GLOBAL CLIMATE CHANGE

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GLOBAL CLIMATE CHANGE

• CAUSES
• EVIDENCE
• CONSEQUENCES
• UNCERTAINTIES

Prof. C. Ronald Carroll Co-Director for
Science River Basin Center for Science and
Policy Odum School of Ecology, Univ of Georgia
Ecol 3530 Fall 09
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The Working Group I Report
IPCC 2007

• Started 2004
• Completed February 2007
• 152 Authors
• 450 contributors
• 600 expert reviewers
• 30,000 review comments

http//ipccwd1.ucar.edu/
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Temperature change C
85 of worlds glaciers are retreating. The
majority of Greenland and Antarctica ice caps
melting twice as fast as expected only five years
ago. 0.5 degree C rise in SST 40 increase
hurricane activity.
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WHAT IS DRIVING THIS RAPID AND LARGE INCREASE IN
GLOBAL TEMPERATURES?
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Why the sawtooth pattern?
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RAPID INCREASES IN GHGSINCE THE INDUSTRIAL
REVOLUTION
Nitrous Oxide
Carbon dioxide
Methane
Carbon dioxide
Methane
Nitrous oxide
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WE ARE THE CAUSEBUT HOW DO WE KNOW THAT? IN
OTHER WORDS, HOW DO WE KNOW THESE MODELS ARE
RIGHT?
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Volcanic eruptions used to test model effects of
particulates and aerosols
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Aerosols, especially sulfur dioxide, reflect
incoming radiation thereby acting against global
warming.
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Only models that include human releases of GHG
match the actual historic temperature trend.
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Understanding and Attributing Climate Change
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But, the skeptics of climate change say, The
earth has been cooling for the past ten
years. Is this true?
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No, the warming trend continuesand if it didnt
for a decade or so? So what.
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TOO MANY WORISOME POSITIVE FEEDBACK LOOPS

• MEANING CHANGES THAT CAUSE MORE CLIMATE CHANGE
• IT IS NOT JUST CO2
• WARMING RELEASES METHANE
• WARMING RELEASES WATER VAPOR
• MELTING ICE INCREASES WARMING

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• Tundra, underlain by permafrost, is melting.
• Releasing methane and CO2 gases
• Large positive feedback loop

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Water Vapor Feedback
Warming increases water vaporwhich holds more
heat thereby increasing global warming and
intense storms.positive feedback loop
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Arctic ice caps reflect solar radiation (high
albedo). Melting caps expose ocean water which
absorbs much solar radiation. Therefore, water is
warmer and ice melts faster. However,
phytoplankton blooms in the open water may absorb
C02 thereby reducing global warming. Must
measure the relative strengths of these opposing
effects.
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In the pipeline and what could come

• Warming will increase if GHG increase. If GHG
  were kept fixed at current levels, a committed
  0.6C of further warming would be expected by
  2100. More warming would accompany more
  emission.

CO2 Eq
3.4oC 6.1oF
850
2.8oC 5.0oF
600
1.8oC 3.2oF
0.6oC 1.0oF
400
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Projections of Future Changes in Climate
Summer
Winter
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A World of Drought
Many dry areas are getting drier as soils dry
out. Observed sea surface temperature (SST)
and links to the pattern of rain in Africa? SSTs
and Sahelian rainfall have co-varied in the past.
Some studies suggest links now to the widespread
ocean SST trends and global warming.
Sahelian rainfall decline is reproduced in many
models
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And the role of African dust??Most comes from a
small part of Mali
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Will the Sahelian climate become drier or
wetterclimate models give contradictory
scenarios. But. Overgrazing by goats is
increasing dust storms in Africa.
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What else happens in a hotter world?
Observations of sea level rise from satellites,
1993-2003. The global average SLR for the 20th
century was about 6 inches (0.17m), mostly from
expansion of the hot ocean, and with
contributions from glacier melt (Alaska,
Patagonia, Europe.).
Future changes just from these processes could be
up to 1.5 feet (0.5 m) by 2100, and up to 3 feet
(1 meter) within about 2-3 centuries, depending
on how much GHGs are emitted. BUT.. what about
other processes? Rapid ice melt?
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A different world in the Arctic present and
future
The Arctic was also warm in the period 1925-1940,
but the extent of warmth was not global at that
time. Large future changes in Arctic sea ice are
very likely. Changes in sea ice dont
significantly affect sea level because this ice
is already floating. Changes in land ice
(glaciers, ice caps, and ice sheets) do affect
sea level.
Clear decreases in Arctic sea ice. Water
absorbs more solar radiation than iceanother
positive feedback loop (but phytoplankton
effects??).
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Most recent (2008-09) information

• Sea level almost certain to rise 1 meter in less
  than 100 years. Could rise several meters if
  current rate of Greenland and Antarctic ice cap
  melting continues.

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Hurricane Katrina
Sea surface temperature
Depth of warm layer
Hurricane Katrina intensified when it crossed the
warm, deep Loop Current
R. Scharoo
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Hurricane Bertha. July 2008
birth intensification direction death
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All models indicate a significant decrease in
summer rainfall and a significant increase in
evaporation drought? Most recent (2007) version
of the Hadley models show convergence, i.e.
hotter and drier alternate with hot and wet.
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Projections of Future Changes in Climate
Summer
Winter
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GLOBAL CLIMATE CHANGE..MOSTLY WARMING..IS
OCURRING.DO WE SEE ANY ADAPTIVE RESPONSES?
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Thoreaus Walden Pond is warmer !