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Chapter 23: The Atmosphere, Climate and Global Warming

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Title: Chapter 23: The Atmosphere, Climate and Global Warming


1
Chapter 23 The Atmosphere, Climate and Global
Warming
2
The Origins of the Global Warming Issue
  • Concern arises from two kinds of evidence
  • Increase in average surface temperature of the
    Earth from 1860 to the present
  • Increase in carbon dioxide concentrations in the
    atmosphere.
  • Measured on Mauna Loa in Hawaii by Charles Keeling

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The Origins of the Global Warming Issue
  • Relationship between chemistry of planets
    atmosphere and planets surface temperature.
  • Certain gases trap heat energy and warm the plant
  • Since this idea was first introduce has stirred
    controversy

6
Structure of the Atmosphere
  • Made up of several layers
  • Troposphere- bottom layer
  • Where weather occurs
  • Temperature decrease w/ elevation
  • At the top is tropopause- acts as a lid
  • Stratosphere- above the troposphere
  • Stratospheric ozone layer just above the
    tropopause
  • Protects again UV radiation

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Atmospheric Processes
  • Pressure and temperature These components of
    atmosphere are physically related to one another.
  • Pressure is force per unit area.
  • Caused by the weight of overlying atmospheric
    gases on those below
  • Decreases w/ altitude
  • Low pressure systems usually bring clouds
  • High pressure systems usually bring clear skies

9
Atmospheric Processes
  • Atmosphere moves because of the Earths rotation
    and differential heating.
  • Produce global patterns of prevailing winds and
    latitudinal belts of high and low pressure

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What Makes the Earth Warm
  • Almost all the energy from the sun.
  • Sunlight comes in a wide range of electromagnetic
    radiation.
  • Long to short wavelengths
  • Most of the radiation that reaches the Earth is
    in the infrared and visible wavelengths

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15
Weather and Climate
  • Weather is whats happening now w/ the atmosphere
    near the ground.
  • Its temperature, pressure, cloudiness,
    precipitation, winds Very LOCAL
  • Climate is the average weather GLOBAL and
    Regional
  • Usually refers to long periods of time
  • Classified mainly by latitude and amount of
    precipitation

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The Climate is Always Changing
  • Climate has warmed and cooled many times in
    Earths history
  • Times of high temp involve relatively ice free
    periods
  • Times of low temp involve glacial events

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Causes of Climate Change
  • Three kinds (non-anthropogenic) of changes occur
    to cause climate change
  • (1) Earth is unable to keep its poles at a
    constant angle in relation to the sun. The wobble
    makes a complete cycle in 26,000 years.
  • (2) The tilt of wobble also varies over a period
    of 41,000 years
  • (3) The elliptical orbit around the sun also
    changes. Sometimes it is a more extreme ellipse
    other times it is closer to a circle and this
    occurs over 100,000 years.

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Causes of Climate Change
  • The combination of these lead to periodic changes
    in the amount of sunlight reaching the Earth.
  • Milankovitch showed that these variations
    correlated w/ the major glacial and interglacial
    periods.
  • Called Milankovitch cycles
  • Dont account for all climate variations

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Solar Cycles
  • The Sun Goes Through Cycles Too
  • Sometimes hotter, sometimes cooler
  • Documented by differing amounts of isotopes
    trapped in glacial ice
  • Appears that variability of solar input of energy
    explains some of the climatic variability too.

25
Atmospheric Transparency Affects Climate and
Weather
  • How transparent the atmosphere is to radiation
    coming into it affects the temp of the Earth
  • From the sun and from the Earths surface
  • Dust and aerosols absorb light
  • Volcanoes, forest fires and farming put dust into
    the atmosphere
  • Chemical and physical composition of atmosphere
    can make it warmer or cooler

26
The Green House Effect
  • Each gas in the atmosphere has its own absorption
    spectrum
  • Certain gases are especially strong absorbers in
    the infrared
  • They absorb radiation emitted by the warmed
    surfaces of the Earth
  • They then re-emit this radiation
  • Making the Earths surface warmer

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The Green House Effect
  • Coined because of the way a greenhouse traps heat
  • Major green house gases are
  • Water vapor
  • Carbon dioxide
  • Methane
  • Some oxides of nitrogen
  • CFCs

29
The Roles of Major Greenhouse Gases In Affecting
Climate
  • Nobody doubts that the greenhouse effect exists
    and affects planets.
  • The puzzle arises on the Earth about relative
    importance of greenhouse gases in affecting
    climate.
  • Evidence indicates that carbon dioxide, methane,
    and temperature rise and fall together.
  • From this most scientists conclude that
    greenhouse gases are causing climate change.

30
Positive and Negative Feedbacks
  • The atmosphere and its interactions w/ the ocean
    and land surfaces experience positive and
    negative feedbacks.
  • Negative feedback
  • Warms temps warm air and lead to increased
    evaporation
  • Evaporation leads to more cloud formation which
    reflects more sunlight which could cool the
    surface.

31
Positive and Negative Feedbacks
  • Positive feedback
  • Warms temps warm air and lead to increased
    evaporation but instead of clouds forming remain
    as water vapor.
  • Water vapor is a greenhouse gas. The warmer it
    gets the more water vapor, and the process
    continues.
  • The warmer it gets, the more people use their AC
    thus increasing demand for electricity that
    increases CO2 levels and temperature

32
The Oceans Effect on Climate Change
  • Water has the highest heat capacity of any
    compound.
  • Large amount of heat energy can be stored in
    oceans
  • Ocean can absorb CO2
  • As CO2 increases in atmosphere it also increases
    in the oceans (increasing acidity or lowering
    the pH)

33
The Oceans Effect on Climate Change
  • Part of what drives the climate system is the
    ocean conveyor belt.
  • A global circulation of ocean waters
  • If the conveyor was shut down, major changes in
    climate would occur because of the capacity the
    ocean have to move heat from one part of the
    planet to another

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El Nino and Climate
  • El Nino refers to a certain kind of periodic
    variation of currents in the Pacific Ocean.
  • Under non-El Nino conditions
  • Trade-winds blow west across the tropical Pacific
  • Warm surface water pile up in W. Pacific

36
El Nino and Climate
  • During El Nino years
  • Trade winds weaken
  • Western moving current weakens or reverses
  • As a result eastern equatorial ocean being
    unusually warm
  • High rates of precipitation and flooding in Peru
  • Changes global atmospheric circulation
  • Causes changes in weather in regions that are far
    removed from tropical Pacific

37
El Nino and Climate
  • Rise in temp of sea surface waters off the SA
    coast (west side near Peru and Ecuador) inhibits
    the upwelling of nutrient-rich cold water from
    deeper levels.
  • Upwelling releases carbon dioxide
  • El Nino events reduce the amount of oceanic
    carbon out-gassing

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What a Global Warming World Might be Like
  • Global surface temp has increased 0.2C/ decade
    in the past 30 years.
  • Since 1998, the ten warmest years have occurred.
  • Continued warming of 0.2C /decade is projected.

41
What a Global Warming World Might be Like
  • By 2030 the concentration of CO2 in the
    atmosphere will have doubled from preIndustrial
    Revolution concentrations.
  • The average global temperature will have risen
    approximately 1 to 2C
  • W/ greater temperature increases toward the
    poles.
  • Polar amplification

42
Artic sea ice coverage receding sequentially
43
Potential Environmental, Ecological, and Human
Effects of Global Warming
  • Changes in River Flow
  • Melting of glacial ice and reductions in snow
    cover are anticipated to accelerate throughout
    the twenty-first century.
  • Rainfall will likely increase, but runoff will be
    more rapid than if snow slowly melts.
  • Reservoirs will fill sooner and more water will
    escape to the ocean.

44
Potential Effects of Global Warming
  • Rise in Sea Level
  • A major warming could increase sea levels because
    of
  • 1. Expansion of liquid water as water warms (a
    physical relationship)
  • 2. Melting of ice sheets on LAND whose waters
    then flow into the ocean. (This is unlike sea ice
    melt)
  • About half the people on Earth live in the
    coastal zone.
  • Sea level and population rising, the number of
    people vulnerable to coastal flooding increases.

45
Potential Effects of Global Warming
  • Rise in sea level could
  • Threatens island nations
  • Increase coastal erosion on open beaches and
    cause property loss.
  • Cause landward progression of estuaries and salt
    marshes
  • Lead to lost of coastal wetlands
  • Threaten ground water supply in coastal
    communities

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Potential Effects of Global Warming
  • Glaciers and Antarctic Ice Cap
  • Many more glaciers in the world are retreating
    than advancing.
  • Not all due to global warming
  • E.g. Mt. Kilimanjaro
  • Northern Hemisphere sea ice coverage has declined
    an average of 10.7 / decade since 1970s

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Potential Effects of Global Warming
  • The central ice cap on Antarctica is growing
  • This is consistent w/ prediction of global
    climate change models.
  • As Earth warms, more snow falls on Antarctica.
  • The rate of melting of the Greenland ice sheet
    has doubled since about 1998.

50
Potential Effects of Global Warming
  • Changes in Biological Diversity
  • The Intergovernmental Panel on Climate Change
    (IPCC) report states that
  • approximately 220 of species assessed so far
    are likely to be at increased risk of extinction
    as global mean temperatures exceed a warming of 2
    to 3C above preindustrial levels.

51
Potential Effects of Global Warming
  • Black guillemots
  • Birds that nest on Cooper Island, Alaska,
  • The abundance of this species has decreased.
  • Recession of sea ice occurred before chicks were
    mature enough to survive on their own.
  • Parent birds feed on Arctic cod found under the
    sea ice.
  • Distance from feeding grounds to nest must be lt30
    km
  • In recent years its been as much as 250 km from
    the island
  • As a result, birds lost an important source of
    food.

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Potential Effects of Global Warming
  • Agricultural Productivity
  • Globally, agriculture production is likely to
    increase in some regions and decline in others.
  • A climate shift could have serious negative
    effects on mid-latitude food production. (United
    States and much of Brazil)
  • In addition, lands in the southern part of the
    Northern Hemisphere may become more arid.
  • soil moisture will change.

54
Potential Effects of Global Warming
  • Human Health Effects
  • Health status of millions of people could
    potentially be affected through
  • Increases in malnutrition
  • Increased deaths, diseases, and injury due to
    extreme weather events
  • Increased burden of diarrhoeal diseases
    (Dysentery)
  • Increased frequency of cardio-respiratory diseases

55
Adjusting to Potential Global Warming
  • There are two kinds of adjustments people can
    make to the threat of global warming
  • Adapt Learn to live with future global climatic
    change.
  • Mitigate Work to reduce emissions of greenhouse
    gases.

56
Adjusting to Potential Global Warming
  • How can carbon dioxide emissions be reduced?
  • Energy planning that relies heavily on energy
    conservation and efficiency
  • Use of alternative energy sources, use of natural
    gas
  • Use of mass transit
  • Greater economic incentives to energy-efficient
    technology, higher fuel-economy

57
Adjusting to Potential Global Warming
  • Burning forests to convert land to agricultural
  • Accounts for about 20 of anthropogenic emissions
    of carbon dioxide into the atmosphere.
  • Minimizing burning and protecting the worlds
    forests would help reduce the threat of global
    warming.
  • Reforestation
  • Planting more trees
  • Increase biospheric sinks for carbon dioxide.

58
Adjusting to Potential Global Warming
  • Geologic sequestration of carbon is another
    possible mitigation measure.
  • The idea is to capture carbon dioxide from power
    plants and industrial smokestacks.
  • Compressing the gas and changing it to a mixture
    of both liquid and gas and then injecting it deep
    underground.
  • Have the potential to sequester as much as 1,000
    gigatons of carbon.

59
International Agreements to Mitigate Global
Warming
  • Two major approaches are
  • international agreements in which each nation
    agrees to some specific limit on emissions
  • Carbon trading

60
International Agreements to Mitigate Global
Warming
  • In carbon trading, a nation or nation agrees to a
    cap of carbon emissions.
  • Then corporations and other entities are issued
    emission permits, allowing a certain quantity of
    emissions.
  • These can be traded.

61
International Agreements to Mitigate Global
Warming
  • First international meeting to discuss limiting
    greenhouse gases held in Toronto, Canada in 1988.
  • In 1992, Earth Summit in Rio de Janeiro, Brazil.
  • General blueprint for reduction of global
    emissions suggested
  • US thought it would be to costly and no legally
    binding limits were set.

62
International Agreements to Mitigate Global
Warming
  • In 1997, legally binding limits discussed in
    Kyoto, Japan.
  • US eventually agreed to cut emissions to 7 below
    1990 levels (leading scientists recommend cuts
    60-80 below)
  • Became a formal treaty in 2006
  • US did not want to sign because it allowed
    developing countries to pollute at will without
    penalty
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