Chapter 20
Climate Change and Ozone Depletion
Core Case Study: Studying a Volcano to Understand Climate Change
 Volcanic eruptions—avalanches of hot gas and ash roared down the sides of the
mountain and filled valleys with volcanic deposits
 Global Warming: a rise in the average temperature of the entire earth
 Figured that global temperatures are likely to rise several degrees during this
century and affect the earth’s global and regional climates, economies, and human
way of life
Past Climate Change and the Greenhouse Effect
Global Warming and Global Cooling Are Nut New (Science)
 The earth has experienced prolonged periods of global warming and global
cooling
 The planet’s climate change has been altered by volcanic eruption, changes in
solar input, continents moving slowly as a result of shifting tectonic plants, strikes
by large meteors, and other factors
 The troposphere has experienced prolonged period of global cooling and global
warming
 Glacial and interglacial (between ice ages) periods: the alternating cycles of
freezing and thawing
How Do We Know What Temperatures Were in the Past? (Science)
 Scientists have used a number of techniques to estimate past temperatures
 Temperature changes are estimated by analysis of radioisotopes in rocks and
fossils; plankton and radioisotopes in ocean sediments; tiny bubbles of ancient
glaciers; temperature measurements taken at different depths from boreholes
drilled deep into the earth’s surface; pollen from the bottoms of lakes and bogs;
tree rings; and historical records
 Changes in the troposphere levels of CO2 correlate fairly closely with variations
in the average global temperature
The Natural Greenhouse Effect (Science)
 The sun and the presence of certain greenhouse gases warm the troposphere and
the earth’s surface
 Three major factors shape the earth’s climate:
o The sun
o A natural process called the greenhouse effect that warms the earth’s
lower troposphere and surface because of the presence of several gases
called greenhouse gases
o The oceans that cover most of the planet and influence climate by storing
carbon dioxide and heat, evaporating and receiving water as part of the
hydrologic cycle, and moving stored heat from one place to another in
currents
 Natural cooling process takes place at the earth’s surface
o Large quantities of heat are absorbed by the evaporation of surface water,
most of it from the ocean
Major Greenhouse Gases (Science)
 The major greenhouse gases in the lower atmosphere are water vapor, carbon
dioxide, methane, and nitrous oxide
 Four natural greenhouse gases in the troposphere
o Water vapor (H2O)
o Carbon dioxide (CO2)
o Methane (CH4)
o Nitrous oxide (N2O)\
 Fluctuations in the troposphere concentrations of these gases plus changes in solar
output are the major factors causing the changes in the average temperature of the
troposphere
 Increase in these levels is from burning fossils fuels, clearing and burning forests,
and planting rice and using inorganic fertilizers
 In 2004 the US was the largest emitter of greenhouse gases with 22% global
emissions
 The U.S. and Canada have some the of the world’s highest greenhouse gas
emissions per person
Climate Change and Human Activities
Signs That the Troposphere Is Warming: The Human Connection (Science)
 There is considerable evidence that the earth’s troposphere is warming, mostly
because of human actions
 Emission were low until about 8,000 years ago
 Co2 emission rose as the population increased
 Our ancestors may have unknowingly saved us from a much cooler world by
inventing and expanding agriculture
 The earth is the hottest it has been in 400 years and likely that it is hotter than it
has been in 1,000 years
 Global temperature of the troposphere near the earth’s surface has risen about 0.6
C (1.1 F) over the entire globe and about 0.8 C (1.4 F) over the continents.
 Most of the increase has taken place since 1980
 The 10 hottest years have occurred since 1990
 Artic temperatures have risen almost twice as fast as those in the rest of the world
 Glaciers and floating sea ice in some parts of the world are melting and shrinking
at increasing rates
 Warmer temperatures in Alaska and Russia and in other parts of the artic are
melting not-so-permanent permafrost, releasing more CO2 and CH4 intro the
troposphere, which may accelerate troposphere warming
 During the last century, the world’s average sea level rose by 10-20 centimeters
mostly because of runoff from melting land-based ice and the expansion of ocean
water as its temperature increases
The Scientific Consensus about Future Climate Change (Science)
 There is strong evidence that human activities will play an important role in
changing the earth’s climate during this century

Coupled general circulation models (CGCMs): the earth’s climate system that
simulate interactions among the earth’s sunlight, clouds, land masses, oceans and
ocean currents, concentrations of greenhouse gases and pollutants, and positive
and negative feedback loops within the climate system
o They couple, or combine, the effects of the atmosphere and the oceans on
climate
 Global Warming: refers to temperature increases in the troposphere, which in
turn can cause climate change
 Global climate change: is a broader term that refers to changes in any aspects of
the earth’s climate, including temperature, precipitation, and storm intensity and
patterns
 Consensus among scientists that global warming is occurring, that human
activities are major factor in this temperature increase, and not human activities
will even have a greater impact now
 Climate skeptics:
o One groups consists of a few prominent climate scientists who believe that
we do not know enough about how the global climate system works to
make accurate projections about global warming
o Another group consists of scientists (a number of them not climate
experts) whose climate research is largely supported by some coal, oil,
automobile, and utility industries with a vested finical interest in not
having CO2 regulated as a pollutant
 To analysts this use of scientific uncertainty as an excuse for paralysis has been a
tragic loss of our most precious resource—time
Why Should We Be Concerned about a Warmer Earth? (Science, Economics, and Ethics)
 A rapid increase in the temperature of the troposphere during this century would
give us little time to deal with its harmful effects
 We are not talking about normal swings in local weather but a projected global
change in climate—weather averaged over decades, centuries, and millennia
 It’s not only temperature changes threat we should look for, it’s how rapidly it
occurs
 Such rapid change could drastically affect life on earth
 Tipping point—the point in which it will be too late to reverse catastrophic
change for tens of thousands of years
 We do not know how close we are to the tipping point
 A way to prevent it is to try to cut carbon dioxide emissions in half over the next
50 years to reduce the risk of triggering changes in the earth’s climate system that
would last for tens of thousands of years
Factors Affecting the Earth’s Temperature
Harmful and Corrective Feedback in the Global Climate System (Science)
 Some factors can amplify and some can dampen projected global warming
 Amplify: positive feedback
 Dampen: negative feedback
 There are more positive feedback loops than negative feedback loops
Can the Oceans Store More CO2 and Heat? (Science)
 There is uncertainty about how much CO2 and heat the oceans can remove from
the troposphere and how long the heat and CO2 might remain there
 The oceans help moderate the earth’s average surface temperature by removing
almost half of the excess CO2 our activities pump into the troposphere
 The oceans absorb heat from the troposphere and slowly transfer some of it to the
deep ocean
 Solubility of CO2 is going down as temperatures are rising, therefore CO2 is
being released into the atmosphere
 The upper part of the ocean has warmed since 1995
Effects of Cloud Cover (Science)
 Warmer temperatures create more clouds that cloud warm or cool troposphere
 Warmer temperatures lead to more clouds
 These additional clouds have a warming effect (positive feedback) by absorbing
and releasing heat into the troposphere, or a cooling effect (negative feedback) by
reflecting more sunlight back into space
 They can decrease surface warming because they reflect back sunlight
 An increase in thin clouds can warm the lower troposphere and increase surface
warming
Effects of Outdoor Air Pollution (Science)
 Aerosol pollutants and soot produced by human activities can warm or cool the
atmosphere, but such effects will decrease with any decline in outdoor air
pollution
 They are released by volcanic eruptions and human activities
 Most aerosols cool the atmosphere and thus temporarily slow global warming
 The second biggest contributor to global warming is the tiny particles of soot or
back carbon aerosols—produced mainly from incomplete combustion in coal
burning, diesel engines, and open fires
 Aerosols and soot fall back to the earth or are washed out of the lower atmosphere
within weeks or months, whereas CO2 and other greenhouse gasses remain in the
atmosphere for decades to several hundred years
 Aerosols inputs into the atmosphere are being reduced—especially in developed
countries
Effects of Higher CO2 Levels on Photosynthesis (Science)
 Increased CO2 in the troposphere can increase plant photosynthesis but several
factors can limit or counter this effect
 Large amounts of CO2 in the atmosphere could increase the rate of
photosynthesis in some areas with adequate water and soil
o This would remove CO2 from the troposphere and help slow global
warming
 This is only temporary for four reasons
o The increase in photosynthesis would slow as the plants rate maturity and
keep less CO2 from the troposphere
o Carbon stored by the plants would be returned to the atmosphere as CO2
when the plants die and decompose or burn
o Increased photosynthesis decreased the amount of carbon stored in the soil
o Tree growth might temporarily slow CO2 emissions in the southern
hemisphere but is likely to increase CO2 emissions in the northern
hemisphere
Effects of a Warmer Troposphere on Methane Emissions (Science)
 Warmer air can release methane gases stored in bogs, wetlands, and tundra soils
and accelerate global warming
 Global warming could be accelerated by an increased release of methane from
two major sources:
o Swamps and other freshwater wetlands and ice-like compounds called
methane hydrates trapped beneath artic permafrost and the deep ocean
floor
 Methane releasing is going to go up if the permafrost in tundra and boreal forest
soil melts
 Positive feedback loop: a warmer troposphere could lead to more methane release
and still more warming in another positive feedback loop
Effects of Global Warming
Effects of a Warmer Troposphere: An Overview (Science)
 A warmer climate would have beneficial and harmful effects but poor nations I
the tropics would suffer the most
 Poor people and wildlife species in the tropics will suffer the most harm
Melting Ice and Snow (Science)
 Some of the world’s floating ice and land-based glaciers are slowly melting and
are helping warm the troposphere by reflecting less sunlight back into space
 Temperature increases tend to be much greater in polar regions
 The earth’s poles and mountaintop glaciers are the planet’s air-conditioning
system
o Because they reflect the sunlight back up
 Melting of all of the ice will make the earth a darker surface and less reflective
resulting in a warmer troposphere
 Floating ice does not contribute to the rising sea-levels
 Routes are opening up for ships to go through, which will make it less expensive
 There will be severe water shortages because there will be a shortage of glacial
runoff
 Rivers that are fed by mountain glaciers could shrivel
Rising Sea Levels (Science)
 During this century rising sea levels are projected to flood low-lying urban areas,
coastal estuaries, wetlands, coral reefs and barrier islands and beaches
 Effects from the sea level rising:
o Threaten half of the world’s coastal estuaries, wetlands and coral reefs
o Disrupt many of the world’s coastal fisheries
o Flood low-lying barrier islands and cause gently sloping coastal lines to
erode and retreat inland by about 1.5 kilometers
o Flood agricultural lowlands and deltas in coastal areas where much of the
world’s rice is grown
o Contaminant freshwater coastal aquifers with salt water
o Submerge some low-lying islands in the Pacific ocean, the Caribbean Sea,
and the Indian Ocean
o Flood coastal areas with large human populations, including parts of some
of the world’s largest cities
Changing Ocean Currents (Science)
 Global warming could alter ocean currents and cause excessive warming in some
parts of the world and severe cooling in other areas
 The currents act like gigantic conveyor belt, moving CO2 and heat to and from
the deep sea, and transferring hot and cold water between the tropics and the poles
 Thawing ice in the Arctic region might slow or disrupt this conveyor belt
 Global warming can lead to significant global cooling in some parts of the worlds
Warmer and More Acidic Seas (Science)
 A warmer troposphere can decrease the ability of the ocean to remove and store
carbon dioxide by decreasing the nutrient supply for phytoplankton and increasing
the acidity of ocean water
 The vast number of photosynthesizing phytoplankton in the sea help counter
global warming by removing about a third of the carbon dioxide released by the
burning fossil fuels from the troposphere
 Nutrients for these phytoplankton is not going to come up to them because the
ocean will not be able to lift that from the bottom
 Positive feedback loop: it will decrease both primary productivity in surface
waters and CO2 removal from the troposphere. The more the ocean warms, the
greater this effect in yet another positive feedback effect
 A lower pH results in a lower concentration of carbonate ions, which can decrease
the ability of corals and other calcifying organisms to make calcium carbonate
shells and bodies and thus provide long-term storage of some of the CO2 removed
from the troposphere
 Such changes can upset the ocean food chains and reduce the removal of CO2
from the atmosphere in other positive feedback loop that becomes stronger as the
troposphere and ocean surface water become warmer
Changes in Precipitation and Weather Extremes (Science)
 Global warming will lead to prolonged heat waves and droughts in some areas
and prolonged heavy rains and increased flooding in other areas
 Some areas will get more water and other areas
 This is will affect where people can live and what they can grow
 Droughts will be more severe and last longer
o Deserts will expand, and there will be large amounts of environmental
refugees
 Areas will experience increased and more severe flooding from heavy and
prolonged precipitation
 Predictions are heat waves
Effects on Biodiversity: Winners and Losers (Science)
 Warmer temperatures will affect the distribution and species makeup of many of
the world’s ecosystems
 A warmer climate could expand ranges and populations of some plant and animal
species that can adapt to warmer climates
o But this would include certain weeds, insect pests, and disease-carrying
organisms
o Changes in structure and location of wildlife habitats could cause
extinction of plant and animal species that could not migrate to new areas,
and those with specialized niches or a narrow tolerance for temperature
change would also be threatened
o The ecosystems most likely to suffer disruption and species loss are coral
reefs, polar seas, coastal wetlands, arctic and alpine tundra, and highelevation mountaintops
o Some types of forests unable to migrate fast enough will decrease and
other such as oak-pine and oak-hickory forests in the U.S. may expand
northward
o Shift in regional climates, will wipe out the positive effects of current
efforts to stem the loss of biodiversity
 Global warming will reduce the biodiversity that is one of the four pillars of
sustainability, and in turn this likely to accelerate global warming
Effects on Agriculture and Fish Stocks: Winners and Losers (Science)
 Food production may increase in some areas and decrease in others
 Global warming will upset this stability by shifting climates and speeding up the
hydrological cycle
o This means changes in precipitation and water, and more crop pests and
diseases
 In a warmer world, agricultural productivity may increase in some areas and
decrease in others
 Models project a decline in agricultural productivity in tropical subtropical
regions, where many of the world’s poorest people live
 High-elevation snowfall and glaciers could lead to a sharp decline in agricultural
productivity in some heavily irrigated areas
 Crop and fish production in some areas could be reduced when rising sea levels
flood river deltas which are home to some of the world’s most productive
agricultural lands and coastal aquaculture ponds
Effects on People (Science)
 Global warming will increase deaths from heat and disruption of food and
supplies in some areas, spread some tropical diseases to temperate areas, and
greatly increase the number of environmental refugees from drought and flooding
 Heat stress will increase death and illness, especially among older people. Those
with poor health, and the urban poor
 Fewer people will die from colder weather
 With warmer weather, the mosquitos live through the weather, so there is more
disease being carried around by the mosquitos since they did not die in the winter
 Flooding and drought will force migration by tens of millions




Increased CO2 levels led to greatly increased of poison ivy and production of its
harmful chemical
Increased CO2 levels will lead to more allergy-causing ragweed and pollen, and
beetles, and other insects that devastate forests
Devastated forests are more likely to burn and produce more CO2 in another
positive feedback loop
Climate change already prematurely kills more than 150,000 people a year and
this number could double by 2030
Dealing with Global Warming
Why is Climate Change Such a Difficult Problem to Deal with? (Science, Economics,
Politics, Ethics)
 The problem is global. Dealing with this threat will require unprecedented
international cooperation
 The effects will last a long time. Once climate change is set into motion its effects
will last hundreds to thousands of years
 The problem is a long-term political issue. People and elected officials generally
respond well to short-term problems, but have difficulty acknowledging and
coping with ling-term threats
 The harmful and beneficial impacts of climate change are not spread easily. There
will be winners and losers. Winning notations are less likely to bring about
controversial changes or spend large sums of money to slow down something that
will benefit them. The catch: we will not know who wins and who loses until it is
too late to avoid harmful effects
 Many actions that might reduce the threat of climate change, such as phasing out
fossil fuels, are controversial because they can disrupt economies and lifestyles.
Solutions: What Are Our Options? (Science, Economics, and Politics)
 There is disagreement over what we should do about the threat of global warming
 Two basic ways to deal with global warming:
o Migration that reduces greenhouse gas emissions to slow down the rate of
temperature increase and buy time to learn more about how the earth’s
climate system works and to shift to other noncarbon energy options
o Adaptation, in which we recognize that some warming is unavoidable and
devise strategies to reduce its harmful effects
o We need to use a mixture of both
 Two major schools of thought concerning what we should do now to reduce the
effects of global warming
o Wait-and-see strategy, with some scientists and economists calling for
more research and better understanding of the earth’s climate system
before we make far-reaching and controversial economic and political
decisions such as phasing out fossil fuels
o Or: act now to reduce the risks from climate change brought about global
warming. They argue that the potential for harmful economic, ecological,
and social consequences is so great that action to slow the rate of change
should not be delayed
Solutions: Reducing the Threat (Science, Economics, and Politics)
 We can improve energy efficiency, rely more on carbon-free renewable energy
resources, and find ways to keep CO2 we produce out of the troposphere
 The mitigation solutions come down to three major strategies:
o improve efficiency to reduce fossil fuel use
o shift from carbon-based fossil fuels to carbon free renewable energy
resources,
o sequester or store as much CO2 as possible in soil, vegetation, the
underground, and the deep ocean
 The effectiveness of these strategies would be enhanced by reducing population
and by reducing poverty
 Prevention:
o Cut fossil fuel use
o Shift from coal to natural gas
o Shift to renewable energy resources
o Improve energy efficiency
o Reduce deforestation
o Limit urban sprawl
o Slow population growth
 Cleanup:
o Store CO2 by planting trees
o Sequester CO2 deep underground
o Sequester CO2 in the deep ocean
o Repair leaky natural gas pipelines and facilities
o Remove CO2 from smokestack and vehicle emissions
Removing and Storing CO2 (Science)
 We can prevent some of the CO2 we produce from circulating the troposphere,
but the costs may be high and the effectiveness of various approaches remains
unknown
 Soil sequestration: removes CO2 from the air and stores it in the soil, but with
warmer temperatures, it can increase decomposition in soil and return some of
this CO2 to the troposphere
 Reduce the release of carbon dioxide and nitrous oxide from soil: no-till
cultivation and setting aside depleted crop fields as conservation reserves
 To remove CO2 from the smokestacks, pump it deep underground into unminable
coal seams and abandoned oil fields or inject it into the deep ocean
Government Roles in Reducing the Threat of Climate Change (Economics and Politics)
 Governments can tax greenhouse gas emissions and energy use, increase
subsidies and tax breaks for saving energy and using renewable energy, and
decrease subsidies and tax breaks for fossil fuels
 Three major methods to promote the cutting of CO2 emissions
o Carbon taxes on each unit of CO2 emitted by fossil fuels or energy taxes
on each unit of fossil fuel burned
o Level the economic playing field by greatly increasing government
subsidies for energy-efficiency technologies, carbon-free renewableenergy technologies, carbon sequestration, and more sustainable
agriculture, and by phasing out or sharply reducing subsidies and tax
breaks for using fossil fuels, nuclear power, and unsustainable agriculture
o Technology transfer: governments of developed countries could fund the
transfer of energy-efficiency, carbon-free renewable-energy, carbonsequestration, and more sustainable agriculture technologies to developing
countries
Can We Afford to Reduce the Threat of Global Warming? (Economics)
 A crash program to slow and adapt to global warming now is very likely to cost
less than waiting and having to deal with its harmful effects later
What is Being Done to Reduce Greenhouse Gas Emissions?
International Climate Negotiations: The Kyoto Protocol (Politics and Economics)
 Getting countries to agree on greatly reducing their greenhouse gas emissions is
difficult
 Requires developed countered to cut their emissions to an average at least 5.2%
Moving Beyond the Kyoto Protocol (Politics)
 Countries could work together to develop a new international approach to slowing
global warming
 Hard to do because the global warming is not the same everywhere
Actions by Some Countries, States, Cities, Businesses, Schools, and Individuals
(Economics and Ethics)
 Many countries, states, cities companies, schools and individuals are reducing
their greenhouse gas emissions, improving energy efficiency, and increasing their
use of carbon-free renewable energy
 Reducing CO2 Emissions
o Drive a fuel-efficient care, walk, bike, carpool, and use mass transit
o Use energy-efficient appliances and lights
o Reduce garbage by recycling and reuse
o Plant trees to shade your house during the summer
o Wash laundry in warm and cold water
o Use compact florescent bulbs
Solutions: Preparing for Global Warming (Science, Economics, and Ethics)
 Many countries and cities are looking for ways to cope with the harmful effects of
climate change
 Since we have waited so long, we are stuck with some climate change
Ozone Depletion in the Stratosphere
Threats to Ozone Levels in the Stratosphere (Science)
 Less ozone in the stratosphere allows more harmful UV radiation to reach the
earth’s surface
 This layer keeps up to 95% of the UV radiation from reaching the earth’s surface
 The stratosphere is thin or almost nonexistent about the Artic and Antarctica the
sun is being reflected back into the atmosphere
What causes Ozone Depletion? (Science)
 Widespread use of several long-lived chemicals has reduced ozone levels in the
stratosphere

CFCs/Freons became popular because they were inexpensive, but it turned out
that they were lowering the average concentration of ozone in the stratosphere
 CFCs remain in the troposphere because they are insoluble in water and
chemically unreactive
 Over 11-20 years theses heavier –than-air compounds rise into the troposphere
mostly through convection, random drift, and the turbulent mixing of air in the
troposphere
 Once they reach the stratosphere, the CFC molecules break down under the
influence of high energy UV radiation, which leads to chlorine, fluorine and
bromine atoms are a result and they accelerate the breakdown of Ozone into O2
and O in a cyclic chain of chemical reactions
 Each CFC molecule can last in the stratosphere for 65-385 years, depending on its
type
o During that time, each chlorine atom released during the breakdown of the
CFC can convert hundreds of O3 molecules to O2
Annual Drops in Ozone Levels over the Earth’s Poles (Science)
 During four months of each year up to half of the ozone in the stratosphere over
Antarctica and a smaller amount over the Arctic is depleted
 Ozone thinning: the ozone depletion varies with altitude and location
 Polar vortex: a huge mass of vary col air that circulates over Antarctica and
isolates its air from the rest of the atmosphere until the sun returns a few months
later
Why Should We Be Worried about Ozone Depletion? (Science)
 Increased UV radiation reaching the earth’s surface from ozone depletion in the
stratosphere is harmful to human health, crops, forests, animals and materials such
as paints and plastics
Case Study: Skin Cancer (Science)
 Exposure to UV radiation is a major cause of skin cancers
 Three types of skin cancer
o Squamous cells
o Basal cells
o Malignant melanoma: this type can spread to other organs, kills about onefourths of its victims
Protecting the Ozone Layer
How can We Protect the Ozone Layer? (Science and Politics)
 To reduce ozone depletion, we must stop producing all ozone-depletion chemicals
 Even doing this, it will take about 60 years for the ozone layer to return to the
1980 levels
 There is CFC smuggling and this is making it harder to phase this out