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Title: Lecture Outlines Natural Disasters, 7th edition


1
Lecture OutlinesNatural Disasters, 7th edition
  • Patrick L. Abbott

2
Climate ChangeNatural Disasters, 7th edition,
Chapter 12
3
Early Earth Climate An Intense Greenhouse
  • Inner planets atmospheric compositions
  • Venus
  • Intense solar radiation, trapped by dense
    CO2-rich atmosphere ? surface temperatures 477oC
  • Mars
  • Less solar energy, but thin atmosphere is rich in
    CO2, so holds heat effectively, surface
    temperature -53oC
  • Venus, Mars atmospheres changed little in last
    4 billion years
  • Earths atmosphere radical change from CO2-rich
    to CO2-poor

4
Early Earth Climate An Intense Greenhouse
Insert Table 12.1 here.
5
Early Earth Climate An Intense Greenhouse
  • Changes in Earths atmosphere caused by life
    processes
  • Plants remove CO2 from atmosphere by
    photosynthesis
  • Atmospheric CO2 dissolves in water, is absorbed
    by marine life
  • CO2 is chemically tied up in limestone (CaCO3
    from shells, reefs, mineralized tissue of
    invertebrate animals, algae)
  • Early photosynthesizing life on Earth removed
    enough CO2 from atmosphere for other animal life
    to survive ? animals made skeletons of CaCO3 ?
    further reduced atmospheric CO2 ? lessened
    greenhouse effect on Earth ? lowered temperatures

6
Early Earth Climate An Intense Greenhouse
  • Changes in Earths atmosphere caused by life
    processes

Figure 12.1
7
Early Earth Climate An Intense Greenhouse
  • Before life, atmosphere full of CO2, greenhouse
    effect ? surface temperature about 290oC
  • Greenhouse effect
  • Incoming visible light is admitted at short
    wavelengths
  • Atmosphere warms up, heat is given off as
    infrared (longer wavelength) radiation
  • Longer-wavelength outgoing energy is trapped
  • Greenhouse effect produced by glass (in
    greenhouse, windows of car) or by gases in
    atmosphere (CO2, H2O vapor, methane (CH4),
    chlorofluorocarbons (CFCs))
  • CO2 is most important greenhouse gas

8
Early Earth Climate An Intense Greenhouse
  • Present CO2 is 0.038 of atmosphere ? weakened
    greenhouse effect
  • Average temperature is 34oC higher than without
    CO2
  • Earth has always been influenced by greenhouse
    effect
  • Life has always been in dynamic equilibrium with
    greenhouse effect
  • Humans now changing atmospheric CO2 concentration
  • Burning tremendous volumes of living plants
    (trees and shrubs) and dead plants (coal, oil,
    natural gas)
  • Relatively small amounts but may be enough to
    trigger climate shifts

9
Climate History of the Earth Timescale in
Millions of Years
  • Sedimentary rocks contain information about
    climate at time they formed
  • Warm climates indicated by
  • Fossil reefs, limestones
  • Aluminum ore bauxite (tropical soils)
  • Evaporite minerals
  • Cold climates indicated by
  • Erosion by glaciers (distinctive marks and debris
    deposition)
  • Certain fossil organisms indicate
    paleo-temperatures
  • Can derive history of Earths climate

10
Climate History of the Earth Timescale in
Millions of Years
  • Climate depends on balance between incoming and
    outgoing heat may be gaining or losing overall
  • Earth divided into belts of frigid, temperate and
    torrid by latitude
  • Ice Age
  • frigid zone expands to larger area
  • torrid zone shrinks but does not disappear
  • Torrid Age
  • torrid zone expands to larger area
  • frigid zone shrinks but does not disappear

Figure 12.4
11
Climate History of the Earth Timescale in
Millions of Years
  • Late Paleozoic Ice Age
  • 360 260 million years ago
  • Major factors (requirements for Ice Age to
    occur)
  • Large landmasses near poles to accumulate
    snowfall, build continental ice sheets
  • In late Paleozoic, Pangaea (supercontinent) moved
    across south polar region

12
Climate History of the Earth Timescale in
Millions of Years
  • Late Paleozoic Ice Age
  • 360 260 million years ago
  • Major factors (requirements for Ice Age to
    occur)
  • Continents blocking equatorial (east-west) ocean
    circulation
  • Water must first evaporate from ocean for clouds
    to form and precipitate snow (to build ice
    sheets)
  • Warm water evaporates more easily than cold water
  • If continents divert warm ocean currents to flow
    north and south to the poles, more water will
    evaporate to form clouds, to drop more snow
  • Ice Age may have ended because Pangaea broke apart

13
Climate History of the Earth Timescale in
Millions of Years
  • Late Paleocene Torrid Age
  • 65 55 million years ago
  • Equatorial zones similar to today, poleward
    latitudes much warmer
  • Less temperature difference between tropical and
    polar ocean waters
  • Absence of cold, dense, sinking water at poles
  • Less temperature difference between surface and
    deep ocean waters
  • Sluggish ocean circulation
  • Less temperature difference in atmosphere
  • More peaceful weather, absence of strong seasons,
    evenly distributed rainfall ? warmer and wetter

14
Climate History of the Earth Timescale in
Millions of Years
  • Late Paleocene Torrid Age
  • Factors to create Torrid Age
  • Equatorial zones were oceans, allowing more
    absorption of solar radiation by water
  • As oceans warmed, snow and ice melted ? more land
    was exposed
  • Land absorbs more heat than snow and ice
  • Opening North Atlantic Ocean erupted huge amounts
    of lava and huge volumes of gases to atmosphere,
    increasing global warming by greenhouse effect

15
Climate History of the Earth Timescale in
Millions of Years
  • Late Paleocene Torrid Age
  • Factors to create Torrid Age
  • Heaviest ocean water may have been dense, salty,
    oxygen-poor tropical water, as polar waters
    became warmer
  • Tropical waters would have sunk to bottom,
    warming oceans from bottom up ? massive
    extinction of ocean life
  • Warming of ocean water may have melted methane
    hydrates on seafloor, releasing methane gas (CH4)
    to atmosphere over 10,000 years
  • Methane gas is powerful greenhouse gas, caused
    further warming

Figure 12.7
16
In Greater DepthOxygen Isotopes and Temperature
  • Use ratio of stable isotopes of oxygen in CaCO3
    sea life fossils
  • Oxygen may be 16O, 17O or 18O
  • Evaporation removes more light 16O, leaves behind
    more heavy 18O
  • Atmospheric water becomes depleted in 18O
  • 18O-depleted water is trapped on land as snow or
    ice during Ice Age
  • Oceans become 18O-enriched
  • Marine organisms use 18O-enriched water in making
    CaCO3 shells
  • Measurement of 18O/16O ratio in CaCO3 fossils is
    indicator of climate when organism lived
  • High 18O/16O ? colder climate
  • Low 18O/16O ? warmer climate

17
Climate History of the Earth Timescale in
Millions of Years
  • Late Cenozoic Ice Age
  • Long-term cooling from temperature peak at 55
    million years ago ? current Ice Age
  • 55 million years ago methane reduced in
    atmosphere, began cooling
  • 40 million years ago Antarctica surrounded by
    cold water
  • 34 million years ago glaciers widespread in
    Antarctica
  • 14 million years ago continental ice sheet on
    Antarctica, mountain glaciers in northern
    hemisphere
  • 5 million years ago Antarctic ice sheet expanded
  • 2.5 million years ago continental ice sheets in
    northern hemisphere

18
Climate History of the Earth Timescale in
Millions of Years
  • Late Cenozoic Ice Age
  • Factors in cooling
  • Ongoing breakup of Pangaea
  • Opening and closing of seaways ? altered ocean
    circulation and heat distribution around globe
  • Continental masses in polar regions (Antarctica
    at South Pole and Eurasia near North Pole) to
    build ice sheets
  • Accumulation of snow and ice at poles increased
    albedo ? more sunlight reflected

19
Climate History of the Earth Timescale in
Millions of Years
  • Late Cenozoic Ice Age
  • Factors in cooling
  • Closing of Mediterranean and uplift of Isthmus of
    Panama stopped east-west ocean circulation,
    forcing warm water to poles
  • Less area of shallow ocean ? less water surface
    to absorb sunlight
  • Uplift of Tibetan plateau and Colorado plateau
    deflected west-to-east atmospheric circulation in
    midlatitudes

20
Climate History of the Earth Timescale in
Millions of Years
  • The Last 3 Million Years
  • Old, stable ice sheet on Antarctica little
    short-term climate effect
  • North American and Eurasian ice sheets expand and
    shrink, affecting global climate
  • Formation of Isthmus of Panama 3 million years
    ago blocked westward-flowing ocean water, forcing
    it north
  • Warm water in north Atlantic Ocean increased
    evaporation and snowfall, to build glaciers
  • Continental ice sheets in northern hemisphere
    undergo complex cycles of advance and retreat

21
Glacial Advance and Retreat Timescale in
Thousands of Years
  • Last 1 million years about 10 glacial advances,
    retreats
  • Worldwide glacial advances lasting almost 100,000
    years
  • Followed by retreats lasting decades to few
    thousand years much faster than advance
  • Caused by cycles in Earths orbit around Sun
    affecting amount of solar energy received by
    Earth
  • Changes postulated in 1920s by Serbian astronomer
    Milutin Milankovitch and supported recently by
    Greenland ice cores

Figure 12.10
22
Glacial Advance and Retreat Timescale in
Thousands of Years
Milankovitch defined changes in Earths orbit,
tilt and wobble ? changes in amount of solar
radiation received by Earth
  • Amount of solar radiation at high latitudes
    during summers determines how much snow remains
    from winter to next winter, allowing glaciers to
    grow

Figure 12.12
23
Glacial Advance and Retreat Timescale in
Thousands of Years
  • Changes in Earths orbit
  • Eccentricity of orbit around Sun varies every
    100,000 years from circular to elliptical (less
    solar radiation received when elliptical) as
    dominant control of glacial advance and retreat
  • Tilt of Earths axis 21.5 24.5o off vertical
    in 41,000 year cycle
  • Precession of tilt direction of tilt changes
    (wobble in spin of toy top) in double cycle of
    23,000 and 19,000 years

Figure 12.11
24
Glacial Advance and Retreat Timescale in
Thousands of Years
  • Around 20,000 years ago
  • Glaciers at maximum extent, covered 27 of
    todays land
  • Virtually all of Canada, part of northeastern
    U.S.
  • Seawater necessary to build glaciers lowered sea
    level 130 m
  • Current Ice Age continues (current glacial
    retreat)
  • 10 continents still buried under ice
  • If ice melts, sea level would rise 65 m

25
Glacial Advance and Retreat Timescale in
Thousands of Years
Around 20,000 years ago
Figure 12.14
Figure 12.13
26
Climate Variations Timescale in Hundreds of
Years
  • Temperature conditions following 20,000 years
    ago
  • Warming began, then interrupted by Older Dryas
    cold stage
  • Cold interval replaced by warmth of Bolling
    period
  • Temperatures fell through Allerod interval and
    bottomed in Younger Dryas stage 12,900 to 11,600
    years ago
  • Current interglacial period
  • Temperature changes of 3o to 5oC occurred in
    several years

Figure 12.15
27
Climate Variations Timescale in Hundreds of
Years
  • Cause of sudden drops or jumps in temperature
  • Melting of continental ice sheets left behind
    huge cold lakes with ice dams
  • Failure of ice dams released enormous amounts of
    fresh, cold water into surface layers of ocean,
    disrupting oceanic circulation pattern for 1,100
    years
  • Constant rise in sea level from melting of
    glaciers

Figure 12.16
28
Climate Variations Timescale in Hundreds of
Years
  • At 7,000 years ago
  • Warmer global temperatures, higher rainfall
    totals ? climatic optimum
  • Since then average global temperatures have
    fallen 2oC
  • Smaller cycles of
  • glacial expansion and
  • contraction within
  • cooling trend

Figure 12.17
29
Shorter-Term Climatic Changes Timescale in
Multiple Years
  • El Nino
  • Typical conditions in Pacific (without El Nino
    effect)
  • High pressure over eastern Pacific causes trade
    winds blowing west and toward equator from north
    and south
  • Westward winds push surface water to western
    Pacific
  • Western Pacific water absorbs solar energy,
    evaporates easily
  • Heavy rainfalls in Indonesia and southeast Asia
  • Eastern Pacific has upwelling of cold, deep water
    to replace surface water blown westward

30
Shorter-Term Climatic Changes Timescale in
Multiple Years
  • El Nino
  • Typical conditions in Pacific (without El Nino
    effect)

Figure 12.18
31
Shorter-Term Climatic Changes Timescale in
Multiple Years
  • Ocean-atmosphere coupling arrival of warm ocean
    water to Peru, Ecuador near Christmastime,
    affecting climate, every 2 to 7 years
  • El Nino conditions in Pacific
  • When westward blowing trade winds are absent,
    piled-up warm surface water flows downhill from
    western to eastern Pacific
  • Warm surface water evaporates easily and causes
    increased rainfall to western North and South
    America
  • Decreased hurricane risk to Atlantic Ocean

32
Shorter-Term Climatic Changes Timescale in
Multiple Years
  • El Nino conditions in Pacific

Figure 12.19
33
Shorter-Term Climatic Changes Timescale in
Multiple Years
  • El Nino 1982-83
  • Cold-water fisheries off Peru and Ecuador
    collapsed
  • More evaporation ? torrential rainfall, floods,
    landslides killed 600 people in Peru and Ecuador,
    economic loss
  • Heavy rainstorms in western U.S. 300 million in
    damages, 10,000 people evacuated, 12 people
    killed in California
  • Tropical rain belt in central Pacific formed
    hurricanes hitting Tahiti and Hawaii
  • Australia and Indonesia had lower rainfall and
    droughts ? bushfires killed 75 people, 2.5
    billion in damages

34
Shorter-Term Climatic Changes Timescale in
Multiple Years
  • El Nino 1997-98
  • Winds flowing eastward caused heavy rains and
    floods in California
  • Higher rainfall, tornadoes to southeastern U.S.
  • Helped break apart Atlantic and Caribbean storms
    ? fewer hurricanes
  • Warmer winter in midwestern and northern states
  • More economic gains than losses, fewer fatalities
    in U.S.

35
Shorter-Term Climatic Changes Timescale in
Multiple Years
  • Cause of El Nino
  • Southern Oscillation in south Pacific Ocean
    usual low pressure replaced by high pressure,
    migrating from Indian Ocean (ENSO)
  • Globally connected weather system
  • Tropical atmosphere goes through changes that
    link up around world
  • Takes four years to circuit globe

Figure 12.21
36
Shorter-Term Climatic Changes Timescale in
Multiple Years
  • La Nina
  • Occurs when cooler waters move into equatorial
    Pacific
  • Brings cold air and high rainfall to northwestern
    U.S. and western Canada, below average rainfall
    to rest of North America
  • Encourages hurricanes in Atlantic Ocean,
    wildfires in southwestern U.S.

37
Shorter-Term Climatic Changes Timescale in
Multiple Years
  • Pacific Decadal Oscillation
  • Lasts 20-30 years
  • Midlatitude Pacific Ocean conditions, secondary
    tropical effects
  • El Nino lasts 6-18 months, conditions of
    tropics, secondary effects on mid-latitudes
  • Warm phase with increased storms and rainfall
  • Occurred from 1925 to 1946, from 1977 to 1998

Insert Figure 12.23
Figure 12.23
38
Volcanism and Climate
  • Large Plinian eruptions blast fine ash and gas to
    stratosphere, above troposphere where weather
    occurs
  • Ash and sulfuric acid (from sulfur dioxide gas)
    remain in stratosphere as haze for years,
    blocking incoming sunlight

39
Volcanism and Climate
  • El Chichon, 1982 Four big Plinian eruptions
  • Smaller than eruption of Mount St. Helens, but
    more than 100 times SO2 gas emitted into
    stratosphere
  • SO2 cloud took 23 days to circle globe ?
    spectacular sunsets
  • Lowered global average temperature 0.2oC
  • Followed by El Nino (may be more likely after
    major eruption)

Figure 12.24
40
Volcanism and Climate
  • Mount Pinatubo, 1991
  • Eruption pumped 20 million tons of SO2 into
    stratosphere
  • Reflected 2-4 of incoming solar radiation ?
    20-30 decline in solar radiation reaching ground
  • Average global temperatures dropped 0.5oC
  • Included 1oC drop in U.S., offsetting global
    warming

Figure 12.25
41
Volcanism and Climate
  • Tambora, 1815 Eruptions reduced 4,000 m volcano
    to 2,000 m high caldera, producing 175 km3 of ash
    and debris
  • Made 1816 the year without a summer
  • Average global temperatures lowered 0.3oC
  • Triggered cholera epidemic
  • Toba, Indonesia, 74,000 years ago erupted 2,000
    km3 of ash and debris
  • Youngest known resurgent caldera eruption
  • Ash and sulfuric acid cloud estimated to have
    lasted in stratosphere up to six years
  • Global cooling possibly as much as 3-5oC ?
    volcanic winter

42
Volcanism and Climate
  • Volcanic Climate Effects
  • Plinian eruptions affect climate for few years,
    resurgent caldera eruptions for several years
  • Possible for several different volcanoes to erupt
    over several successive years in a row (by
    chance)
  • Might have long-term effects on climate ? Little
    Ice Age
  • Greenland ice-core record shows high acid during
    this time
  • Factors in volcanisms effect on climate
  • Size, rate of eruptions
  • Height of eruption columns
  • Types of gases, atmospheric level of placement
  • Low latitude vs. high latitude (weather patterns
    spread debris)

43
Volcanism and Climate
  • Volcanic Climate Effects
  • Worst-case scenario Flood basalt eruptions such
    as Deccan Plateau (India) 65 million years ago
    (extinction of dinosaurs)
  • 2.6 million km3 of basaltic lava erupted in only
    500,000 years
  • Possible effects
  • Increase in atmospheric CO2 ? temperature
    increase of 10oC
  • More acidic ocean waters
  • Depleted ozone layer

44
In Greater Depth The Mayan Civilization and
Climate Change
  • Great accomplishments in agriculture, irrigation,
    social organization, mathematics, astronomy over
    1,000 years
  • Century-long pattern of decreased rainfall ?
    droughts ? abandonment of urban areas, stop in
    monument construction, breakdown of social and
    political order ? wars, return to life of rural
    subsistence
  • Significant decline in Mayan civilization due to
    string of events triggered by long-term climate
    change

45
The Last Thousand Years
  • Combined effects of eccentricity, tilt, wobble
    caused cooling trend with numerous variations
  • Variations studied to learn more about
  • Extent of temperature fluctations
  • Whether regional or simultaneous around globe
  • Causes of changes
  • Other variations within cooling trend being
    studied with
  • Oxygen isotopes in glacial ice layers
  • Annual growth rings of corals
  • Tree ring widths and densities
  • Tax records of grain and grape crops
  • Advances and retreats of mountain glaciers
  • Paintings of frozen lakes, rivers, ports
  • Weeks per year of sea ice around Iceland

46
The Last Thousand Years
  • Variations within cooling trend
  • Medieval Maximum warm period from 1000 to 1300
    C.E.
  • Little Ice Age cold period from 1400 to 1900
    C.E. epoch of renewed but moderate glaciation
  • Smaller scale coolings and warmings within Little
    Ice Age
  • Maunder Minimum cooler period from 1645 to 1715
    C.E.
  • Minimal sunspot activity ? Sun possibly .25
    weaker

Figure 12.28
47
The Last Thousand Years
  • Processes in climate changes of last thousand
    years
  • Changes in Earths orbital patterns caused
    cooling
  • Lessened solar-energy production caused cooling
  • Volcanism caused changes
  • Interactions between ocean, atmosphere, ice
    sheets
  • Millennium cycle? Warm centuries followed by cold
    centuries
  • Twentieth century may have been beginning of warm
    centuries

48
Side Note Stradivari Violins
  • Most famous violins increased size, secret
    varnish ? superior tones
  • May have benefited from Maunder Minimum cold
    temperatures
  • Longer winters and cooler summers promoted slow,
    even tree growth ? dense wood with narrow rings
  • May be cause of superior tones of Stradivari
    violins

49
The 20th Century
  • 20th c. began as warm as any time in past 1,000
    years
  • Average global surface temperatures rose 0.6oC in
    20th century, from 1910-1944 and since 1977
  • 1910-1944 warming hotter Sun, lack of volcanism
  • Warming since 1977 twice that of 1910-1944
    likely mostly due to greenhouse gases in
    atmosphere
  • Natural causes 0.2oC
  • Changes in Earths orbital patterns ? 0.02oC
    decrease
  • Hotter Sun ? more than 0.2oC increase
  • Human activities 0.4oC increase

50
The Greenhouse Effect Today
  • Greenhouse effect has always acted to warm Earth
    climate strength has varied
  • Greenhouse gases (currently being added to
    atmosphere by humans)
  • Carbon dioxide (CO2)
  • Methane (CH4)
  • Nitrous oxide (N2O)
  • Ozone (O3)
  • Industrial gases such as CFCs

51
The Greenhouse Effect Today
  • The Greenhouse Effect Today
  • Earths atmosphere reflects back about 30 of
    incoming solar radiation
  • 23 passes through atmosphere to power hydrologic
    cycle
  • Remaining 47 is absorbed by land, sea and air
  • Absorbed heat builds up, some is reradiated
    outward in longer, infrared wavelengths but
    trapped by greenhouse gases in atmosphere
  • Greater volume of greenhouse gases ? greater
    amount of trapped heat

52
In Greater Depth When Did Humans Begin Adding to
Greenhouse Warming?
  • Burning oil, natural gas, coal, and wood
    currently releases huge amounts of CO2 to
    atmosphere
  • 8,000 years ago cutting, burning forests for
    agriculture began adding CO2 to atmosphere
  • 5,000 years ago wetlands technique of
    rice-growing began adding methane to atmosphere
  • These agricultural practices may have warmed
    climate by as much as 0.8oC over thousands of
    years
  • May have prevented some Little Ice Ages, kept
    climate stable
  • Occurred over thousands of years, unlike current
    changes over decades

53
The Greenhouse Effect Today
  • Carbon Dioxide (CO2)
  • Causes about 60 of greenhouse warming
  • Carbon cycle
  • Major building block of life on Earth
  • 20 of CO2 removed from atmosphere by
    photosynthesis
  • At plant death, oxidation returns CO2 to
    atmosphere, into water
  • Humans decompose plants at faster rates (burning
    wood and fossil fuels) ? CO2 increases in
    atmosphere and water

54
The Greenhouse Effect Today
  • Carbon Dioxide (CO2)
  • Carbon cycle
  • 1800 CO2 concentration in atmosphere 280 ppm
  • 2006 CO2 concentration in atmosphere 382 ppm
  • CO2 removed from atmosphere 20 by
    photosynthesis, 25 dissolves in ocean water, but
    55 stays in atmosphere

Figure 12.32
55
The Greenhouse Effect Today
  • Methane (CH4)
  • Causes about 16 of greenhouse warming
  • 21 times higher heat-trapping ability than CO2
  • Risen more than 150 since 1750 (700 ppb)
  • Released during decomposition of vegetation in
    oxygen-poor environments, by mud volcanoes
  • 70 given off by human activities
  • Burning fossil fuels
  • Growing rice
  • Maintaining livestock
  • Melting of methane hydrates ? torrid climate
  • Landfills
  • Burning wood
  • Rotting animal waste and human sewage

56
The Greenhouse Effect Today
  • Nitrous Oxide (N2O)
  • Produced naturally by bacteria removing nitrogen
    from organic matter, especially in soil
  • Produced by humans in agricultural activities
  • Chemical fertilizers
  • Combustion burning of fuels in engines
  • Ozone (O3)
  • Ozone in stratosphere absorbs UV radiation,
    shields life
  • Principal component of smog in urban atmospheres
  • Produced by gases interacting with sunlight
  • Irritates eyes and lungs ? shortens lives

57
The Greenhouse Effect Today
  • Chlorofluorocarbons (CFCs)
  • Produced solely by humans (do not occur
    naturally)
  • Coolants in refrigerators and air conditioners,
    foam insulation in buildings, solvents, etc.
  • Aid in destruction of ozone in stratosphere
  • Remain in atmosphere for up to century (catalyst)
  • Twentieth-Century Greenhouse Gas Increases
  • Byproducts of industrial and domestic energy
    production, rice and livestock agriculture
  • 20th century population growth (doubled twice)
  • Lifestyle of industrialized world

58
The 21st Century
Intergovernmental Panel on Climate Change (IPCC)
Insert new Table 12.6 here
59
Heat Waves
  • Heat is biggest killer of all severe weather
  • 21st century is likely to experience more
    frequent heat waves
  • Heat Wave in Chicago, July 1995
  • Heat records broken, with high maximum and
    minimum temperatures (no cooling at night)
  • Deaths occurred for days after 465 deaths over
    two weeks

Figure 12.35
60
Heat Waves
  • Europes Heat Wave, 2003
  • Summer brought record-breaking heat waves (of
    last 150 years)
  • Delayed recognition of number of deaths over
    35,000
  • City areas are urban heat islands, with
    night-time temperatures up to 5.5oC higher than
    surroundings
  • Heat waves will occur more frequently as climate
    warms

Insert Table 12.7 here
61
Global Climate Models
  • Climate change involves complex questions and
    many variables
  • Questions are addressed by constructing global
    climate models (GCMs)

Insert Table 12.8 here
62
Drought and Famine
  • Times of abnormal dryness in region, without
    usual rain
  • Expected rains do not arrive ? vegetation begins
    to die ? food supplies shrink ? famine
  • Tends to drive people apart rather than bring
    together
  • Early stage food available but inadequate
  • Lose up to 10 body weight, still alert and
    vigorous
  • Advanced stage body weight decreases by about
    20, body reduces activity levels, apathy
  • Near-death stage 30 or more body weight lost,
    indifference to surroundings and others

63
Drought and Famine
  • U.S Dust Bowl, 1930s
  • Several years of drought turned grain-growing
    central U.S. into dust bowl
  • Position of jet stream caused upper-level,
    high-pressure dry air to sink ? hot, dry winds
    killed plants and eroded soil into dust clouds
  • Drought began in 1930
  • Dust storms increased in 1934, 1936
  • Blame mistakenly put on farmers for plowing up
    native grasses
  • May have exacerbated situation
  • Droughts typical but infrequent in North America

64
Ice Melting and Sea-Level Rise
  • Glacial ice holds 2.15 of water on earth
  • If all melted, sea level would rise 65 m (210 ft)
  • This will not happen in foreseeable future
  • However, there are regions of concern
  • Arctic sea ice decreased by 7.4 per decade, may
    be gone by 2030
  • Possible tipping point
  • Greenland continental glacier melting has
    increased, large-scale catastrophic collapses are
    possible
  • Possible tipping point
  • A sea level rise of 4-6 m in upcoming centuries
    would cause major problems worldwide for major
    cities and low-lying deltas

65
Oceanic Circulation
  • Major climatic shift if present deep-ocean
    circulation pattern is altered by inflow of fresh
    water from melting glaciers in north Atlantic
    Ocean
  • Unknown what natural changes will occur, such as
    more or less solar energy, cooling effect from
    volcanism, etc.
  • Unpredictable natural changes may offset or
    accentuate human effects

Figure 12.42
66
Signs of Change
Insert revised Table 12.9 here
67
Mitigation Options
  • Widely perceived need to reduce greenhouse gas
    emissions
  • Will require changing energy-usage technologies
  • Cap-and-trade
  • Emission allowances are placed on companies
  • Companies can by or sell credits
  • Drastic Engineering
  • Imitate volcanoes, giant shades, create clouds
    over oceans
  • Efforts may create bigger problems than they solve

68
In Greater Depth Tipping Points
  • Change is usually a gradual process, but not
    always
  • Points at which small changes suddenly produce
    large effects
  • History of change may not predict future

69
In Greater Depth Lag Times
  • Changes in climate are occurring slowly
  • Full effects will not be felt for decades
  • IPCC estimates oceans will continue to warm
    throughout 21st century (0.6ºC)
  • There are lag times in temperature changes and in
    the melting of the ice sheets

70
End of Chapter 12
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