G. Tyler Miller’sLiving in the Environment

Chapter 18

G. Tyler Miller’sLiving in the Environment

Chapter 18

Climate Change and Ozone Loss

Key ConceptsKey Concepts

Changes in Earth’s climate over time

Factors affecting climate

Possible effects of global warming

Adapting to climate change

Human impacts on the ozone layer

Protecting and restoring the ozone layer

Temperature and climate have been changing throughout the earth’s history.

Climate shifts have occurred due to volcanic emissions changes in solar input, continents moving on shifting plates, meteor strikes, and other factors.

Alternating cycles of freezing and thawing are known

as glacial and interglacial periods.

Past Climate ChangesPast Climate Changes

• Antarctic ice cores indicate the current interglacial period could last another 15,000 years.

• Direct temperature records go back to 1861.

• The Intergovernmental Panel on Climate Change (IPCC) was formed in 1988 to evaluate possible future climate changes.

Past Climate ChangesPast Climate Changes

Past globaltemperatures

Past globaltemperatures

Recent trends in global temperatures

Recent trends in global temperatures

Today’s global average temp 59oF, 15oC

The Earth’s Natural Greenhouse Effect The Earth’s Natural Greenhouse Effect A natural process called the greenhouse effect warms

the lower troposphere and surface. Incoming solar must be balanced by equal amt. of outgoing energy.

A large process also takes place at the earth’s surface due to heat absorbed by surface water. Provides an natural cooling effect on earth

The earth’s average surface temperature is about 15 degrees Celsius.(59 F)

The two major greenhouse gases are water vapor and carbon dioxide. Water vapor has remained constant. Carbon dioxide has fluctuated 190-210 ppm

What is the Greenhouse EffectWhat is the Greenhouse Effect

Fig: 6-14

Table 21-1Page 464

Table 21-1Page 464

Table 21-1 Major Greenhouse Gases from Human Activities

Greenhouse Gas

Carbon dioxide (CO2)

Methane (CH4)

Nitrous oxide (N2O)

Chlorofluorocarbons(CFCs)*

Hydrochloro-fluorocarbons (HCFCs)

Hydrofluorocarbons(HFCs)

Halons

Carbon tetrachloride

Average Time in the Troposphere

100–120 years

12–18 years

114–120 years

11–20 years (65–110 years in stratosphere)

9–390

15–390

65

42

Human Sources

Fossil fuel burning, especially coal (70–75%), deforestation, and plant burning

Rice paddies, guts of cattle and termites, landfills, coal production, coal seams, and natural gas leaks from oil and gas production and pipelines

Fossil fuel burning, fertilizers, livestock wastes, and nylon production

Air conditioners, refrigerators, plastic foams

Air conditioners, refrigerators, plastic foams

Air conditioners, refrigerators, plastic foams

Fire extinguishers

Cleaning solvent

Relative Warming Potential (compared to CO2)

1

23

296

900–8,300

470–2,000

130–12,700

5,500

1,400

Climate Change and Human Activities Climate Change and Human Activities

Humans have increased levels of greenhouse gases in the troposphere by use of fossil fuels, farming, use of inorganic fertilizers, burning forests, etc.

Greenhouse gases are at higher levels than in the past 160,000 years.

Burning of fossil fuels has generated much of the CO2 increase.

Deforestation and clearing grasslands release CO2 and N2O.

Increased cattle raising, and other livestock, has added methane release.

Use of inorganic fertilizers in rice cultivation releases N2O into the troposphere.

Estimated long term varation in average global temp. of the atmosphere and average CO2 levels in past 160,00years.

U.S. and Greenhouse GasesU.S. and Greenhouse Gases

4.6% of the world’s population, yet 24% of emissions of CO2

From just U.S. coal burning exceeds 146 other nations with 3/4th of world population

Per capita yearly 500 tons

Also large CH4

Is the troposphere warming?Is the troposphere warming?

There is considerable and mounting evidence that the troposphere is warming “quickly”

• Rate of change

IPCC found:

1) 20th Century warmest in past 1,000 years

Is the troposphere warming?Is the troposphere warming?

2) Since 1861 global avg. temp increase 0.80C or 1.40F (mostly post 1980)

3) 16 of the warmest years on record occurred since 1980 (hottest 1998 followed by 2001 and 2003)

4) Glaciers around world melting quickly and poles warming more pronounced

5) Global sea levels rose 4-8 inches during 20th Century and continue to rise.

Is the troposphere warming?Is the troposphere warming?

Few skeptics still exist, most just argue it is not human caused warming

• Global warming versus Global climate change--- what is the difference?

Do NOT confuse it with ozone depletion

New TerminologiesNew Terminologies

• Global warming refers to temperature increases in the troposphere, which can cause climate change.

• Global climate change is a broader term that refers to changes in any aspects of the earth’s climate.

Factors Affecting the Earth’s TemperatureFactors Affecting the Earth’s Temperature

Changes in solar output

Changes in Earth’s albedo

Moderating effect of oceans

Clouds and water vapor

Air pollution

Oceans 5%

Bare sand 30–60%

Grass 15–25%

Clouds 50–55%

Snow 80–90%City 10–15%

Forest 5%

Figure: The Albedo or reflectivity of the incoming solar energy.

Warning Signals From GlaciersWarning Signals From Glaciers

Positive Feedback: more ice melting = more warming = more ice melting….

Melting floating ice has

little impact on sea level rise (WHY?)

“Fresher” water in ocean, what are the consequences?

Warning Signals From GlaciersWarning Signals From GlaciersMount Kilimanjaro

glacier free in 15 years?

80% of South American glaciers gone also in 15 years?

• Less fresh water sources

• Tourism loss

Any good impacts?

Projecting Future Changes in Earth’s Climate

Projecting Future Changes in Earth’s Climate

Climate models

Apparent influence of human activities

Apparent influence of human activities

Could be natural changes

Climate modelsClimate modelsScientists have

developed complex mathematical models of the earth’s climate system.

Inputs:• Solar energy• Earth’s land • Ice• Greenhouse gases• Clouds, winds, water

vapor

Troposphere

Aerosols

Greenhousegases

Warmingfromdecrease

Cooling from increase

CO2 removal by plants and soil organisms

CO2 emissions from land cleaning, fires, and decay

Heat andCO2 removal

Heat andCO2 emissions

Ice and snow cover

Natural and human emissions

Land and soil

Shallow ocean

Long-termstorage

Deep ocean

IPCC Reports “Best Science”IPCC Reports “Best Science”IPCC

(Intergovernmental Panel on Climate Change)

1990, 1995, 2001 and now 2007 reports

Three Major Finding From 2001

1) Latest climate models closely match changes since 1850

IPCC Reports “Best Science”IPCC Reports “Best Science”2) “There is strong

evidence that most of the warming observed over the last 50 years is attributable to human activities.”

3) It is likely that the world will warm 1.4oC to 5.8oC (2.5oF to 10.4oF) between 2000 and 2100

Ocean Storage of CO2 and HeatOcean Storage of CO2 and Heat

Ocean currents act to redistribute heat arriving at equator moving it north.

Example: Gulf Stream

Deep ocean currents not well understood.

Ocean Storage of CO2 and HeatOcean Storage of CO2 and HeatEvidence has shown that

ocean currents have shifted and even stopped during times in the past.

Effect of salinity levels (cold, salty water more dense)

“Day After Tomorrow” movie effect…

Ocean Storage of CO2 and HeatOcean Storage of CO2 and Heat

Oceans also act to trap about 29% of CO2 released into the atmosphere as part of global carbon cycle.

Cloud CoverCloud Cover

Warmer Troposphere =

More Evaporation =

More Clouds =

WARMER OR COOLER?

Why might it be a

positive feedback?

Why might it be a

negative feedback?

Cloud CoverCloud Cover

• Day versus Night Impacts

• Thick clouds versus thin clouds

• High clouds versus Low clouds

• Latent heat release during cloud formation

Possible Benefits from a Warmer AtmospherePossible Benefits from a Warmer Atmosphere

• Less severe winters

• More precipitation in some dry areas

• Less precipitation in some wet areas

• Increased food production in some areas

• Expanded population and ranges of some species

Some Possible Effects of a Warmer World

Some Possible Effects of a Warmer World

Solutions: Dealing with the ThreatSolutions: Dealing with the ThreatScientists debate the causes, how rapidly the changes

might occur, the effects on humans and ecosystems, and the responses that should be taken.

Economists and policymakers disagree on whether:

• economic costs of reducing greenhouse gas emissions are higher than the economic benefits;

• developed countries, developing countries, or both should take responsibility for reducing greenhouse gases; and

• actions to reduce greenhouse gas emissions should be voluntary or required.

Four schools of thought have emerged from this controversy.

Dealing with the Threat of Climate Change

Dealing with the Threat of Climate Change

There is little disagreement that our planet is warming, where most disagreement lies is in what to do about it.

1) Are economic costs of reducing greenhouse gases higher than benefits?

Dealing with the Threat of Climate Change

Dealing with the Threat of Climate Change

2) Developed or developing countries, how should take responsibility?

3) Voluntary cuts or mandatory laws?

Arguments transcend politics, economics, scientific, cultural….

Solutions: Dealing with the ThreatSolutions: Dealing with the Threat

Options

Do nothing

Do more research

Act now to reduce risks

Precautionary principle

What can be done?What can be done?

• Improve energy efficiency

• Reduce fossil fuel use

• Renewable energy sources

• Reduce population growth

• Reduce deforestation• Carbon sequestration

Treeplantation

Coalpower plant

Tanker deliversCO2 from plantto rig

Oil rig

Crop fieldSwitchgrass

Spent oil reservoir isused for CO2 deposit

CO2 is pumpeddown to reservoir through abandoned oil field

Abandonedoil field

CO2 ispumped downfrom rig for deepocean disposal

= CO2 deposit

= CO2 pumping

Removing CO2 from the Atmosphere

Reducing CO2 Emissions

What Can You Do?

• Drive a fuel-efficient car, walk, bike, carpool, and use mass transit

• Use energy-efficient windows

• Use energy-efficient appliances and lights

• Heavily insulate your house and seal all drafts

• Reduce garbage by recycling and reuse

• Insulate hot water heater

• Use compact fluorescent bulbs

• Plant trees to shade your house during summer

• Set water heater no higher than 49°C (120°F)

• Wash laundry in warm or cold water

• Use low-flow shower head

Figure 21-20Page 483

Figure 21-20Page 483

What is Being Done to Reduce Greenhouse Gas Emissions?

What is Being Done to Reduce Greenhouse Gas Emissions?

• The Kyoto Protocol, developed in 1997, would require 39 developed countries to cut emissions of some gases by about 5.2% below 1990 levels by 2012.

• Developing countries would not have to make cuts until a later date.

• By mid-2004, it had been ratified by more than 120 countries.

• In 2001, President George W. Bush withdrew the U.S. from the Kyoto Protocol.

• Scott Barnett, an expert on environmental treaties, believes the Kyoto Protocol is a badly thought out agreement and it will not work.

Many countries, companies, cities, states, and provinces are reducing greenhouse gas emissions, improving energy efficiency, and increasing their use of carbon-free renewable energy.

Great Britain reduced its CO2 emissions to its 1990 level by the year 2000, well ahead of the Kyoto target goal.

China reduced it CO2 emissions by 17% between 1997 and 2000 by phasing out coal subsidies, shutting down inefficient coal-fired electric plants, and restructuring its economy toward use of renewable energy resources.

Some major global companies have established targets to reduce their greenhouse gas emissions by 10–65% from 1990 levels by 2010.

Estimates are that current emissions of greenhouse gases must be cut by at least 50% by 2018 to stabilize concentrations at their present levels.

Loss of the Ozone Layer: Reasons for ConcernLoss 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

Long-lived chemicals and ozone levelLong-lived chemicals and ozone level1. The first chlorofluorocarbon (CFC) was discovered in 1930. Many

use, became very popular and dream chemicals.

2. In 1974, chemists Rowland and Molina found that CFCs were lowering the average concentration of ozone in the stratosphere.

3. Four major conclusions from their research:a. CFCs remain in the atmosphere because they are insoluble in

water and chemically unreactive.b. Over 11–20 years, these chemicals are lifted into the

stratosphere, mostly by convection currents and turbulent mixing of air.

c. CFC molecules break down under the influence of high-energy UV radiation. Chlorine is released and is highly reactive. Fluorine, bromine, and iodine are also released. This causes ozone to be broken down faster than it is formed.

d. These CFC molecules can last in the stratosphere for 65–385 years.

4. In 1988, after 14 years of delay tactics, the CFC industry acknowledged and agreed to stop manufacturing them.

5. Rowland and Molina received the Nobel Prize in chemistry for their work. (1995).

Ozone Depleting ChemicalsOzone Depleting Chemicals

Chlorofluorocarbons (CFCs)Halons(used in fire extinguishers)Methyl bromide (dry cleaning)

Carbon tetrachlorideMethyl chloroformHydrogen chloride

Former Uses of CFCsFormer Uses of CFCs

• Air Conditioners• Refrigerators• Spray cans• Cleaners for electronic parts• Sterilizing medical instruments• Fumigants for granaries and cargo ships

Seasonal Ozone Layer Thinning at the PolesSeasonal Ozone Layer Thinning at the Poles

During four months of each year, up to half of the ozone in the stratosphere over Antarctica is depleted.

Ozone loss is often called the ozone hole, but it is actually ozone thinning.

The total area of stratosphere that suffers from ozone thinning varies from year to year. In 2003, the area was the second largest ever.

The primary culprits are CFCs and other ODCs.

• The polar vortex is a swirling mass of very cold air that is isolated from the rest of the atmosphere for several months.

• Ice crystals in this mass collect CFCs and other chemicals and set up conditions for formation of CIO, the molecule most responsible for seasonal loss of ozone.

• As sunlight returns to Antarctica in October, the light stimulates CIO molecules and within a matter of weeks the ozone is reduced by 40–50% on average.

• It is predicted that the worst ozone thinning will be between 2010 and 2019.

• Increased UV radiation reaching the earth’s surface from ozone depletion is harmful to human health, crops, forests, animals, and materials. Figure 21-24 lists the effects of ozone depletion.

• Exposure to UV radiation is a major cause of skin cancers.

• Caucasians are most susceptible to melanomas.

Basal Cell Carcinoma

Melanoma

Squamous Cell Carcinoma

Effects of Ozone Depletion

Natural Capital Degradation

Human Health• Worse sunburn• More eye cataracts• More skin cancers• Immune system suppression

Food and Forests• Reduced yields for some crops• Reduced seafood supplies from reduced phytoplankton• Decreased forest productivity for UV-sensitive tree species

Wildlife• Increased eye cataracts in some species• Decreased population of aquatic species sensitive to UV radiation• Reduced population of surface phytoplankton• Disrupted aquatic food webs from reduced phytoplankton

Air Pollution and Materials• Increased acid deposition• Increased photochemical smog• Degradation of outdoor paints and plastics

Global Warming• Accelerated warming because of decreased ocean uptake of CO2

from atmosphere by phytoplankton and CFCs acting as greenhouse gases

Solutions: Protecting the Ozone LayerSolutions: Protecting the Ozone LayerCFC substitutes Montreal Protocol : 1987; 35 nations to cut CFC by

35% in 2000Copenhagen Protocol: phase out of all

ozone depleting chemicals

Protecting the Ozone LayerProtecting the Ozone Layer

If we immediately stop, it will take 50 years to return to 1980 levels and about 100 years to return to pre-1950 levels.

The goal of the 1987 Montreal Protocol was to cut emissions of CFCs by about 35% between 1989 and 2000.

The Copenhagen Protocol, adopted in 1990 and 1992 that accelerated the phase out of key ozone-depleting chemicals.

These agreements have now been signed by 177 countries.

A study in 1998 stated that ozone depletion has been cooling the troposphere and helped to disguise as much as 30% of the global warming.

Restoring the ozone layer could lead to increased global warming, but the alternative is worse.