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Global Warming

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Global Warming: Talking with Skeptics C. P. Leslie Grady Jr. R. A. Bowen Professor Emeritus Environmental Engineering and Earth Sciences Clemson University – PowerPoint PPT presentation

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Title: Global Warming


1
Global Warming Talking with Skeptics
C. P. Leslie Grady Jr. R. A. Bowen Professor
Emeritus Environmental Engineering and Earth
Sciences Clemson University Clemson, South
Carolina
2
Many skeptics are at an early stage of the normal
response to a life-altering event.
  • Stages of grief (per Kubla-Ross)
  • Denial
  • Anger
  • Bargaining
  • Despair
  • Acceptance
  • Recognition of climate change
  • Denial
  • Anger
  • Faith in technology
  • Minor changes in life-style
  • Major changes in life-style

Be aware that many skeptics are in the first two
stages and respond appropriately to them.
3
It can be helpful to know in advance the
assertions that skeptics may make.
  • On November 12, 2007, Richard Black of BBC News
    published on BBCs website the top 10 reasons why
    climate skeptics dispute the evidence that
    human activities are altering Earths climate1.
  • Black compiled the reasons by e-mailing the 61
    scientists from around the world who signed a
    letter in April 2006 to the Canadian Prime
    Minister expressing their doubts about climate
    change and the influence of humans.
  • Black received advice on the list from S. Fred
    Singer, coauthor of Unstoppable Global Warming
    Every 1500 Years, and a prominent skeptic about
    the role of humans in climate change and a signer
    of the letter.
  • Black also presented counter-arguments made by
    scientists who agree with the assessment of the
    Intergovernmental Panel on Climate Change (IPCC).
  • Black received advice on the counter-arguments
    from Gavin A. Schmidt, a climate modeler at the
    Goddard Institute for Space Studies and the
    Center for Climate Systems Research at Columbia
    University.
  • The information to follow was based on Blacks
    report, but was augmented with information from
    my own reading and study.

1. Climate scepticism The Top 10 by Richard
Black, BBC News, November 12, 2007.
http//news.bbc.co.uk/2/hi/in_depth/629/629/707460
1.stm
4
Skeptic Assertion 1 Evidence that Earths
temperature is getting warmer is
unclear.Counter-argument A multitude of
evidence tells us that global warming is
occurring, including temperature measurements and
reconstructions, observations of glaciers and
polar ice caps, frequency of extreme weather, and
changing ecosystems.
5
Skeptic Assertion 2 If the average temperature
was rising, it has now stopped. Observations
from satellites and balloons show no warming
compared to 1998.
  • Variability from year to year is expected.
  • 1998 was an exceptionally warm year because of a
    strong El Nino effect.
  • Picking a specific warm year to start an analysis
    is cherry-picking.

Counter-argument
Figure from http//www.globalwarmingart.com/ wiki/
ImageSatellite_Temperatures_png
6
Skeptic Assertion 3Earth has been warmer in the
recent past. During the medieval warm period
(950-1300), temperatures in Europe were warmer
than today. The Arctic was warmer in the 1930s
than today.
7
Counter-argument There have been many periods in
Earths history that were warmer than today, but
the causes dont apply today.
  • Caused by variations in
  • Earths orbit around the sun (400,000 and
    100,000 year cycles).
  • Changes in the tilt of Earths axis (41,000
    year cycle).
  • Precession of Earths axis (26,000 year cycle).
  • Changes in solar output.
  • Changes in Suns gravitational field.

Figure from http//www.clearlight.com/mhieb/WVFos
sils/PageMill_Images/Temp_0-400k_yrs.gif
8
Counter-argument NOAA has stated that the idea
that the medieval warm period was warmer than
today has turned out to be incorrect.
Medieval Warm Period
Current temperatures in the Arctic are warmer
than in the 1930s.
Figure from Jansen, E., et al., 2007
Paleoclimate. In Climate Change 2007 The
Physical Science Basis. Contribution of Working
Group I to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change
Solomon, S., et al. (eds.). Cambridge
University Press, Cambridge, United Kingdom and
New York, NY, USA.
9
Skeptic Assertion 4Computer models are not
reliable. They are unable to model all of the
processes influencing climate.
  • Counter-argument
  • Climate is so complex that models are the only
    way to see how the various factors interact.
  • Current models are highly sophisticated and
    include land, ocean, sea ice, vegetation, and the
    atmosphere interacting in a fairly realistic way.
  • All of the robust results from modeling have both
    theoretical and observational support.

10
Counter-argument (contd) Recent models can
replicate 20th century climate.
  • 58 simulations were performed with 14 different
    climate models.
  • Temperature anomalies are relative to the
    period 1901-1950.
  • Observed temperatures (black lines) are from
    the Hadley Centre/Climatic Research Unit gridded
    surface temperature data
  • set (HadCRUT3).

Figure from Hegerl, G.C., et al., 2007
Understanding and Attributing Climate Change. In
Climate Change 2007 The Physical Science Basis.
Contribution of Working Group I to the Fourth
Assessment Report of the Intergovernmental Panel
on Climate Change Solomon, S., et al. (eds.).
Cambridge University Press, Cambridge, United
Kingdom and New York, NY, USA.
11
Skeptic Assertion 5The atmosphere is not
behaving as models predict. Models predict that
the troposphere should be warming faster than
Earths surface. Measurements show the opposite.
  • Counter-argument

Measurements show that the troposphere is warming
as fast as or faster than Earths surface.
Figure from http//www.globalwarmingart.com/ wiki/
ImageSatellite_Temperatures_png
12
Skeptic Assertion 6Climate is mainly influenced
by the Sun. Earths climate has regularly
responded to changes in the Suns energy output.
Current warming can be attributed mainly to
variations in the Suns magnetic field and solar
winds.
  • Counter-argument
  • Solar variations do affect climate.
  • The difference between the solar minimum and
    maximum over the 11 year solar cycle is one-tenth
    the effect of greenhouse gases.
  • Instruments to study variations in the Suns
    magnetic field and solar winds have not been
    available long enough to establish trends with
    certainty.
  • If variations in solar output are indeed
    contributing to warming, their effects will be
    amplified by elevated greenhouse gas levels.

13
Skeptic Assertion 7Historical increases in
carbon dioxide have lagged behind temperature
increases. They have not preceded them.
  • Counter-argument
  • Indeed, ancient ice cores show CO2 lagging
    temperature increases by about 700 years.
  • Historical temperature changes were caused by
    variations in Earths orbit.
  • Todays CO2 levels (35 increase over
    pre-industrial levels) are higher than they have
    been in 650,000 years of ice core records, and
    possibly higher than at any time since 3,000,000
    years ago.
  • The energy imbalance caused by GHGs requires
    Earths temperature to increase even though
    orbital changes should be causing it to cool.

14
Skeptic Assertion 8 Satellite records are too
short to justify claims that hurricanes are
becoming stronger or more frequent, or that there
is anything exceptional about the apparent
shrinkage in Arctic ice.
  • Counter-argument
  • Systematic collection of data in parts of the
    Arctic began in the late 18th century.
  • Organized reconnaissance for Atlantic storms
    began in 1944.
  • Although these data are not from satellites, they
    are sufficient to draw conclusions.
  • IPCC does not claim that global warming will make
    hurricanes more frequent only more intense.

15
Skeptic Assertion 9Water vapor is the major
greenhouse gas, accounting for about 98 of all
warming. Carbon dioxide and other GHGs have a
relatively small impact.
  • Counter-argument
  • The statement that water vapor is 98 of the
    greenhouse effect is simply false. It
    contributes about 50 clouds add another 25
    CO2 and other GHGs contribute the rest.
  • Water vapor is essentially in balance with
    Earths temperature on annual time scales and
    longer.
  • Other GHGs stay in the atmosphere on a time scale
    of decades to centuries, causing a lag in their
    effects.
  • Water vapor concentrations increase in response
    to warming temperatures, causing a positive
    feedback effect, which is included in climate
    models.

16
Counter-argument (Contd) Simulations with
mechanistic models establish the importance of
CO2 and other anthropogenic GHGs on Earths
temperature.
  • Natural forcings include the effects of water
    vapor, solar variations, volcanoes, etc.
  • The yellow and light blue lines are the results
    from several models run under different
    conditions. The red and dark blue lines are
    averages.
  • Observed temperatures (black lines) are from
    the Hadley Centre/Climatic Research Unit gridded
    surface temperature data
  • set (HadCRUT3).

Figure from Hegerl, G.C., et al., 2007
Understanding and Attributing Climate Change. In
Climate Change 2007 The Physical Science Basis.
Contribution of Working Group I to the Fourth
Assessment Report of the Intergovernmental Panel
on Climate Change Solomon, S., et al. (eds.).
Cambridge University Press, Cambridge, United
Kingdom and New York, NY, USA.
17
Skeptic Assertion 10Problems such as HIV/AIDS
and poverty are more pressing than climate
change. Governments and societies should respond
proportionately, not pretend that climate change
is a special case.
  • Counter Argument
  • Certainly problems such as HIV/AIDS and poverty
    require our attention, as do many other problems
    associated with the developing world.
  • The IPCC report shows that global warming will
    have disproportionately large effects on poor
    nations. Thus, it is imperative that we address
    it at the same time we are addressing other
    pressing issues.
  • Developed nations caused the problem of global
    warming, so we bear a responsibility to solve it.
  • Sharing our technology for alternative energy
    with developing nations will help them develop in
    a clean manner, a win-win solution for all.
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