Geologic evidence of recurring climate cycles and their implications for the cause of global warming and climate changes in the coming century Don J. Easterbrook - PowerPoint PPT Presentation

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Geologic evidence of recurring climate cycles and their implications for the cause of global warming and climate changes in the coming century Don J. Easterbrook

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Title: Geologic evidence of recurring climate cycles and their implications for the cause of global warming and climate changes in the coming century Don J. Easterbrook


1
Geologic evidence of recurring climate cycles and
their implications for the cause of global
warming and climate changes in the coming
century Don J. Easterbrook
2
  • Geologic issues about
  • global climatic warming
  • Is global warming real?
  • What is the evidence for CO2 as the cause of
    global warming?
  • What is the geologic evidence for natural cycles
    as the cause of global warming?

3
Some Geologic Facts
  • Global climate warmed 0.6 C from 1910 to
    1940.
  • Global climate cooled 0.5 C from 1940 to
    1977
  • Global climate warmed 0.5 C from 1977 to
    2000.
  • Global climate cooled 0.3 C between 1880 to
    1910 and was 0.9 C cooler in 1890 than 2000
  • The global climate has been warming since the
    Little Ice Age (400 years).

4
Evidence that CO2 is the cause of global warming
  • CO2 and global temperature have both risen
    over the past 30 years.
  • Computer models can be adjusted to show
    temperatures parallel to global temperatures.

5
Composition of the atmosphere
CO2 now makes up 0.038 of air
Before human input, CO2 was 0.028 to 0.030
Human input has raised CO2 by 0.008
6
  • Facts
  • 1. Half of the warming in the past century
    occurred before CO2 began to rise sharply.
  • For 30 years after CO2 began to soar, global
    cooling occurred, rather than warming.
  • Of the many global warmings and coolings, only
    the last one (the past 30 years) corresponds to
    rising CO2.
  • .

7
80 of CO2 emissions have occurred since 1945
8
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9
Greenland warming has followed the global pattern
10
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11
Past climate changes
  • Our civilization has never experienced any
    environmental shift remotely similar to this.
    Todays climate pattern has existed throughout
    the entire history of human civilization.
    (Gore, 2006)
  • Temperature has spiked within the past few years
    unlike any previous temperature spike in
    history. (Mote, 2007)
  • Current warming is 10 times greater than ever
    before seen in the geologic record. The chance
    that warming is natural is less than 10
    percent.. (Newsweek, August 13, 2007)

12
10 episodes of global warming/cooling in the past
15,000 yrs
13
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14
What the data shows
  • Global temperatures have risen 1 F in the
    last century.
  • Temperatures in Greenland changed abruptly at
    least 9 times in the late Pleistocene.
  • Temperature changes of 18-23 F/100 yrs
    occurred 3 times.
  • Temperature changes of 13-14 F/100 yrs
    occurred 3 times.
  • Temperature changes of 5-7 F/100 yrs
    occurred 4 times.
  • None of these temperature changes could have
    been caused by manmade CO2 emissions.

15
Holocene climate changes
16
Rapid cooling and warming at 8200 yrs. B.P.
17
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20
Medieval Warm Period
  • The Medieval Warm Period was a time of warm
    climate 9001300 AD.
  • Grain crops flourished in Europe.
  • The population more than doubled and many new
    cities arose.
  • The Vikings took advantage of the warm climatic
    to colonize Greenland.
  • Wine grapes were grown as far north as Britain.
  • Prolonged droughts affected the southwestern
    U.S.
  • Western North America warmed, glaciers receded.
  • An eastern Antarctic Peninsula ice core shows
    warmer temperatures
  • Sediments in Lake Nakatsuna in Japan record
    warmer temperatures.
  • Sea surface temperatures in the Sargasso Sea
    were approximately 1C warmer than today.
  • Equatorial east Africa was drier from 1000-1270
    AD.
  • The Medieval Warm Period appears to have been a
    global event.

21
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22
LITTLE ICE AGE
  • 1300 AD, temp. dropped 4 C (7 F ) in 20 yrs
  • Much colder and wetter, 4 C cooler than present
  • Violent storms, early snow, flooding
  • Glaciers advanced all over the world.
  • Massive crop failures in Europe--large population
    decline in Europe 1.5 million people died
  • Wine production dropped sharply
  • Themes River in London froze over

23
Solar irradiance, sunspots, and glaciers
24
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25
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26
Boulder Glacier, Mt. Baker
1956 to 1979
1940 to 1956
27
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28
Easton Glacier, Mt. Baker
1940 to 1956
1956 to 1979
29
Comparison of glacial activity and ocean
temperatures
30
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31
Facts About Global Climate Change Over the Past
Century and Millennia
  • Evidence for recurring cycles of global climate
    change over the past centuries and millennia
    clearly show many natural climatic warming and
    cooling events, long before CO2 emissions raised
    atmospheric CO2 levels.
  • Greenland ice core isotope and temperature data
    show 10 periods of climatic warming far greater
    than recent warming (up to 20 times greater per
    century). Glacier fluctuations and ice core data
    show a repeating pattern of warm/cool episodes in
    the past 500 years and we are right on schedule
    with two cooling periods and two warming periods
    this century. All of the global warming in the
    past 500 years can be explained by these natural
    climatic cycles.
  • Past climate changes follow cyclic 25-35 year
    patterns that can be traced for the past 4001000
    years in Greenland ice cores, glacier
    fluctuations, and historic observations.
  • The Earth is now near the end of a 30year warm
    cycle, fitting the pattern of comparable cycles
    over the past 200 years.

32
  • The current warm cycle coincidently corresponds
    to high atmospheric CO2 levels. However, the
    preceding 30year global cooling cycle
    (1945-1977) occurred despite the dramatic rise in
    CO2 emissions that began about 1945).
  • About half of the global warming of the past
    century occurred before 1945, so increased
    atmospheric CO2 clearly did not control global
    climate changes then. The abrupt shift in 1977
    from the 1945-1977 cool period to the 1977-2007
    warm period was not reflected by any significant
    change in CO2.
  • The only physical evidence for CO2 causing global
    warming is that warming and CO2 have both risen
    for the past 30 years. After CO2 began to soar
    in 1945, global cooling occurred for 30 years,
    rather than warming.

33
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34
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35
CO2 began to rise sharply in 1945, but global
temperatures declined for 30 years
36
  • Global climate changes correlate well with
    changes in
  • Solar irradiance.
  • Numbers of sunspots.
  • Production of 10Be and 14C in the atmosphere
    from radiation.

37
Few sunspots during the Little Ice Age
38
Global temperature change and sunspots
39
Solar irradiance and global warming
  • 25-30 yr. global warming/cooling phases that
    occurred during the past century coincided with
    changes in solar irradiance.
  • Global climate changes in the geologic past have
    coincided with changes in production rates of 14C
    and 10Be.

40
Where are we headed during the coming century?
41
ICPP predictions Global temperatures will
increase as much as 10 F by 2100
42
Predicted global temperature changes this century
43
Predicted global temperature changes this century
44
  • The IPCC predicts that global temperature will
    rise 1 F (above present temp) by 2011, whereas
    the pattern of natural warm/cool cycles predicts
    slight cooling. The difference is so large, that
    in only 3 years we should know which direction
    were heading.
  • The predicted IPCC temperature increase by 2011
    is 1 F greater than that predicted by
    extrapolation of past climatic cycles and nearly
    2 F greater by 2030. These differences are
    greater than warming of the entire past century,
    so should be easily detectible. Thus, the next
    few years may tell us whether we're heading for
    the global catastrophe predicted by IPCC or minor
    warming predicted by climate cycles.

45
What lies ahead in this century?
  • Two choices
  • If past climate cycles persist and climate cools
    in the next 30 years (rather than soaring), the
    IPCC will have been the greatest scientific
    boondoggle in the history of science.
  • If IPCC predictions are correct, were headed for
    the greatest global catastrophe since the Little
    Ice Age.
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