiation

i.i. Measurements of exposure: 100 Measurements of exposure: 100 rad = 1 grayrad = 1 gray

ii.ii. Relative biological effectiveness Relative biological effectiveness (RBE): alpha = up to 20, neutron (RBE): alpha = up to 20, neutron varies, beta/gamma/X-Rays = 1varies, beta/gamma/X-Rays = 1

iii.iii. Measures of effect: rad * RBE = Measures of effect: rad * RBE = rem, gray * RBE = sievertrem, gray * RBE = sievert

iv.iv. Since gamma exposure is likely to Since gamma exposure is likely to be source of most radiation be source of most radiation poisoning, rad usually = rem and poisoning, rad usually = rem and gray usually = sievertgray usually = sievert

f. Radiation Poisoning f. Radiation Poisoning (Acute Radiation (Acute Radiation

Syndrome)Syndrome)i.i. Triggered by Triggered by

cumulative cumulative exposure – exposure – hourly dose * hourly dose * hours exposedhours exposed

ii. LD ii. LD 50 is 50 is 4.5 4.5 GraysGrays

g. Danger of Internal g. Danger of Internal AbsorptionAbsorption

Strontium-90 is chemically similar to Strontium-90 is chemically similar to Calcium Calcium incorporated into bones incorporated into bones

Iodine 131 is absorbed by the Iodine 131 is absorbed by the thyroidthyroid

Cesium 137 is chemically similar to Cesium 137 is chemically similar to potassium and absorbed throughout potassium and absorbed throughout the bodythe body

3. Distribution of Fallout3. Distribution of Fallout

a.a. Fallout = “point-source pollutant” Fallout = “point-source pollutant” (exposure almost always decreases (exposure almost always decreases with distance)with distance)

i.i. Key variables = speed and direction of Key variables = speed and direction of wind.wind.

ii.ii. Closer to source usually more Closer to source usually more dangerous – but downwind “hot spots” dangerous – but downwind “hot spots” are possibleare possible

1 Mt Surface Burst: 1 Mt Surface Burst: Cumulative and Hourly Cumulative and Hourly

Radiation ExposureRadiation Exposure

““Hot Spots” from Castle Hot Spots” from Castle Bravo TestBravo Test

b. US-USSR Predictionsb. US-USSR Predictions

Immediate Deaths:Immediate Deaths:

Fallout (1977 Fallout (1977 estimates):estimates):

Fallout (1990 Fallout (1990 Estimate)Estimate)

Fallout (USSR Fallout (USSR Estimate)Estimate)

4. Half-Life4. Half-Life

a.a. Definition: Time for 50% of a Definition: Time for 50% of a radioactive substance to decayradioactive substance to decay

b.b. Short half-life: These isotopes are Short half-life: These isotopes are very radioactive but don’t last longvery radioactive but don’t last long

c.c. Long half-life: These are less Long half-life: These are less radioactive but also long-livedradioactive but also long-lived

Example: 100 KT Surface Example: 100 KT Surface Blast, Fort Hood Main GateBlast, Fort Hood Main Gate

100 KT = larger than ordinary 100 KT = larger than ordinary fission bomb, smaller than largest fission bomb, smaller than largest Russian weaponsRussian weapons

15 psi: Virtually all dead

5 psi: 50% dead, 45% injured

2 psi: 5% dead, 45% injured)

1 psi: 25% injured

Example: 100 KT Surface: Example: 100 KT Surface: FalloutFallout

1 hour: Lethal2 hours: Lethal3 hours: Lethal4 hours: Lethal and 50% Lethal5 hours: Lethal and 50% LethalPossible Zone of Sickness

B. Nuclear Winter B. Nuclear Winter TheoryTheory

1.1. Key variable = soot and smoke from Key variable = soot and smoke from fires ignited by nuclear weaponsfires ignited by nuclear weapons

2.2. Targeting cities or heavily forested Targeting cities or heavily forested areas increases risk (major assumption)areas increases risk (major assumption)

3.3. Recent model (2006) suggests 10-year Recent model (2006) suggests 10-year cooling cycle from “small” nuclear war cooling cycle from “small” nuclear war (100 Hiroshima-sized bombs used on (100 Hiroshima-sized bombs used on population centers) population centers)

4.4. One recent paper (2007) predicts 10-20 One recent paper (2007) predicts 10-20 fewer growing days for several years, fewer growing days for several years, leading to mass starvation in Asialeading to mass starvation in Asia

5. Objections5. Objections

a.a. Model assumes carbon lofted into Model assumes carbon lofted into stratosphere – but this process is only stratosphere – but this process is only confirmed for very small particles (diesel confirmed for very small particles (diesel soot)soot)

b.b. Model assumes urban targeting – bases may Model assumes urban targeting – bases may be more logical targetsbe more logical targets

c.c. Model assumes one weapon per city rather Model assumes one weapon per city rather than key cities being hit with many warheadsthan key cities being hit with many warheads

d.d. Standard objections to climate modeling Standard objections to climate modeling (flaws in GCMs)(flaws in GCMs)

e.e. General: Very few scholars working in the General: Very few scholars working in the area, so research is “thin” – i.e. it depends on area, so research is “thin” – i.e. it depends on a few simple papersa few simple papers

VI. Other Pollution VI. Other Pollution DilemmasDilemmas

A.A. Ozone Ozone Depletion: Depletion: Some Some chemicals chemicals deplete deplete stratospheric stratospheric ozone when ozone when exposed to UV exposed to UV radiation radiation (usual culprit (usual culprit = CFCs)= CFCs)

1. Ozone Depleting 1. Ozone Depleting SubstancesSubstances

a.a. Chlorofluorocarbons (CFCs): Release Chlorofluorocarbons (CFCs): Release chlorine when exposed to UV radiationchlorine when exposed to UV radiation

i.i. Long-lived, non-toxic, non-flammableLong-lived, non-toxic, non-flammableii.ii. 1960s: used in refrigerators, air conditioners, 1960s: used in refrigerators, air conditioners,

spray cans, solvents, foamsspray cans, solvents, foams

b.b. Hydrochlorofluorocarbons (HCFCs): first Hydrochlorofluorocarbons (HCFCs): first replacement for CFCs, much less destructive replacement for CFCs, much less destructive (1%-10% as CFCs)(1%-10% as CFCs)

c.c. Halons and HBFCs: Release bromine into Halons and HBFCs: Release bromine into atmosphereatmosphere

i.i. Very useful for fire extinguishersVery useful for fire extinguishersii.ii. Up to 10 times as destructive as CFCsUp to 10 times as destructive as CFCs

d.d. Methyl Bromide: Used as a pesticide, about Methyl Bromide: Used as a pesticide, about 40% as destructive as CFCs40% as destructive as CFCs

3. Impacts3. Impacts

Ozone layer absorbs most of the harmful Ozone layer absorbs most of the harmful UV-B radiation so more UV-B means:UV-B radiation so more UV-B means: more melanoma and non-melanoma skin more melanoma and non-melanoma skin

cancerscancers more eye cataractsmore eye cataracts weakened immune systemsweakened immune systems reduced plant yieldsreduced plant yields damage to ocean eco-ecosystems damage to ocean eco-ecosystems more damage to plasticsmore damage to plastics

4. Montreal Protocol: 4. Montreal Protocol: Slow SuccessSlow Success

Vienna Convention in 1985Vienna Convention in 1985 framework agreementframework agreement

Montreal Protocol in 1987Montreal Protocol in 1987 Phase-out schedules for CFCs and halonsPhase-out schedules for CFCs and halons

London Amendment in 1990London Amendment in 1990 accelerated phase outs; additional CFCs, CCl4, accelerated phase outs; additional CFCs, CCl4,

CH3CCl3CH3CCl3 Copenhagen Amendment in 1992Copenhagen Amendment in 1992

added methyl bromide, HBFCs, HCFCsadded methyl bromide, HBFCs, HCFCs

Montreal Amendment in 1997Montreal Amendment in 1997 finalized phase-out schedules for methyl finalized phase-out schedules for methyl

bromidebromide

5. A Timeline of the 5. A Timeline of the Ozone CrisisOzone Crisis

No need to memorize, just see how No need to memorize, just see how concern builds, generates an concern builds, generates an industry response, and eventually industry response, and eventually leads to changeleads to change

Timeline of CFC Development• 1951: DuPont begins mass production of CFCs

• 1971: Scientist James Lovelock first speculates that CFCs released to the atmosphere could still be there.

• 1973: Atmospheric scientists Mario Molina and F. Sherry Rowland hypothesize that CFCs could be reaching the stratosphere, where they can be broken apart and a single chlorine atom could contribute to the destruction of 100,000 ozone molecules.

• 1974: Molina and Rowland publish their theory in the journal Nature; the story is picked up by a science writer at The New York Times and published on the front page.

• 1974: DuPont responds with their own study claiming that CFCs are safe in the troposphere; calls for more research.

Timeline of CFC Development (cont’)

• 200% increase in CFC use from 1968-1975, annual growth in consumption of 10-20%/year.

• 1979: The FDA and the EPA ban “non-essential” uses of CFCs in aerosol cans. Interesting: First ban without definitive proof of harm

• 1982: 20 other nations join U.S. ban on non-essential uses.

Early Warnings of Ozone Depletion• 1982: British scientific team in Antarctica using

ground-based instruments announce 20% decline in O3 levels in the stratosphere (in their spring). U.S. team contradicts.

• 1983: British team reports a 30% decline in ozone levels, U.S. team contradicts.

• 1985: British team reports a 50% decline in ozone levels. U.S. team contradicts, re-checks instruments and then confirms British findings.

• Acknowledgement of “ozone hole” in the media creates public and political alarm.

Early Warnings (cont’)• 1986: Australian government announces doubling of skin

cancer cases in previous 10 years.• 1986: DuPont scientists speculate that tropospheric (“bad”)

ozone will migrate to stratosphere to “fill” the hole.• 1987: Preliminary research indicates that loss of ozone over

Antarctica due primarily to human emissions of ozone-depleting chemicals.

• 1987: UN holds meetings in Montreal, and 45 nations sign the Montreal Protocol to reduce CFC use by 50% by the year 2000. Protocol is ratified in 1989.

• 1988: DuPont continues to argue that CFCs are safe to use, and initially oppose the Montreal Protocol. However, by year end they announce an impending phase-out of CFC production.

Science and Politics of Ozone Depletion• 1990: Follow-up meeting in London leads to new goal of

complete CFC phase-out in developed countries by 2000 and in developing countries by 2010.

• 1992: Follow up meeting in Copenhagen calls for complete phase-out by 1996, DuPont promises to halt production by 1997.

• 1992: Rush Limbaugh publishes book claiming that the ozone depletion “crisis” is a hoax.

• 1995: Congressional hearings also challenge ozone science.

• 1996: Satellite (TOMS) launched to study ozone. Almost immediately confirms depletion.

• 1996: CFC ban begins, but black market appears.