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Global Warming

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Therefore in coral and plankton a higher 18/16 ratio indicates lower average temperatures. ... Plankton and isotopes in ocean sediment ... – PowerPoint PPT presentation

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Title: Global Warming


1
Global Warming
2
Global Warming
  • Our planet has been through many cycles of
    climate change in the past.
  • At the present time, we are undergoing a period
    of global warming.
  • There is almost no disagreement on this point in
    the scientific community.

3
Global Warming
  • It is also widely agreed upon that the cause of
    this warming trend is the increase in greenhouse
    gases in the Earths atmosphere.
  • Is this increase part of a natural cyclical
    process, such as has occurred in the geologic
    past?
  • Or, is human activity responsible for the rise
    in greenhouse gases?

4
  • Most solar energy is in the form of shortwave
    radiation (e.g. visible light, UV rays). Our
    atmosphere allows most of these energy waves to
    pass through it.
  • Earth absorbs this energy and re-emits as
    longwave radiation (infrared or heat).
  • This heat radiates away from the planet at night.
    If all of it escaped, the average temperature of
    Earth would be about -200 C (00 F).

5
Greenhouse Gases
  • Greenhouse gases in the atmosphere do not allow
    infrared radiation to pass through them like
    shortwave radiation. Instead they absorb this
    energy, keeping it close to the Earth.
  • This natural process allows the Earth to maintain
    an average yearly temperature of about 150 C (600
    F). This is necessary for life on the planet.
  • The most important greenhouse gases are water
    vapor (H2O), and carbon dioxide (CO2).
  • Other include methane (CH4) ozone (O3) and
    chlorofluorocarbons (CFCs).

6
  • Until the 19th century, ice core data show
    atmospheric CO2 levels at less than 300 parts per
    million (ppm)
  • By the middle of the 19th century, levels were
    at about 300 ppm (0.03).

7
  • In 1958, Roger Revelle and Charles David Keeling
    started direct monitoring of atmospheric CO2 from
    the Mauna Loa Observatory.
  • Levels have increased to as high as 380 ppm.

8
(No Transcript)
9
Can scientists correlate temperature change with
atmospheric concentrations of CO2?Red line is
atmospheric CO2 ice core dataBlue is
temperature isotope analysis
10
A more recent comparison, using thermometers for
temperature data and direct sampling of
atmospheric CO2
11
Does this mean that human activity is responsible
for global warming?
12
Those who say Yes would argue the following
  • The Earths yearly average temperature has
    increased in the last century.
  • Atmospheric concentration of CO2, a principal
    greenhouse gas, has increased since the mid-19th
    century (the Industrial Revolution). Rise has
    been especially rapid since the 1950s.
  • It is a known fact that humans emit carbon
    dioxide into the atmosphere due to
    transportation and industrial processes.
  • Loss of forested land exacerbates this process,
    since photosynthesis is a process that removes
    CO2 from the atmosphere.

13
And those who would say No?
  • Is it possible that Global Warming is occurring
    naturally?
  • It is only through the reconstruction of past
    climates that we can truly evaluate the magnitude
    of this present warming trend.

14
Paleoclimatology Study of ancient climates
  • What can paleoclimatology tell us about climate
    change that is relevant to society in the future?

15
  • Is the last century of climate change
    unprecedented relative to the last 500, 2000, and
    20,000 years?
  • Do recent global temperatures represent new
    highs, or just part of a longer cycle of natural
    variability?
  • Is the recent rate of climate change unique or
    commonplace in the past?
  • What does it mean if the last century is
    unprecedented in terms of warming?
  • Can we find evidence in the paleoclimate record
    for mechanisms or climate forcings that could be
    causing recent climate change?

16
Climate change in the geologic past
  • How can scientists create a graph like this when
    thermometers, rain gauges and other
    instrumentation did not come into use until the
    late 19th century?
  • By using proxy climate data!
  • What are proxy climate data?
  • What are some examples of proxy climate data
    indicators?

17
Proxy Climate Data
  • Proxy climate data are obtained from natural
    recorders or indicators of climate variability
  • These proxy climate indicators cannot directly
    measure temperature, rainfall, etc. as do modern
    instruments. Scientists must analyze and
    interpret the results.
  • What are some examples of proxy climate data
    indicators?

18
Proxy Climate Data
  • The chart shows sources of climate information
    and the time frame over which they are useful.
    All except the instrument records are examples of
    proxy climate indicators.

19
Measuring recent climate change
  • Instrument records - measure only about the last
    hundred years
  • Historical records accounts recorded as
    records, or in stories
  • Vikings tales of the Little Ice Age (1450-1850)
    and the retreat from Vineland
  • Wine harvest records
  • Landscape paintings, other historical
    archeological accountings chronicle changes over
    the span of human history

20
Climate Data from Historical Records
21
Measuring climate change
  • Tree rings growth rings of trees hold climate
    information (thinner rings mean less growth due
    to lower temperatures or less rainfall
  • Plant pollen the pollen record records what was
    able to grow, which is linked to temperature and
    precipitation
  • e.g.10,500 years ago pines replaced spruce in
    some areas of northern U.S., indicating warmer
    temperatures

22
Oxygen Isotope Analysis
  • How does oxygen isotope analysis enable us to
    study climate changes in the past?

23
Oxygen Isotope Analysis
  • Oxygen isotopes in glacial ice
  • 18O 16O (common isotope) both occur, although
    16O is more common.
  • 18O is heavier, needs warmer air/water
    temperatures to evaporate.
  • Glacial ice is made up of precipitation from
    ocean evaporation.
  • Therefore glacial ice with a higher 18/16 ratio
    was deposited when the earths average
    temperature was greater.
  • Ice from Greenland and Antarctica show a record
    back gt100,000 yrs.

24
Fig. 21-6, p.505
25
Measuring climate change
  • Oxygen isotopes in marine fossils
  • When earths average temperatures are lower, more
    18O remains in the water.
  • Coral take in seawater to make their exoskeleton.
  • Therefore in coral and plankton a higher 18/16
    ratio indicates lower average temperatures.

26
Using d O18 ratios in coral to measure ocean
temperatures
  • Oxygen isotopes in coral
  • When earths average temperatures are lower, more
    18O remains in the water
  • Coral take in seawater to make their exoskeleton
  • Therefore in coral and plankton a higher 18/16
    ratio indicates lower average temperatures

27
Measuring climate change
  • Plankton and isotopes in ocean sediment
  • Shells and other hard parts preserved in marine
    rocks / muds give two lines of information
  • What was alive at the time gives climate
    information
  • 16/18O ratios in biogenic carbonate
  • Rock and fossil record
  • fossils give much information, what lived when
  • Rock records formative environment

28
Fig. 21-7a, p.506
29
Fig. 21-7b, p.506
30
Tectonics and climate change
  • Position of the continents
  • 200 mya, the single continent Pangea was near the
    south pole
  • Continental interiors tend to have more severe
    winters. For a single large landmass, even more
    so.
  • Influences winds and ocean currents

31
Fig. 21-12, p.511
32
Does Data from the Vostok ice core support those
who claim that humans are responsible for global
warming? Why or Why not
33
Human contribution to the Greenhouse Effect
  • Humans release, fossil fuels,CFCs and other
    greenhouse gases into the environment.
  • Concentrations of these gases has increased in
    the recent past
  • The atmosphere has warmed 0.8oC during the last
    century

34
Thermohaline circulation how global warming
could cause global cooling
  • Warmer sea surface temperature could slow or stop
    vertical currents
  • This would stop, or re-route the Gulf Stream,
    which would cool the Earth
  • Thermohaline currents have decreased 30 from
    1988 - 2000

35
If the Labrador Current (Cold) is too fresh to
sink, it may block passage of the N. Atlantic
Drift (warm) which moderates the climate of Great
Britain and Scandinavia
36
Fig. 21-19a, p.519
37
Fig. 21-19b, p.519
38
The Kyoto treaty on greenhouse warming
  • Dec. 1997, 160 nations met to discuss global
    warming
  • By Feb. 2005 a treaty was ratified by many of
    them
  • Creates a global trading market for CO2 emissions
  • Sets limits and goals
  • Caps and goals tied to nations economies
  • Developing nations, eg China, India excluded from
    CO2 caps

39
21.9 The Kyoto treaty on greenhouse warming
  • The U.S. has never ratified the treaty
  • Treaty supporters argue
  • Wealth not necessarily tied to fuel consumption
  • Curbing consumption and emissions could help the
    economy
  • Models show the longer we wait, the worse it will
    get
  • Consider the alternatives runaway temperature
    changes, famine, global unrest.
  • The treaty expires in 2012 the sequel is
    looking less than inspired.

40
Fig. 21-20, p.520
41
Possible Consequences of Global Warming
  • Sea-level changes sea-level has risen markedly
    from 1900 to 2000
  • water expands when warm
  • Glacial (ice on land) melting is increasing
  • Effects on people
  • Tropical diseases flaring up in new areas
  • Population stress on food and water supplies as
    well as other global systems

42
Fig. 21-15, p.514
43
The Kyoto treaty on greenhouse warming
  • Dec. 1997, 160 nations met to discuss global
    warming
  • By Feb. 2005 a treaty was ratified by many of
    them
  • Creates a global trading market for CO2 emissions
  • Sets limits and goals
  • Caps and goals tied to nations economies
  • Developing nations, eg China, India excluded from
    CO2 caps

44
21.9 The Kyoto treaty on greenhouse warming
  • The U.S. has never ratified the treaty
  • Treaty supporters argue
  • Wealth not necessarily tied to fuel consumption
  • Curbing consumption and emissions could help the
    economy
  • Models show the longer we wait, the worse it will
    get
  • Consider the alternatives runaway temperature
    changes, famine, global unrest.
  • The treaty expires in 2012 the sequel is
    looking less than inspired.

45
Fig. 21-20, p.520
46
Fig. 21-21, p.521
47
Fig. 21-16, p.515
48
Fig. 21-18ab, p.518
49
Fig. 21-18c, p.518
50
Climate change in the geologic past
  • Early Precambrian Time (4-2.7 bya)
  • Sun was 20-30 fainter, delivered less energy
  • Effect offset by large greenhouse effect of
    Earths early atmosphere, largely composed of
    CO2, and H2O.
  • Late Precambrian to Permian (2.7 bya to 250 mya)
  • Severe ice ages occurred at least five times in
    this period

51
Climate change in the geologic past
  • Mesozoic to Present
  • Climate mostly warmer than today.
  • Most recent ice ages occurred over the last 2
    million years.
  • Some scientists think the last 10,000 years
    represent an interglacial warming episode and the
    ice will return.
  • Recent records show mean temperature increase
    from the late 1800s.
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