IPCC Intergovernmental Panel on Climate Change

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IPCC Intergovernmental Panel on Climate Change

• Established by UN Environmental Program and the
  World Meteorlogical Society in 1988
• Consists of 2000 experts in appropriate fields
• 3 working groups I assess the scientific issues
  II evaluate impact on global climate change III
  risk management and mitigation
• Third Assessment January 2001
• Fourth Assessment Feb 2007 was the point at which
  conclusive evidence convinced most that the
  climate is changing due to anthropogenic causes
  (debate ended overall besides in the political
  and economic arenas and a minority of skeptic
  scientists)

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Atmospheric Structure
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IPCC Assessments

• Third Assessment 2001 Human activities are
  influencing global climate change
• Fourth Assessment 2007
• global climate change is now occurring
• caused by rising levels of anthropogenic
  greenhouse gases
• global impacts will be unprecedented and severe

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Impacts of Global Warming

• Melting of polar ice caps
• Flooding of coastal areas
• Massive migrations of people inland
• Alteration of rainfall patterns
• Deserts becoming farmland and farmland becoming
  deserts
• Significant losses in crop yields

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The Earth as a Greenhouse
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Greenhouse Gases and Sources ranked by highest
radiative forcing to lowest

• Water vapor
• CO2
• Methane
• Nitrous oxide
• CFCs and other halocarbons

• Hydrological cycle
• fossil fuel, respiration
• Animal husbandry
• Chemical fertilizers
• Refrigerants

contribute to ozone depletion in stratosphere
as well
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Radiative Forcing (Watts/m2)positive forcing
leads to warmingnegative forcing leads to cooling
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Radiative forces relates energy into vs. energy
leaving tropospherepositive forcing leads to
warmingnegative forcing leads to cooling
Sulfate aerosols result from chemical reactions
in the atmosphere of SO2 from fossil fuel burning
and have a short life in the air (so only
localized cooling effects)
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Current CO2 levels are 387 ppm (or 387,000
ppb) 35 higher than before industrial revolution
and higher than any time in the last 400,000
years (see next slide) Thus our insulating
blanket is thicker and it is reasonable to expect
higher temperatures to follow Methane CH4 level
have more than doubled since before the
industrial revolution and likely more than in
last 400,000 yrs also
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Global Carbon Cycle
Data is given in GtC (billion metric tons of
carbon). Carbon pools are in the boxes, and
fluxes are indicated by the arrows.
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Evidences of Climatic Change

• 17 of the hottest years on record have occurred
  since 1980 (Fig. 20-5)
• Since mid 1970s, average global temp has risen
  0.6oC (1.1oF) and 0.8oC (1.4oF) over last century
  (remember 5oC swings between ice ages and warm
  periods)
• Wide-scale recession of glaciers
• Dramatic temp. increases in northern latitudes
  and melting of permafrost
• Sea level rising
• Increased severity of extreme weather?
  (hurricanes, monsoons, flooding, droughts, etc)

IPCC Predicted mean global temperature change by
2100 is between 1.5 and 4.5 Co
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Fourth Assessment CO2 Concentrations from Mona
Loa Observatory
Why seasonal variation (the wiggle in the graph)?
with CO2 rising in fall and winter and CO2
decreasing in spring and summer.
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Comparison between actual temperature data (thick
black line) and the runs of 13 models shown in
color
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The hockey stick curve of temp over last 1000
years
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IPCC Report Model Projections of global mean
warming with various scenarios from commitment
where GHG
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Climates in the Past
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Key Findings of the Fourth Assessment

• Increased warming climate change
• Differing regional impacts
• Heat waves more frequent and last longer
• Vulnerable ecosystems - arctic
• Widespread water concerns increase in extremes
  ( and -) of daily precipitation
• Agriculture largely unaffected
• Thermohaline conveyor system expected to slow
  down
• Rising sea levels
• Storm intensities expected to increase

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Arctic Climate Impact Assessment in 2004

• Arctic climate is now warming rapidly (twice as
  fast as global mean and 4-7oC in next 100 yrs)
• Arctic warming and its consequences will have
  worldwide implications
• Arctic vegetation zones will shift, and animal
  ranges and distribution will change (aquatic and
  terrestrial)
• Reduced sea ice and earlier seasonal melting
  likely to increase marine transport and access to
  resources
• Thawing ice permafrost will disrupt
  transportation, buildings, and other
  infrastructure

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Decline of Arctic Sea Ice
Tracking sea ice at the end of northern summer by
satellite images.decline of more than 8 per
decade
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Arctic Albedo Feedback loop positive radiative
forcing
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What About the Antarctic?

• Holds most of the worlds ice
• Could be a huge factor in future sea level rise
• Although unlikely to fully melt, Greenland and
  Antarctic ice sheets hold enough water to raise
  sea level by 230 feetfor perspective
• Losing as much as 36 cubic miles of ice/year
  enough to raise sea level by 0.4mm/year

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Response I to Climate Mitigation

• Framework Convention on Climate Change
• Kyoto Protocol Copenhagen Climate Conf
• U.N. Climate Control Conference
• U.S. Policy
• Global Climate Change Initiative
• Climate Change Science Program
• National Climate Change Technology Initiative

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Response 2 Adaptation

• Reduced crop yields
• Water scarcity
• Increased heat and moisture ? infectious diseases
  and lethal heat waves
• Increased intensity and severity of storm events
• Impoverished nations will be most affected
  adaptation not an option